The Ultimate Enthusiasts Guide to Fully become One with the TDI, as told by Burpod....

burpod

teh stallionz!!1
Joined
Nov 27, 2004
Location
cape cod, ma
TDI
82 rabbit vnt ahu, 98 jetta vnt ahu, 05 parts car, 88 scirocco.. :/
economy, longevity, performance.

fuel, timing, boost.

fasten your seatbelts, get on your bi-focals, walmart cheaters, or beer goggles, and whatever else you might need :) this will be a very lengthy set of documents to explain the TDI and every aspect therein, as i understand it....

Sections:
  1. Boost [empty]- How is boost controlled - n75, turbo actuator, vacuum
  2. Fuel [1st draft]- How is fueling determined, and what does "IQ" mean, how does it relate to "hammer mod"?
  3. Timing [in progress]- What is optimal "timing", including how it relates to physical pump timing
  4. Summary [empty] - How does Fuel/Timing/Boost all work together?
  5. VCDS Logging [1st draft] - Everything you need to know about the basics!
  6. Diagnostics + Troubleshooting (Hardware) [1st draft] - All the most basic and common issues related to engine performance
  7. Modifications [1st draft] - What are the best bang-for-buck mods for mild and wild-but-not-insane performance gains
  8. Tuning [empty] - Tuning basics, in a general sense
  9. More on Logging for Diagnostics [empty] - More info on logging, interpreting data

i am going to force myself to make time to write up these documents that i've been planning for quite some time now... so stay tuned :) this will get edited a number of times i am sure. i'm hoping if i just get it started, i'll actually get it done somehow....in a timely fashion :)

[[[[[ incomplete prologue ]]]]]

*** if anyone has any suggestions or corrections, feel free to post them up ***

-------- listing of external links to useful documents found in the sections or to be ultimately included -------

- Bosch VE pump PDF
- Bosch VE pump video #1
- Bosch VE pump video #2
- EDC15 functional description
- VAG EDCSuite software download + lots of factory ECU files
- ALH measuring blocks by MOgolf
- IP case relief valv post by jsrmonster
- n75 solenoid valve repair (forget where this was originally posted)
- nozzle size information by GeWilli
-TDI pump timing tread by aNUT
- a graph tool for vcds logs
- the "original big thread" about tuning from ~2013
 
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burpod

teh stallionz!!1
Joined
Nov 27, 2004
Location
cape cod, ma
TDI
82 rabbit vnt ahu, 98 jetta vnt ahu, 05 parts car, 88 scirocco.. :/
Booooooost

Boost is probably the simplest thing to understand with the tdi. We all know it takes more air to burn more fuel, and thus more boost. YAWN....

However, in order to run "efficiently" - whether that be efficiency in terms of mpg, efficiency in bang-for-buck torque/power or flat out raw power, it is important to run just the right amount of boost. But what is "just the right amount of" boost? Once you start thinking of all the different variables/conditions that can come into play and how you want the engine to run, that question leads to the realization that deciding what amount of boost to make is deceptively simple...

Making boost requires some degree of vane closure that will depend on how much fuel and at what rpm the engine is running. Every different turbo will have it's own characteristics as far as how much vane closure is needed to make X amount of boost for a given IQ/rpm condition. Sounds simple, but it is, of course, much more complex. Intake air temps, altitude, coolant temp, fuel temp, compression, camshaft, exhaust type and likely other factors come into play. Not only are these physical factors affecting how much vane position is needed to make the boost, but they can also affect how much boost might be the "most optimal" - and what is most optimal will also depend on how the rest of tune is dealing with these factors, if/when EGR is active and what the SOI (start of injection - aka timing) is. We'll go over timing later, but the SOI/EOI (start of injection, end of injection) will have an impact on how much boost is "good" (and affect boost control), as, like most other things in the engine, timing and boost are very much intertwined, and this can certainly be affected by such things as vehicle weight/drag.... So all of the sudden we've gone from simple to possibly confused :ROFLMAO:

So what is optimal boost?

[incomplete]

How does boost control work?

[incomplete]


For reference, here's the stock ALH target boost + n75 (pre-control) map:



For comparison, here's a VW PD150 (ARL) boost + n75 map:

 
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burpod

teh stallionz!!1
Joined
Nov 27, 2004
Location
cape cod, ma
TDI
82 rabbit vnt ahu, 98 jetta vnt ahu, 05 parts car, 88 scirocco.. :/
Fuel

The injection system is the foundation of the TDI engine.

I will be using ALH (VE pump) as the example here, like most of the rest of the document. The maps for PD/CR fueling will be different since they are both different injection systems, but the same general principles will apply.

Stock ALH engines with manual transmission came with 10mm + .184u hole size nozzles and automatics came with 11mm + .158u nozzles (although one document I've read seems to imply they are actually .170u and .138u, but that I believe applies to the older injectors with slightly lower pop pressures). Here is a old nozzle size information sheet on myturbodiesel written quite some time ago by an old timer tdiclub guy :)

For reference, here's the stock ALH pump maps. You could open these images up in another browser window/tab to reference them along with the information here. Also for reference/comparision is a stock AFN pump map (10mm + .205s).

ALH 10mm + .184u nozzles (manual):



ALH 11mm + .158u nozzles (automatic):



AFN 10mm + .205 pump map:




How does the VE pump work?

In order to understand the pump map, it's very helpful to understand a little bit how the pump works and what pump voltage is. The Bosch VE pump is truly a fascinating engineering masterpiece of both simplicity and complexity. It boggles my mind how one could invent such a small "black box" that does what it does so well and for such a long time, when fed quality filtered fuel. Here is a document on the Bosch VE diesel injection pump PDF. This is an awesome document. It can take some time (and many re-reads) to even begin to comprehend and wrap you mind around, but very worthwhile to do so :) Here is an old official Bosch YouTube video on how it works, and another very good video. Both excellent and highly suggested :)

In a nutshell, for a VE tdi, the position of the control collar on the plunger determines how much fuel is injected. What it's really doing is changing how long in terms of crank degrees (or cam, however you look at it) the delivery valves are open to the injector to supply pressure. AFAIK, nobody except Bosch actually knows the exact relation of pump voltage to crank degrees, but essentially the more pump voltage, the longer the duration in degrees and thus more fuel.

What is the pump map?

The pump map spells out for each IQ/rpm amount a pump voltage (which translates to a duration in crank degrees) to supply that amount of fuel. So for 10mm/.184s, at 2000rpm to supply 15mg of fuel, it needs 2.2v worth of duration. The ECU interpolates the numbers in-between. A healthy stock TDI needs say ~4.0mg worth of fuel to idle at 903rpm when hot which would translate to 1.73v. Since pump voltage correlates to crank degrees, generally, as rpms increase the pump needs more duration (crank degrees) to supply the same amount of fuel because the time the delivery valves are open is less. 10deg of duration at 2000rpm is a significantly longer amount of time compared to 4000rpm - if pump voltage were to be the same, 2.2v @ 4000rpm would supply less fuel than 15mg @ 2000rpm.

If you look at the pump map, it should be fairly obvious it's not linear. I believe this is because as rpm increase, pump case pressure increases which will affect the resulting final pressure when the plunger is compressing the fuel. Nozzle size will also come into play, not just simply because it is flowing more fuel faster, but perhaps due to the larger pre-chamber volume within the nozzle (causing some delay?). Looking carefully at the pump maps for 10mm/.184 and 10mm/.205 and comparing differences in pump voltage values across rpm/IQ ranges you can see that - or at least I believe I can :)

Give how complicated the hydraulics are, it's not surprising that to create a truly accurate pump map for a given pump + nozzles, one would need access to some very expensive Bosch lab equipment. Seeing how different even just the 10mm/.184 map is from the 10mm/.205 maps are should also make it obvious that you can't simply just use a stock pump map with different nozzles and have accurate fueling, let alone use the same pump map for different pumps/nozzles and expect anywhere near the same results, even by hammer modding - but more on that later. I believe with a good understanding of things, some basic math, and a lot of testing, one can come up with a relatively accurate pump map for any given pump/nozzle combination. It will never be perfect, but reasonable accuracy of IQ numbers is better than none.

***as a side note, you can see in the AFN map clearly, that not all of the map contains real, accurate values - outside the limits of fueling for the AFN (iirc 43mg is the max fuel), at the "51mg" column, the pump map is just clearly fudged in with high values that cannot be accurate.

