In my constant pursuit of turning this little car into a competitive racer, here are the speed vs rpm ratios for the OEM gear ratio and the modified differentials I have found on the aftermarket.



https://www.crossfireforum.org/galle...cat/500/page/1

 

Hey I'm curious to know, since you'll be running higher RPMs, what are you going to do about the mileage on your car? It's going to get messed up and say you have way more miles than you do. I even noticed this on my old car just from changing the tire size, it added about 2-3% more miles.

 

One of the many advantages to modern technology is that the speedo is adjustable via computer interface. It's ajusted all the time on newer cars. A good mechanic / tech can do it in five minutes...

 

Njspeed:
You can also check your proper speed easily with a hand held GPS, they are really close. If you are out some mph, do as HTTP suggests and see the dealer.

 

Bob G: I think NJ Speed was wondering what to do with re-calibrating the speedometer when the final gear ratio is changed the speedo would be off... And, in order to recalibrate it can be done based on the gear change at the dealer. Pretty simple with the darn computer interfaces they have for these cars.

 

HTTP: Yeah, that's what I thought to. What I meant was, if he wasn't sure if the speedo was now right or not, a quick drive with a hand held GPS unit would tell him. Myself and alot of my buddies have GPS's as we are fishing nuts and use them all the time. If there was no change, it would save him a dealer trip. The GPS units today are really accurate, mine will tell me how fast I walk. Amazing ain't it?

 

Bob:

There will be a change in the speedo with the final gear ratio change. Mathmatically it should be the percentage of change vs. the original ratio. For example, since our car is currently geared at 3.27:1 and you install a new 3.69:1 differential the percentage of change is 13% which means your speedo would read 13% faster. The same would hold true if you put smaller wheels on the car.

The speedo is calibrated for the current gearing and wheel size and can be recalibrated very easily by a good MB or DC tech / mech.

PS: I have found a 3.69:1 MB pumpkin that will fit the Crossfire and am waiting for delivery.