Low Boost and Timing Pull

[ruiadf]

Hi All,
I bought my 08 mkV GTI 3 months ago would appreciate your help with the following issue.
Initially, the car was peaking at 16psi boost and holding around 13/12psi.
However, I recently notice the boost was no longer reaching those values and it was instead peaking at 11/10psi and holding at 10/9psi.
Initially, I thought it was the DV valve and decided to replace it with a new Rev.G, however it made no difference.
I have then run a few logs in VCDS and found the following:
https://drive.google.com/open?id=1bvvk9fJ0jb-iUY-Hufu5FoabHaKm1Fs4

I am not sure what is causing the low boost, could you please give any ideas to what to look for?

[pudding]

To me that looks exactly how a standard GTI should run.  12 psi spike, 10 psi held. The MAF value at ~5800rpm puts you at 193bhp.  Would probably hit 160+g/s air mass near redline for your full ~200hp.  Timing regulator looks pretty normal too.

Seems like you've lost your 16 psi spike.  Have you checked if your engine is remapped?  Go into VCDS > Engine > Advanced ID and see what the flash status is.  Flash attempts should be 0 on a standard car.  1 or more = remapped.  If it has a Revo map and the battery has been disconnected recently, it defaults to a lower power mode.

[Dan_FR]

Peak boost is not a static figure, it is a dynamic based on operating conditions and load.

Unfortunately I can't open documents like these in work or I would take a look, but from what Pudding says, it sounds spot on

FYI when I bought my car it was running Revo's 'standard power' setting on their Stage 1 map. I had it on the dyno at R-Tech and it made exactly 197HP at the flywheel which was spot on for a standard car. The one thing that stood out was the fuelling however, which differed from the standard mapping as it defaulted to a much richer mixture during the pull

*edit* Managed to get in for a look. Logging fuelling would have helped. 95 RON fuel? Quite a bit of timing pull at lower revs with the ECU closing throttle ever so slightly as a result. Boost level is fine, next time log up to the limiter

[ruiadf]

Thanks for your thoughts!
My main concern was the timing pull, I would imagine it should be lower on a stock car, which in turn could be the reason for lower boost.
I will check the Flash count.

[pudding]

Indeed.  The actual amount of spike pressure you get varies on the weather, fuel pump keeping up etc etc.  But generally speaking, stock is a mild spike (2-3psi) and tuners usually go for half a bar, (sometimes more) before settling on a stable pressure.....unless of course you choose a linear boost map.

Was that with the Performance Mode B1,T0,F0 map? Aka the 'battery yanked' default settings.  That does indeed over fuel, and not quite as much boost as 'stock mode', well, from what I've seen when logging an Edition 30 at least.  It requests silly AFRs like 11.8 for just 8psi of boost!  The engine oil stinks after only 100 miles running that map.

I can't see the point of that map, it just destroys the engine oil, which won't help cam follower lifespan.  It should just default to stock mode when the battery is yanked.  I think it's a deliberate copyright tactic personally, but can't say for certain.  No other tuner does that, so I don't believe it's down to how the ECU works (as they claim), unless Revo specifically are accessing the ECU memory a dodgy way compared to other tuners, which makes their code vulnerable to theft.

[ruiadf]

Peak boost is not a static figure, it is a dynamic based on operating conditions and load.

Unfortunately I can't open documents like these in work or I would take a look, but from what Pudding says, it sounds spot on

FYI when I bought my car it was running Revo's 'standard power' setting on their Stage 1 map. I had it on the dyno at R-Tech and it made exactly 197HP at the flywheel which was spot on for a standard car. The one thing that stood out was the fuelling however, which differed from the standard mapping as it defaulted to a much richer mixture during the pull

*edit* Managed to get in for a look. Logging fuelling would have helped. 95 RON fuel? Quite a bit of timing pull at lower revs with the ECU closing throttle ever so slightly as a result. Boost level is fine, next time log up to the limiter

The car is running Tesco Momentum 99 RON.
Please find below a link with a small log of the Fuel Rail Pressure:
https://drive.google.com/open?id=1T_aq8_SyvhhOF0ZwfmZYAZ0oSJAXqHfD

Do you find anything wrong with it?

