Observations On WVO Using VAG COM

VAG COM is such a great tool to have and it has proven a worth while asset while burning WVO. It has given me answers to a lot of the questions that I have had and I will explain what I have found. More than likely some of you have found this but to reiterate, allow me to share my findings.

There are a lot of variables involved with timing done by the ECU. Whether it be coolant temp, air temp, fuel temp, engine temp or mechanical variables such as pop pressures, there are a lot of things monitored and involved with timing in a TDI engine.

The conclusions that I have drawn from what I monitored, measuring block 004 and measuring block 007 is that the ECU indeed retards timing due to extreme fuel temperatures. (nothing new)

My timing at idle on diesel fuel is set advanced. It is tyipcally halfway between the middle and top line of the graph. My engine at operating temp with coolant of 190 and fuel temps of around 100 degrees is 2.0-2.2 deg BTDC (advanced)

I was only on diesel fuel for a short while before I switched to WVO but in any driving situation during that time, I never saw any readings of ATDC (retarded timing) Whether it be high RPM, high load or low RPM, low load

After switching to WVO I found a lot of things that may interest the WVO community.

1) Greasecar with the FPHE is the absolute s***. I am seeing consistent 180-185 oil temps all the time read right off the fuel temp sendor.

2) I have a fuel temp sendor on my return line. My return line temps stay between 150-165 depending on fuel demand. Which proves that the oil cools off between the IP and the injectors, at least IMO. Proving injection line heaters worth it.

3) Back to timing.... Timing was alot less advanced and infact retarded in low load situations. All of my tests were done at a consistent 2500 RPM (cruise control) for 20-30 minutes straight monitoring timing. High load (going up decent grades) showed advanced timing anywhere from 2-4 degrees advanced which seemed a bit low to me beings I was seeing 2-2.2 at idle on diesel.
At low load, flat road situations I finally saw retarded timing numbers. .4 deg ATDC was the lowest I saw but again, retarded timing is never good on WVO. A lot of the time, timing was sitting at 0 deg being neither advanced or retarded. An interesting note, group 4 has two categories one being specifed timing and one being actual timing. It seemed at low load operations specified timing always wanted to be more retarded (1.6 ATDC) however actual always stayed within .4 ATDC and above. It seems the ECU wanted to pull timing back even further, however the mechanical aspects of the pump did not allow it to do so.

So this leads me into my point. The fuel temp sendor modification is VERY IMPORTANT. I have not done this yet but will do so very soon and again perform the same tests. I believe this will solve any issues of retarded timing and if not I can raise a deg or two by using VAG COM in adaption 4.

Another note of importance. My timing is advanced by nature on diesel. It is how it is physically set up to be. .4 deg retarded may or may not be a problem but I know advanced timing on WVO is always better. For people who don't have a VAG COM or don't do their own work on there car, they do not know where there timing is set on regular diesel fuel. If your timing is not set advanced you may run into MUCH more problems with retarded timing on higher fuel temperatures. Going back to how specified and actual were different, it seems to me that if your timing is set up in the middle of the graph or towards the bottom of the graph (retarded) the ECU may be capable of pulling timing back even further.

The ECU retards timing on higher fuel temps, this is a definite. However, this is the bigger problem with this. How much retardation to the point where it could cause combustability problems is different on everyones car. If your timing is set on the middle line of the graph or even part way retarded, you could have major problems with running retarded, i.e problems with combustion, deposits....you know the drill.

As a wrap up. It seems the ECU is very capable of pulling back 2-3 degrees of timing in normal highway, consistent RPM driving. Depending on where your timing is set to be, this could be a huge problem or maybe a small concern. For my car it seems to be a small concern, however I will still do the fuel temp sendor mod. 2 deg more advanced on WVO seems to be a great number to shoot for collected from different forums.

Just my two cents....I will report again with fuel temp sendor mod in effect. Tonight I also may have the opportunity to idle on WVO after my long highway run to maybe see where timing is on my TDI graph.

VAG COM is a great tool!!!!

Haven't been running WVO for a while, but when I was......

1. After a TB job at a local import shop, my timing was set halfway between center and bottom. I didn't know that until many 1000s of miles later when I got access to a VagCom. I set it to halfway between center and top. Never measured timing while driving, but at idle, I seemed to stay about wher it was set regardless of fuel temp.

