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Discussion Starter · #1 · (Edited)
Over the past few days, quite a bit of discussion and testing has been going on in the "Let's discuss boost!" thread about various logs. Some of these logs showed strange issues with air intake flow (g/s), throttle valve position and timing retardation. Several people have pointed to these issues possibly arising due to poor readings at the Mass Airflow Sensor (MAF).

On our cars (and any turbo car, especially those equipped with aftermarket cold air intakes), a poor MAF reading or air that enters the intake tract after the MAF can produce a lean condition in the engine. The ECU's O2 sensor reads and reports these conditions and the car will apply a "fuel trim" correction in order to get the engines AFR back to where it should be.

In addition to that, when the car senses a lean condition it can retard timing or reduce throttle valve position in order to protect the engine. This is visible to us through VCDS/VAG-COM logs when we have a throttle position of less than 99.6% at WOT during a logging run.

More info into the problem can be found here (particularly pages 5-9): http://forums.vwvortex.com/showthread.php?5852779-Let-s-discuss-boost!

We decided to start this thread to bring everyone's attention to this potential issue. Some people may not want to sift through a 9 page thread, and we think that this issue may be a lot more widespread than we thought, so a new thread was created in order to get the information out better.

IF YOU HAVE AN AFTERMARKET INTAKE AND ACCESS TO VCDS please check your fuel trim values going to Select Control Module -> 01 - Engine -> Meas. Blocks - 08. Type the value "032" into the block and scan. The car does not need to be moving, as it scans memory for this value.

SAFE values for Block 032 are between +0-10%. More than that and you are running lean, have too much fuel trim and are probably losing timing or throttle position to compensate for the lean condition. The closer to 0% the better, but 0% is an impossible value (the stock intake reads at +3%).





(Push Meas. Blocks 08 instead of the button pictured.)


For information on how to do a full datalog, go here: http://www.goapr.com/support/datalogging.php

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The following intakes have been observed to cause "lean" conditions with the Golf R MAF and have produced fuel trim values exceeding what is generally considered a "safe" value:

Stock Intake: Fuel Trims from +0 to +5% - Safe
APR Carbonio: +0 to +8% - Safe
Forge WINtake: +10 to +25% - CEL Possible
Forge TWINtake: +5 to +15% - CEL Unlikely
EVOMs Intake: +0 to +~5% - Safe
CTS Turbo Intake: +0 to +~5% - Safe
Neuspeed P-Flo Intake: +0 to +~8% - Safe
VWR Intake: +5 to +20% - CEL Possible
VWR Intake (Post-Warranty Modification): +0 to ~8% - CEL Unlikely
Volant Intake: +0 to +~5% - Safe
Injen Intake: +5 to +20% - CEL Possible
BSH Intake: +0 to ~10% - CEL Unlikely
 

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Discussion Starter · #2 · (Edited)
I would like to see 2-3 logs of each intake at an abnormal fuel trim value before we add it to the list, as some could be isolated issues (clamps not tight, bad MAFs, etc. etc.). We have seen several intakes producing values >+10%, but only one or two scans.

If you have an aftermarket intake, PLEASE log your Block 032! You could be losing power without even knowing it!

We need scans of:

VWR
Forge WINtake
Forge TWINtake
Volant
BSH
CTS/EVOMs
And any others.
 

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If you scan 100 stock vehicles, you'll find they are not all identical, even if they don't have any obvious issues.

Here are just a few things that can alter the readings:

Leak after the MAF
Leak after the Turbo
(Boost/Vacuum Leak)
Faulty or slightly different reading maf sensor
Faulty or slightly different spraying injector
Faulty or slightly different pumping fuel pump
Faulty or slightly different reading rail pressure sensor
Faulty or slightly different reading oxygen sensor
(Faulty airflow/fueling sensors/components)
Incorrect diameter MAF housing.
Incorrect MAF tolerances.
Turbulent airflow.
MAF housing placement.
Seal around the MAF sensor (tolerances).
Altered MAF/Fueling scaling in software (Should'd be altered unless big turbo with bigger maf, bigger injectors, etc).

As a basic rule of thumb:

High positive fuel trim values = Oxygen sensor reporting more air / less fuel than expected. (Adding Fuel to fix the issue)
High negative fuel trim values = Oxygen sensor reporting less air / more fuel than expected. (Removing Fuel to fix the issue)

Also, clearing fault codes, even if none exist, will reset fuel trims.
 