[pudding]

Nothing wrong with the fuel pump.....up to ~5000rpm at least.   You need to redline it to get the full picture.

We also need IAT.  That could explain the timing pull if the intercooler is heat soaked. 

That isn't a lot of retard at all considering you've mashed the pedal to the floor at 2000rpm, in 4th probably?  It's a lot of weight and a tall gear to accelerate from such little momentum.  That kind of retarding is standard behaviour in every heavily loaded petrol engine.

The retard is virtually nothing once the revs and boost climb, which is the only area you need to be concerned about.  It's correction factor anyway.  Retarding 0.3 of a degree is, well, retarded, the engine won't even notice it.  It's just a correction, not actual degrees.  It's a weird bosch algorithm that retards in 0.75 deg increments, derived a weird calculation. Anyway......nothing of concern there.

[ruiadf]

Nothing wrong with the fuel pump.....up to ~5000rpm at least.   You need to redline it to get the full picture.

We also need IAT.  That could explain the timing pull if the intercooler is heat soaked. 

That isn't a lot of retard at all considering you've mashed the pedal to the floor at 2000rpm, in 4th probably?  It's a lot of weight and a tall gear to accelerate from such little momentum.  That kind of retarding is standard behaviour in every heavily loaded petrol engine.

The retard is virtually nothing once the revs and boost climb, which is the only area you need to be concerned about.  It's correction factor anyway.  Retarding 0.3 of a degree is, well, retarded, the engine won't even notice it.  It's just a correction, not actual degrees.  It's a weird bosch algorithm that retards in 0.75 deg increments, derived a weird calculation. Anyway......nothing of concern there.

So I have just checked the flash attempts and it seems to be stock.
Please see below:
Flash Status
     Programming Attempts: 0
     Successful Attempts: 0
     Programming Status: 00000000
     Required Conditions: 00000000
Software
     A000
     A4.9.6

Could you please confirm what you mean with IAT, i.e., which MB I should log?
Also, how do I check if the car is running rich or lean?

The only issues I found so far is the following Fault Code and a dying battery, however, I believe this should not make any difference.
001089 - EVAP Emission Control Sys
               P0441 - 002 - Incorrect Flow - Intermittent

Apologies for the stupid questions, but I am still a newbie to the GTI world.

[pudding]

Yep, 100% standard.

IAT = Intake Air Temperature.  Over 45 degrees, the ECU will start to retard the ignition for component protection.

For your short term lambda adjustments, log "Lambda Control" channel (Block 31 from memory).

For target and actual lambda, log "Lambda Control - Bank 1 (Specified)" and "Lambda Control - Bank 1 (Actual)".  Lambda 1 (14.7 AFR) to 0.80 is the normal fuelling range for a stock engine.

Those 3 will tell you the commanded air fuel ratio, the actual air fuel ratio, and live adjustments the ECU makes to meet the target.   On the live adjustment, you're looking for small numbers.  +/- 10% at the most when up to temperature.   Ignore any - or + 15-20% figures if you start logging from cold, that's normal, as is a LOT of ignition retard (15-20 degrees) as that is part of the EGT strategy.

If the Battery code relates to "B30", that means it was disconnected, not necessarily faulty.

Yeah the evap is common, could be the N80 purge valve, or a knackered petrol cap, or a spent charcoal can, or a leaking hose, or even an over filled tank.  Very sensitive circuits.

[ruiadf]

Yep, 100% standard.

IAT = Intake Air Temperature.  Over 45 degrees, the ECU will start to retard the ignition for component protection.

For your short term lambda adjustments, log "Lambda Control" channel (Block 31 from memory).