2. My WVO temps INCREASED post IP, usually 10-20 degrees (170 in, 180 out). I think this is why there is a fuel sensor in the IP. Since the IP loops the diesel and is connected to the block, heat from combustion will transfer to fuel in the IP. Now, my preIP sensor was on the supply valve outlet and my post-ip sensor was in the WVO filter head, so maybe it was just cooling from filter to supply valve, but my vegtherm was in that line, so I doubt it. FYI, YRMV.

I have always wondered if the "reported timing" is the actual timing or just the raw data the ECU is using to makes its decision?

T's, with the fuel temp sensor mod, be aware that a few folks got a CEL with this mod. On mine it took several days before the CEL appeared. FWIW. Seems to happen on newer cars, mine's an 03.

Honeydew said:

T's, with the fuel temp sensor mod, be aware that a few folks got a CEL with this mod. On mine it took several days before the CEL appeared. FWIW. Seems to happen on newer cars, mine's an 03.

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Heh been there done that already. Got that "off road use" EGR block off right now and I get the BS "excessive flow...blah blah" code that I stare at all the time. It makes me want to get chipped just so I can ask them to put it out.

I thought codes were being set when they did both the fuel temp sendor and air intake (FAT mod, if you will) From what I gathered in that thread the fuel temp resistor took well but the ECU set the code when doing the same thing with the air intake.

sdeck said:

My WVO temps INCREASED post IP, usually 10-20 degrees (170 in, 180 out). I think this is why there is a fuel sensor in the IP. Since the IP loops the diesel and is connected to the block, heat from combustion will transfer to fuel in the IP. Now, my preIP sensor was on the supply valve outlet and my post-ip sensor was in the WVO filter head, so maybe it was just cooling from filter to supply valve, but my vegtherm was in that line, so I doubt it. FYI, YRMV.

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I think my temp sendors are placed in more accurate spots to make the conclusion that it cools the oil. I was reading 180-185 in through VAG COM readings in group 4. My 150-165 is read right off the return line from the pump. Theres about 4 inches of hose and then my temp sendor. Your temp sendor could be giving false readings because yours is located where oil is being heated from coolant, IMO.

T'sTDI said:

I thought codes were being set when they did both the fuel temp sendor and air intake (FAT mod, if you will) From what I gathered in that thread the fuel temp resistor took well but the ECU set the code when doing the same thing with the air intake.

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I got fuel temp sensor implausible with the fuel temp sensor mod only, air intake stock.

Edit: another 03 w/ same experience

T'sTDI said:

I think my temp sendors are placed in more accurate spots to make the conclusion that it cools the oil. I was reading 180-185 in through VAG COM readings in group 4. My 150-165 is read right off the return line from the pump. Theres about 4 inches of hose and then my temp sendor. Your temp sendor could be giving false readings because yours is located where oil is being heated from coolant, IMO.

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Perfectly plausible by me. FWIW, I seemed to have a disconnect between my temp sender and the VagCom reading. Always seemed about 20 degrees off between them. IDK which is right. I also noticed that if I grounded my vegtherm near the temp sender ground, it really screwed up the sender reading. Also, when running on WVO (VT off) in summer traffic, my pre-IP readings would often get to >220F (I would switch back to dino). I don't think the heat could come from the coolant heater since my thermostat always reads 190 (I know dash gauge +/- 50 or so), so I always assumed IP was heating it up. Can't prove it either way from my end, just my 2/100ths of a buck

sdeck said:

Perfectly plausible by me. FWIW, I seemed to have a disconnect between my temp sender and the VagCom reading. Always seemed about 20 degrees off between them. IDK which is right. I also noticed that if I grounded my vegtherm near the temp sender ground, it really screwed up the sender reading. Also, when running on WVO (VT off) in summer traffic, my pre-IP readings would often get to >220F (I would switch back to dino). I don't think the heat could come from the coolant heater since my thermostat always reads 190 (I know dash gauge +/- 50 or so), so I always assumed IP was heating it up. Can't prove it either way from my end, just my 2/100ths of a buck

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Its funny I have the same sort of problem with my temp sendor off of my FPHE. I wanted it to be as close as possible to my FPHE to know when I could switch over the fastest. Our coolant is 190 deg, or so the gauge reads.... my FPHE temp sendor has shown temps in excess of 225 just as yours seems to do also. So what gives??? Unless our coolant temp gauges are lying, I have no idea where I'm getting the extra heat. It truly baffles me.

