Gear change calculations

[Magpie]

I have put together an excel file to calculate gear changes based on the data I have on my engine, especially the torque dip at 5,500. I need to make sure that any gear change is done so that the revs don't drop below 5,500. Based on the current configuration this is not possible in first. It would appear that the only way to 'fix' the issue is a custom gear set and this is not on my list of things that I want to do. So I just need to time the gear change etc.

1st - 8,000 = 57 kmh (revs drop to 5,000)
2nd - 7,500 = 89 kmh (revs drop to 5,500)
3rd - 7,000 = 114 kmh (revs drop to 5,500)
4th - 7,000 = 150 kmh (revs drop to 5,500)
5th - 6,500 = 175 kmh (revs drop to 5,500)

If you want to use the file you will need to know the HP of your engine at least every 500 rpm. It also includes some of the common gear set ratios as well as the ability to change final drive ratio. Just make changes in the orange coloured cells B3:B10 and H3:H15.

If there is an error please let me know and I will correct it. However from my data logging I know the RPM, Gear Ratio, Final Drive, Tyre Circumference comes close to the speed calculated in the file.

[MattR]

Or use this......As attached
Gear calc is great and I have used it for a lot of my cars that see track time or have had different gearboxes and diffs put in them, like my Charger.

Mark, this will probably be easier for you as you can play with ratios etc and the outputs give you what you need at 10km/h increments.

Out put is .txt files. i have files for the Zed for slicks, wets and semis in various sizes and the 200SX for various diff ratios and also tyre choices. Under the tools there are a variety of standard gear sets to choose from as well as inputting custom ratios for what if scenarios.

[Magpie]

Thanks MattR I will have a look at it!

[oztrackdays]

Spend 4k on the gearbox or spend another few thousand getting more poke ?

If you rarely drive on long tracks then you could consider the final drive ratio.

[Magpie]

Plan is to live with it, final drive could be changed anyway because it will never reach the calculated max speed in 6th.

[16bit]

i suggest adding a turbo.

[Magpie]

NO TURBO and no more mods! I want to enjoy the car and get some seat time in it.

MattR, your progamme is a lot neater than my excel! My only issue is that I need to avoid the torque dip at 5,500 and Gear Clac works on Max Power and if I use its suggestion and change at max power (7,592 RPM) I'll drop below on 2-3 and come very close on 3-4 but all in all it is very close to what I calculated (manually).

Now I need to look at QR and Lakeside and work out the gearing for corners and start running it in my head. For arguments sake turn 1/2 at QR at 130 I should be in 4th however below 120 kmh I'll risk being in the torque dip.

[project.r.racing]

doubt you'll chagne from 1st to 2nd more than once, so dont worry about that change.