Finding your shift point with dyno printouts

[MechaniX_034]

In response to the "where should I shift" thread, I decided to put this one up. For the price of a dyno pull, you'll be able to tell where you should be shifting. Every car is different, and even fully stock the peak power or torque might occur a bit sooner or later. The curve might not even be completely identical. The curve may be effected by altitude, fuel as well as engine wear. Or a combination of all three, if you discount modifications. This is the reason I would encourage a dyno run for those who are looking for their very own shift points, relative to their own cars and sets of modifications.

Righto.

That should explain everything. Now, basically there is a dropoff behind peak power(this is the graph off of an R6 BTW, not off of a car. Its pretty textbook and its all we need for this demo.) There isn't a reason to go past the shift point(here at approx 12,800rpm) because you are not making any more power(you will be stressing your engine needlessly and actually losing your forward motion) Thus, shift at peak power or just after it(to compensate for rev dropoff at the time the throttle is lifted)

[el kabong]

this article has a different approach, and says that the transmission gear ratios must be taken into account, and when you do, it usually makes sense to shift at the redline:

'Not all cars should be shifted at the redline for maximum performance. But it's true for many cars. You can determine optimal shift points by graphing ... transmission torque vs. RPM. Engine torque alone will not determine shift points.'

Horsepower vs torque

i'm not sure how to apply this approach to a japanese sport bike cause their dyno is so much different than a car (the bike is all horsepower and little torque)

[MechaniX_034]

The dropoff is still evident in the graph; even if you're in 5th and at WOT, you'd have to note that the torque dropoff still occurs. When this happens, you generally are no longer accelerating. Its also harder on your engine.

However, it depends on the course as well; sometimes you need to pull past the peak torque/hp point in order to get a better exit(some corners are diliberately set up to muck around with your gearing ie. the big W at Winton Raceway)

[trev0006]

nice graph