twospoons

http://rogerlarsen.home.comcast.net/ratio.html

oh well, nice web layout :P

anyways, I just made this tool to be able to figure out the optimal rpms I should have when changing gears..

Punch in eg. 7500 rpms in the first box, and the tool will calculate rpms on the next gears and end speed at each gear..

you need a browser which supports java script..

/twospoons..

syntrix

You need to do a program that inputs dyno figures. This just tells you what your speed is when you shift at a certain rpm.

There are tools avail on the net for this, but make sure you find one with not just gear ratios, but ALSO final drive!!!

And coefficient of friction, weight of the car, etc etc etc.

twospoons

Do you have any raw dyno data I can look at?..

Anyways, there are some simple physics I could implement…

With dyno data showing power / torque at different rpms I could calculate the time it takes to accelerate to a certain speed, and theoretical max speed.
Wind resistance is easy to account for. The more tricky part is tire friction.
One could assume that you have a prefect grip, and never have the tires spin and do the calcs based upon that.

Another issue I would leave out is the possibility of turbulence at certain speeds / air temps since this factor can be disregarded at low speeds.

With the weight of the car added one can do some pretty interesting power / weight ratio observations.

Does anyone know what the rx8 scored in the wind tunnel?

/twospoons

syntrix

.31 cf, it's on the mazdausa.com website.

There are some excel and online calculators out there that take torque into consideration for the shift points.

I did a quick search one night, and most are for 5speed, and a lot leave out the gear ratios AND final drive.

I'll have to hack one of them someday.

There are dyno plots online here, but don't know if the owners posted the raw data. You could probably come close by guessing what the curve is doing at specific rpms.

wakeech

member Buger looked at this stuff a long long time ago.

basically, the shift up point is at precisely the rpm where you'll have more force at the wheel in the next gear than you have in the current gear. with the current tune of the 13BMSP, this never happens in any gear at any rpm, so let the buzzers ring .

twospoons

Well, the problem is that the HPS flattens out after 7500..

One could argue that pushing the car above 7500 would lead to worse acc.. As long as the rpms in your next shift is above 4k you should be ok.. or?

/twospoons