hitting max torque vs max HP and shifting...
 

My brother in law are in a friendly discussion that goes something like this:

He says: For a 1/4 mile track, you will go slower (time not speed) if you red line/shift your car for each gear vs shitting when you hit the max torque for each gear.

I say, both need to hit their max during each gear, no matter which one, torque or HP hits first vs second.

So is there any logic in either opinion? This conversation started after we saw a dyno graph for a 2021 ZL1 that showed the below and he said "that guy needs to find the max torque for each gear and shift at that rpm!

max Max Power = 715.62 @ 6659rpm and Max Torque = 696.51 @ 4443rpm

I also am shitting when I hit the max torque for each gear... lol

You will absolutely go far slower shifting at 4500 rpm, do it on the street and see how it feels for yourself. The next gear will be trying to come back up from probably 3,000 rpm, that's far from performing to its potential.

I believe that argument is about hit max torque in the gear you are shifting to. So you start that pull in that gear at max torque.
This may apply in the 1-2 shift.

You shift at the right rpm in 1st so you’re at peak torque in 2nd.idk I alway just wring it out.

This might work on the 1-2 or 2-3. Prob would have to test it out.

18.2SS.1LE & 6spd... interesting info. I'll get the dragy app and give it a try !

Torque is to get you moving...once moving you want to stay up in peak power to accelerate the fastest.

Here's a good way to test it out. Do 1 run shifting at your max torque, let's say 4500 and then do another run shifting at max HP, let's say 6600 rpms.

I bet you'll have a faster time AND speed during the 2nd run.

You’ll be slower shifting at max torque because the torque sent to the rear wheels is lower than the torque sent to the rear wheels at a higher rpm and lower gear—the lower gear multiplies the torque. Horsepower, or power, is the amount of work done over time. Torque is just a force. So hp wins races because it’s work over time—more power equals more work over the same amount of time. Torque feels fast in a short time frame but may not actually be that fast.

But it’s also true that for a given gear your car will accelerate fastest at the torque peak. Eg. 3rd gear will accelerate faster at 4500 rpm than 6000 rpm when the engine torque has begun dropping off.

Most cars accelerate the quickest shifting after the hp peak.

The torque multiplier effect for each gear drops when you upshift. So the power put to the ground through the rpm range up to redline in that gear exceeds the power put down in the next gear. If you want to go fast and quick you shift as close to redline as you can.

Good info above! So with out me knowing the physics involved, I feel I was on the right track. Hit max HP and shift. I guess it would take a dyno graph for each gear to know your cars max HP for a 1/4 track run (1st - 3rd or 1st - 4th). But good info, good discussion!

I've not considered a trans tune yet. But is this why they are actually really important or not?

Thanks

Just follow GM's OEM logic. 1st gear shifts 300 RPM early. 2nd gear shifts 100-200 rpm early. 3-4-5-6-7 shift close to redline.

This is how you go the fastest. Don't overthink it.

Actually, horsepower is not work done over time, it is the rate at which work is done. You will always accelerate most by staying somewhere near peak torque. Horsepower, on the other hand, will limit your top speed on a track of unlimited length, where you are not accelerating but overcoming drag.

Power is literally work divided by time in physics. For example, 1 Watt = 1 joule/1 sec. Joule is work and is defined as the force over a certain distance. Divide that by time and you get power (Watt). Watt converts directly to hp with a simple multiplier. Rate implies a given time frame, often 1 second. So with more power means more work done in the same amount of time, like I already said.

And I also already said FOR A GIVEN GEAR you will accelerate fastest at torque peak. However, when there’s a lower gear available that multiplies the torque more than the torque has dropped at peak power it will accelerate faster, so for a car with gears, it will be fastest shifting at or beyond peak hp.

How do you think low torque/high revving cars accelerate quickly? Low gears that allows them to get into the power band.

Look at it this way: if torque won races then the ZL1 would pull away from a GT500. But it doesn’t. Above 60 mph or so the GT500 accelerates quicker.

ZL1 is 240 lbs lighter and has 650 ft lbs of torque vs 625 ft lbs in the GT500. Difference is 650 hp vs 760 hp.

Similarly, a GT3 RS has about half the torque as a ZL1 but 83% of the weight, yet it is about as quick as a ZL1 in a straight line due to gearing taking advantage of the high revving low torque engine.

Average horsepower is what makes them fast.

Shifting ~500rpm after peak power will typically result in the highest trap speed.

Every combo is different. You can get close with a dyno but testing at the track or with a dragy are what actually matter.