The importance of a good Scantool
Hi all,
Just thought I'd give you a screen shot demo of a feature in the EFILive scantool that we believe is only available in EFILive.
We have created some special PID's that not even the GM dealers get with the Tech2!!.
It allows you to monitor all the parameters that make up the final spark timing values. The results are interesting......
The first screen shot shows a cold start on a cammed LS1.
Things to look for -
1 - Scan Spark, this is the timing figure you see reported by all other scantools.
2 - Base Spark, a special EFILive PID, this is the timing value the PCM has read from the current timing map it is using (eg, High Octane, or closed throttle in gear, etc).
3 - Cat Spark, a special EFILive PID, this is the amount of timing the PCM is subtracting from the base timing figure for Cat Converter lightoff. Unfortunately GM changed the code for spark summing over the years and some programs 'subtract' the timing figure from the base spark (like this example), others 'add' the timing figure, in those cases the values in the Cat Converter Lightoff table would be -6, -2 etc, not positive numbers.
4 - Idle Spark, a special EFILive PID, this is how the PCM attempts to control idle speed using timing (it adds and subtracts timing).
5 - Also shown but no values are being used are the special EFILive PID's - ECT Spark, IAT Spark, Trq (Torque Reduction) Spark, Bst Konck (Burst Knock) spark.
6 - Run Spark, yet another special EFILive PID, this is the final timing figure the engine will see once all corrections have been applied.
So from this image you can see with any normal scantool you would be seeing a timing figure of approx 14degrees, you would then be asking yourself, BUT, i have over 20 degrees in the timing map it is running in!!.
Now, using these special PID's you can see the reason why....
Base Spark = 23.3degrees.
minus Cat Lightoff retard = 23.3 - 10.2 degrees = 13.1degrees
plus Idle Spark = 13.1 + 1.2 = 14.3degrees
Well, well, there is our actual timing value (Run spark).
Unfortunately the spark sums are calculated alot faster than the scantool can grab data from the PCM, so you can see differences of 0.2, 0.4 degrees in the final result simply because a parameter was updated faster than the scantool could grab it.
In any case, it just opens up the window to exactly what the PCM is upto......
But wait there's more, we have in development some more special PID's just like these that will help take the mystery out of Idle and Fueling.
Cheers,
Ross
Of interest here's some other shots from the same car -
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Originally Posted by GMPX
