Agree on all points - although in my experience the error is probably more like 1-2%. I know that may sound low but it definitely follows my experience. I've organized many dyno days at many different locations and have been witness to hundreds of cars being dynoed, many cars I knew and saw dyno at other places. Cars making 410hp to the rear wheels would generally be from 408 to 412... the 5% number would be 20hp, and I never saw that much variation other than dynoing a car that was at room temperature right after it was started, vs. dynoing the same car when it was totally heat soaked... and even then the difference was generally 10-15hp at most. Just my experience... of course all cars will react differently when heat soaked, so 5% is probably a generous number that encompasses the full range of error. Good post.
Well Mike I need more data. There are just too many variables and I don't like the way I have gotten different results from the different dynos. I think a 19 HP RWHP difference (7%) between machines is pretty significant. Well maybe not. All I know is that I use my Dynojet to measure changes due to modifications and that is all. I don't care that a Mustang will show different numbers unless I want to be bragging about what a modding, tuning stud I am.
do a search on: dynojet vs mustang dynos. there are some great reads out there peppered in with the average knucklehead here and there though.
