Check this out:

auto:Math is a utility that helps simplify the calculation of various automotive parameters. auto:Math eliminates the need to memorize formulas and provides numerous categories and groups of calculations. Using a simple interface, just enter the requested inputs, hit Calculate and get your answer instantly. This program is a great tool for any car enthusiast.
Calculation categories include:
-Displacement, Stroke & Bore
-Compression Ratio
-Piston Speed
-Brake Horsepower & Torque
-Indicated Horsepower
-Weight Distribution
-Center of Gravity
-gForce and Weight Transfer
-Quarter-Mile Elapse Time and MPH
-Instrument Error
-MPH, RPM, Gears & Tires
-Tire Sizes and Their Effects
-Average MPH and MPG
The App can be found on the App Store and is priced at $1.99
http://itunes.apple.com/us/app/auto-mat ... 15349?mt=8
Sample Screenshots:
Let me know if you download it and what you think. Definitely worth having.
