exiged

Hi Guy's,

I've recently picked up a late petrol S4 and loving everything about it so far. Coming from 3.0 bmw diesels obviously its a completely different driving experience.

Basically me and a friend always put our new cars up against each other for a bit of fun in a rolling start from say 40-50, and i was wondering what kind of revs its best to hold at to start a pull like this, and whether its better to just let the box shift up, or shift manually at a specific rev range?

HCGxKaLiBeR

I'm willing to bet most of the members here don't do paddle shifters. Not to mention the best RPM/gear for a rolling pull. lol

I would say just let the box to do its thing.
Unless you want to go hardcore, leave it at 4k RPM, slight brake boost (may need some practice and coordination with both of your feet), take off when ready.

superswiss

Hehe...yeah not many responses. This question goes to the heart of driving. I guess if you have to ask, then I assume you have never driven a manual transmission car. Letting the box shift itself is better if the driver doesn't understand when to shift, but in all likelihood when you start it'll be in a too high gear and first has to kick down. The ZF8 has a slow kickdown, especially with Audis implementation, so you'll likely be faster if you start off in the right gear yourself to avoid the transmission having to kick down first. As far as which is the right gear, for that you have to understand that maximum acceleration is achieved at peak engine power. Contrary to popular believe, it's horsepower that accelerates a car, not torque. Torque is the force you feel, but power is the rate of work performed and the faster you wanna accelerate the more work needs to be performed in a given time. So for the fastest rolling start you wanna be in the lowest possible gear closest to peak power, but still have some room left in the powerband, so you don't have to shift immediately after taking off. Torque and Power are obviously related as Power = Torque * rpm / 5252. So the variable you control there is the rpm. The higher the rpm the more power the engine makes, and the faster the car will accelerate. One caveat with the S4 is that you don't have a true manual mode. Even if you are in manual mode, it will automatically upshift near redline, so likely the best approach is to manually put it in the right gear to start and then let it upshift automatically, otherwise if you are too slow upshifting manually, then it will upshift automatically followed by your manual upshift so you end up with a double upshift. The RS models have a true manual mode, so you don't have this issue, although the latest RS models like the B9 RS5 I believe automatically do the 1-2 upshift, so it's not a 100% true manual mode as in past RS models and other high performance cars.

HCGxKaLiBeR

Good info and good point.

I forgot about manually upshift in an automatic is slower. Because
1. There is an delay when the paddles/shifter commands the transmission to shift.
2. There is another delay when the transmission to shift (although it is almost unnoticeable)

I would say manually leave it at a desired powerband initially so the car holds the RPM higher.
Then let it do its thing since it upshifts in manual mode regardless.

superswiss

It's not necessarily that manual upshifting is slower, although the ZF8 is not the crispest shifting thing and definitely has some lag, but it's more the reaction time of the driver. Due to the unavoidable automatic upshift, you have to shift slightly early and leave some power on the table. You can't ring it out all the way and shift just before hitting the rev limiter. So the automatic upshift will be faster, because it will be at the precise time. Also, I believe as opposed to the RS, the S4 doesn't have the shift lights that let you know when it's time to upshift.

One trick I forgot to mention to start out in the correct gear and I believe works now in the S4 as well, is if you press and hold the downshift paddle for about a second, it will automatically drop down to the lowest possible gear for maximum acceleration.

Bobby Kinstle

Most of the time it's auto, but when I'm driving for fun, it's manual.

HCGxKaLiBeR

Yup me too. I would do pull in auto. But when I'm having fun on a nice day I would do manual mode.

Brrrrr pfft, crackle crackle, pop pop never gets old in manual mode.