For the PD engines, the fueling is a little more complex and there are more maps than just a single "pump map" to determine fueling. The PD "pump map" uses duration in crank degrees as opposed to the pump voltage to the QA, so despite being more complicated, it's almost a little easier to understand. From my understanding, since the injectors are driven by the cam lobes, pressure will be different depending on SOI - the further away from TDC, the less pressure is available, and thus a longer duration is needed - but of course it's non linear because the cam is always moving... So essentially, there are a set of maps for 0-25+TDC that set the durations needed for each IQ/rpm amount.

What is "IQ"?

The "IQ" is simply the reported IQ amount as looked up in the pump map when the ECU is running the program to idle the car. It uses the start IQ maps to determine how much fuel (and thus pump voltage) is needed to start the car for the conditions (air/coolant temps, altitude) and then simply tries to maintain idle using the pump map as a guide for the IQ/pump voltage. Ultimately, the ECU relies on pump voltage to maintain idle so the "IQ" you see is that which corresponds to the pump voltage needed.

On a factory tune, or a proper tune that doesn't rely on fudging IQ values to change fueling, it would be a realistic value like 3-5mg. Personally, from my experience, I believe a healthy stock tdi takes closer to 3.5-4.5mg to hot 903 idle with all accessories off in "normal" moderate temps (say 40-70F). Higher/lower temps can, for a variety of reasons, change the IQ a bit. One could test and see what IQ is at -20F when at hot operating temp idling, as well as when it's 90+F out - making sure all accessories are also off. Ideally, one would hope it wouldn't change too much if the tune is doing the best it can to be efficient for the conditions.

What does IQ adaptation do?

The default adaptation, like the rest, is 32768. Setting an adaptation to a number [X] higher than this will ADD (X - 32768) to the whole pump map. A lower number will SUBTRACT (32768 - X) to the whole pump map. Or, from another perspective, you ADD (X - 32768) to the whole pump map. If X is less then 32768 X will be negative :p

So looking at the pump map, if one subtracts an amount from it, say -50, that is reducing the durations across the board by .050v. When you're idling, the IQ number looked up will now be a higher value. The (stock 10mm/.184) ECU is still going to need ~4g of actual fuel to idle with ~1.72v worth of duration but now 4mg in the tune isn't really 4mg anymore, it's less. Changing the adaptation is essentially the same thing as if you changed the pump map yourself and re-flashed the car. It's a simplistic "convenience" function the tune allows - either for testing purposes or to fudge fueling a little bit to make up for very slightly different flowing pump/nozzles perhaps due to wear or manufacturing tolerances *shrug*. For IQ adaptation, the max value it allows is only +16 for 32784 probably just so people can't screw things up too much :rolleyes: , which is likely not even noticeable. Lowest value is something like -100.

The Quantity Adjuster - how and why does "hammer mod" affect IQ?

On the VE pump, the position of the QA on the pump determines the "base point" of the control collar. the PD/CR engines work entirely differently, and do not have any such notion, so this is very specific to the VE. The position of the QA would be set on the bench to be precise for a particular nozzle size + ecu/application (or perhaps on the engine to achieve the exact correct IQ, I'm not really sure exactly but sounds plausible). When one hammer mods, one is moving the whole QA - and thus the control collar - such that either more or less pump voltage is needed to inject the same amount of fuel. Hammer modding "up" is moving it farther "away" and thus requiring more pump voltage to achieve the same duration. Hammering "down" will result in less pump voltage needed. If more voltage is needed, just like with IQ adaptation, when at idle the reported IQ is going to be higher. It really helps to visualize this as shown in the videos linked above and things will be "crystal clear" :rolleyes::D🤯.

So... what does this mean if one were to hammer mod down on a tune, say a stock tune? On the stock pump map 15mg @ 2000rpm is still calling for 2.2v worth of duration (say that is 5 crank degrees), but since the collar is that much closer to the point at which fuel will begin to be delivered, 2.2v now will inject fuel over maybe 5.2 crank degrees and perhaps 16mg of fuel will be delivered.. 2.2v doesn't mean the same as when the QA was in the factory calibrated position. If you hammer modded from stock 4mg/1.72v to 3mg that would mean, looking at the pump map, you would be at~1.67v and you could look at block 001 to confirm that. That means you've added about .05v to the whole pump map! Simple math :) Because the pump map isn't linear, 1mg difference @ 903rpm doesn't mean at 35mg @ 2500rpm will be 36mg - you would need to look it up in the pump map and interpolate the values. For example, 30mg @ 3500rpm on stock calibrated map is 3.56v - but you are now doing 3.61v for "30mg" @ 3500rpm - which looks up to ~30.7mg; 30mg @ 1750rpm is 2.97v factory, and 3.02v would be ~31.1mg. For the stock pump map, you will get more of an increase in fueling in the lower rpms than higher rpms. So how much one hammer mods/adjusts IQ adaptation could vary a good bit depending on the nature of the pump map. It should be noted, that at idle the ECU is rapidly trying to adjust fueling to get a smooth idle, so there is going to be some error in determining exactly how much "pump voltage's worth" you've hammered by, but at least one get a relatively good idea.

Many people say that "edc16" or "PD" or "CR" is harder to tune, but I would argue that, with accuracy of fueling being the entire crux of creating a good tune, the VE is much more difficult and nebulous to understand and get accurate. The mapset of edc16/17 is definitely a lot larger so it is more complicated in one sense - but a HUGE number of maps will simply be ignored as most people who tune delete things like EGR, DPF, etc anyway, and once you take away all those maps, the rest is very much manageable and very similar, albeit different fueling maps. And while the fueling maps may be a little more complicated, they are also defined in much clearer terms of crank degrees, rather than the mystifying pump voltage values.

What effects does changing "IQ" have?

Now that one understands hammer modding and IQ adaptation does, it shouldn't be too hard to deduce how this affects timing. If one has "lowered IQ" then injection times across the board have been increased - either because the starting point collar has moved or pump voltage values have been added to via adaptation. The start of injection (SOI) as determined by the timing maps has not changed but now the end of injection (EOI) is now going to be later - thus effectively retarding timing. In the timing section, one can look at those maps and get an idea of exactly how much and what sort of change can be affected. Changing the timing, whether it be EOI/SOI, will also have cascading affects on boost and boost control maps... one thing always leads to another.

What's the difference between hammer modding and IQ adaptation?

With hammer modding, you are changing the physical limits of the pump. For example, on your tune you are maxxing out the pump voltage at 50mg and 4.6v @ 3000rpm - that is the pump is not allowing more than 4.6v - and your current IQ is 4.0mg. You could hammer mod the pump down by ~.05v and then -50 from IQ adaptation such that your IQ is the same as it was before hammering. The tune will run exactly the same as before, except now above 3000rpm (for a little higher up in rpm) you will actually be able to put out more fuel than before.

Fueling accuracy - are IQ numbers real and does it matter?

[unfinished] Without fuel being accurate, timing + boost won't be well-matched and everything (boost, timing + all the various correction maps for varying conditions) would have to be skewed/fudged to compensate for how "wrong" the fueling is.

----------------

Here's some other information related to fueling on a tdi....

Torque limiter:

The torque limiter limits the allowed fuel based on barometric pressure. On a stock alh it doesn't do any limiting of fuel for barometric, The higher the altitude, the lower the barometric will be. When tuning for more fuel, one would most certainly want to limit fuel based on barometric in order to keep the engine/turbo safe. At 4000' air pressure will be roughly ~140mbar (2psi) less than at sea level, which of course means the turbo will have to close the vanes and spin the compressor that much faster to make up for that - how much would depend on choice of turbo and whatever other factors you decide on - for example, do you want to allow more fuel, but reduce boost and increase advance to a certain amount for a given barometric pressure? One would want to ideally measure EGTs and IATs in making such decisions.



MAF smoke limiter:

The MAF smoke limiter will limit how much fuel can be delivered based on current MAF readings. This is essentially used to induce a little "lag" when mashing the pedal to reduce smoke (as the name implies) as the ecu will do a more controlled "ramp up" of fuel combined with possibly manipulating the vane position differently.



MAP smoke limiter from a 1.6PD which is a map-based tune from the factory:

The MAP smoke limiter works the same way as the MAF limiter, except it's using current boost pressure as its metric. Done right, it works very well and one could likely never tell the difference. This factory map, like many others, looks rather funky lol.

