MAF fluctuation under WOT?
04-27-2012, 12:44 PM
#1
MAF fluctuation under WOT? Just did some logs to look at MAP readings to see if I have an intake tract restriction (btw I'm 92-94kpa at WOT above 5000rpm).
But I noticed that the MAF readings did not steadily increase, they go up but fluctuate by 1-2lbs/min as they rise. Is this normal or does it mean the MAF curve needs work or there is too much turbulance in the intake piping?
My peak was 43.71 lbs/min at 6350rpm in 2nd. WOT a/f from wideband is within 0-.3 of my commanded so I think that is pretty good.
I am attaching the log from EFI live in case that helps.
But I noticed that the MAF readings did not steadily increase, they go up but fluctuate by 1-2lbs/min as they rise. Is this normal or does it mean the MAF curve needs work or there is too much turbulance in the intake piping?
My peak was 43.71 lbs/min at 6350rpm in 2nd. WOT a/f from wideband is within 0-.3 of my commanded so I think that is pretty good.
I am attaching the log from EFI live in case that helps.
04-27-2012, 04:16 PM
#2
TECH Senior Member
Hi Thunder,
What elevation are you located at...? Do you have pics of your MAF plumbing...?
Those small squiggles you see in the MAF waveform at WOT are normal... your squiggles are smaller than most.
What elevation are you located at...? Do you have pics of your MAF plumbing...?
Those small squiggles you see in the MAF waveform at WOT are normal... your squiggles are smaller than most.
04-28-2012, 09:30 PM
#3
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I've seen unstable MAF readings on an over-ported 85mm
I was playing with. The MAF curve itself should be nice
and monotonic (and I prefer a near-factory MAF with
one of the factory curves, as it's near impossible to do
better without a flow bench and easy to fool yourself
"2 wrongs make a right" style).
To judge intake tract restriction, look at (BARO-MAP)/BARO
at the top end. That's your fraction "left on the table" from
everything before the plenum.
I was playing with. The MAF curve itself should be nice
and monotonic (and I prefer a near-factory MAF with
one of the factory curves, as it's near impossible to do
better without a flow bench and easy to fool yourself
"2 wrongs make a right" style).
To judge intake tract restriction, look at (BARO-MAP)/BARO
at the top end. That's your fraction "left on the table" from
everything before the plenum.
04-30-2012, 08:24 AM
#4
Thanks guys, just making sure I didn't do something incorrectly when I retuned the MAF scale table for the 85mm MAF.
Elevation here is around 1400ft I believe.
I do not have a picture of the current intake setup. It is a rubber 90* elbow which goes to the passenger side, attaches to the MAF, another 90* down with 3" OD PVC for a few inches to a 3" ID outlet K&N cone. It was ran this way to see if pulling cooler air from under the car instead of the engine bay would help IAT and track times.
Elevation here is around 1400ft I believe.
I do not have a picture of the current intake setup. It is a rubber 90* elbow which goes to the passenger side, attaches to the MAF, another 90* down with 3" OD PVC for a few inches to a 3" ID outlet K&N cone. It was ran this way to see if pulling cooler air from under the car instead of the engine bay would help IAT and track times.
04-30-2012, 11:04 AM
#7
The MAF is in between 2 90* elbows so I left the screen in it. When I redo it with 4" ducting I am going to eliminate 1 of the 90* bends.
This is what I will have but I want to try a straight piece of 4" between the MAF and the filter:
This is what I will have but I want to try a straight piece of 4" between the MAF and the filter:
