ECMlink AirflowPerRev

[dudeX]

Alright, my airflowperrev hovers around .20gm/rev. From what I've seen I need to be around .25 but cant seem to get there. I have no clue what I'm doing wrong here. Trying to dial in my new FIC 1120's and cant seem to get past the first step. Attached is a short idle log. Totally lost here.

 

[snowborder714]

Bring your 50Hz MAF Comp slider back up to 0 and see what happens. When you drop 0-50Hz MAF sliders, the AirflowPerRev value drops.

 

[dudeX]

Ok, I'll go rock a short idle log real quick and post it up.

 

[dudeX]

I dont know if it makes any difference but I live in South Dakota and the elevation here is just over 3000 feet. Just thought I'd throw that out there.

 

[snowborder714]

Not sure if the log in post #3 was to be an updated one or not. It isn't though.

From Dave over on the ECMTuning forum:

AirflowPerRev at idle should be pretty close to that expected at sea level. The engine still has to generate enough energy to overcome internal friction, and that doesn't change due to altitude.

 

[dudeX]

I changed all the sliders up to 100hz to 0% during the log. It got the gm/rev up to .22 for most of the log but not to the .25 I'm looking for. It seems most people are trying to come down from .30gm/rev. Any idea why I'm having trouble going up?

 

[snowborder714]

Your deadtime numbers might be slightly off. Try playing with the global deadtime value at idle and see if you can adjust that to bring the AirflowPerRev value up. Then you can transfer those settings to the InjBatteryAdj table.

 

[dudeX]

Is there some scenario where even if the settings are correct the gm/rev will still be low?

 

[snowborder714]

Is your valve cover vented to the atmosphere?
Do you have any boost leaks?

Found another quote from Dave that might be of some help:

A negative average CombinedFT at idle despite a low AirflowPerRev suggests that either the injector settings are a bit off, probably a higher than needed deadtime adjustment value, or the fuel pressure regulator is being overrun at idle by the rewired Walbro. If the FPR is being overrun, the simplest configuration fix is to just run a lower than actual AirflowPerRev reading at idle.

And one from Tom:

Just keep in mind that getting AirflowPerRev to a specific value is something you should consider doing if you're having other problems like the low fuel trims being out of line or something like that.

Then again, how do you know if whatever settings you're using are "correct"?

 

[dudeX]

Should I be okay with the .22gm/rev as my baseline and leave the mafcomp alone and adjust fuel to get wbratio and fuel trims in line?

 

[snowborder714]

That should be fine. I'd probably adjust the fuel settings to get it in check - it's not too far off and shouldn't require a huge adjustment.

 

[wags122]

What effect would a vented valve cover had on air flow per rev? Not trying to thread jack just curious.

 

[snowborder714]

Not positive - just saw Dave ask that question in a thread on the ECMTuning forums in regards to someone posting about a lower value.

 

[dudeX]

Would low compression have an effect on this value? I think my motor has 100psi across the board shamefully.

 

[snowborder714]

That's a good question and one I would probably post about over on the ECMTuning forum to get Tom or Dave to reply. I'd be interested to hear if/how compression would affect some of the readings.

 

[steve]

What effect would a vented valve cover had on air flow per rev? Not trying to thread jack just curious.

Anything that provides an alternative unmetered path for air to reach the cylinders will lower the AirflowPerRev.

 

[curt-s]

Ooooh, steve's in the thread graveyard with a shovel.


it's all good, AirflowPerRev is one of those damn things that's annoying to get right sometimes