 
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burpod

teh stallionz!!1
Joined
Nov 27, 2004
Location
cape cod, ma
TDI
82 rabbit vnt ahu, 98 jetta vnt ahu, 05 parts car, 88 scirocco.. :/
Timing section

Timing basics:

[incomplete]

Physical pump timing- basic settings timing graph:

[incomplete]

What is optimal timing?

[incomplete]

For reference, here are some fun pics :)

Stock ALH 10mm + .184u nozzles (manual) hot 86C timing map:



Stock ALH 11mm + .158u nozzles (automatic) hot 86C timing map:




As an example of one timing correction map, here is the map for changing timing based on IATs. For a stock ALH, it advances timing by the % of the values in this map between 20C and 10C. At 20C, there is no timing advance, and "gradually" down to 10C,it will advance by the full amount - that is the number divided by 100. 350 would be +3.5deg advance.

 
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burpod

teh stallionz!!1
Joined
Nov 27, 2004
Location
cape cod, ma
TDI
82 rabbit vnt ahu, 98 jetta vnt ahu, 05 parts car, 88 scirocco.. :/
VCDS Logging section - How to take VCDS logs, what logs to take, and how understand the data

Understanding Logging:

VCDS is probably one of the most under-utilized tools out there. I myself was guilty of it for a long, long time. I could read fault codes and clear them, change some little behaviors with the CCM for locking/unlocking doors, disable seatbelt chime, etc. Yay, cool! Take boost logs but the only thing i really understood was whether it was spiking, overboosting or underboosting, but nothing about truly why or how, and what really to do about it other than the common (not always right) mantras of armchair technicians saying to "lengthen the actuator rod", "check for vac leaks", "hammer mod" etc and often sending people on wild goose chases or throwing wrong parts at it blah blah

So in order to use VCDS as far as understanding the engine, you need to be able to take data logs. The ecu provides a limited way to get data from it in the form of what's called "measuring blocks" - a group of three possible data values which are polled from the ecu at a fixed rate of time.

On the edc15 ecu for example, data can be polled ~3 times/second and includes a timestamp in seconds starting from when the log was begun. on a edc16 ecu (BEW for example), with TURBO mode, data can polled ~10 times/second - a huge improvement and very much satisfactory. If you have a edc16 ecu (all US PD engines), you would ALWAYS want to log in TURBO mode. Edc15 (alh) does NOT have turbo mode. In order to activate turbo mode, you MUST click the TURBO button before clicking the "Log" button. If you don't, you need to back out of measuring blocks and redo it.

It's important to understand how rough the sample rate is in order to take meaningful logs and what sort of driving is conducive to that. With VCDS standard measuring blocks you can record up to 3 measuring blocks in one log. However - only one block can be polled at any given instant, which means for each additional logged block, it takes up a polling spot. Logging 2 blocks will effectively cut your sample rate in half, and then again with 3. If you were to log 011-001-004 together, you would only get 011 (boost) data about once every second, which is almost useless except for steady state highway driving or long 5th gear pulls. Even with logging only one block, you only get data about once every third of a second, which for such a rapidly changing dynamic environment as a turbo diesel engine revving up to possibly 5000rpm, that is very poor and leaves much to be desired. For data that doesn't change rapidly, like coolant or air temps, it's not a big deal - but for boost and n75 data (as well as timing data), it can sometimes be tricky to understand or guess what might be happening between the lines (namely n75).

How to setup a log:

Key on - go to standard measuring blocks. You can start a log even before the car has started, as long as you don't turn the key off, of course. Select the first block to measure, say 011 for boost data (target boost, actual boost, n75 duty cycle). 99% of the time we are going to want to see boost in the log. About the only times you aren't going to want to see boost is if you're looking for something very specific like tracking timing values to see how well the pumps timing mechanism might be working by compared specified vs actual timing. If you select boost data (011) as the first block to measure, this will make things easier if you ever use VC-scope (see below) to replay your log data with graphs since it defaults to graphing the first measured block in the log and 99% of the time that's boost stuff. It also makes it easier for someone who might be looking at logs (*cough*) if 011 is always first for consistency when combing over CSV files. Then select whatever additional blocks you may want logged.

Then click the "Log" button. You will now see a default logfile name on the left, something like "Logs\LOG-01-011-001.CSV". The intiial "Logs\" part of the name indicates the logs will be saved in the "C:\Ross-Tech\VCDS\Logs" sub-folder on your computer. If you delete the "Logs\" portion, it will save the file in "C:\Ross-Tech\VCDS" main directory. You can start the filename with a "C:" in which case it will save it in that exact location as you specify. If a logfile of that name already exists, VCDS will append new log data to the existing file!!!!!

The log has not started until you click the "Start" button. As soon as you click Start, the log file will be created and data is appended to it as long as VCDS is connected. I suggest after clicking Start ,move the mouse cursor away from the button as it now is a "Stop" button and it's easy to accidentally somehow click it and stop the log, not realize it, and then you complete your drive you wanted to log and have zero data. If you do not click STOP to stop the log, you might lose the last few (or more) seconds of data - how much data lost would vary from computer to computer, so it's best to click Stop, especially if you are logging fueling and want to see what hot idle IQ is at the end of the log.

So make sure to click Start!

It's really critical and beyond helpful to make sure each log you take has a unique name, else data gets jumbled and it's a real pain to anaylze. It also soon becomes meaningless because you can't remember the conditions for which the log was taken. Maybe you took a log, then adjusted the actuator rod length, changed IQ adaptation, fixed a boost leak, whatever. Then took another log. For that day, if that's all you care about, that's fine. But more than likely, you still have other problems to fix, or it's not quite fixed yet, or other tweaks to make, or retuning to do and you take more logs. Without keeping track of what's what, you lose a lot of the value the data has, which leads to lost time, wasted fuel, lack of understanding, confusion, etc. Say you're putzing with rod length, if you don't record in the log name what you're doing and take 3 sets of logs, you won't be able to understand the true affect it's having. Sometimes, you won't see it in one session and need to go back to it and revisit it in a week, but now you can't remember which log was which....

An ideal logfile name would include at least the most basic data - like date, some unique identifier, + info about any changes made like this:
Logs\silvergolf-Nov11-8am-commute-011-001.CSV or maybe:
Logs\silvergolf-Nov11-shortenrod1turn-011-001.CSV

So by taking an extra 5 seconds to give the logfile a unique name, you can preserve the value of the log data and avoid a whole lot of confusion if you need to return to the log to compare it to other logs you will likely take in the future.... If you care about how well your tdi is running and want to understand the why's and how's, this will be necessary. If it's not easy to do or make sense of the logs, it will be just that much more difficult to progress and one will likely just give up and remain confused or, worse yet, make wrong assumptions and come to incorrect/flawed conclusions.

What logs to take and How to drive for meaningful logs:

This is going to be a very diverse answer depending on what you're looking for so this short section isn't going to list out all the types of logs one can take, but more to describe the thought process involved with logging. So I will ramble...

Generally, most people are only concerned about boost - but even for boost, the standard 011 "3rd gear WOT from 1500-4000rpm pull" is about one of the least informative logs to take. If it looks great, things are most likely good (but not necessarily - it's very possible for a boost log to look perfect but the car perform poorly, be slow, still smoke, etc). Usually the reason why we're taking the log is because something seems amiss. I myself have yet to see a single decently long 011 log that shows what i would call basically decent boost control across the board and no hint of troubles. The results of that one pull does very little to answer any question as to what is wrong - is it fuel, timing, boost control? Could intake air temps be too hot? When air temps are too hot, what is the tune doing about it? Is it "pulling fuel" as many people mistakenly think? Is timing behaving and is specified timing being reached or is timing lagging and retarded from spec? Is the spec timing even "good" for the fuel/boost? Is pump voltage maxxed out? A boost/fuel (011-001) log of your entire commute has far more meaning when it comes to figuring out what may be wrong with your boost or boost control.

