RI A6

One $349 Ross-Tech HEX-USB + Can
One laptop with VAG-COM.

- Select Control Module
- Select Drivetrain
- Select 01-Engine
- Select Fault Codes
- Clear Codes
- GoBack
- Select Drivetrain
- Select 11-Engine II
- Select Fault Codes
- Clear Codes

Voila, you now have up to 6 more HP!
You heard it hear first.
Amazing but true.
YMMV

Clearing the codes on both engine banks resets fuel trim and timing adaptation parameters. It seems our ECU(s), there are two, can get a bit conservative on timing adaptation over time. (We don't know why). Reseting will force the ECU to the original factory settings, and cause it to do close loop fuel and timing adjustments, even under Wide Open Throttle (WOT). It turns out that the new MED 9.1 ECU is capable of keeping closed loop lambda control even under WOT, by monitoring the wideband O2 sensor.

So how do I know this? Well, a little dyno told me so.

I took my car down to EPL in Stratford, CT and did a couple hours with Tony. Great guy, by the way. We're prepairing to do some dyno benchmarking of my RS4 stock, with Milltek Catbacks, and then with Milltek downpipes. But before I do that benchmarking, I wanted be sure that we understand how the ECU adapts, so that multiple dyno runs can be performed in an apples-to-apples comparison. Well, the thinking goes that the ECU needs time to "adapt" fuel trim and timing before the engine produces full power.

So, we made three runs of the car as it came in off the street. The curves were all repeatable and just about overlayed on top of each other.

Then, we reset the ECU. Well, actually we reset the Fault Codes on just one of the ECUs, but not the other. (Silly us, you'd think that resetting one Engine ECU would also reset the other!) The next dyno pull showed about a 3 HP increase. Hmmm, something interesting is happening here. Then we figured out that the 2nd Engine Bank had not been reset, so we did, and did another dyno pull. Yet another 3 HP increase, for a total of 6 HP. And then we ran again just to check for consistency. The results were quite consistent.

If I recall correctly, off the street, the car was pulling around 309 whp. After the ECU was reset, it was pulling around 315. However, I'm not sure if my memory is absolutely correct here. As soon as Tony sends me the data, I'll post some dyno plots. However, it does stimulate some interesing questions about the ECU.

Remember that VAG-COM cable you wanted to buy, but just couldn't justify it. Well now it just about pays for itself with the additional power you'll see. When you're ready, just pull her out, reset the ECUs, and you're off to the races.

James P.

Very interesting... when are you planning on doing the catback & down pipes ?

Silver Fun

I wonder how much hardware vs. software is different in the 450 HP motor supposedly being put in the '08 RS4?

s4for5_TTfor2

"Clearing the codes on both engine banks resets fuel trim and timing adaptation parameters"
Who told you that ?

I can't imagine just clearing a non existent code resets anything ?
Since when is there a reset for each side of the engine ?
No mention of this on Ross-tech's site either.
I think something else has caused your different results.
Just my opinion of course, please prove me wrong, but I think someone is yanking your chain

Bob W.

this doesn't really help much....after a few days of driving, the fuel trim and timing are probably back where they were, right?

Bob W.

remove power from the ECU, and eventually the memory resets to the factory default settings...at least it worked that way on my old TT.

daveak05

I'm having a hard time wondering why risk ECU gremlins for 6 hp.

Tony@EPL

Clear your code (even if there arent any). Check block 32 again and compare before and after values.

Repeat on engine II.

Reseting DTC's will reset most short and long term adaption. This is fact!

s4for5_TTfor2

Tested just now, block 32 reset to zero after clear done on engine 1, no engine 2 access ?

The Drivetrain\Engine 2 controller does not respond on my B6 with latest Vag-Com

I was wrong, something reset on block 32 per the Vag for sure.

adg44

Your post is slightly misleading. This isn't a way to maintain a gain in power, like an intake or an exhaust.

It's not like doing this is going to hurt anything (as someone implied above), other than what I might assume will worse gas mileage temporarily.

- Anthony