Just a quick question.

On my rolling road peak torque was at 2650rpm and the bhp climed to 4500rpm and then stayed flat at 200bhp until 5000rpm -redline. (performance remap).

My question is....

Is it better to change gear at a point when the rpm would drop to max torque on gear change or would it be better taking it right to the redline?

Cheers

change up at the point where the new revs would put you on max torque or close to it when at max bhp.

Basically the ideal power/torque curve would have a large gap between max torque and max power to give you the biggest power band and you match the gear ratios so that you were changing up at peak bhp and arriving at max torque in the new gear.

Diesels produce a lot of torque at lower revs but with a narrow power band which is why you need to stir the gears more to stay "on it" than you would with a petrol.

OK great. So I know it all depends on gear ratios but If I rev to say 4300rpm and then change gear and it drops to around 2500/2700 (peak torque) that would be about right for gear changes?

I suppose there is no real way to find where the peak torque is in each gear as a rolling road in done in 5th?

Cheers

^ - But don't let it drop too low because you need to keep the turbo on full whack, so I generally I end up hitting red if pushing it. Learning to change the 'box is crucial; I barely even touch the left pedal, just kind of give it a rub at the right time and the stick falls into the right place.

My map is here: http://www.briskoda.net/forums/topic/130332-a-few-of-you-have-been-waiting-for-this-cr-170-curve/

I imagine your map follows a similar curve, so you'll notice the skill of driving doesn't really change, since the curves follow each other; you always have to make the best of what is there....and do it smoothly. Unless you are really pelting it, save yourself the clutch and agro and just change when the revs are nicely matched!

It also depends on how far you are going. Many people frown upon it, but I miss 1,2 or even 3 ratios regularly if I want to briskly get to, say 50 or 70 - the good thing with the oil lump is that once you get to the speed you want you can be in sixth - and this works from 30+

OK great. So I know it all depends on gear ratios but If I rev to say 4300rpm and then change gear and it drops to around 2500/2700 (peak torque) that would be about right for gear changes?

I suppose there is no real way to find where the peak torque is in each gear as a rolling road in done in 5th?

Cheers

Pretty much. As zachery says though the turbo is a big part too and you don't want to end up below where the turbo is spooled properly or you will introduce turbo lag (although smaller modern turbos dont suffer this as bad as big ones). You also need to to play with the throttle on a manual during the gear change to match the revs properly and prevent them falling too low during the gear change. All of which amounts to generally holding on slightly longer before changing up even though you will have passed peak bhp briefly. And indeed sometimes its actually beneficial to hold on further and skip a gear as long as you don't end up way below the turbo spool point. The best thing is get on a track and practice practice practice at all speeds and through all the gears so you get a proper feel for the way your car behaves wrt the power curves, gear ratios, turbo etc

I just slip it into S mode then floor it and relax.

Seriously though i would wager the DSG box has been set up in S mode to be optimal. Problem is i have never taken note at what revs it shifts as TBH i cant see it making much difference. I think it changes at 4500rpm but im am only guessing, hopefully someone else has studied it closer. Thing is the DSG changes so fast there is virtually no loss or torque, in a manual you might be better revving it a tad higher to compensate for the torque interuption as you change gears.

Edited 8 March, 201313 yr by Jockdooshbag

I just slip it into S mode then floor it and relax.

Seriously though i would wager the DSG box has been set up in S mode to be optimal. Problem is i have never taken note at what revs it shifts as TBH i cant see it making much difference. I think it changes at 4500rpm but im am only guessing, hopefully someone else has studied it closer. Thing is the DSG changes so fast there is virtually no loss or torque, in a manual you might be better revving it a tad higher to compensate for the torque interuption as you change gears.

"optimal"? Hmm... "maximal" I think! S mode is crazy!!

My 1.8TSi changes at around 4000 rpm under gentle/moderate acceleration and at around 6500rpm when I floor it in S mode - 500rpm into the "OK but don't do it too often" bit of the red zone

"optimal"? Hmm... "maximal" I think! S mode is crazy!!

My 1.8TSi changes at around 4000 rpm under gentle/moderate acceleration and at around 6500rpm when I floor it in S mode - 500rpm into the "OK but don't do it too often" bit of the red zone

S mode is supposed to be the "max" though. D is for normal driving S is for the full beans so i would expect it to change gear high up the rev range. When i say "optimal" i mean optimal in terms of delivering out right acceleration. In D mode optimal would mean changing for maximum MPG at the desired speed.

Edited 8 March, 201313 yr by Jockdooshbag

I understand that with a DSG and "S" mode (which mine is too) it is all a bit different in that the engine mapping is actually different for S and D modes. In S mode the throttle response tends to be firmed up amongst a few other bits and bobs, hence it will be more aggressive than simply changing down in D.

For the quickest progress, change when the power starts to drop off.

I need a nice long private air field I have worked out that in 3rd and 4th changing at around 4300rpm drops the rpm down to 2900 which is perfect. 5th is different though, it doesn't drop as far in rpm.

Thanks for comments

At 3k rpm it's probably only making around 160bhp. Looking at torque only is fine for slow / static conditions where Newtons basic law of acceleration applies: F=ma, where force is the equivalent reaction of the tyres against the road surface as a direct function of the engine torque. Once the car is rolling, there is a level of power that the engine has to develop just to maintain that speed, let alone accelerate. To accelerate above that speed, the engine has to produce sufficient force to increase the velocity of the car + maintain the resistive drag / frictional forces. At some point, these all balance out at Vmax. Vmax is determined by the max power output (all other things being equal of course), so, if you want to make the fastest getaway, change up at max bhp, not max torque.