- 291
- Oxfordshire
- Bread_45
I though I'd throw in my 0.02, this is admittedly similar to what others have advised above.
You want to make the best average power throughout the rev range used in a gear. The rev range used depends on when you arrive in that gear from the previous upshift, and when you shift out of the gear. This obviously depends on the gear ratios in your box, and when you choose to shift. You need to know the "departure rpm" when you shift, and the "arrival rpm" which you get when arriving in the next gear.
Highest average power means, when looking at the dyno graph:
i) you want to stay close to the power peak.
ii) you don't want a drop, or increase in power, when you shift.
You can draw lines across the dyno curve to illustrate this, between departure and arrival rpms (see my pics). You want a flat line whenever possible! Literally, as a quick and dirty method, you can go up to your TV with a ruler or biro, hold it straight and judge the revs by eye.
If your power is higher after you shift into the new gear then you should have shifted a bit earlier. If your power has dropped after shifting then you were better off holding on to the previous gear. This is sometimes unavoidable because you hit redline and must shift.
if you are using an adjustable box you can tweak the relationships between the ratios and/or choose shift points. The red and blue lines below show different ways of choosing ratios. Remember they are close to the power peak (they straddle it), and they are horizontal i.e. flat.
Note the "gearing factor" which is the ratio of the individual gear ratios, and also the rpm ratios. I don't know if there is a more professional term for this, but I just call it gearing factor. By adjusting Final Drive you can retain the gearing factor and individual ratios, you just make the whole box shorter or longer.
If you are using a fixed gearbox then you have to make do with the ratios provided, the only thing you can choose is shift points.
Reasons to deviate from the way I have suggested you set up an adjustable box are:
i) GT won't let you choose the ratios you want.
ii) The ratios mean you are shifting part way through some corners, and this upsets the car balance. You can change final drive to compensate, but on long tracks with many corners you will probably have a few corners that aren't optimised, no matter how you set the gears.
iii) In enduro races, if you want to short shift to save fuel.
When tuning, a gearbox which is set well for a track can knock seconds off the lap time. Its usually a bigger effect than suspension etc tuning.
You want to make the best average power throughout the rev range used in a gear. The rev range used depends on when you arrive in that gear from the previous upshift, and when you shift out of the gear. This obviously depends on the gear ratios in your box, and when you choose to shift. You need to know the "departure rpm" when you shift, and the "arrival rpm" which you get when arriving in the next gear.
Highest average power means, when looking at the dyno graph:
i) you want to stay close to the power peak.
ii) you don't want a drop, or increase in power, when you shift.
You can draw lines across the dyno curve to illustrate this, between departure and arrival rpms (see my pics). You want a flat line whenever possible! Literally, as a quick and dirty method, you can go up to your TV with a ruler or biro, hold it straight and judge the revs by eye.
If your power is higher after you shift into the new gear then you should have shifted a bit earlier. If your power has dropped after shifting then you were better off holding on to the previous gear. This is sometimes unavoidable because you hit redline and must shift.
if you are using an adjustable box you can tweak the relationships between the ratios and/or choose shift points. The red and blue lines below show different ways of choosing ratios. Remember they are close to the power peak (they straddle it), and they are horizontal i.e. flat.
If you are using a fixed gearbox then you have to make do with the ratios provided, the only thing you can choose is shift points.
Reasons to deviate from the way I have suggested you set up an adjustable box are:
i) GT won't let you choose the ratios you want.
ii) The ratios mean you are shifting part way through some corners, and this upsets the car balance. You can change final drive to compensate, but on long tracks with many corners you will probably have a few corners that aren't optimised, no matter how you set the gears.
iii) In enduro races, if you want to short shift to save fuel.
When tuning, a gearbox which is set well for a track can knock seconds off the lap time. Its usually a bigger effect than suspension etc tuning.
