MAF and a large diameter air intake

[jpowel29]

Trying to educate myself on any potential issues that I might encounter with the MAF sensor when I go up to a 6" diameter air intake.

A little background on my truck:

07 LBZ Drag Race project truck (not street driven). Built motor (15:1 compression, 60% over inj, twin CP3, aftermarket cam, GT4202 turbo, and a good tuning baseline - Thank you Nick). With an ATS 4" cold air intake I had no issues with anything MAF related and I never paid any attention to it.

New for this season is a larger turbo so I am moving from an ATS cold air intake tube to a full 6" cold air intake.

What should I expect to need to adjust? I have read that a few guys have had issues with low rpm fueling when going to a large diameter intake. My truck is still getting pieces made for it so I have not experienced any issues nor do I know if I will at all. I know these questions are pretty open-ended. I am trying to better understand how the ECM will interpret the new set-up and where to look to change in response to any.

Thanks
John

[bballer182]

To be honest with you the MAF really has nothing to do with anything tuning-wise. there are no MAF limiting tables in the LBZ and there are no tables dependent on MAF reading. In and LBZ the only thing a MAF is good for is metering air for logging purposes. Someone can correct me if im wrong. Ross has even investigated this too and the code for a MAF limiting like in the LMM's does exist in the OS but is unused in the LBZ's. I do have a theory that the MAF may be compared to boost vs. RPM in some way as error checking of some sort.

[bballer182]

If you really want to tune that up though; what you could do is figure out the velocity of the air at given flow rates on the stock diameter pipe and then use some math to figure out what the new velocities would be for the same flow rated in a larger diameter pipe.

[jpowel29]

Thank you - one less thing to be concerned with (as far as tuning goes) is fine with me.

[JoshH]

To be honest with you the MAF really has nothing to do with anything tuning-wise. there are no MAF limiting tables in the LBZ and there are no tables dependent on MAF reading. In and LBZ the only thing a MAF is good for is metering air for logging purposes. Someone can correct me if im wrong. Ross has even investigated this too and the code for a MAF limiting like in the LMM's does exist in the OS but is unused in the LBZ's. I do have a theory that the MAF may be compared to boost vs. RPM in some way as error checking of some sort.

I have found that to be not true. I fully believe there is a table somewhere that uses MAF in some what to limit fueling. I guess Ross just hasn't found it yet. If you want to do a test, go into your MAF scaling table, B0201, and change it so there are no values over say 15 lbs/min. See what kind of fuel the ECM commands.

[jpowel29]

Been data logging MAF pids along with fuel while staging and launching (I have a 6" diameter intake).

At 25% throttle position (2094rpm, 45mm of calc fuel flow, around 130mpa of rp, 1250us pulse, holding the brakes hard while staging) MAF voltage is 1.8v and lbs/min shows around 13.

At 100% throttle position (2400rpm and rising) calc fuel flow drops to 32.8mm, rail pressure drops 123mpa, MAF voltage is now 1.0 and lbs/min bottoms out at 6.3.

I have not re-scaled the stock LBZ MAF table yet. Anyone have a good method to help dial this back in?

[LBZ]

I have found that to be not true. I fully believe there is a table somewhere that uses MAF in some what to limit fueling. I guess Ross just hasn't found it yet. If you want to do a test, go into your MAF scaling table, B0201, and change it so there are no values over say 15 lbs/min. See what kind of fuel the ECM commands.

I agree. I've messed with it as well and found it does affect fueling.

I think to rescale it you just have to do it by the seat of your pants. It's what I am going to do shortly to see if maybe it isn't the table that seems to be limiting my fuel at WOT.

[bballer182]

I agree. I've messed with it as well and found it does affect fueling.

I think to rescale it you just have to do it by the seat of your pants. It's what I am going to do shortly to see if maybe it isn't the table that seems to be limiting my fuel at WOT.

B0795 and B0796 have been found and added to the LBZ calibrations since this thread died quite some time ago.