td80

Are the differences between Audi's higher output 4.2L platforms and the V8 S5 massive ones? I have been curious lately if a reasonable bump in horsepower can be had with the S5 without drastic changes to the engine construction like new heads, valvetrain, etc?

I see the tunes from GIAC and APR provide small bumps in power as well. Does the ECU in the S5 require physical modification for a tune to be applied or can it all be done through the diagnostics port as it was in previous Audi vehicles I have owned? With previous vehicles I applied and removed the tune as needed for service and never received any backlash from the service folks, but wasn't sure if that was still possible to maintain warranty etc?

As a disclaimer: I'm not one to cheat warranty -- and if I DID end up having issues with the motor that could have very well been due to the tune, that's something I'd feel I was responsible for. What I'm mainly trying to avoid is the "Oh you had a tune installed so we didn't cover the failure of the MMI system!" type issues.

QuattroWerks

The 4.2L motor in our car is very different v. the R8/RS4:

http://www.6speedonline.com/forums/a...is-4-2-v8.html

The car is absolutely tuneable via the OBD port but the gains are (as expected) relatively small as compared to what you can get from a forced-induction motor.

As respects the warranty, not going to jinx my car by commenting :-) But seriously, "if you to play, you may need to pay" depending on your dealer relationship.

td80

Excellent post, thanks! Thats exactly the info I was wondering about. I Figured displacement was about the only thing that was the same between those (rs4 vs s5) motors, which appears to be correct. Thanks much for the link.

On that note, have you dyno'd your car before and after your mods? Seem's you have done quite a bit. The sprint booster is one intriguing item that I would like to get soon as I feel the S5 suffers severely from a lack of throttle response. While not gaining anything powerwise, I think that tactile improvement would help it feel much more lively.

QuattroWerks

https://www.audiworld.com/forums/sho...sprint+booster

https://www.audiworld.com/forums/sho...ht=custom+tune

A5_4GP

I found this while surfing the web for Audi 4.2L info. It is from an Audi service training program. The S5 uses the same 4.2 as the Q7 in the documantation. It shows the difference between the 2 types of 4.2L engines.

http://www.jlosee.com/images/RS4/PDF...ssp.921603.pdf