any one can tell me what are the optimum gear shifting rpms for a 997 C2 ?thanks

 

there is no such thing as 'optimum' - do what feels right in the circumstances.

If cruising along next to the ocean with (as Monty Python says, 'Your Best Girl on your arm'), you might shift as soon as you can, if driving up the mountain early in the morning, taking it out to the red line in each gear and hearing the noise echo back to you off the canyon walls as you go up and down the box is perfect.

On Maximillianstrasse, my favourite car street in the world (eat your heart out Rodeo Drive), people who make a lot of noise in an 'ordinary' car lose all credibility. To be unordinary takes some doing, although a Veyron did back up the traffic once and people make space for a GT1 if it appears. However, the tram lines really set off the TC.

R+C

 

I would say 500 RPM before it stops making maximum power/torque.. on the track.

 

Why?

What is wrong with red line? That's what PAG expects.

If you had said '...500 rpm before the red line, in the interests of longevity', I could understand.

R+C

 

Red line is not always the best place to shift. You have to look at the HP and torque vs RPM. You want to shift where the enginge speed on the upshift lands in the largest part to the torque curve.

 

That works on the drag strip, otherwise the tendency is to take the car out to the red line. When driving on the track, in almost all circumstances, you probably have other things to worry about than whether you change at 8,000 or 8,200.

On a road circuit, its better to worry about improving your technique in other areas.

Incidentally, if you look at the torque curves of many modern turbos, there is a flat torque curve from, say, 3,000 to 6,500 rpm, although the bhp might peak at 7,000 and be redlined at 7,600. This doesn't mean that you can change when the engine will be doing 3,000 in the next gear.......

R+C

 

The question was what is the optimum gear shift rpm, assuming he means max accleration, not how to be faster on the track. I'm not saying that where you shift (in terms of RPM) is the most important thing when you're driving on the track- obviously not. However, any professional racer (which I am not) figures out the best shift points for accleration by looking at his dyno sheet and his drive/gear ratios. Does that mean he shifts at 6200 for 2nd to 3rd all the time? No, what it does give him is a reference point and allows him to know how close to redline he needs to go for maxium accleration.

On the track, I'm like you. I shift near redline. My track time depends a lot more on technique. For professional racers, carrying 1 more mile per hour into or out of a corner is huge, so everything counts.

I don't drive a turbo, but other things are important like preventing turbo lag.

 

How about - 500 RPM before the power starts to drop off or 500 before redline if it makes good power the whole band up to redline... or when your shift light goes on

 

I'm being picky now, but it depends on.

To optimize the acceleration you need to look at the power band travel. So even if the power drops in the end, it can result that you pick up next gear a bit higher up in the revs (usually giving you more power). Then it should be applied to what section of the track you are at and how many gear changes you get in it.

 

Here we go again...a search will reveal some heated threads on this topic.

 

+1

 

You shift when you hear a valve slammin a piston!

 

According to this article it's best to optimize power. That is, shift to maintain the highest power, rather than shifting to maintain the highest torque.

 

This isn't correct. You want to shift where the wheel torque(engine trq x gearing) from the next gear matches the torque for the current gear. Although sometimes the torque in the next gear will never have the same amount of torque from the current gear, in which case you'd shift at redline. For instance for my car is 7000(redline) for 1-2 and 2-3, 3-4 is 6800, 4-5 is 6500.

 

This is true, only if the gear spacing is wide enough and the torque curve falls off fast enough to out pace the change in gear ratios.
generally, amost all cars pay to shift at redline. there are some, and yours might be one, the break even to shift a little earlier.
for sure, max torque of the engine, is NEVER really a factor.

Acceleration = power/(mass x velocity) this means that you need to maximize HP at any vehicle speed, to get the max acceleration.

If longevity is an issue, then you need to back things off a little

MK