I hooked up VAG COM and was very pleased and relieved to find the fuel temps at the sensor in the pump showing 180-185 deg. This "mystery" if you will, could be the reason for our discrepencies.

sdeck said:

just my 2/100ths of a buck

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I would reccommend having the mechanical timing at the top of the graph. You can also set the idle adaptation to 3-4 deg BTDC at idle (I have no issues).. but I am not sure if that should be set on WVO or not because I don't run that. I am thinking that idle timing isn't affected by the fuel temp, because when I did the fuel and air temp mod, I didn't notice any timing change at idle.

Good luck and hope you can keep your grease burners happy with advanced timing!

Update

I performed the fuel temp mod. Fuel temps were reading 9.8 deg C instead of the 30 or so it was reading before. Timing went up from 2.2 deg before the mod to 2.4-2.6 deg BTDC. I also bumped up the timing a bit in adpation 4 to 2.6-3.0 deg BTDC and I am very happy with that. I noted less smoke at idle, which I have had problems with and more low end power at lower RPM. Overall, car feels much more stronger.

Heres where it gets even better. Injecting vegetable oil at 180-185 temps (VAG COM confirmed) with the fuel temp sendor in effect, the temps were only reading a maximum 20.5 deg C. Timing also stayed in check especially in low load conditions. I stated above that timing was somewhat retarded in low load situations, .4 ATDC.

Timing was never seen below 1.3 deg BTDC on vegetable oil. Timing was even more impressive on acceleration as it seemed to adjust timing just like it was on diesel fuel.

I noted less EGTS 50 deg or so.... and it seemed on veg it was more responsive, not that it was lacking response by no means. Another thing I noticed is before the mod my engine was a lot more quiet when injecting WVO. This has nothing to do with the lubrication of WVO but has everything to do with combustion. It is quieter because of the retarded timing. After the fuel mod my engine sounded very similar, such as that on diesel fuel.

I can't emphasize how important the fuel temp sendor mod is for the WVO crowd. I can't emphasize how important knowing where your timing is while burning WVO. Retarded timing is a problem and is IMO, one of the reasons why deposits occur on WVO. Timing NEEDS to be advanced for the longevity of your engine internally. Sure it will run fine on retarded timing, however the combustability is not that of what it was on diesel fuel.

This is a very easy modification and a very important one!!!!

Good data Tony, keep it coming. Would you recommend that members either have vag-com or a scangauge to run a setup like yours to keep track of timing?

nicklockard said:

Good data Tony, keep it coming. Would you recommend that members either have vag-com or a scangauge to run a setup like yours to keep track of timing?

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Speaking only from experience with VAG COM, I think its a very important tool to have period but it really shines when you have questions burning WVO (at least I did). There are important things to know that VAG COM provdies that can contribute to a long life on WVO or a very short one.

I love knowing exactly what the oil temp in my IP is. With finding this, I found there is a good amount of support that proves the IP actually cools the oil before it hits the injectors. I know for certain that the oil does actually cool and that just because its 180 in the IP does not mean its 180 at the injectors.

Having a VAG COM not only will give you timing in any situation you can put your car through, but it will show you that hot fuel temps will indeed pull timing back to where it could be a problem. Assuming that mechanically your Cam shaft timing is setup right, you can adjust timing to what you want it to be, no more than 3 deg adv or 2 deg retarded is what popular opinion is here.

Group 13 in measuring blocks has to be the most useful information it can provide. Off the top of my head I don't know what its called, but in laymans terms it shows how hard the ECU is working the IP to derive a smooth idle across all 4 cylinders (at least in my words). All four injectors are monitored at idle and it can be a great way to catch an injector not up to Pop pressure spec or a streaming injector. AKA huge problems and major engine damage if let go for enough time.

I feel some engine modifications are needed on the TDI to be successful. For those who are not running the resistor inline with your fuel temp sendor, I can assure you in many cases your running retarded timing which is not a good thing. Popular opinion by a lot of people from the IDI crowd feel timing should be adjusted 2 deg advanced and this makes sense to me. It gives the oil the max amount of time to atomize and burn, and I will also note, I see no smoke through rearview headlights at night on the highway on veggie.

This is only the tip of the iceberg that I have done with my car to burn WVO but having a VAG tool to take readings and doing the fuel temp resistor mod are both simple and good ideas while on WVO.

By the way.... I took timing readings at idle with the TDI timing graph and the fuel temp resistor mod in effect and it was uneffected. It basically read the same thing and came up with a fuel temp of 70 deg, could of very well been the actual fuel temp, however when I rechecked group 4 the fuel temp was 10 deg C. Interesting.....

What resistance did you use for the fuel temp? Was it the same as listed in the thread for the mod? Also, did you do the intake air temp too? I did it, since supposedly warmer air retards timing too, which is probably due to NOx concerns originally.