First and foremost, you need to know if all of the sensors are working and reading correctly. Boost pressure reading incorrectly is of course bad :) Everyone who has a standard MAF tune is always having problems with MAFs reading right - those generally have more tangible and visible side effects. However, if your coolant temp sensor is reading the wrong temp (seen a number of times, sometimes reading flaky for a minute, other times seeming to read normal. or maybe consistently reading low/high), the tune is going to be using the wrong timing maps for the actual conditions - which can greatly affect things. How much so would vary wildly from tune to tune. On some tunes (including factory), depending on the conditions and actual readings, might even show an improvement :p but not necessarily across the board. If CTS is reading a bit low, for example, you might gain some efficiency cruising because of some added advance (results may vary if EGR is intact or deleted), but lose some torque/response in the midrange of IQ or higher up because of too much advance... Every error has compounding/cascading affects and rarely is it a simple answer.

A 011-001-004 log will log the most crucial data all at once - boost, fuel, timing. If you have logged intake air temps before (007 block contains fuel, air, and coolant temp) and know generally how well your intercooler setup performs, if you note the ambient temps in the log file name, you can have a pretty good idea of what those would be and apply that knowledge to what else you see in the log. So the sample rate is horrible with 3 blocks measured, but if you're logging a commute and it's mostly highway or at least more steady-state driving with little 1-3 gear pedal mashing, you will still get good data out of it. You'll see how coolant temps track for the type of driving you did (maybe find a flaky CTS or CTS wiring), you can spot check how well the spec/actual timing values match up, see how boost/fuel is affecting coolant temp, generally how well the boost is on target. If you do any WOT pulls, you can see what the timing maxxes out at roughly and if pump voltage is maxxing out and when.

Taking full-drive logs is the most informative - like logging a trip to the grocery store, homedepot or a commute. Start the log before leaving the driveway, and stop it when you get to your destination. You can't have too much data, and it's easy and quick to fast-forward or scroll through all the areas that are "fine and good". Sometimes you won't realize the usefulness of a log until later - perhaps after having made modifications, retuning, or simply miss something. Another reason why it's important to name logs with a unique and semi-meaningful name.

Putting the most amount of data in the log file name that is generally static, or that which can be easily deduced with a good degree of certainty, is a very good way to get better data granularity in your logs. As mentioned, IATs is one such thing. If you've changed timing or IQ adaptation and take a log for something, you don't necessarily need to include 004 (timing) in the log, just tack on "_timing32668" to the log file name to indicate you have taken off -100 for -1.0 deg of advance. Log might be "Logs\silvergolf_air75F_timing32668_nov11-011-015.CSV" for a boost log to track boost + see difference between actual delivered IQ and driver wish IQ. Knowing the air temps is really critical, because tunes can/do change timing based on air temps, and also change the target boost, and of course, air is denser when colder - so all important stuff to be aware of when watching the boost/fuel.

The Marker Button:

VCDS provides a very simplistic way to add "markers" into a log to signal some sort of event. Every time you click the marker button, it puts an ever-increasing number into the marker column at the current time in the log. So the value of the marker button isn't in itself, but what you make it to be (yes, a little philosphical lol). There are a number of ways you can use this to your advantage, especially when logging alone. If you want to use this feature, after start the log, what I do is place the mouse cursor over the marker button, so when you want to mark something you just reach over and click the mouse button and you don't even need to take your eyes off the road.

One example of using the marking button would be in efficiency testing. You're logging 011-015-004 (boost, fueling + consumption in L/hr, and timing) and want to compare efficiency between cruising @ 65mph on your tune (Factory or otherwise) with normal timing vs adding 1.5deg advance using timing adaptation of +150. You would of course need to do the logs on days with little-no wind and similar ambient temps. On these logs, every time you are approaching a flat section of road you will be maintaining 65mph, you click the marker button. If you can't watch the live data and keep it in your head, you now have it in a log to review later. You wouldn't necessarily need to log 004 - you could just log 011-015 and note in the log name the timing adaptation value to get better sample rate, but in a case like this when you're doing steady state driving you don't necessarily need the best sample rate and having the convenience of seeing the actual timing values in the log is might be worth it. You could do the same thing but with comparing different tunes or tune versions, or even across your multiple TDIs - most people have more than one :D

Another example would be to use the marker button to indicate moderate/heavy smoke. You do a big 5th gear pull, or maybe 4th gear moderate throttle @ 1400rpm going up a hill, you see smoke of a concerning amount, you click the log button right after the fact. Back at home, you can review what conditions were and try to figure out why. Such a log might likely be 011-001-004; or if you know the tune (so you can deduce the fueling), 011-004 if you suspect timing and you want better data granularity.

There are a lot of possibilities and by getting creative you can squeeze out a lot of information/results....

Advanced Measuring Values:

This is just a convenience function of VCDS, however, it can lead to even worse sample rate. I'm not exactly sure how this works, but my guess is the ecu can poll any number of blocks (not just 3, but VCDS must just limit it to 3) and the advanced measuring values simply polls whatever blocks it needs to to get all the data you want. So if the data you want comes from 4 measuring blocks, you're going to get even worse sample rate/data granularity. I never use this, except when using VCDS-mobile on my phone, since that's all that's available, but I'm careful to pick and choose what data I want in order to keep a better sample rate if desired. I usually use my own custom measuring blocks :) (see below).

Custom Measuring Blocks:

The measuring blocks and what they contain are defined in the "tune". One can change them completely from stock, or you can simply add new measuring blocks containing the data you want into unused slots. This is incredibly useful, as the stock measuring blocks leave a lot to be desired if you care about getting more informative logs. There is a lot of redundant information in the stock blocks (like rpm, which can be easily interpolated) and it's not even possible to get all the data you might want with just 3 blocks! As an example, one block i define is 014, which is: IQ, spec timing, intake air temp, and coolant temp - some of the most critical data aside from boost. In order to get that data, you would have to use 4 measuring blocks (011, 004, 007, 001) and sample rate would be absolutely useless for boost other than highway driving. With two blocks, the sample rate is decent enough that it's still good data for most driving. Not ideal, but usable, and a lot more informative than the usual 011-001 log since you rarely are needing to inspect pump voltage or duty cycle values for that, rpm is redundant so all you're getting from that is essentially IQ.

Some paranoid tuners delete measuring blocks by blanking them out so one can't "steal the tune" from log data. lol, that's a good one... but of course now you can't log or view ecu data even on your own car, you would have to rely completely on your own gauges.... :rolleyes:.

Using VC-Scope:

VC-scope is an awesome little tool that allows you to watch in real-time (or fast-forward) your log data as pretty graphs. 99% of the time this is just going to be target/actual boost + n75; but with the timestamps, you can then go into the .CSV file using excel and closer examine the numbers. I believe it comes packaged with VCDS, but if not, it's a free download from ross-tech. Easy to use - simply start it up, and open up a log file and click play :) If you always use 011 as the first measuring block to log, it will default to displaying the boost graphs,. So please, if you're logging 011, always select that as first block to log.

There's a couple features i wish it had that would make it immensely more helpful:
- being able to scroll through the log. as it is, you can only play it, pause it, or rewind it completely- annoying for long logs
- being able to have multiple graphing windows up at once so you can watch/pause two or more logs at once and scroll through them and compare the graphs visually at the same time

Bottom Line:

Without being able to understand how to take good meaningful logs and make sense of the data, troubleshooting or trying to improve the performance of a TDI is virtually impossible. You are blind. You can spend a lot of time and waste a bunch of $$ throwing parts at things, asking questions online that have been asked and answered (correctly or not) a million times... or log... and log the right data, and if you don't understand what you're looking at, at least you have something you can post up and hopefully get help with and have a starting point to ask other pertinent questions to narrow things down. With the right logs and intelligent thought/questions, most problems can be pinpointed and resolved very quickly with least amount of time and $$ down the drain. And you learn something.

When it comes to figuring out issues on tuned TDIs, the answer is rarely as simple as "adjusting rod length" or "hammer mod", but unfortunately, IMO, most people have been lead to believe otherwise. But this gets into a much more "subjective" topic :) It would be in ones best interest to thoroughly log a tune and understand what it's doing and how well it's truly running. This can be difficult if you don't have anything to compare it to other than itself, similar tunes, what you remember a stock TDI to be like, and all the other stuff you read online and take to be true...
 
