Joe (zyxt)

Is there a "proper" way to use a G-tech to measure horsepower? It just occured to me a few weeks ago as I was watching some cars doing dyno runs. They always appear to do dyno runs in 3rd gear. Should I do the same with the G-tech?

And why 3rd gear? I'm guessing it is because 3rd gear on most cars is closest to 1:1 gearing ratio. Alternatively, if someone has a car where 4th gear is 1:1, should 4th gear be used on the dyno rather than 3rd?

Augie

In the lower gears, you lose a lot of acceleration (and thus measured power) due to engine and drivetrain inertia. In the higher gears, you lose acceleration, and thus measured power, due to escalating wind (and, to a lesser extent, rolling) resistance. I'd expect measured power to show higher values in third rather than first, but not necessarily higher in fourth than in third.

The key will be to measure in whatever gear, over whatever speed range, on whatever stretch of pavement, and after you make a change, do it exactly the same way again, in similar weather conditions.

The value is in the comparison (I.E. - measuring the effects of a change) - not the actual numbers.

Joe (zyxt)

I'll just duplicate my previous runs for comparison sake. I'm comparing my previous chipped K03 to my new K04. I should be able to at least see some noticeable differences.

But what about dyno runs? That removes the whole wind resistance factor. Why do dyno runs always get done in 3rd gear? (At least all the runs I've seen.)