T'sTDI said:

I love knowing exactly what the oil temp in my IP is. With finding this, I found there is a good amount of support that proves the IP actually cools the oil before it hits the injectors. I know for certain that the oil does actually cool and that just because its 180 in the IP does not mean its 180 at the injectors.

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I really like all the work you are doing determining the how timing affects combustion and think this is important stuff in moving towards a better WVO system. and increased reliablility.

This is the one part i am kind of uncomfortable with. When you use an inline temp sensor on the IP return line and compare that value against the IP's built-in temp sensor, i think you may be making some assumptions that may skew your results. The 2 sensors are not calibrated the same and will have some variation in scale that can be affected by a number of variables. You may be correct in saying that the WVO temp decreases from the time it enters the IP to the time it gets to the injector, but i'm not quite sure about it. I think that the best way to measure how much the IP causes the fuel to heat up or cool down is by using two identical sensors. OIne placed on the IP supply line as close to the IP as possible, and one placed on the return line as close to the IP as possible. The returned fuel should be a fairly accurate measure of the injector fuel temp since the returned fuel actually comes from the injector itself, with some factor taken into account for any losses along the way.

Anyways, likle i said, i like the work you're doing and as soon as i get some time, i will look into the sensor mod.

Steve

robnitro said:

What resistance did you use for the fuel temp? Was it the same as listed in the thread for the mod? Also, did you do the intake air temp too? I did it, since supposedly warmer air retards timing too, which is probably due to NOx concerns originally.

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I chose not to do the air intake because from what I gathered in the thread, that was where people were having problems with throwing CEL's. IMO, I feel fuel temps may have more of an impact on timing then air temp because we are purposely injecting extreme oil temps that the ECU was never suppose to see. However, I don't know if this is true or not because I myself have not experimented with it.

One reason is I don't feel I need to because I am seeing timing where I want it to be. Timing was taken in the summer so my timing is set up for hotter temperature and again timing is where I want it to be, so I don't see it as a huge issue.

I may have the opportunity to take some readings at idle on VO tonight back home from my commute.

What I have learned from all of this research is that a few deg of timing makes one hell of a difference. Without a doubt, I can audibly hear differences with combustion noises before I messed with timing parameters and I knew that was not a good thing. After performing the modification, there are very few differences between my car on d2 and on oil.

Knowing the above, I feel TDI's need to address this because they are a unique breed that logs many parameters with timing. Old IDI's never had this capability. Food for thought.....

O yeah... by the way the resistor was the same as used in the thread. 2.5K 1/4 watt, I followed exactly what jackbombay did. I have mine setup to where I can remove it very easily. I removed the resistor (open circuit) and temp readings defaulted to -5.4 deg C and also threw a code (FYI). I made it removable because I was unsure if a 2.5k resistor would be enough to accomplish what I wanted. I was pleased to see that it keeps temps very close to what they are when you start your engine. It definitely "resists" and slows readings. On an hour drive I saw my temps only go up about 10 deg and it held steady on VO. So it don't look like I will need a different resistor.

kingkos said:

I really like all the work you are doing determining the how timing affects combustion and think this is important stuff in moving towards a better WVO system. and increased reliablility.

This is the one part i am kind of uncomfortable with. When you use an inline temp sensor on the IP return line and compare that value against the IP's built-in temp sensor, i think you may be making some assumptions that may skew your results. The 2 sensors are not calibrated the same and will have some variation in scale that can be affected by a number of variables. You may be correct in saying that the WVO temp decreases from the time it enters the IP to the time it gets to the injector, but i'm not quite sure about it. I think that the best way to measure how much the IP causes the fuel to heat up or cool down is by using two identical sensors. OIne placed on the IP supply line as close to the IP as possible, and one placed on the return line as close to the IP as possible. The returned fuel should be a fairly accurate measure of the injector fuel temp since the returned fuel actually comes from the injector itself, with some factor taken into account for any losses along the way.

Anyways, likle i said, i like the work you're doing and as soon as i get some time, i will look into the sensor mod.

Steve

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Yeah this is very plausible. Keeping variables limited, almost sounds like a science experiment Like I said, I didn't say it was totally true, just basing off what I have experienced with my own setup.

O yeah anyone looking into line heaters to maximize heat going to the injectors post IP will be saddened to hear I saw no temp differences read by my return line temp sendor Those things get hot as hell to, almost dangerously hot but I just don't think the fuel sits in the injectors lines long enough to exchange heat. This was based off long highway runs, I think low flow city driving may prove there worth but for highway runs, there somewhat useless, just more strain on the charging system.