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burpod

teh stallionz!!1
Joined
Nov 27, 2004
Location
cape cod, ma
TDI
82 rabbit vnt ahu, 98 jetta vnt ahu, 05 parts car, 88 scirocco.. :/
Diagnostics + Troubleshooting - All the most common hardware issues related to engine performance

This will just be a listing of all the basic checks, in one place, that can be done easily by most anyone with the most basic of tools to ensure the basics of the hardware are in good working order as related to the engine, in rough order of importance. I've probably forgotten some and will add as i remember or am suggested to add :)

Condensed checklist:

- Vac supply is 29+ HG
- n75 gets 24-25HG and hits the stop screw during VCDS n75 output test / charge pressure control test
- rod length is standard 18HG (or whatever it is factor for your turbo), vane lever move 100% free and actuator holds vac for 20sec
- does the vane lever itself move 100% freely (disconnected from actuator)
- pressure test boost piping - boost leaks?
- air bubbles in IP supply line?
- all temp sensors reading accurate
- thermostat good?
- MAP/barometric sensor reading sane
- all major engine electrical connections clean
- if EGR is present, is it clean?
- is MAF reading correct? (who cares lol just delete it :))
- injector balance good?
- pump timing behaving? pump voltage maxxing out anyhere?
- IP case relief valve good?


Vac supply:

Healthy vaccuum supply on a TDI is 29+ HG. If it's less than that, measured at the main brake booster line, then you have a leak somewhere. Most often the vacuum pump nipple becomes loose and that can easily cause a 1-3HG drop. The grommet on the brake booster might not be sealing well and cause a similar drop. Both of these can often cause intermittent vac supply loss, you can hook up your mityvac or other gauge and wiggle/push on the lines and see for yourself. A wiggly vac pump nipple can be fixed but hard to do with 100% sucess on the car, sometimes internal seals can fail which can be easily replaced. Generally, the pump itself seems to be pretty hardy and lasts a long long time. Brake booster could possibly be leaky. Turbo actuator could be old and leaky internally, etc. The brake booster hard line is known to sometimes split. As long as you have 24-25HG vac supply, it shouldn't be affecting boost control to any noticeable degree, but it would be in ones best interest to fix the leak regardless. With mityvac it shouldn't take more than 10 minutes to figure out where exactly the problem is :) Sometimes people get the little n75 checkvalve on backwards resulting in no vac to the turbo and thus virtually no boost with vanes always open.

VCDS Charge Pressure Control Test:

Tee mityvac into the vac line to the turbo actuator, or directly to the n75 output barb itself. car idling, warm, go to basic settings then from the drop-down menu select the charge pressure control test. This will cycle the vanes from full open (100% duty cycle on an ALH) to full close (0% duty cycle on an ALH) - edc16+ is the opposite numbers for duty cycle. You want to see 0HG when vanes fully open, and 24-25HG when vanes fully closed. If you see less than 24HG and your vac supply is >24HG, you might have a faulty N75 valve, wiring, or other strange electrical issue and possible boost issues. If you're seeing <18hg you will most definitely have boost issues. If the vac line is connected to the turbo actuator (mityvac teed in or not), use thinnest feeler gauge or your finger/eyeballs to make sure when vanes fully closed, it is hitting the stop screw, and when full open, the vane lever has retracted all the way to the internal stop - if you can use your finger to pull up on it and get it to open more, then either the actuator or the vanes are sticky a bit there. Likewise if it doesn't hit the set screw.

For a vnt15, during the test, you should see a decent deviation in boost shown in VCDS, something like 100mbar, i forget exactly. The larger the turbo, the smaller the deviation as 900rpm and ~4mg of fuel simply cannot spin the large compressor enough to create boost - one might even see boost values less than current barometric.

N75/vane actuator/rod length:

All the common factory Garrett turbos, far as i know, set the "rod length" to be ~18hg. So with mityvac, you should most likely want to be hitting the set screw at 18HG, and it should be confirmed that the set screw is in the factory set spot and that it is correct. The actuator should hold 18hg for at least 15-20 seconds - if not, it's leaking... As above, using a feeler gauge makes it a little more precise to measure. If you don't have a feeler gauge, you can just use a folded over piece of packing tape cut to a convenient size to hold. Move it back and forth a little as you pump it up and stop when you feel it hitting the feeler gauge/tape. There should be no hint of binding or sticking. I'm fairly certain, that when under boost in the real world, because there is some in/out play of the vanes against the machined surfaces in the turbo, even the slightest bit of stickiness while "at rest" could result in more severe sticking when under boost if that boost is pushing the vanes in/out. An old turbo can develop some pitting on those machined surfaces which can cause more soot buildup and worse sticking.

Broken vane lever:

Sometimes, the vane lever can break. I can't imagine how this would be possible unless the lever has been forced with a tool to try and free up sticky/seized vanes but i think it has happened... If the turbo is brand new or very clean, there should be *almost* no resistance in moving the vane lever - but there should be very small amount as it's moving the control ring and all the vanes If you listen carefully, you should be able to feel/hear it moving inside. If the vane lever is snapped, it will be completely floppy loose and most likely the vanes are seized at some point. Even if the vanes are stuck wide open, the turbo can still make a decent bit of boost. How much will depend at which point they are seized, the fueling, timing, rpms + turbo characteristics. More fuel will of course drive more boost, but having more advance can create a surprising amount of boost even with vanes wide open. A broken vane lever will reveal itself by producing consistent boost results for fuel/rpm points (in same conditions) regardless of what the n75 values are saying in the log. As always, conditions (temps, gearing, etc) will affect this

Another sanity check for turbo/boost/vanes:

This is a test that demonstrates how much the vane position can affect ... [incomplete]

Symptoms of sticky n75 valve/vanes:

[incomplete]

Cleaning the Turbo:

To really fix sticky vanes, or if the vanes are completely seized, the turbo needs to be disassembled and cleaned. If the turbo is old and rusty, it might not want to come apart no matter how much penetrating oil you use. Be careful how you attempt to crack it open as to not break it (BTDT once). If it's that old, one might consider having a turbo upgrade on hand in case of no success :) To clean, I use an old baking tray, jar of leftover/used paint thinner + toothbrush. finish it off some a shot of brake cleaner and compressed air, the machined surfaces where the vanes might come into contact with need to be inspected for any pitting/burrs and dremeled off. Before re-installing the actuator, make 100% sure vanes are moving freely!! I hear stories that supposedly sometimes you can spray oven cleaner into the turbo and that might fix it, but i think it's a crapshoot. If you've ever taken apart a turbo, you'll wonder how it could even be possible to clean much at all if any that way... ???

Boost Pipe Pressure Testing:

Get a $70 cheap pressure testing kit (or scrounge up your own with a couple PVC/silicone bits) and pressure test your boost pipes. Easiest to do from the rubber hose to the compressor to the elbow to the ASV/race-pipe. You can't really get a good pressure test into the head unless you take the cam out. You could also pressure test from the turbo inlet pipe up to the ASV/race-pipe but of course have to plug the CCV inlet and i'm not sure if it would be a good idea to put 25+ psi through the stock turbo inlet pipe. It's amazing how many people (myself included) have boost leaks they didn't realize they had until they actually did a pressure test. On a stock TDI, a common problem is the black plastic scoop in front of the intercooler rubs a hole or two in the intercooler or leaks at the crimped end-tanks. a quick visual check would spot a bad leak, as it would most likely be all covered in oily dusty gunk. Boost leak + high IATs :) While you're at that, make sure the fins of the intercooler look all in good shape. Somehow, not all leaks produce oily seepage, even with CCV hooked up to the intake, so just because you don't see the usual tell-tale sign of a boost leak, don't assume you don't have one.... I know a couple people who will attest to this, including myself :)

Air Bubbles in the IP Supply Line:

Contrary to what many think, there should never be air bubbles in the clear IP supply line. Perhaps an occaisional air bubble is benign, like maybe you ran the tank down empty and were doing some tight cornering and it sucked up some air. If you consistently see an air bubble or two, then you have an air leak and it can most definitely cause problems, likely even if it's not noticeable. The IP creates a vast amount of suction, and likey at higher revs under load, quite a bit more. On a road trip once in my mk1 tdi with a metal gas tank, long story short, somehow the tank vent became clogged and it literally caved in the tank enough that it became loose on the straps and started rattling around. I also thought the engine had been feeling strained, but it was gradual, it was hard to tell exactly what I was feeling. At the motel, i opened the gas tank cap and there was a huge woooosh as the vacuum was released. Rest of the tip home i drove with the fuel cap off and all was good :) The IP will find even the smallest leak in the fuel system and suck air in, but by the time you've parked the car and open the hood it may have purged most of the air and you will never know how much air it was sucking in during higher rev/load driving.

