Contour Enthusiasts Group Archives Forums General Dyno and Drag dyno science

I'm curious, and don't know much about this.. yet

Has anyone ever dyno'd multiple times _without_ making changes? say on the same day, or perhaps like a week later?

There is a point to this question...

yes, results vary. graph can vary too depending on what happend during the run. its just a measuring tool, subject to error like anything else.

Sure have. With my most recent runs, there were 2 done right after one another, several times. The first run of the 2 was always higher by typically 2 HP & TQ due to the intake being warmer on the second run. The car was then turned off, a fan placed on the engine for about 10 minutes, then 2 runs done again - with the same HP & TQ spread.

That sounds pretty reasonable. Any feeling for how well the temperature/atmoshperic pressure compensation works?

EDIT: Also, is there any sort of standard or reference that these things are calibrated to to ensure some sort of consistency from one shop to another?

AFAIK, Dynojet uses the same correction factors on their machines, so as long as you stick with Dynojet, city to city, you should be consistent. I'd imagine other dyno makers would do the same. As far as temperature and that it's tough to tell a difference, but if I was to comment, I'd say I may have gotten (and seen) better numbers in the summer, meaning the correction factor would be overcompensating ... but by only maybe 2-3 HP.