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/showthrea...-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
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