I think anyone that drives a TDI could benefit from this modification, but especially the VO crowd. I know 100% any VO burner will experience benefits from this modification. Its a simple mod, that makes a huge difference.

It is a great thing to know where your timing is set, knowing that this very well could be one of the big reasons why incomplete combustion has been a problem for some

I don't know about you all, but I definitely noticed audible differences in combustion when I first injected VO and that to me was a bit of a scare. Doing the modification, adjusting timing using adaption 4 and seeing exactly what kind of timing I am running now. I feel its very close to that of diesel fuel and I almost know it is now because combustion between the two fuels sounds the same. This has also been confirmed at different load conditions and RPM.

T'sTDI said:

I chose not to do the air intake because from what I gathered in the thread, that was where people were having problems with throwing CEL's.

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The air intake resistor throws this code: 16490 manifold/ barometric pressure sensor

The fuel temp resistor mod without air intake resistor gives a CEL for fuel temp sensor implausible.

I added a link to JackBombay's experience with this to my earlier post in case you want to ignore my experience. Advocating this mod is great because it does work on some cars. People need to be aware of the codes it can throw so they don't misdiagnose a problem, however. Both Jack and I removed both resistors because each caused a CEL on our 2003 cars.

Honeydew said:

The air intake resistor throws this code: 16490 manifold/ barometric pressure sensor

The fuel temp resistor mod without air intake resistor gives a CEL for fuel temp sensor implausible.

I added a link to JackBombay's experience with this to my earlier post in case you want to ignore my experience. Advocating this mod is great because it does work on some cars. People need to be aware of the codes it can throw so they don't misdiagnose a problem, however. Both Jack and I removed both resistors because each caused a CEL on our 2003 cars.

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When it comes to codes there are of no concern to me. I didn't choose to ignore your post, to some it may be very worthwhile to know, they just don't have much relevance in my situation. But with all due respect, if you just put a resistor inline your fuel temp sendor and you pull a code reading fuel temp sensor implausible, you would be pretty silly to misdiagnosis that code and not realize it occured to what you have done to your car. This would assume you do your own work on your own car and if thats not the case, its a little different.

I stare at a constant yellow CEL light all day because I have blocked my EGR. They don't bother me because my state does not hold emissions for TDI's and my dad is the only mechanic that will ever touch my car. I have yet to see if mine tripped a code (only had it on for 2 days) but I will check.

Regardless, both my EGR excessive flow and fuel temp implausible codes (if I have one), IMO are very small and very irrelevant compared to the benefits derived. I have modified my car wth full intentions of burning WVO, eliminating areas that I see as trouble and problematic. If its at the expense of tripping codes, so be it, the benefits far outweigh the cost.

If you had to do the fuel temp mod and were worried about codes, I would make sure I had a reader that can delete CEL's and wire it to where it can be removed and everything put back to normal. A simple scangauge can delete CEL's I am pretty sure.

T's I understand what you are saying and agree with your reasoning regarding codes and CELs. My only reason for posting was to correct your misinformation about what might trigger the CELs in case others follow your advice, especially those without a code reader.

Please don't read into it, you'll not see me on here telling others what they should or should not do to or burn in their own cars.

I'd agree VAG-COM gives some nice insights into what is going on in your engine.

I played about with a variable resistor in the ECU coolant temperature sensor loop (there are two 'sensors' built into the same four wire sensor. One pair of wires do the dash gauge the other pair are read by the ECU.)

I found that the relationship between the coolant temp and timing was somewhat complex.

Since then I've opened up my ECU desoldered the chips and decoded the data and found that the way the ECU controls timing is rather sophisticated.

Main influences on timing are engine speed and amount of fuel to be injected - coolant temp, inlet air temp and atmospheric pressure also have effects.

I spent a fair bit of time looking for the fuel temperature related timing adjustment and was unable to find anything?!? I could be missing it but I have looked fairly extensivly in a few different European ECU files - I'd like to find the time to search again. (just spent a hour or two finding a US spec file for a late VP37 Tdi - this has much more complex timing control to all other VP37 pumped VW group Tdis I have looked at similar to that used on the PD motors - unfamiliar with the intracacies of how this type of control works so not helped much..... Found a file from a 028906021GQ which I think may be a older US ECU? this one has timing control very similar to my car but a slightly more retarded at low loads, but not as much as my friends UK 98 Passat!!)

