I know this is a subject that will have many different views. I want to know what you all think. Is it better to shift at Peak HP, After peak HP, or where the torque and hp cross? The conversation I was in sunday was that you want to shift when they cross that way you have peak torque at the wheels after the shift, with this in mind you will get to peak HP quicker because torque falls off while the HP increases rapidly at this time. The other thing is shift at peak HP, this way you shift into the power band where the HP is climbing the fastest and torque is falling off. Lastly shifting after peak HP. This puts you at a higher HP when you shift into the new gear but lower torque. I can see the logic behind all of them, but I am not sure what is the best. What are the thoughts of some of you who have done more racing than I have???

Shift at the redline, while all those arguments work they fail to take into account the transmission, while you may be shifting at a point where power is dropping off in say 2nd gear, the power is multiplied to the transmission gears, then again at the rear end gear, and again at the tires. So while you may not be making the most horespower, you are going to be putting the most power to the ground. If you shift early you might be in the peak RPM, but the multiplacation factor has dropped as your now in 3rd gear @ say 5000 RPM rather than 2nd at 6000 RPM.

If 2ns gear was say a 2.5:1 gear, and third being a 2.0:1, and if your making 350 HP @ 5000, and 340 @ 6000, doing the math,

2.5 * 340 = 875
2.0 * 350 = 680

We see that there is more power put down in the lower gears. So while you may not be in the peak power of the engine, your still putting down more power than you would be if you shifted to the peak power in a higher gear.

But remember, it's power (torque and HP) that you are trying to maximize and your torque curve may drop off quicker, causing you to actually put more power to the ground in the higher gear.

To answer the question - ultimately you should run a dyno, then plug all the numbers into a simulator that will give you optimum shift points. then you really should figure gage lag out and shoot for a point right under that optimum to take that into consideration.

BUT - given the relatively flat torque curve of a near stock LS1 - Nocturn is right - shift right before redline and you are going to be all good.
Dan

That is what I thought at first. I have been reading some articles about how to determine the proper shift points. What it has come down to, is they recomend shifting at the rpm that allows the smallest difference between torque outputs. For instance, you should decrease the change in torque between gears for best performance. So going to redline and say 310 ft.lbs and shifting, bring rpm to about 4300 and say 350 ft. lbs is not better than shifting at 4500 with 320 ft. lbs going to 3500 rpm with again 320 ft. lbs. Please keep in mind these are numbers grabbed out of air because I have forgotten what the exact curve looks like. I read that to find the shift point, take the higher gear ratio at tranny, divide by lower at tranny, and multiply by peak torque rpm to get the sift point. Does this sound close?

Best thing to do is try different combos until you discover what works best for your car and tires combined with your driving style. Personally, I usually shift at peak HP. This is generally a few hundred RPM before redline. This allows you to drop right back into your high torque curve. There are a couple other advantages of shifting before redline too. Such as lower RPM will help engine longevity, plus allows a little room for driver error. What I mean is if during the excitement you shift a little late, then you aren't bumping into the rev limit yet.

If you were to shift where they cross, every car made would be shifting at ~5200 as that is where they all cross. Ideally you want to shift a few hundred rpm after peak HP. But you also have to take in affect gear spacing. LS1's typically like 6K shift points. Power peaks earlier but is pretty flat and doesn't fall off as fast as most cars. Shifting at 6K brings it back into the peak torque again.