For people with an aptitude for audio electonics there is an amazingly accurate method of measuring changes in horsepower. It does this by measuring the exhaust beat frequency over a constant acceleration course. You can achieve precision of <1%. Do a search on Home Dyno. You need a digital recorder and their program to analyze. This seems to be the most accurate (cheap method) for same car comparisons to determine whether performance mods have an effect. It does not do car to car comparisons very accurately.

[Edited by Lou Nielsen on 04-05-2001 at 01:45 PM]