85mm Mass Air help
I log some wot with my efi live v7 and the mass air lbs/min at ( 52.88 ) and in my efi tuner v7.3 is showing (43.72) lbs/min. at 6200 rpm , none of the lbs/min matches at all ,there all way out ,this just a example at one point in the log. Does my mass air need recalibrated, its a 85mm SLP . If so how would i do this. Shouldn't they match ?
Da dum, dum...SLP's early idea to add a resistor to a 85mm truck MAF to "lean" out the factory rich situation bites yet another. No worries, do a search on making a MAF rescaling map in the scan tool. Essentially, you will have MAF frequencies on a col and wideband BEN values that you will log with the vehicle in Open loop with fuel trims and other modifiers off to correct/rescale the MAF. I would highly suggest removing the added resistor first. If you are not adept at soldering/desoldering then take it to someone who is. It is very easy to destroy it unintenionally by the well meaning unitiniated modder.
2000 Silverado Full Size 4x4: Forged 6.2, H/C F1R Procharger
98A4 Z28: 02 PCM H/C Forged 347, 9" Moser 3.73
V1 V2 99+up RR COS #5 OLSD Dual Stg N20
www.efialchemy.com
www.greatamericancarwar.com
I answered this on LS1Tech.com...but what I don't understand about your post Doc is this. If the PCM is reading a raw frequency from the MAF, how would it know whether or not there was a resistor in the MAF itself? He's saying the MAF frequency logged out of the PCM is 'x', but the PCM is ignoring it and looking up frequency 'y' in the table. Doesn't add up to me...
Yes the PCM is cal. for 43.72 lbs.min at that Hz. but in real life i am pulling 50.88lbs.min. at the same Hz. I wish i could post the graft from the logged file but i dont know how.
if these two dont agree, then either your VE or MAF aren't calibrated. tune them both and you wont have this problem.
The following is my caveman interpretation...Originally Posted by SSpdDmon
The way the pcm "reads a raw frequency" is this... the litttle resistors in the ckt have current running thru them. The ckt does it's best to maintain current flow as translated by the calibration(MAF table) which is presented to us humans as a Frequency. As air rushes over the resistors, cooling them down the ckt is forced to increase current to maintain the desired flow. This is how it "knows" what airflow is actually coming thru. This raw current is converted to a Freq and then to an actual airflow value. This explains why at idle the pcm is sampling btw the MAF and the VE table; at idle the engine is huffing in and out to a degree and MAF readings alone are not valid, however at above 4000 or whatever B0120 is set at, there is sufficient airflow rushing in to fully use the MAF Cal and readings. That said, in the dark ages of LSx tuning SLP found out that by soldering in a resistor they could change the total resistive value of the ckt significantly enough to lean out the already factory fat fueling.
Sorry gotta grab my towel, my movie is starting in 42 min...
2000 Silverado Full Size 4x4: Forged 6.2, H/C F1R Procharger
98A4 Z28: 02 PCM H/C Forged 347, 9" Moser 3.73
V1 V2 99+up RR COS #5 OLSD Dual Stg N20
www.efialchemy.com
www.greatamericancarwar.com
Where exactly is the resistor soldered (I've never looked too closely at an SLP MAF)...?
If it's soldered in the bridge then it could well be shifting the frequency up (or down)...
Mine has a resistor soldered in across the bridge, Should i remove it , when tuning or adjusting the mass air ,witch would lean out wot a little, raising or lowering lbs.min.
Ok, I am back now. I just saw Tenacious D-good movie. Wrong picture-my mistake. The arrow is pointing at the IAT sensor. Trying to find a pic of the huge resistor- you can't mistake it.
If you feel comfortable with either desoldering it-with a precision solder station that can provide instant substantial heat- with flux to get in and out and not put to much heat for too long-that can fry other components in the vicinity. You could just cut the legs with diagonal cutters...Bottom line if you don't feel dexterous about it find somebody who can.
But by all means remove it one way or another if you have any mods other than just a lid as you will go too lean. The worst possible combo I have personally seen was on a guys camaro that had a SLP Maf and the Hypercrap caned tune in it. You could litterally hear the "can of marbles" pinging at WOT. I'll remove your resistor if you could come over and help me pull my tranny tommorrow.
2000 Silverado Full Size 4x4: Forged 6.2, H/C F1R Procharger
98A4 Z28: 02 PCM H/C Forged 347, 9" Moser 3.73
V1 V2 99+up RR COS #5 OLSD Dual Stg N20
www.efialchemy.com
www.greatamericancarwar.com
Yes, that's exactly where it is at. And other "aftermarket" MAFs I have seen are doing the same thing. Granatelli-sp?
2000 Silverado Full Size 4x4: Forged 6.2, H/C F1R Procharger
98A4 Z28: 02 PCM H/C Forged 347, 9" Moser 3.73
V1 V2 99+up RR COS #5 OLSD Dual Stg N20
www.efialchemy.com
www.greatamericancarwar.com
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