For target and actual lambda, log "Lambda Control - Bank 1 (Specified)" and "Lambda Control - Bank 1 (Actual)"

Those 3 will tell you the commanded air fuel ration, the actual air fuel ratio, and live adjustments the ECU makes to meet the target.   On the live adjustment, you're looking for small numbers.  +/- 10% at the most when up to temperature.   Ignore any - or + 15-20% figures if you start logging from cold, that's normal, as is a LOT of ignition retard (15-20 degrees) as that is part of the EGT strategy.

If the Battery code relates to "B30", that means it was disconnected, not necessarily faulty.

Yeah the evap is common, could be the N80 purge valve, or a knackered petrol cap, or a spent charcoal can, or a leaking hose, or even an over filled tank.  Very sensitive circuits.

Thanks!
I will do some logging over the weekend.

Regarding the battery I did not get a code, however, it is still the original one and the car is struggling to start when cold.

Funny thing happen today, on my way to work after a short 20min drive I had to stop for circa 20/30 mins and when restarted the car again for another 15min drive the boost was again spiking on 16/17psi (and the car felt a lot faster), I couldn't do a proper run because of traffic and I was already late, will try again in the afternoon, but it is strange...

Could it be related to the weak battery at cold starts, which is forcing some kind of lower performance map?

[pudding]

It could be wastegate or dump valve issues if the boost is inconsistent.  Have you checked for a split DV?

Battery voltage is also in the VCDS measuring blocks, which is the actual voltage the ECU receives, so see what that is with the ignition on and with the engine running.  Looking for 12 or more engine off, and around 14 with it running.

[ruiadf]

It could be wastegate or dump valve issues if the boost is inconsistent.  Have you checked for a split DV?

Battery voltage is also in the VCDS measuring blocks, which is the actual voltage the ECU receives, so see what that is with the ignition on and with the engine running.  Looking for 12 or more engine off, and around 14 with it running.

The DV valve was the first thing I replaced, installed a brand new Rev.G.
The wastegate seems fine, as per the following log:
https://docs.google.com/spreadsheets/d/1-dVuB82whaUuQY-TfiTq6JTeHBjQZ2Lg2iwAo865vZw/edit#gid=0

For some reason, it seems the engine is not specifying a lot of boost, in the above log it only specifies.11psi and then drops to 9.7psi.

I have ordered a new battery as the car is still on the original one, and has less than 12v with the engine off.

I am running out of options here, but I do feel the car has an inconsistent "power feel", sometimes feels more powerful than others.

[pudding]

Requested amounts can vary 'on the fly', they're not always set in stone. Commands are load, rpm and vehicle speed dependant....as well as exhaust gas monitoring etc.

11-12 psi is the standard pressure request, with a 14-15psi spike around 3000rpm depending on certain factors.  Your ECU is working as it should. 

You might have a weak wastegate spring, or the penny valve isn't sealing well consistently, meaning you get good boosting some days and not others.

[ruiadf]

Requested amounts can vary 'on the fly', they're not always set in stone. Commands are load, rpm and vehicle speed dependant....as well as exhaust gas monitoring etc.

11-12 psi is the standard pressure request, with a 14-15psi spike around 3000rpm depending on certain factors.  Your ECU is working as it should. 

You might have a weak wastegate spring, or the penny valve isn't sealing well consistently, meaning you get good boosting some days and not others.

Thanks once again Pudding!
I will try not to think too much on it and carry on with the other small repairs in the hope it will either cure itself or point into an exact cause.
I have planned the following works:
   - replace the battery;
   - track down the EVAP Fault, starting with the N80 vale replacement;
   - replace the cam follower;
   - replace the PCV as the one installed in the car does not seem to be OEM quality.

[pudding]

Aha, well there you go then....a non genuine PCV is certainly a potential candidate for inconsistent boost!  You could also have leaking boost pipes.  Check for oily patches on your belly tray where the boost pipe connections are.