Usually the culprit is the o-rings at the crappy thermo-tee or connections at the fuel filter. There are check-valves by the fuel filter as well as back by the sender which are possible to develop a crack in. Corrugated lines in the fuel sender can crack. If the sender is clogging, it will make any weak connections more susceptible to leaking air in. Personally, I use an aftermarket setup stanadyne fm-100 which has ports for gauges/etc and plenty of good filter options available (currently use Donaldson). There are several other options available that do away with the thermo-tee as well as provide perhaps better filtration + may be cheaper than oem. I lived in northern MN for a few years where winters were frigid and never felt like I was missing any fuel-temp related performance without the thermo-tee. Just my 2cents.

IMO, the best solution is get a in-tank BEW lift pump. Many of them flow enough fuel to keep the car running if it craps out, at least for a while, until the extra resistance likely will introduce an air leak and you likely will eventually get an air lock. You can check this on the bench with your mouth or mityvac and pull a suction on it. If you keep a mityvac + 17mm wrench in the trunk, you should always be able to get it going again enough to get where you need to go. Wiring it up can be very easy. No hacking or splicing into existing wiring, add a fuse into the fusebox and a relay into the relay panel.

Temp sensors:

After car has sit overnight or any other time when car has been sitting in fairly stable temps, with key on/car off - check block 007 to confirm fuel, intake air, and coolant temps all read the same or sane. Maybe it was 20F all night and you check it in the morning and it's warmed up to 30F. One would expect the air temp to probably be a bit higher closer to ambient temp, but fuel/coolant still closer to 20F. This will at least sanity check the sensors at "baseline" temps, but there's always a chance a sensor could taper off with its accuracy as temps increase.

Thermostat/CTS:

Best to change out the thermostat every TB change. Sometimes it can be tricky to tell if your thermostat is bad or the coolant temp sensor is reading wrong, and both will likely hurt performance if not operating correctly. I have seen a few t-stats (<1yr old from quality vendors) be stuck closed/mostly-closed, too. To sanity check the thermostat, you can drive the car from a cold start for a bit (how much depending on ambient temps) until say the coolant temp sensor reads 70C. Maybe its 10C (50F) out and you drive for 5-7 minutes and are at 70C. Stop the car, and put your hand or heat gun on the lower radiator hose - it should be pretty cold. If it's noticeable warm, most certainly your thermo-stat is stuck open to a degree. If you've driven long enough that the car should be fully up to 87C and it's warm out, and coolant temps are still reading a good amount <87C, it's probably the coolant temp sensor or possibly faulty wiring connections. If the lower radiator hose is consistently cool compared to the upper, t-stat might be stuck partly-closed and coolant temps will be much higher than normal.

Barometric/MAP:

Sanity check to make sure you barometric sensor in the ECU reads the same as manifold pressure at rest, and barometric is sane for your altitude. key on/car off look at block 010 and check :) Should read within 15mbar of each other.

Electrical Connections:

Faulty electrical connections and sensors reading wrong is something that consistently comes up causing many headaches. Make sure all of the main engine electrical connectors are clean, have no signs of corrosion in the terminals, have no kinked or frayed wires around the ends. IP connector, crank sensor, 3rd injector, MAF, MAP, ASV, etc. De-pinning the connector is the most surefire way to check and clean well. Sometimes there can be corrosion at the crimp/faulty crimp. Spray a little electrical contact cleaner on the terminals and actuate the connector, blow out with compressed air. If you have some spare wiring, take a wire lead with a male pin on it and push it in/out to get some more cleaning action going on - much easier to do one pin at a time. You can use dielectric or other safe grease on the connector seals which will help the connector slide together easier, seal out water, and prevent the seal from binding or tearing when you connect/disconnect it. Do not get dielectric grease on the terminals themselves - it's an insulator!! and will cause problems!! Always be careful when trying to unlock the plastic tabs on the D-shaped connectors as they break easily, especially in cold weather and as they get old. I personally much prefer the wire-lock square type of the mk2-mk3 era.

EGR:

Always, Always, Always make sure the EGR valve + intake manifold is not clogged up with EGR crap. even if you just cleaned it 30k ago and you're having boost issues, pop the hose off and shine a flashlight in there to be sure. Make sure there are no exaust leaks at the craptastic egr flex pipes or cooler. Stock ASV can often weeps a bit of boost/oil, especially at higher than stock boost levels. If you can, it's really just best to delete all that IMO. Clogged egr will cause boost issues and therefore low MAF readings and one might mistake it for bad MAF. If the engine can't breath, it can't spin the compressor and make boost!

MAF:

[incomplete, MAFsuck, maf-delete tune ftw :)]

Injector health:

When car is warm, log 013 only and get a short log of a 5 sec warm idle, few medium-to-heavy pulls in 4-5 gears + a last hot 5 sec of idle. It's important to get both idle and a few pulls. At idle, the ecu is running an idle stabilization program where the ecu is trying to compensate for variations in each injector to make for a smooth idle. When above a certain rpm and under load, the injector balance is simply reported with no funny business. i think ideally you want a deviation of <1.0; .5 would be good. >1.0 would be pause for concern; >2.0 would be definite cause for concern. First you can check for cleanliness and/or clean terminals on the crank sensor + 3rd injector (brake cleaner or contact cleaner + actuator the connectors a few times + blow out with compressed air). Sometimes bad contacts or wiring can cause bad readings. Never use dielectric grease on the contacts themselves, that's not it's purpose - it is an insulator!! It IS good to put on the connector seals to help keep water out and ensure the seals slip into the mating connector without binding up causing either tears or a bad seal. One could try running a can of straight diesel purge through the pump with a funnel + inline filter setup. Nothing can ruin an engine quicker than a poorly spraying injector combined with a tune that's both over-advanced and over-fueled... doesn't end well :D Even a "good" tune pushing a healthy amount of fuel... plain old bad news! One can hope a bad injector balance is just sensors not reading accurately or at least different enough pop pressures across the set.

Pump timing/voltage:

For stock measuring blocks, log 004 by itself (for best granularity of timing data) or 011-004; Can be done cold, or at operating temp to determine if problems exist in both cases, or only one. You want to see how well actual timing follows specified timing. This is nearly as important as actual boost tracking with target (well, assuming the boost map in the tune is well-matched for the hardware of course.. not always the case!) So basically, you just want to drive under a number of various conditions: 1-5 gear pulls, normal cruising, normal driving, pedal mashing, etc. It would be a good idea to note in the log name what the ambient air and fuel temps are. if it's -10F out, you might see problems that you wouldn't normally see in the spring-summer-fall. Remember, if you have pump timing set very advanced, you very well might see lower rpm actual timing not meet spec because it can't retard enough - but this would be totally dependent on where exactly it's set and what tune. If pump timing is retarded, at very high rpm and heavy fuel, actual timing might not meet spec. again, dependent on tune. If you're logging 001, you can see when your pump voltage maxes out, and combined with boost/timing, you can see and perhaps understand what might be wrong with that.

IP case relief valve:

Very common on old pumps, the valve starts to walk out of itself / fall apart. I don't know exactly how this works, but i do know that the timing pin is hydraulically controlled and dependent on case pressure. A walked out relief valve can cause smoky starts and poor performance especially down low rpm. Results could also vary tune to tune on what you experience. I would think it possible it could cause issues across the rpm band, but perhaps not always so noticeable, depending. You should be able to get it out with a 10mm wrench, but depending on it's orientation, you might need to finagle it a bit with another tool or two to get a grip on it but it's 100% possible without the special bit and most likely just with whatever's in your toolbox. Make sure to clean around it thoroughly first, you don't want crap falling into the pump. Blow the area with compressed air ideally, then toothbrush + brake cleaner + more air. Push valve back together if it's walked out. There is a "keystone" mod but it's kind of a pita. You can tack weld it so it never comes apart again. Not sure how long it takes to start walking out again after pushing it back in, so if you don't make the fix permanent, just remember that :)
 
Last edited:

burpod

teh stallionz!!1
Joined
Nov 27, 2004
Location
cape cod, ma
TDI
82 rabbit vnt ahu, 98 jetta vnt ahu, 05 parts car, 88 scirocco.. :/
Modifications - What are some of the best bang-for-buck modifications for mild performance upgrades? and for even more power? this is a list of basic mods i would do to any TDI that i owned. all my OPINIONS, of course.

