Harry's GPS Suite Forum

This is something I never really thought about that much but the ideal shifting point varies depending on the gear you are in and your engine's torque graph. While most people I know (including myself) shift somewhere at the power graph peak of their engine the ideal point might actually be lower the higher the gear is based on the fact most engines have more torque at lower RPMs (especially NA engines).

Here's my feature request:

Either add to HLT the ability to calculate that ideal point (I think everything needed already is in HLT: gear ratios, wheel sizes, power and torque figures...) and for example display a green shift screen

or

at least add the ability to manually add such shifting lights for each gear.

What do you think, useful?

Do you think it will make a lot of difference? I thought about allowing users to defined the torque curve (e.g. by defining 4 base points) and add some more intelligence for both up and down shift indicators based on this curve.

Once you start making this more sophisticated than the current implementation, it makes probably sense to analyze it completely. A good shift point depends on your current state, the near term future (further accelerating or braking), and the engine situation you will get to after shifting... But again, I'm not sure this is worth the effort... The best source would probably be the automatic transmission logic from a recent sports car... Next step would be to anticipate the future from recorded reference laps

- Harry

For maximum acceleration, you want to shift at the point where the acceleration in the higher gear is about the same as in the lower gear. This will always mean you shift past the torque peak. How far past depends on how fast the torque falls off with rpm. My car has a very flat torque curve with peak horsepower only about 200 rpm below the red line. So shifting just before the rev limiter kicks in is optimum. My previous car had a torque curve that fell off a cliff about 4500 rpm. The optimum rpm for shifting was then a function of the ratio of the lower to the higher gear. You went to the red line in first and shifted at lower and lower rpm with each gear change. In theory, you should be able to look at the lineal acceleration curve for straight line acceleration and see if your shift points are close to optimum, for maximum acceleration anyway.

Or you can plot torque curves in each gear as a function of speed rather than rpm and see where they overlap. Remember to multiply the torque by the transmission gear ratio. The rear axle ratio and the tire size are not important as they don't change.