I've been hanging around A4.org/Audiworld for years and just found this forum last week. It's exciting to discover so much helpful information about my car. It's going to take a while to sort out my priorities (and finances) for putting all this knowledge to into practice, but I'm pretty sure there's a velocity stack looming in the near future.

Anyway, my question:

I've seen it stated on this forum and elsewhere that cars with automatic transmissions stand to benefit most from throttle body modifications. Would any of you be able to shed some light on why this may be the case? Thanks.

(drive line loss) is significantly higher for the automatic car, ie; less wheel HP due to the additional power used by the transmission. The autotmatic also adds 100lbs to the car unless it's FWD. The rule of thumb for B4/B5 chassis cars is "subtract 200lbs for FWD/Add 100lbs for automatic."

I don't believe the actual gains for an automatic to be any greater than a manual tranny car as much as I believe them to be more-easily perceived. And how or why that phenomenon exists is still a big question to me. But since I have a 90S (auto) sitting beside my manual A4 in the garage I can also attest to the validity of the perception. The automatic car is perceptably faster feeling with any/all of the modifications I make that we try on that car than the same modifications we put on my car. But when we go out to the track identically prepared I always pull on him by the same distance. That is to say we both achieve about the same benefit from each modification but there's no question the 90S "feels" faster with each individual or additional modification.

There are a few mods that I make today that without benefit of the automatic car for testing I would've given up on as insignificant or not worth the effort if I were only using a manual transmission platform. Stage 3 MAF is one such item. I originally installed the Stage 3 MAF on my car with little, if any perceptable gain felt over Stage 2. Then I put it on my sons car and it was an easily perceived benefit... not subtle at all. When my sons car started gaining on me in a "rolling start" race with the Stage 3 installed and I was running a Stage 2 it gave me pause. I then turned up another Stage 3 and put it on my car and now I was back to pulling him as I've always done before, yet it still doesn't "feel" any faster to me than a Stage 2 but his Stage 3 does feel faster. Even after swapping MAF's with him, same thing. Go figure! Yet I could not "feel" the difference in my manual tranny car but absolutely can feel it in his car. And our little rolling start races have borne this out time and time again with every mod. The automatic, for some reason, just presents a more sensitive, responsive and feelable platform than the manual transmission car does.

I think any mod that benefits a manual car benefits the auto car (and vice versa) in a similar, if not almost identical manner. But for some weird reason I don't fully understand, the automatic car is just a better platform for feeling those improvements that may appear subtle, vague, ambiguous and oft-times of no benefit whatever in the manual transmission car. But then my son starts to gain on me again and I'm forced to re-think the situation. At a 50MPH rolling start with him in sport mode I can tell before we hit 70mph if the latest mod we're testing has any merit whatsoever. Something I can't always do just driving my car alone at any speed or timed distance.

Thanks for the comprehensive response. I knew there was a severe penalty for convenience/laziness with the automatic - 1.8 freakin' seconds 0-60 according to AW's model guide. I developed the preference during my days as a sales rep when a free hand for a map, phone, pen, or coffee cup weighed heavily in the decision-making process. Even so, I plan to whittle away at that 1.8 sec gap.

I'd come up with a couple of possible reasons why the auto SEEMED to benefit more from engine modifications. With a manual trans, the driver determines all aspects of shifting - which gear, how long in each gear, interval of clutch disengagement/engagement, etc. An auto trans is, in a sense, a torque "interpreter". Several shifting behaviors are influenced by the amount of torque supplied. Under modest acceleration, upshifts in my car are imperceptable, seemingly infinitely variable. Under hard acceleration, shifts are abrupt kicks in the lower back. There are other factors in the design of these transmissions that affect how they shift but torque certainly influences their behavior. The driver of a auto trans car with engine modifications should, for a given throttle input, experience more direct "lock-up", quicker shifts, etc. vs. an unmodified car. Essentially the same feedback that the driver was formerly experiencing at larger throttle inputs?

Another, possibly additive perceptual difference might stem from the auto trans driver's relative isolation from the process. He/she just pushes the pedal on the right. In the sense that he/she is the audience for what is taking place, rather than the conductor, might make observation of any differences less distracted?

Or . . .

it could be something I've completely overlooked.