0) goes without saying a good tune goes along with all of this....

1a) get rid of crappy horrible stock intake manifold in favor of pd150 manifold + racepipe ($215 shipped from xman), physically remove the EGR. with a 3/4 male-male barb you can make the perfect cut and re-use the existing hoses, and swapping one of the small coolant lines around + a little cut, get rid of the tee. looks just like factory except for that splice. can be done neatly, the same way, with both automatics and manuals (different coolant flanges/hoses coming off the head).

1b) get rid of all the useless vac lines for asv/egr, the n75 check valve and the vac ball (does nothing). the only vac lines you would need are a) vac line from brake booster to n75 VAC barb, b) vac line from n75 OUT barb to turbo, and c) vac line from n75 ATM to a short vac line with a $2 inline filter + plug the airbox nipple. all of this really frees up a lot of space under the hood, making things easier to keep clean and work on.

1c) delete the maf - pop the screens out and chop the sensor off, or make a block-off plate, or leave it entirely out of the piping if you have custom piping. never flush $$ down the toilet for a maf again, or waste time chasing maf issues. not needed with egr deleted and a good maf delete tune. you'd never notice. has zero effect on efficiency.

1d) regarding egr delete and warmup time/performance - tuned right for the fueling you have, warmup-times should not suffer at all. warmup period performance can be clean, crisp, perky, smoke-free and pretty efficient. you'd never notice a difference. cylinder glow plug times can be reduced (allowing ecu to divert more energy to coolant glow plugs), coolant glow plug times extended a bit too - to help even more. IMO, "bigger" fueling will very much improve cold weather warmup performance as you can really reduce the amount of advance. drives very, very nice.... unfortunately, a lot of tunes do not really put much effort into optimal timing, and run far too much advance.. throughout the coolant and air temp range. it can be painful to drive, at least once you've seen the light ;)

2) BEW lift pump - get your lift pump from your favorite vendor + ~$50 max in wiring supplies - you can wire it in like factory with no hacking, splicing, drop-in harness. add a fuse into the fuse panel, and a relay "53" into the relay panel, with one ring terminal wire going to the fuel shutoff on the pump. i would suggest testing lift pump prior to install to see if it will pull a vacuum without much resistance - if so, that should mean car should still run if it dies, although will put a strain on things... some lift pumps will not flow fuel at all if it dies.

3) along with the lift pump, get rid of the stock filter with craptastic thermo-tee that causes countless people endless grief leaking and letting air into the fuel supply. just happened to me again, with this car i was working on. thermo-tee o-rings not sealing right, letting air in. unless you've run the tank down, there should never be any air bubbles in the supply line. perhaps a random occasional small one is fine, else it means you have a leak plain and simple, and it will affect performance and affect the pumps ability to meet timing request. and when you're really up in the rpms, beating on it, who knows how much air is getting sucked in... the thermo-tee IMO has virtually zero benefit, only causes issues. in theory, it makes sense. but i have a hard time believing such a dinky cheap device can really do the job it's meant to do without malfunctioning to a degree. . you can get a $18 filter head on amazon for a caterpillar filter, $25 2micron spin-on caterpillar filters. make sure to fully clean and flush the filter head - those cheap filter heads (or any head really) might contain shavings from manufacture. i would run the lift pump with the supply line going to a jar for a minute to make sure any debris is pushed out, then dump that in the tank. get better filters, cheaper, never have air. and easy to change on the side of the road without tools if you were ever to get that random bad batch of fuel and clog up a filter.

4) open up the exhaust a bit - if you don't want to spend $$ or can't make one yourse, at least lose the muffler and drill out the cat (and then it acts like a resonator). added noise will be barely noticeable imo (the tune will play a fairly significant role in the sound levels)

5) .681 gear from cascadegerman - easy to install if you know how to use a gear puller, great bang-for-buck if you can't afford to go to a real tdi 6spd. you do need a gear puller that will fit. i know i have used a cheap autozone gear puller that i modified with my grinder so the teeth will fit behind the gears - it's a little tight. eurotuning.cz is also a great option, but expensive (but good time to do an LSD). an 02S 6spd from a gasser is also another option with perfect gearing for the tdi, and could likely be had fairly cheap at a junkyard.

6a) bit larger turbo - vnt17 minimum pretty cheap from xman, maybe $700 shipped - flows exhaust faster, combined with freeing up intake/exhaust, you can most definitely get better higher rpm highway cruising efficiency and likely lower EGT/IATs. a bv39 is also a great responding turbo, if you get a deal on one. a GTD1449vz for a medium ~25psi level turbo would be best yet in all respects, but requires downpipe modification to fit v-band clamp flange, but the weld job should be trivial. other than that it's just typical boost pipe futzing to fit. no more crappy 3stud flange on the downpipe that is always a struggle unless you live in the southern states, california...

6b) going bigger..... like a gt1856v size or equivalent gtb/gtd - really has very minimal lag down low - just little bit <2000rpm, 2400+ - none, instant boost.. it's completely drivable and peppy done right in the <2000rpm range. but if you're driving style/situation for some reason demands lightning fast spool/high boost @ 1800rpm (perhaps not the healthiest on the engine), then it might not be the best choice. however, fueled/timed right it can make quit a bit of boost @ 1900-2000rpm (at least from my testing of gt1856v) and put done some good torque. for most non-teenager drivers, i couldn't' imagine anyone would be dissatisfied with the performance in the lower rpms. just takes a hair longer to get there with a bit of smoke to get it spooling quick. GTD would surely be faster spooling down low, but have not personally yet tested those. i'm quite happy with the performance of my gt1856v but ready to move on to a gtd2060vz (journal bearing). i would have preferred slightly smaller, but the only other options i have found are 1756vrk which is ball-bearing and don't have 100% faith in those, yet.

7) "stronger" fueling - 11mm + .260s is my favorite combo - IMO, shorter injection times means more optimal combustion window if the tune is correctly dialed in. 11mm with higher pressures should atomize the fuel better, and using higher than stock pop pressures should also theoretically help a tiny bit. you can make the same amount of power but with much less advance (compared to say, 10mm/.205s) - thus getting more bang-for-buck for your fuel, less stress on the engine with theoretically lower PCPs - as you've got much less combustion happening before or right at TDC. you can pinpoint it to be on the downstroke at a more ideal spot. correctly tuned, you can run as big of fueling as you want even with small turbo and be 100% smoke free - you simply just limit the fuel to what the turbo can handle. say 55-60mg max for a vnt15. or if you want to push things, extend the max fuel to 65-70mg but you'd surely be getting a haze at a true 70mg (how much can depend on choice of SOI) and would be wise to have an EGT gauge if you ever do any extended 4-5th gear pulls and would also likely start overboosting the turbo even with vanes wide open.. so one must be careful.

8) of course with all of that comes the likely need for a clutch - i wouldn't bother with anything less than an SBC2 daily + single-mass stock weight flywheel. but if you truly know you never want to go beyond 250 ft-lbs, a cheap vr6 clutch should be fine, although those (in years past at least) i think might have had a bit more chatter to them, i dunno. but unless you got some bum parts or somehow screwed up the install, a good SMF/clutch is smooth as butter at idle. KY clutch and ACT are other options to look into.

9) bigger intercooler - if you are going for bigger power, you'll ultimately want to increase intercooling efficiency - but you don't necessarily have to do that right away. it just means in the warmer months primarily, you'll be limited in top end fueling as the temps dictate. long power pulls will heat soak the stock smic but you can probably get away with short bursts of power. in the colder months, it will be less of an issue. a larger SMIC is better, but it's questionable whether the effort/cost is worth it. an fmic will always be superior, but involves a bunch of futzing and bumper trimming. multiple ways to do it. my preferred way of doing it is with a cross-flow intercooler that will fit mounted below the crash bar, with a boost pipe coming up over the trans to a driver side facing pd130 intake manifold - makes for a nice clean simple loop, rather than crammed in around the TB area, and crossflow intercoolers, afaik, have better cooling efficiency.

10) coolant heater - great bang-for-buck for those in colder climates. it's a shame the alh/bew blocks didn't have a provision for the small block heater like the AHU/1z did. depending on the temps, 2-3hrs max of plugging that in gives an ideal bump in temps right where you want it - all in the block. i suspect it's more efficient use of electricity. it also doesn't take up any real estate like a coolant heater, which generally has a rather flimsy mount point on the battery tray. but it's still nice to have. not hard to rig up a cheap timer if you have a steady commute so it comes on 2hrs before starting the car.

