calc rwhp pid

[stick100]

if the scan tool is set up propley how accurate is the calc rwhp pid? i know its never going to been as good as a dyno but can it give you a good idea

[joecar]

The pid CALC.RWHP has absolutely no correlation to the RWHP numbers produces by any dyno (load bearing or otherwise)...

when you drive your vehicle down the road, the engine must develop sufficient power to overcome the "friction" (losses due to mechanical, air, tire/road, etc)...

when the engine produces exactly the same power as is being absorbed by "friction" the vehicle speed remains steady...

when the engine produces more than what is being absorbed by "friction" the vehicle is accelerating (i.e. any left over power is being used to accelerate the vehicle).


CALC.RHWP is simply a measure of power left over after "friction" has been overcome, and is calculated simply as m * v * dv/dt (where dv/dt is acceleration).

When the vehicle is coasting down in neutral, CALC.RWHP is negative and is a measure of the power being lost to friction (if you add the absolute value of this to the values logged during acceleration (correlated by vehicle speed) you get a reasonable approximation of FWHP).

[stick100]

thats a bummer i thought i'd hit jack pot when i saw 680hp @6200 lol

[joecar]

thats a bummer i thought i'd hit jack pot when i saw 680hp @6200 lolThat means one or more of the following are applicable:
- vehicle mass entered was too high;
- tires spinning loose;
- accelerating downhill;
- accelerating on a non-loading dynomometer;
- sampling rate on the VSS pid is insufficient;
- your engine makes sufficient torque and/or power to accelerate your vehicle at a measurable 680 RWHP.


If you select a suitable stretch of open road and if you have to pay attention to consistency, you can use the pid for comparing significant mods.

[stick100]

thanks joe