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Originally Posted by 986Jim
You guys can do all the math and internet jibba jabba you want, but the fact of the matter is you always shift at the highest RPM you possibly can, no matter what your torque curve looks like.
The engine accelerates faster at it's highest RPM regardless of HP. Your car will accelerate faster if you shift at redline even if your power is down lower. Talk about physics and engineering all you want.
When the lights drop the BS stops, and if you don't shift at redline your in second place. PERIOD.
Here is the dyno plot from my Dad's Maxima that he drag races. It has a VQ35DE in it (350Z motor) and makes a maximum of 259whp and 239ft/lbs of torque normally aspirated at the wheels (this isn't the max dyno plot just one of them I snapped. The car has cams and torque convert and headers etc few trick and stuff.
Look at the HP and torque curve. That says you should shift at 6200rpm. When he does that the car runs 13.3 @ 100mph or worse. When he shifts at 7200rpm as indicated on the dyno, the car is faster, best now 12.8 @ 106mph. Almost a half a second and in terms of racing thats a long time.
Acctually this dyno before I tuned the car (emanage ultimate) made 236whp and 219ft/lbs of torque. We picked up 21hp peak with my tuning. Between 6000-7000 power was dropping below 180whp and with timing and air fuel tuning I bumped it to what you see there. I made 60whp extra between 6000-7000rpm over stock with my tuning tricks on his car. It should run a 12.4-12.5 now I would think with 60whp extra in the top rpm range.
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I really hate to argue with this statement because it's been covered already, but it's not correct. You could have an engine who's torque curve drops off dramatically after peak due to breathing issues or two gear ratios that are very close to each other and it would be beneficial to shift before redline.
Just looking at a horsepower/torque curve DOES NOT tell you when to shift. IT DOES NOT TELL YOU WHEN TO SHIFT! You have to look at gear ratios and speeds in gears, just as I've done for you guys.
Typically, however, you happen to be right, but without understanding why this is true, you won't always be right.