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I'd like to mention a couple things.

1) Removing or changing the canister won't do anything for fuel trims, the MAF is too far down stream.

2) The issue is likely in the piping ID and the nature of the gas as it passes over the MAF. Every intake including OEM has a 90* before the MAF, its a fixed bend. The amount of piping used to make this bend and how far off the MAF is from this point can be altered, although I don't think this is the problem. The OEM is an oblong shape, if you were to do the math correctly and get the correct cross sectional area the velocity of gas between OEM housing and cylinder could be much different. The OEM collects air from an open space and runs it through the MAF that sits in an oblong housing, this could cause a funnel effect. The intake piping if a typical cylinder is going to have a different characteristic than this, it will definitely have a different delta of velocity or rather acceleration of gas across the sensor than the OEM MAF housing.

3) How the MAF physically sits in the OEM, its much different than how it'd fit in aftermarket intake piping. Perhaps to experiment it could be inserted at slight angles and moved further into the housing. A good example of this is this picture -




What is the best course for anybody making an intake? If causing a positive fuel trim, unmetered air is getting past the MAF. By upping velocity this would have the MAF recognizing a greater flow and lower fuel trims. I would create a funnel effect similar to OEM by scaling the ID down by 1 or 2mm, I would take the section that the MAF sits in and have it mandrel bent to a slight oblong and make sure the transitions for this are both consistent and solid. This pirce can be done seperately and then welded on to the tradition cylindrical intake piping, making this slightly oblong will make how the MAF sensor sits more accurate. Lastly I would have the compressor inlet hose shaped as a funnel that goes from intake piping diameter to compressor diameter in a smooth transition. Another thing that needs to be considered is that as flow increases the slope of this would have to match the slope of how flow increases over the OEM housing.
 

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Discussion Starter · #5 ·
Some good extra info there Arin. :thumbup:

From logging the ten or so vehicles with several different intakes in the Boost thread, there seems to be an issue with some aftermarket intakes and not others that produce high fuel trim numbers. Since most of our cars are still mostly stock as far as injectors, MAFs and so on, AND mostly new, most of the parts you pointed to should still be working as intended or expected. There definitely appears to be relationship issues with some aftermarket intakes and the stock R MAF. What is actually causing the problem with a specific intake could be, as you said, a number of things but hopefully we might be able to make some guesses and it will be great to have a thread where a large number of logs and readings are posted.
 

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Over the past few days, quite a bit of discussion and testing has been going on in the "Let's discuss boost!" thread about various logs. Some of these logs showed strange issues with air intake flow (g/s), throttle valve position and timing retardation. Several people have pointed to these issues possibly arising due to poor readings at the Mass Airflow Sensor (MAF).

On our cars (and any turbo car, especially those equipped with aftermarket cold air intakes), a poor MAF reading or air that enters the intake tract after the MAF can produce a lean condition in the engine. The ECU's O2 sensor reads and reports these conditions and the car will apply a "fuel trim" correction in order to get the engines AFR back to where it should be.

In addition to that, when the car senses a lean condition it can retard timing or reduce throttle valve position in order to protect the engine. This is visible to us through VCDS/VAG-COM logs when we have a throttle position of less than 99.6% at WOT during a logging run.

More info into the problem can be found here (particularly pages 5-9): http://forums.vwvortex.com/showthread.php?5852779-Let-s-discuss-boost!

We decided to start this thread to bring everyone's attention to this potential issue. Some people may not want to sift through a 9 page thread, and we think that this issue may be a lot more widespread than we thought, so a new thread was created in order to get the information out better.

SAFE values for Block 032 are between +0-10%. More than that and you are running lean, have too much fuel trim and are probably losing timing or throttle position to compensate for the lean condition. The closer to 0% the better, but 0% is an impossible value (the stock intake reads at +3%).

The following intakes have been observed to cause "lean" conditions with the Golf R MAF and have produced fuel trim values exceeding what is generally considered a "safe" value:

Intakes will be added here as logs are posted.
You've certainly learned a lot since yesterday ;)

I can't believe how drasticly/quickly a couple of my comments about how the MAF sensor works, how it alters the vehicles performance and what to look for changed this entire forum with regard to aftermarket intakes. This is good, I wish GolfMK5 would've caught on like this, they all believe "an intake, is an intake" and most of them have probably never logged how everything is working for them.
 

