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Go Back   TDIClub Forums > TDI Model Specific Discussions Areas > VW MKVII-Mk7 Golf family including Golf Wagon (~ 2015 +)

VW MKVII-Mk7 Golf family including Golf Wagon (~ 2015 +) Discussions area for the Mk7 (2015+) Golf and Golf Wagon TDIs based on the MQB (Modularer Querbaukasten) platform.

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Old April 21st, 2017, 05:05   #16
2015vwgolfdiesel
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Your poor TDI!
Guilty as charged

whipper snapper ~~ your day will come ~~ Maybe ~~ speed kills
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Old April 21st, 2017, 08:46   #17
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The sound is definitely changed. A car guy would notice but others might not. It's not like installing an aftermarket exhaust or anything like that, it is subtle. A bit throatier under load during acceleration and more diesel clatter at times especially during warmup. But highway cruising and low load situations it is pretty much just smooth and silent.

I think this new factory calibration has less emphasis on "can't tell it's a diesel" type stuff and that's where they were able to find room to improve emissions and performance too. In the original factory calibration, I'm guessing that sacrifices were made in the name of "refinement" and with the aim of making the engine less objectionable to the largest number of people for broader market appeal. To change minds about diesel so to speak. Giving up on that vision of appealing to the largest possible number of people, freed up wiggle room to put the effort where it really matters to us diesel enthusiasts.
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Old April 21st, 2017, 09:00   #18
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Originally Posted by KERMA View Post
The sound is definitely changed. A car guy would notice but others might not. It's not like installing an aftermarket exhaust or anything like that, it is subtle. A bit throatier under load during acceleration and more diesel clatter at times especially during warmup. But highway cruising and low load situations it is pretty much just smooth and silent.
Wonder if the timing has been advanced.
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Old April 21st, 2017, 09:31   #19
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I'd think so. From what I understand the whole fuel injection strategy is different now. More injections per cycle, and new modelling routines.

I'm sure KERMA can comment on this more in depth, but from everything I've seen the fix is a lot more than a simple "re-tune".

Also, for posterity sake, we are talking about a 2015 2.0 TDI, correct?

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Maybe I should pay MYSELF to do bad work on my car!
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Old April 21st, 2017, 10:38   #20
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Originally Posted by IndigoBlueWagon View Post
Wonder if the timing has been advanced.
now that's an interesting question. LOL

fair warning: what follows tries to convey something that is technically complex in overly simplified terms

TLDR answer: the "timing" as such is not adjusted from before, but changes have been made that have an effect in the cylinder that is similar to what "changing timing" would do.

These cars don't necessarily control the "start of injection" in the same way we are used to thinking of it in the older cars. Instead, the control target is ultimately the "start of combustion" when the burn starts, not the needle lift event per se. Regulating the raw "start of injection" requires assumptions regarding ignition delay, which is less precise than monitoring the burn profile. (or else its just what's been empirically mapped on the engine dyno during the initial development to meet the desired emissions target) The newer CR cars have the ability to regulate the actual burn profile by dynamically adjusting how fuel is delivered, so less guessing is needed, allowing for more precise emissions controls. Of course, then the design decisions get made as to which is the highest priority for the tradeoffs. My assumption is that they decided a bit more noise than before is acceptable in the present situation.

I guess what I'm trying to get around to saying here, is that what are thought of as the "tuning maps" so to speak are pretty much not changed from before. (wait wut? so what was "updated" lol keep reading) But there are fewer of them because the "cheat mode" has been removed.

So the answer to the question "is the timing changed" is "no" if you only look at the "tuning maps" of VCDS logs of "timing". However, the number of preinjection states is changed, and some are gone, and the selection criteria appear to be different. And rail has similar state selection changes. This has the "effect" of changing the shape of the pressure profile and what happens in-cylinder... which is what we really want. So the answer is "no" at the basic level, but it is also "yes" if you want to consider what is actually happening in the cylinder.
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Old April 21st, 2017, 11:13   #21
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Actually one of the main inputs is something more esoteric that you may not expect, and I've never heard it mentioned anywhere before. It's called the purge ratio which consists of the ratio of intake manifold pressure to exhaust manifold pressure. Very key input to the internal regulation.
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Old April 21st, 2017, 11:14   #22
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Question ...am I getting close....

the way I understand how these things work is the glowplug is equipped with a sensor that measures precisely the combustion event while it is taking place.

And the start of injection is still at the same time but is moderated and change from previous settings which were controlled by the adjustment to improve real world driving programming.

With that programming removed adjustments of event length & quantity have been made leading to power increases. But these changes come at the cost of a shorter emissions system life after treatment parts are burned up & damaged from continual use to meet requirements now...


These changes are allowed by the increase in urea use, along with the requirement now of emissions system replacement on a schedule of @ 60k miles...