As is well documented in VW tech docs the ECU uses the fuel temperature to determine fuel density as the fuel heats it becomes thinner so the ECU will inject for a longer period to provide a bigger volume (to maintain the correct mass of fuel). In line with this I would expect ECU should advance the timing as the fuel heats - unless there is some more control I am missing.

It would be an interesting experiment to do some logs with VAG-COM at steady loads and have a switch to so the ECU either reads the correct fuel temp or bypass the sensor giving no resistance on the sensor wire, or possibly better a variable resistor that was set to give the same resistance as say 80 deg C fuel which would show if the ECU does retard for hot fuel.

T's, What does VAG-COM show the VAG number of your ECU to be when you connect to it?

I posted some info about Tdi timing on the Tdi page on the OBEDwiki - see the link in my sig. below

Darren, the Euro-spec base files and North American-spec base files differ substantially in this regard. The NA files definitely retard timing with increased fuel temps in order to minimize NOx, which is very heavily regulated here. Emissions regulations are very different beasts in your neck of the woods and the files are rather different. One of the popular tuners here offers a "Euro spec" tune file because it has no retarded timings (also as customer retention/ proprietary reasons, but that's another story.)

All the tuners here can offer a "Euro spec" timing profile and tune for mpg, or WVO, or power, you name it, they can do it. You just have to ask.

DarrenUK said:

Since then I've opened up my ECU desoldered the chips and decoded the data and found that the way the ECU controls timing is rather sophisticated.
Main influences on timing are engine speed and amount of fuel to be injected - coolant temp, inlet air temp and atmospheric pressure also have effects.

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Boy you said a mouth full there. Sophisticated might be an understatement.

DarrenUK said:

I spent a fair bit of time looking for the fuel temperature related timing adjustment and was unable to find anything?!? I could be missing it but I have looked fairly extensivly in a few different European ECU files - I'd like to find the time to search again. (just spent a hour or two finding a US spec file for a late VP37 Tdi - this has much more complex timing control to all other VP37 pumped VW group Tdis I have looked at similar to that used on the PD motors - unfamiliar with the intracacies of how this type of control works so not helped much..... Found a file from a 028906021GQ which I think may be a older US ECU? this one has timing control very similar to my car but a slightly more retarded at low loads, but not as much as my friends UK 98 Passat!!)

As is well documented in VW tech docs the ECU uses the fuel temperature to determine fuel density as the fuel heats it becomes thinner so the ECU will inject for a longer period to provide a bigger volume (to maintain the correct mass of fuel). In line with this I would expect ECU should advance the timing as the fuel heats - unless there is some more control I am missing.

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I was hoping you would find this thread Darren, I know you've done quite a bit adjusting your car with VAG COM as well.

My experiments were done in a relatively controlled environment. Same speed, same place, same RPM, nothing else changed except for the fuel temp sender modification and a tad bit of advancement through adaption 4. (nothing too substantial though)

Before the resistor, I was seeing ATDC readings, .4 being the lowest that I saw, keep in mind I was trying to drive at the same time Running the same road the next day I saw no ATDC readings, in fact the lowest I saw was 1.3 or so deg advanced timing (this was at low load, flat road, 73 MPH, 2499 RPM) I'm thinking I should have logged injected quantity along with this as it would provide more to the argument.. (will do when I get the chance)

So the only thing that changed was the temp the ECU was reading. And I did indeed see retarded timing adjustments.

DarrenUK said:

It would be an interesting experiment to do some logs with VAG-COM at steady loads and have a switch to so the ECU either reads the correct fuel temp or bypass the sensor giving no resistance on the sensor wire, or possibly better a variable resistor that was set to give the same resistance as say 80 deg C fuel which would show if the ECU does retard for hot fuel.

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Although I didn't perform this with a switch, I did somewhat resemble this experiment over the course of two days, running the resistor and not running it. But I see what you mean, throwing a switch should show changes in timing and you could continue driving at the same RPM, same constants etc....

DarrenUK said:

T's, What does VAG-COM show the VAG number of your ECU to be when you connect to it?

I posted some info about Tdi timing on the Tdi page on the OBEDwiki - see the link in my sig. below

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You'll have to excuse my ignorance on this one as I am a bit new to VAG COM. I'm assuming these are the numbers that appear when you hook your VAG COM up correct? The top 4??? I don't know this right now but I'll figure it out for you. Is there a reason why this would be important???

nicklockard said:

Darren, the Euro-spec base files and North American-spec base files differ substantially in this regard. The NA files definitely retard timing with increased fuel temps in order to minimize NOx, which is very heavily regulated here. Emissions regulations are very different beasts in your neck of the woods and the files are rather different. One of the popular tuners here offers a "Euro spec" tune file because it has no retarded timings (also as customer retention/ proprietary reasons, but that's another story.)

