OK this may sound stupid…but… for instance…on my 06 gti with apr tunning, its making the most horsepower at about 4700RPMs. after that its pretty much flat untill redline. So my question is, in a race, i should shift at about the 5K rpm mark becuase basicly reving past that would be pointless as the engine wont be making as much power as it would at the 4.5K-5K mark.
get a dyno graph, do calculus, determine maximum power under the curve
:tspry:
the key to this is where you make the most power near that 4700. usually, shifting a few hundred rpms past your peak hp will then drop you back into similar power of the next gear on its way back up to peak hp. if you make power until redline and shifting puts you back near your peak, it is better than shifting near your peak and falling out of the power on the next gear. all depends on your power curve and gearing
wheres your max torque happen? for instance in my old car redline was 6600 and thats where the max horsepower was and max torque happened at 4500 or so so as long as i shifted high and keep it above the max torque i knew i was doing good…
another case:
my daily beater makes a whopping 70 hp at 4500 and 90 torque at 2800 redline is 6000 i rarely go over 5k cuz its pointless, because power goes down like a rock…
in your case if your horsepower stays flat and doesnt drop off then you should keep on the throttle till the gear is done…just my opinion why shift and lose time when you can stay in it and have the same power at 6k as you can at 7k it would be a wasted shift and time, unless your power falls off, then shift where the power falls off on the curve.
TUNNING!?!?!?!?!
Exactly.
With a dyno & Your gear ratios You can figure out the best shift points for almost anything.
Shift points can also be determined by feel.
If the car stops pulling above a certain RPM even tho it isn’t the redline, then go with it. Redline in most cases doesn’t = shift point.
yeah in my Porsche, the tach was really strange because it had a reverse-sweeping motion (the best way to describe it is take a conventional tach and turn it upside down and backwards). point is that i could never get used to looking at it, so i would alwaus just go by feel. there was also some stupid little light that came on when it would ‘recomend’ that you change gears and it was annoying as hell to me. just my .02
Lower gear ratio / higher gear ratio X RPM at peak Torque = Shift RPM
You can’t granny shift and you have to double clutch like you’re 'sposed to.
But yes firehawk is right. You can pretty much feel where the car is not making is power anymore so you just shift at that point.
Sometimes it is better to stay in gear past peak horsepower as shifting wastes time.
In other intances it is better to stay in too high of a gear, not downshift, and fall out of the power band.
For example my lap times only improved ~.5 a sec when I would downshift, rev it out and upshift. Considering engine conservation, gas conservation (for endurance racing), and the possiblity of missing a shift it is sometimes better to stay in the higher gear and be a little down on power.
GOod points. but when do you hit the noss?
I guess the question would be if your on a track or simply dragracing.
Yes some of the time on a track you will leave it in the “wrong” gear because traction > max power depending on where you are. as in cornering or in a strait.
yea…i learned when i went to the dyno my car makes power from 4500 all the way to 7000rpm…but the torque curve starts to drop at 6000rpm…so why bother using 6-7000 rpm range when i can shift and get righ tback to higher torque again…go to the dyno
As was stated, to be sure you need to plot out torque to the the wheels in the different gears v. rpm to determine optimum shift points. But in general, for the ratios in street cars, taking it to redline produces the best acceleration. That’s for a manny tranny or an auto with a street type converter. A drag race car with a high stall converter may be a bit different. I just did the calcs for a friend with a drag car with a 4-speed with “wide” ratios (similar to street ratios) and that’s how it worked out.
Rich
i have a similar situation with a much slower car
where my power starts to drop at about 5600-5700…i usually shift right about 6k…now with the addition of my new intake manifold it will make power all the way to 6800 but thats in the future…my torque starts to srop at about 5k but then hp takes over to keep the boat somewhat pulling
You had a 944 didnt you? Because if it was like that, it was wrong, and some stupid 80’s 911 owner fucked with it.