ISP of my car?

[MrChumley]

I was just wondering if calculating such an equation is feasible? What is the ISP of a geo-metro compared to a hummer? How about one of those new hybrid cars? How about a Alcohol fueled drag racer?

[stupid_chris]

ISP can't be calculated for a car as a regular gas engine doesn't work the same way as jet or rocked engines. Your everyday's car engine consume fuel to make tires spin, while jet and rocket engines expel the fuel at high velocity to thrust themselves forward. And exhaust velocity is an important part of ISP calculations. So no, you can't calculate your car's ISP. There's probably other ways to calculate it, but not this way really.

Additional info

[Mr. Scruffy]

Okay, another one (since we are at it): What about the mentos/coke-drive? Say one mentos, 0.2l of coke, a container of the same volume with an opening of 0.5cm²?