All the tuners here can offer a "Euro spec" timing profile and tune for mpg, or WVO, or power, you name it, they can do it. You just have to ask.

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Well that answers the question I believe.

I'm liking this euro tuning idea. I would love to eliminate my EGR code and probably my fuel temp code as well. Is there any other possible tuning parameters other than eliminating retarded timing that could be a possible benefit??? Is the tune for MPG increase efficiency due to advanced timing only or is there more sophisticated fueling maps???

Isn't it true you can switch tuning files via VAG COM instantly??? It would be the cats meow if you could have your fun with a performance enhancing tune and then switch when you want to burn VO.

Yes I want my cake and I want to eat it to....

Nick, since we are on the topic of Nox, real quick. I know Water injection was to help limit nox emissions, this was due to cooling the combustion chamber correct???

My observations were retarded timing increased my EGT's about 50-75 deg in some cases. Since I have advanced my timing, I am seeing relatively the same EGT's as I do on diesel fuel. So if my logic is correct it seems advanced timing would limit Nox???

Another question for anyone that knows. What numbers in group 13 measuring blocks should be alarming to me??? Mine are all within .5, injector 3 being the one thats high but I've been told thats because of the needle lift sensor????

T'sTDI said:

Well that answers the question I believe.

I'm liking this euro tuning idea. I would love to eliminate my EGR code and probably my fuel temp code as well. Is there any other possible tuning parameters other than eliminating retarded timing that could be a possible benefit??? Is the tune for MPG increase efficiency due to advanced timing only or is there more sophisticated fueling maps???

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You'll have to ask them, but there are other coefficients and single-variable parameters which effect various 3-d maps besides raw adjustments to timing. Some of the coefficients are no doubt related to sensitivity/response (slope) to temps and whatnot.

Tony said:

Isn't it true you can switch tuning files via VAG COM instantly??? It would be the cats meow if you could have your fun with a performance enhancing tune and then switch when you want to burn VO.

Yes I want my cake and I want to eat it to....

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Not that I'm aware, but I wish it were so!

Tony said:

Nick, since we are on the topic of Nox, real quick. I know Water injection was to help limit nox emissions, this was due to cooling the combustion chamber correct???

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Yes. It limits peak cylinder temperatures.

Tony said:

My observations were retarded timing increased my EGT's about 50-75 deg in some cases. Since I have advanced my timing, I am seeing relatively the same EGT's as I do on diesel fuel. So if my logic is correct it seems advanced timing would limit Nox???

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Advancing timing will always increase PCT's and NOx production, AFAIK, but what is worse? Making a tiny bit more NOx or ruining an engine? That would increase your carbon footprint quite a bit, no?

(snipped)

http://forums.tdiclub.com/showthread.php?t=203479&highlight=rocketchip+switchable

If you read Jeffs last post, it seems this is possible. Seems even better than I imagined, not even needing a computer??? It could be wired to a switch??

Now that would be cool. Have all the fun in the world and being able to save money on the long highway runs. I need some money....

nicklockard said:

Darren, the Euro-spec base files and North American-spec base files differ substantially in this regard. The NA files definitely retard timing with increased fuel temps in order to minimize NOx, which is very heavily regulated here. Emissions regulations are very different beasts in your neck of the woods and the files are rather different. One of the popular tuners here offers a "Euro spec" tune file because it has no retarded timings

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If the 028906021GQ is an American ECU (which I think it is?) then at least the base timing is very similar to the European spec files I have seen. And A quick search still could not find the elusive high fuel temp. timing adjustment.

There are of course slight differences in timing for vehicles that use different sized injectors, turbos, injector pumps.

When I have a bit of time I'll look into any differences between the CQ file and Euro spec ones a bit more.

T'sTDI said:

My experiments were done in a relatively controlled environment. Same speed, same place, same RPM, nothing else changed except for the fuel temp sender modification and a tad bit of advancement through adaption 4. (nothing too substantial though)

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How many degrees advance did you give with adaptation 4? What ever it was you'll be that much different at all engine conditions.

I've not tested, but there are timing limits which I think adaptation takes precedent over.

