You're the king of the road. You think you're the fastest thing on four wheels. You know how to launch a car with a manual gearbox to accelerate the fastest, but do you know when to shift? Jason Fenske from Engineering Explained is here to drop the science about shifting to make sure that you have the facts.
Fair warning, this is going to involve math. The best way to go fast is to make sure wheel torque is as high as possible. That means your next shift should occur when engine torque has dropped far enough that the current gear is no longer providing that torque advantage. At this point, you need to shift to the next gear to keep things moving as quickly as possible.
This happens for most cars at redline, which seems to make sense to the average person. Jason is not the average person, and he explains what can happen in cars with close-ratio gearsets or lots of gears.
So if you really want to know the best time to shift for the fastest acceleration, you're going to need to know what your horsepower and torque curve looks like, as well as what your your gear ratios are, where your car redlines, and your final drive ratio. Then you need to do the math.
It's always the math...that's the part that's no fun. The rest of it certainly is, though.