G-Force

[killerbee]

dx({SAE.VSS.kph},2)/35.28

this formula yields a fairly jagged logged response. I suspect sampling rate may be to blame. Anyone use something more useful? Can I use the same functions that exist in Excel to dampen the response?

[joecar]

Sampling rate is to blame.

Windshield attached g-meters use a sampling rate of 100Hz or higher.

The raw rwhp to accelerate vehicle is: m * v * dv/dt ...appropriate constants are required for making units match.

dv/dt requires a high sampling rate on v.

[killerbee]

I am not clear on what I can use. The rate of velocity change is as good as any, don't really care about units. I am using it as a PID to evaluate constant throttle smoothness.

What is dx in the formula above? Where is "x" defined?

....and thanks for the help.

[joecar]

In EFILive, dx is shorthand for dx/dt which is the rate of change of x wrt to t (i.e. the slope of function x(t)).

In dx({SAE.VSS.kph},2) x is SAE,VSS.kph.

[killerbee]

would some kind of trailing average smooth out the response?

I am just trying to think of how to make it useful.

[joecar]

Yes averaging would smooth out a signal.

The EFILive scantool supports this function (see page 93 of the scantool pdf):

damp()
Syntax: damp({PID},frame_count)
Arguments: {PID}: a PID name; frame_count (optional): an expression.
Return value: The average value of {PID} from the current frame-frame_count to the current frame.

You might go like this: damp({SAE.VSS.kph},8) or damp({GM.TP},16)

[killerbee]

very nice. :) I will give this a try.