11) cold weather radiator block - simple, quick and dirt cheap to make a stealth (and re-usable) radiator block . aside from having a healthy operating thermostat, in cold climates, this helps bigtime. i've used 1/4" foamboard, or flashing material, even cheap placemat-type material from walmart, that you just tuck in behind the front grills (upper and lower), completely blocking the radiator. once temps get down to an average of 40-50C i put one in. even if air temps get to the 60s, if tune/etc is all good, it won't get too hot either. for a couple bucks in material (or free if you have leftover flashing type material), it's a no brainer... come warmer weather, take it out and hide in the garage/shed...

in summary, IMO, i would always do a minimum of at least pd150 intake manifold + race pipe, egr delete, lift pump + CAT/stanadyne fuel filter with thermo-tee delete - that right there will eliminate a lot of common problems. it's pretty much constant the number of cars i see with EGR/maf related problems and air bubbles in the supply line
 
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burpod

teh stallionz!!1
Joined
Nov 27, 2004
Location
cape cod, ma
TDI
82 rabbit vnt ahu, 98 jetta vnt ahu, 05 parts car, 88 scirocco.. :/
Tuning - Basic information about tuning and how to go about it

[in progress]

here is a stock 10mm/.184 (manual) pump map normalized to that of a stock 11mm/.158 (auto) pump map:



so this is what happens, for exmaple, when you do a 5spd swap and switch to coding 00002, you're running a mismatched tune (really only fueling/timing maps). you can see the injection durations for a given IQ are no longer correct.
 
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csstevej

Top Post Dawg
Joined
Aug 12, 2004
Location
north nj
TDI
2001 golf tdi 4 door auto now a manual, mine, 2000 golf 2 door M/T son's,daughters 98 NB non-TDI 2.0, 2003 TDI NB for next daughter, head repaired and on road,gluten for punishment got another tdi 2001NB,another yellow tdi NB
Nice write up so far .
 

dieseldonato

Veteran Member
Joined
Mar 10, 2023
Location
Us
TDI
2001 jetta
Few thing I've gone though and can confirm. Boost leaks without oil around them. Been having some back and forth with burpod moat of the summer, and intercooler and boost pipe upgrades were done, when I had time. Switched over to t clamps. He was saying my n75 values were a lot lower then other with similar tunes, and I should check for boost leaks. Can't tell you how many times, I've looked for wet/oil around the connections and never found anything.
Well, I had some time one morning and said f-it. Rigged up some fittings, low and behold I had 2 leaks. Neither much to mention about, and neither had oil residue around them. Ended up setting the pressure to 40 psi. (30psi tune.) And making darn sure nothing leaked. (Also a good excuse to clean out behind the fener liners and do any rust proofing.) Simple to do, and netted (me) tangible results.
Second, the supply pressure regulator. For months I was having rough starts, and erratic cold hesitation/smoke issues. Digging through some old notes from my first gen cummins, I had a side note scribble about the keystone mod and the valve falling apart. I just ordered a new valve. My stock one was fully fubar. Dug out the old pieces and installed the new one. My cold smoke/hard starts pretty much went away. Easy to check. I'd definatly reccomend new o-rings. (Which I had on hand.) The old ones were pretty much junk.
Anyway. Rock on @burpod !
 

csstevej

Top Post Dawg
Joined
Aug 12, 2004
Location
north nj
TDI
2001 golf tdi 4 door auto now a manual, mine, 2000 golf 2 door M/T son's,daughters 98 NB non-TDI 2.0, 2003 TDI NB for next daughter, head repaired and on road,gluten for punishment got another tdi 2001NB,another yellow tdi NB
Care to elaborate the p/n’s for the o-ring and regulator and cost?
 

dieseldonato

Veteran Member
Joined
Mar 10, 2023
Location
Us
TDI
2001 jetta
Care to elaborate the p/n’s for the o-ring and regulator and cost?
If you order the valve from idparts, I'm pretty sure the o-rings come with.

Just the o-rings.
 

csstevej

Top Post Dawg
Joined
Aug 12, 2004
Location
north nj
TDI
2001 golf tdi 4 door auto now a manual, mine, 2000 golf 2 door M/T son's,daughters 98 NB non-TDI 2.0, 2003 TDI NB for next daughter, head repaired and on road,gluten for punishment got another tdi 2001NB,another yellow tdi NB

ghohouston

Veteran Member
Joined
Apr 2, 2013
Location
Lewisville, Texas
TDI
2001 Jetta Sedan TDI 5 Speed
Modifications - What are some of the best bang-for-buck modifications for mild performance upgrades? and for even more power?
Ported head and cam, with upgraded dual valve springs. It's a little money, but well worth it. Really really wakes up an alh in the upper rpm range.
 

ts888

Veteran Member
Joined
Feb 18, 2023
Location
PNW US
TDI
03 ALH
Ported head and cam, with upgraded dual valve springs. It's a little money, but well worth it. Really really wakes up an alh in the upper rpm range.
I'm pretty sure burpod is not asking a question, he's creating a chapter header.

Also, not the top mod on a turbo diesel. Not saying it won't help, but if you want more air in the cylinders, just have the turbo pump more air in the cylinders. Boost can shove air in faster than any port job.
 

burpod

teh stallionz!!1
Joined
Nov 27, 2004
Location
cape cod, ma
TDI
82 rabbit vnt ahu, 98 jetta vnt ahu, 05 parts car, 88 scirocco.. :/
I'm pretty sure burpod is not asking a question, he's creating a chapter header.

Also, not the top mod on a turbo diesel. Not saying it won't help, but if you want more air in the cylinders, just have the turbo pump more air in the cylinders. Boost can shove air in faster than any port job.
i'm definitely open to any suggestions and comments :) but yes, i was going to fill in with my 2cents on the subject matter of course 😁 i think a ported head is very much well worth it. speaking of which, just dropped off a head i ported at the machine shop to be finished off :) the factory exhaust ports are pretty choky.
 

ghohouston

Veteran Member
Joined
Apr 2, 2013
Location
Lewisville, Texas
TDI
2001 Jetta Sedan TDI 5 Speed
I'm pretty sure burpod is not asking a question, he's creating a chapter header.

Also, not the top mod on a turbo diesel. Not saying it won't help, but if you want more air in the cylinders, just have the turbo pump more air in the cylinders. Boost can shove air in faster than any port job.
You understand boost is a restriction, and that it isn't everything? People don't spend the money on turbo diesel head porting because they don't necessarily "feel" the power, where they can slap on nozzle, a tune, turbo, whatever and make a notable difference. What they fail to realize is it lowers egt's, allows for more air into the cylinders, more efficiently, and will actually LOWER boost, every other variable left the same.
 

dieseldonato

Veteran Member
Joined
Mar 10, 2023
Location
Us
TDI
2001 jetta
You understand boost is a restriction, and that it isn't everything? People don't spend the money on turbo diesel head porting because they don't necessarily "feel" the power, where they can slap on nozzle, a tune, turbo, whatever and make a notable difference. What they fail to realize is it lowers egt's, allows for more air into the cylinders, more efficiently, and will actually LOWER boost, every other variable left the same.
Umm, kinda. Fluid dynamics basic principles tells us more pressure = more flow given the restriction has stayed the same size. More boost = more flow. Porting amd cams = less restriction. Either way, you're flowing the same amount of air. Given you're within the turbo efficiency range you're not gaining or loosing much by turning the boost up.
Porting/cam has always been the cherry on top when it comes to diesels, does it help? Yep 100%, but it's not the end all be all in a turbo diesel like it is is something naturally aspirated.
 

ghohouston

Veteran Member
Joined
Apr 2, 2013
Location
Lewisville, Texas
TDI
2001 Jetta Sedan TDI 5 Speed
Umm, kinda. Fluid dynamics basic principles tells us more pressure = more flow given the restriction has stayed the same size. More boost = more flow. Porting amd cams = less restriction. Either way, you're flowing the same amount of air. Given you're within the turbo efficiency range you're not gaining or loosing much by turning the boost up.
Porting/cam has always been the cherry on top when it comes to diesels, does it help? Yep 100%, but it's not the end all be all in a turbo diesel like it is is something naturally aspirated.
I agree completely.
 
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