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You've certainly learned a lot since yesterday ;)

I can't believe how drasticly/quickly a couple of my comments about how the MAF sensor works, how it alters the vehicles performance and what to look for changed this entire forum with regard to aftermarket intakes. This is good, I wish GolfMK5 would've caught on like this, they all believe "an intake, is an intake" and most of them have probably never logged how everything is working for them.
I really learned a lot from you, and cannot thank you and people like you enough. :beer:
 

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i'm running a forge wintake, i checked mine before i went to lunch they were showing -0.1% and 21.5% reset the codes and checked blocks 32 both were showing 0.0. I drove to get lunch and back about 2 miles they now show 0.9% and 17%

my vwr intake will be at my house tomorrow. i will try to get some pics of the maf housing of that, get it installed and log some more
 

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Discussion Starter · #9 · (Edited)
A little bit of research goes a long way. :thumbup:

By the way, I guess I should post my logs:



No Turbo button, sorry about that.

APR Stage 2+, APR RSC TBE, APR HPFP, Forge Twintercooler, Forge Wintake. Fuel trim values of -1.5 / +19.5.

i'm running a forge wintake, i checked mine before i went to lunch they were showing -0.1% and 21.5% reset the codes and checked blocks 32 both were showing 0.0. I drove to get lunch and back about 2 miles they now show 0.9% and 17%

my vwr intake will be at my house tomorrow. i will try to get some pics of the maf housing of that, get it installed and log some more
Sounds awesome. Looking forward to hearing about it. Where did you get the VWR intake from? If it comes out to
 

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Just throwing this out there but in the OEM setup the air should be moving slower and more turbulent because of the filter placement. Every aftermarket setup filters first then the air is sent through a smooth pipe over the MAF.

Im probably not adding much to the discussion.
 

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A little bit of research goes a long way. :thumbup:

By the way, I guess I should post my logs:



No Turbo button, sorry about that.

APR Stage 2+, APR RSC TBE, APR HPFP, Forge Twintercooler, Forge Wintake. Fuel trim values of -1.5 / +19.5.


Sounds awesome. Looking forward to hearing about it. Where did you get the VWR intake from? If it comes out to
 

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Here's my rundown...

APR 1+ software
APR HPFP
Forge Wintake

Everything else is stock.

My 032 numbers started out as +0.7 and +18.8%. I cleared it the system, loosened, readjusted and tightened all the hoses and clamps to rule out a leak and went for a drive and and it went up to +19.1%

I have a Volant intake on the way. I'll check it again when that gets installed and see if it fixes the issue.
 

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Discussion Starter · #15 ·
What is your ambient temperature for these logs? The IAT is bumping up 4*C to redline, by the second run its 5*C than the first run.
It was about 60 deg F or 15-16 deg C outside.

I had a lot of "sit and idle" time between the runs as I pulled over and stopped to check VCDS and wait for clear road before the first run and between the first and second run.
 

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Jsausley & notavr - My VWR intake is at +3.1 LTFT, its had a hundred miles of adaptation since swapping it in 2 days ago.

I've owned it for a while and just recently started logging it, its always felt really strong up top.
 

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The boost thread was good stuff. MKV727 and a couple others really did contribute a ton, thanks for the insight and knowledge! I'm glad to see it continuing and more exploring going on. Logging is a wonderful thing.

Don't know if you care about Carbonio numbers on this car but I can give you those if needed. Being that it retains the OEM MAF housing I wouldn't expect the numbers to be too far out from 0.
 

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MKV your expertise is greatly appreciated. If you're going to WITW this year, ill make jsausley buy you a :beer: :cool:

I've tried to learn quite a bit from these 2 threads and everyone else should be too
 

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I am pretty lucky that the EVOMs really shined, esp for a filter on a stick setup, giving high MAF
values and also giving great fuel trim values.
Granted, it was in the - fuel trim area, as well as some OEM values I've seen, but I think -2.2% is
pretty damn good. Should I, or would I prefer a +2.2%? Don't see why, but?
 
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