So there's a lot of calculators out there that will let you punch in a speed, your tire height, axle ratio, and transmission ratio, and it'll spit out what RPM your engine will be at. Which is handy, but it doesn't allow you to see what's going on around that speed. So I decided to throw up a spreadsheet in Excel that would allow me to see what RPM my engine will be at in a given gear at a given speed. Here's what it looks like:
The speed goes out to 150 MPH and there's six gears for those who need it. There's also provisions for idle and redline RPM. Basically, you just punch in your tire height (in inches) and gear ratios. For this, just enter the multiplier part of the ratio (so if your rear axle ratio is 3.23:1, just enter the 3.23. Same thing for the transmission ratios.) When you're done, it'll display what RPM your engine will be at in a given gear at a given speed. In this screenshot I have my setup plugged in, which has the ratios for an A833OD plugged into it.This helped me visualize how my car will behave when I have the new transmission in (I did not expect 2nd gear to wind all the way out to 85MPH!).
You can tweak everything to see how a change in tire size or rear axle (or a new transmission) will affect how your car behaves and performs. I hope you all find some use or at least entertainment from this! Here's the download:
Dropbox - Ratio Chart.xlsx
The speed goes out to 150 MPH and there's six gears for those who need it. There's also provisions for idle and redline RPM. Basically, you just punch in your tire height (in inches) and gear ratios. For this, just enter the multiplier part of the ratio (so if your rear axle ratio is 3.23:1, just enter the 3.23. Same thing for the transmission ratios.) When you're done, it'll display what RPM your engine will be at in a given gear at a given speed. In this screenshot I have my setup plugged in, which has the ratios for an A833OD plugged into it.This helped me visualize how my car will behave when I have the new transmission in (I did not expect 2nd gear to wind all the way out to 85MPH!).
You can tweak everything to see how a change in tire size or rear axle (or a new transmission) will affect how your car behaves and performs. I hope you all find some use or at least entertainment from this! Here's the download:
Dropbox - Ratio Chart.xlsx