With Urea now being used more intrusively these increases, they can now inject more fuel over this time of injection in multiple events that very in quantity & duration from previous settings....

These changes are used to give a more thorough burn producing more NOx that is then burned off to some extent by the injection event changes along with the urea taking care of the rest....

the changes have allowed an entirely new scheme of injection mapping to be used for what was possible with the old programming...And

am I getting close...
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Old April 21st, 2017, 11:20   #23
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Originally Posted by KERMA View Post
Actually one of the main inputs is something more esoteric that you may not expect,

and I've never heard it mentioned anywhere before.

It's called the purge ratio which consists of the ratio of intake manifold pressure to exhaust manifold pressure.

The Very key input to the internal regulation.
So what exactly does the "purge ratio" describe..?...

Are they describing the injection changes which create a characteristic of combustion that helps to more thoroughly remove used combustion gasses while taking in clean air to burn..?...

How does this effect EGR use?? how does it change EGR programming, low & high pressure..??..
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Old April 21st, 2017, 11:45   #24
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So what exactly does the "purge ratio" describe..?...
Are they describing the injection changes which create a characteristic of combustion that helps to more thoroughly remove used combustion gasses while taking in clean air to burn..?...
How does this effect EGR use?? how does it change EGR programming, low & high pressure..??..
Pretty much just input intake and exhaust pressure, fuel IQ and air IQ, and you can accurately measure how well the engine is working. The fuel trim adjustment from glow plugs and IVA/IMA and lambda and the active eeprom adaptations for air/boost/actuator in order to be precise as possible.

EGR and throttle(s) and all that stuff matters... of course. Not really able to adequately discuss in a sentence or two in a forum post but it all matters.
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Old April 21st, 2017, 17:17   #25
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Do you have an overlay with correction turned off? When stock, the ecu is already correcting for altitude/temperature so dyno corrections will skew results.

Example:

Hot weather: ECU asks for more out of the engine to make up for the losses due to the poor conditions. Then the dyno correction artificially adds power to the graph. Result: higher than expected figures.

Cold weather: ECU asks for less out of the engine because conditions are good and less is needed from the engine to produce the prescribed power levels. Then the dyno correction artificially lowers power on the graph. Result: lower than expected figures.
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Old May 1st, 2017, 08:09   #26
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A DSO == injection timing diags. A good project for a automotive or eeng student.

2 channels, one tapped into the piezo on the plugs, so you can see the pressure in the cylinder, another one into the injector control wire.

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Old May 1st, 2017, 09:32   #27
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FWIW I'm seeing 46 MPG in mixed driving on my GSW (MFI, not calculated). First fill, 600 miles on the car. Even if it's optimistic that's pretty impressive.

I find the response to the acclearator a bit flat on tip in, noticeable when taking off from a stop. Otherwise driveability seems fine. Of course it's not like my modified ALH, but it doesn't seem to have any issues.
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Old May 1st, 2017, 09:39   #28
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Quote:
Originally Posted by IndigoBlueWagon View Post
FWIW I'm seeing 46 MPG in mixed driving on my GSW (MFI, not calculated). First fill, 600 miles on the car. Even if it's optimistic that's pretty impressive.

I find the response to the acclearator a bit flat on tip in, noticeable when taking off from a stop. Otherwise driveability seems fine. Of course it's not like my modified ALH, but it doesn't seem to have any issues.
Yup.
Very impressive in stock form. I have been pleased with mpg with my DSG, often hitting similar numbers to the stick guys, so it seems I have not given up much.
It a shame it appears this motor will be the last of the TDI's...it sounds like VW might not invest in any future generations to move on to electric, even in the euro market due to "market forces" aka politics.
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Old May 17th, 2017, 16:33   #29
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These MPG sound better than my '10 unfixed JSW and i believe it after test driving one.
Big difference in torque in my experience though. If i get one i'll be having to use sport mode. Never use in in my current car.
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Old May 19th, 2017, 13:25   #30
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Originally Posted by rotarykid View Post
the way I understand how these things work is the glowplug is equipped with a sensor that measures precisely the combustion event while it is taking place.
And the start of injection is still at the same time but is moderated and change from previous settings which were controlled by the adjustment to improve real world driving programming.
With that programming removed adjustments of event length & quantity have been made leading to power increases. But these changes come at the cost of a shorter emissions system life after treatment parts are burned up & damaged from continual use to meet requirements now...
These changes are allowed by the increase in urea use, along with the requirement now of emissions system replacement on a schedule of @ 60k miles...
With Urea now being used more intrusively these increases, they can now inject more fuel over this time of injection in multiple events that very in quantity & duration from previous settings....
These changes are used to give a more thorough burn producing more NOx that is then burned off to some extent by the injection event changes along with the urea taking care of the rest....
the changes have allowed an entirely new scheme of injection mapping to be used for what was possible with the old programming...And
am I getting close...
How much is the emissions system replacement going to cost?
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