[Diy_efi] Effect of detonation on measured mixture?

Shannen Durphey shannen at grolen.com
Sat Apr 27 02:45:31 GMT 2002



Shawn Fogg wrote:
> 
> Bruce,
> 
> "> I haven't had any non-detonation misfires so I do think my ignition system
> is working fine at the level I'm running.
> 
> Well, without anything to compare it to, how can you say that?."
> 
> The DME measures acceleration of the crankshaft between cylinder firings and will trigger faults, which > pinpoint the cylinder, if if detects an acceleration difference between them due to a misfire. 

I venture to say that the DME only detects misfires which produce excess exhaust
emissions above the maximum allowed by law, and that it only lights the malfunction
indicator lamp if the misfire is severe enough to cause catalyst damaging emissions.

Amd about the pinpointing:  If there's a trouble code for "random cylinder misfire"
then the pinpointing strategy needs to be sharpened.

You should, in the pursuit of knowledge, record changes in crank acceleration (they
are considerable) over a period of time.  Pick an rpm range and stay there (idle is
a great place to start : ).  View the changes w/ respect to the firing order. 
Divide the record into cycles, each cycle consisting of all cylinders in the firing
order.  Overlay the cycles like an old "superimposed" ignition scope display and
notice the differences in crankshaft acceleration for the same cylinder in different
cycles.  Why would there be any differences???
Shannen

> If it is actively retarding timing from knock sensor activity it will not log these faults.



> 
> Also, the throttle response is pretty much identical to how it was before I put the Eaton on the engine.
> 
> Shawn
> 
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