E38 Speed denstity MAF Blending

[4wheelin]

I have a PD blown LS3 with a mild cam that I am retunind from the other software utilizing the MAF and EFI live's virtual VE. I have dialled in the MAF on its own and have disabled the MAF and built a VE table. The car has good fuel trims and WOT mixture is equal to that of the commanded in either SD or MAF(MAF active from 500 rpm up). The issue is when I try to introduce MAF at 2000 or 3000 or 4000 rpm the mixture goes extremely lean to the point of not wanting to run. I've done similar tunes in the past and have never seen this before. I may have missed something. I've raised all the usual air flow limits and so on. Any thoughts appreciated.

[4wheelin]

2030520306

So just to confirm everything I drove for an hour in pure SD, MAF unplugged, checked fuel trims and driveability, all was good. I then switched to enable the MAF from 900 rpm up and repeated, slightly fuel trim adjustment was needed as trims were 10% off in one area however driveability was normal, open loop miuxture good as commanded. When I engaged the MAF at 3000 rpm I go back to the same issue, part throttle driveability and throttle are fine but under acceleleration the car cannot transition, it goes lean, bucks and is undriveable. I have looked at the logs of each and I am aware the air load calculation differs between SD and MAF but have noticed when I compare air flow grams per cly against rpm and MAP that there is a sizeable difference between the two despite them running the same mixture as commanded in both situations SD and MAF. Its like the MAF switch point needs a load reference not just an RPM one, I'm wondering if due to the supercharger I get stable air at quite low rpm and higher load as reversion is not a factor. I did the excercise to find a miss that you get once at WOT at low rpm 1500 rpm in 5th 6th gear as the car accelelerates the mixture goes to the commanded, has a momentary lean bump then returns to the commanded. It does it both SD ad MAF.

[Tre-Cool]

You need to zero out the entire B8003 table when running a blended tune

[4wheelin]

You need to zero out the entire B8003 table when running a blended tune


Is that an E38 issue as I've not had to do that with E67 ecu with similar mods, Cam more boost etc.

[Tre-Cool]

it seems to be hit & miss. some E38/E67 tables are populated with values, some are not.

Apparently the ones that are tend to exhibit more of a problem.

It's also not just a problem isolated to efilive tunes, apparently hpt users suffered a lot from it too.

[4wheelin]

Thanks Tre-Cool. I must have been lucky up to now.

[joecar]

Zero out B8003... ok, understood, thanks.


( I usually see values in the first 3 columns and the last column... ok, so I'll zero all these out )


This table has no description...!!!

[4wheelin]

Ok. Got the car back and that worked. Now has a blended tune. I went to the blended tune to get rid of a momentary lean that doesn't show up on a log, the car will faulter for a moment if you go WOT from quite low rpm 1200-1400 and let it accelerate through to 2500rpm. I can log it in the mixture on the dyno. It doesn't happed immediatly like a transient issue, the car enrichens, drives for a second, hestitates and goes lean then returns to the commanded mixture. I can post a log but there is nothing I've idnetified to see. Hoping someone else has seen this. I have seen it before but most customers don't drive like this. I have one that does.

[joecar]

Ok, good to know that zeroing B8003 fixed the MAF/VE blending, thanks.


Is your log updating at the fastest sample rate (40 times per second or more)...?

Post it anyway, someome may see something.

[4wheelin]

Sorry its a long log. The actual occurence where I test for the problem is at 11.20.23 20367. I go WOT from low revs.