T'sTDI said:

Before the resistor, I was seeing ATDC readings, .4 being the lowest that I saw, keep in mind I was trying to drive at the same time Running the same road the next day I saw no ATDC readings, in fact the lowest I saw was 1.3 or so deg advanced timing (this was at low load, flat road, 73 MPH, 2499 RPM) I'm thinking I should have logged injected quantity along with this as it would provide more to the argument.. (will do when I get the chance)

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Yes logging IQ at the same time would provide more robust results. (I record the data as I drive and look at it sat at home later).

So you saw something like a 1.7 degree advance - but how much of this was due to adaptation?

T's said:

So the only thing that changed was the temp the ECU was reading.

And I did indeed see retarded timing adjustments.

Although I didn't perform this with a switch, I did somewhat resemble this experiment over the course of two days, running the resistor and not running it. But I see what you mean, throwing a switch should show changes in timing and you could continue driving at the same RPM, same constants etc....

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Yes this is what I did for the coolant temp sensor. switch and variable resistor.

T's said:

You'll have to excuse my ignorance on this one as I am a bit new to VAG COM. I'm assuming these are the numbers that appear when you hook your VAG COM up correct? The top 4??? I don't know this right now but I'll figure it out for you. Is there a reason why this would be important???

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I was after your ECU number which I guess will be - 038 906 012 ** or possibly 038 906 018 ** (where ** is either one or two letters). This should come up on the screen after you have waited for VAG-COM to open communication with the engine ECU.

If the tuner knows what he is doing program switching can be done simply through VAG-COM. Most VAG ECUs have a different programs for each transmission type (auto, manual or 4WD) and a good tuner can use each of these for a different tune. Selecting the different program is done with engine coding using VAGCOM. As I understand it even if your ECU does not have all three 'programs' as standard someone who knows what they are doing can write the data into the correct addresses and make this work (maybe not the case with earlier ECUs)

Having a manual switch is more involved and requires hardware mods. either a bigger chip with address switching or stacking a number of chips and switching the power from one to another As Jeff eludes to in the linked thread there are possible issues with the ECU freaking out if you switch while the engine is running. I've not heard of anyone 'hot switching' one of the earlier VAG ECUs (all ECUs pre 038 906 012 ** eg. 038 906 018 ** and 028 906 021 **) switching is done with engine off.

DarrenUK said:

How many degrees advance did you give with adaptation 4? What ever it was you'll be that much different at all engine conditions.

I've not tested, but there are timing limits which I think adaptation takes precedent over.



Yes logging IQ at the same time would provide more robust results. (I record the data as I drive and look at it sat at home later).

So you saw something like a 1.7 degree advance - but how much of this was due to adaptation?


Yes this is what I did for the coolant temp sensor. switch and variable resistor.



I was after your ECU number which I guess will be - 038 906 012 ** or possibly 038 906 018 ** (where ** is either one or two letters). This should come up on the screen after you have waited for VAG-COM to open communication with the engine ECU.

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My adaption was not too much at all because I didn't want to push it too far knowing that is a possibility. You'll read in my post #10 at the top that I adapted another .4 deg more advanced. At that point I was reading 3.0 deg advanced at start up and at idle conditions, which I think is plenty. Judging by my results on the resistor mod, it advanced it another .4. So although this wasn't much, together they both made a difference.

The thing that is great about the resistor is it kept the fuel temps down, seeing nothing above 20 or so deg C. I did not know it would keep the temps down consistently and was the reason why I made it removable just in case I need to use a larger resistor.

So the combination between the two had a good effect on timing, but the resistor prevents any retardation at extreme fuel temps because it won't allow the ECU to see the high temps.

T's,

The resistor mod theoretically makes sense, although I'd want to ensure that it was doing what I thought on any given ECU before presuming everything is good.

Best way I can think to check this is to rig up a switch as described above and switch while driving at a steady pace.

When you are adapting timing you can see exactly how much difference your adaptation is making on the screen where you make the adaptation. You may have to reset to the standard setting of 32768 and move from there.

Timing at low load/engine speed is set rather retarded.

Compare the timing map from my skoda


to a map from a Passat - this map is very similar to the CQ ECU map



See them big spikes in the timing 'trough'. On older cars the emissions standards were not so tight so they had the timing set to provide good fuel economy (read more complete combustion) at the kind of rpm/load where the mpg figures are calculated.

Those spikes rise about 5 degree above the surrounding 'retarded for low NOx' timing.
Having said that high rpm/load timing is already a bit advanced from optimal due to the limited time to get all the fuel in - much more than 2 deg advance and your risking your head gasket......

Of course all that is just when running diesel. Running veg gives more to consider....