In Reply to: GTech posted by Chuck on January 09, 2000 at 13:24:20:
: I measured 219 RWH and thought it was incorrect. I went out last night and made a couple of passes and they avg about 230 RWH. I'm starting to believe this silly thing. All my measurements of other cars has been extremely accurate. I'm so surprised that I'm seeing these numbers from a stock 98 M3. Has anyone else seen sim results?
G-tech "measured horsepower" is dependent on atmospheric conditions
(air temperature, barometric pressure) and
actual vehicle weight.
You can get above "factory spec" numbers simply
by having favorable atmospheric conditions. A
real chassis dyno corrects for this. For example
I dyno'd my E30 M3 and had a correction factor
of 0.94, meaning that the measured HP figures were 6% higher than standard atmospheric conditions.
(it was a cold, high pressure day).
Also, if you don't know the exact weight of your
car, including gas, driver, and any stuff inside,
the measured "HP" will be off accordingly. A full tank of gas is about 4% of the M3's weight. The
driver's weight is an even bigger variable. If
you ignore these factors you will have optimistic
The G-tech might be useful to compare mods, but
only if atmospheric and weight conditions are properly accounted. You can burn a lot of gas
doing acceleration runs, and the temp changes
throughout the day.