What does CFCO do??

[Redline MS]

I have been logging the CFCO timing pid and wanted to better understand the function of this. I see the table that dictates the timing "adder" but it doesn't seem to track the actual logged value.

[Blades]

Timing+CFCO timing adder=cfco timing? Looking at CFCO Spark from a 07 vette posted in another thread, it says "value that spark is ramped down to when cfco is enabled". So why wouldn't it be anything besides that? It has got to be pretty quick.. Short dips in spark values like tq management between gear shifts on an auto. I don't know.. Do the idle underspeed/overspeed coastdown tables come into play with dfco and cfco active?

[Redline MS]

I just noticed that while logging street data that it seems to really be moving around. We are trying to narrow down all the "adders" to see if we can get more predictable control over spark timing.

[grfperformance]

Check my thread on negative advance. I logged -7 to -8 degrees advance with 40 degrees in my high octane table at crusing speeds.

[CJ-WP]

I'm reviving this thread...

Does anyone know exactly what CFCO does? I don't think that it pulls fuel, it seems to ramp down the spark.

I've also done a bit of testing (and lots of searching!) and it seems that it also disables DFCO, which means that disabling CFCO and stepping on the clutch relies on your minimum idle airflow to 'catch' the idling before the engine stalls - a potentially dangerous situation if you have lowered those

Any help would be greatly appreciated!

[Chris@HPTuners]

CFCO is used to prevent engine flaring during shifts on a manual transmission (depressing the clutch) or if neutral is selected on an auto. It is primarily controlled by change in RPM and also throttle. ie. if you are mashing the throttle during a shift before letting the clutch out fully again.

it works similar to DFCO in that it ramps down spark then cuts fuel if needed.

[CJ-WP]

Thank you Chris, that makes sense... it's almost like a "clutch saver."
I'll definitely leave it active.

Cheers

[carlrx7]

plus without it, the engine pops between shifts from too much timing

[TRStech]

Reviving this once more: Im looking into this under the aspect of emission reduction, trying to understand if this funsction could have any impact.

Im in the situation that my MT swap car (LS3 pretty much bone stock, E38) doesnt use a analog clutch sensor. I only have a signal for for fully depressed and for full off. Due to that I disabled CFCO, since quick shifting at WOT + high rpm was horrible before.

The clutch bite point, which is learned by the ECU based on the analog signal, was "learned" at the full off switch but physically is much earlier. So you so got a full engine brake situation within each shift.

Currently im dealing with emission reduction due to legal restrictions I have to fullfil and Im searching for variables which could cause aditional emissions. My question is now, if the deiabling of CFCO could cause anything like a very short rich condition (it was mentined above that the engine can "pop" without CFCO at shifts) or if the timing could cause unburned fuel to exit into the exhaust.

Unfortunately I wasnt able to find a clear description of how CFCO is working. Does anyone have further information about that?

Thanks!