Gear shifting at optimum RPM?

[T3rminator]

How do you work out what RPM would be the best to make your gear shift on for the purpose of drag racing?

Would a dyno graph tell you that?

[Aeron]

I could be wrong, but i think if your car makes maximum HP (we'll say 700HP in this case) at say 6000RPM (although it may have a cut out at 6500RPM), you are best to shift at or slightly after the 6000RPM mark. If you shift before, you aren't using all of your 700HP horse power, and you would have less power at 6250RPM than at 6000RPM so you dont want to shift too late.

I think thats right??

[Casper]

Theres a few things to consider really.
The first is where the car makes peak power, the second is the "shape" of the power curve, the third is the drop in revs from a gear change and the forth is the physical limiters of the car.

Example. Lets say you make peak power at 6000rpm and the shape of the power curve is reasonably flat from 5500rpm to 6500rpm befor dropping dramatically. If the gear change will see a drop of about 1200rpm and the cut out is after 6500rpm then I would change at around 6500rpm. This would put the revs back to 5300rpm in the next gear, just before the car's power starts to flatten out. The end goal is to keep the cars revs in the "sweet spot" for as long as possible in each gear. Theres no point changing right at peak power as you will then probably fall out of the sweet spot and lose time. Try to rev past peak power and change, getting the rpm straight back into the power band again.
A dyno graph will most certainly help you see this.

[rodderz]

Both Rod in his pursuit and Chris in his ute have said that they usually changed gears as close to redline as possible, but both said they got PB's when they tried shifting at 5400-5500rpm or so where the peak power is. Makes sense, although there are the points that Casper pointed out, and there are also the matter of diff ratio's. If you're changing for example into 4th gear just before the line you'de probably do better leaving it 3rd so that the gear change time isnt lost

[T3rminator]

Might have to start practicing this friday at calder :

[xdclevo]

Originally Posted by fullthrottle

Might have to start practicing this friday at calder :

Trial and error is the answer. I make max power at approx 6200rpm,
and when i went to the strip i did 12.6 changing at 6200rpm. I tried
6600 and did 12.5 and then tried 7000rpm, and hit the limiter in 2nd gear
and still ran my best of the nite at 12.4.

[Casper]

Originally Posted by xdclevo

Trial and error is the answer. I make max power at approx 6200rpm,
and when i went to the strip i did 12.6 changing at 6200rpm. I tried
6600 and did 12.5 and then tried 7000rpm, and hit the limiter in 2nd gear
and still ran my best of the nite at 12.4.

I think with a high end clevo with monster torque the rules are probably a bit different as you can use the stump pulling torque to power through. With the I6 and 5.0 V8 it doesnt have that bulk torque to get away with that sort of style.

In some ways the old rule of "no substitute for cubes" still applies.

[MITCHAY]

Ive never gone to drag strips or anything but ive always been told you shift after your peak power to fall back on your powerband when you change gears. Its pretty practical because whenever you change gears you drop revs.

My mate said rev between 500-1000rpm after your peak power so you will drop onto your power band when you shift although i dunno how correct this is.

[jonbays]

Well the best way would be to plot up your dyno rear wheel power against all your gears and speeds and you can see where the car would have more rwkw in the next gear exactly. Shifting it exactly right without a shift light would be a bit harder.

In a modded falcon six I can tell you its simple just change as close to the rev limiter as you can without hitting it.

[SpoolMan]

Originally Posted by fullthrottle

How do you work out what RPM would be the best to make your gear shift on for the purpose of drag racing?

Would a dyno graph tell you that?

your factory limiter is 5850rpm its hard trying to beat the hard cut, so you will have to shift early..
if you have a custom dyno edit tune, you can see whether your engine is making power past the factory limiter, shift it where its making its peak power...

[brenx]

I found with mine changing gears prior to max power worked better. I made max power @ 6600rpm. I was changing gears @ 5800rpm. Over reving the engine wasn't necessary. Reving higher resulted in slower times.

[QUIKXR6]

hi guys....i am making peak power up and close to 5000rpm my rev limited cut off point is 5600 now with the el xr6 ecu in my 6 cylinder xr...i have been shifting gears as close as possible to the rev limited cut off point which is around 5550rpm or close.... i managed to get my quickest times doing that....for example....if i rev out my first gear all the way i reach 60k's...when i change gears 2nd gear goes upto 100k's and 3rd is around 150k's...when i rev out the gears to the max...i manage to pickup at a higher part of the power curve in the next gear and therefor it achieves a quicker ET....i think it also depends on ur mods...my dev5 camshaft makes power all the way upto and close to the rev limited cut off point...

[jonbays]

Frank is right in the Falcon six rev it to just before the cut out its quicker.

V8's have a different torque curve and most benefit by short shifting and winding out hard in the high gears.

[ratter]

You also have to remember that the tacho may be a little slow to read exactly what the rpm's are at. ie the motor may be at 6000 but the tacho may still be on the way to that point and only show 5800 or 5900 rpm

[Aaron_EF8]

If you have a bit of time, and a G-tech Pro, you can map the acceleration out in each gear, then you compare where each gear drops off, and the next gear overtakes it.