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Twin MAF's reading different

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Hey Andre, Fellas.

Haltech PNP on my 32GTR, the MAF's are still in place atm but im tuning via TPS/MAP but I happened to log the MAF's the other day and I noticed one is flowing noticeably more then the other consistently except at 0% TPS then the other flows more...

Is this possibly showing on of the turbos now performing as well as the other?

Or more likely just a problem with the MAF's themself?

Id guess ill have to swap them over and see if the problem follows the MAF or stays with that side... just the wiring doesnt reach to simply swap plugs so will need to actually swap them physically.

I would try psychically switching the MAFs front to rear and see if the issue moves.

Other things which could be an issue, MAF elements are dirty, one turbo out performing the other, intake leak post MAF/Pre turbo etc.

Seeing one turbo work harder/flow more than the other isn't uncommon when you're running no balance pipe between the exhaust manifolds.

When you say noticeably, how much are we talking?

1. I would switch the mafs

2. Check WG opening pressure of each turbo and adjust them the same.

It's not uncommon or unexpected to see a difference in the MAF reading between two MAF sensors. If that wasn't the case then the manufacturer could get away with only using a single MAF sensor and doubling the reading. OE's are pretty tight and don't often add sensors needlessly. There's a number of factors that can add up to result in a flow discrepancy between the two MAF sensors - intake restriction pre MAF, intake path post MAF, wastegate pre load etc.

In general I'd expect to see a discrepancy at low load/low throttle but I'd also expect it to even out to a degree as you reach higher boost levels.

Hi Andre, I'm curious to understand how wastegate pre-load affects the MAF readings..

If they start opening at different points they do

As kickerrzx said, if the preload is different they will start opening at different boost pressures. At the point where one wastegate is open and the other is closed, the turbine speed and hence compressor speed will be mismatched as one turbo is receiving more exhaust flow than the other.

Essentially what you end up with is the two turbochargers working at the same pressure ratio but slightly different compressor speeds which puts them in different areas of their maps and the result is a difference in mass airflow.

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