Is A MAF Sensor Restrictive?
May 11, 2026I thought the answer to this question was no. Until I saw this video. Now I think the answer is, maybe. Maybe a MAF sensor is restrictive.
The Video – Restrictive MAF?
This is the video in question
Flow Measurements
In the same order as the tests in the video.
| Through Normal Compressor Housing | Larger Compressor Housing | Less Optmised Compressor Inlet Transition | Corrugate Pipe 50cm | Rigid Pipe 50cm | MAF Housing | Massive Air Filter | Open | Vac in/h20 | Flow CFM |
| Yes | Yes | Yes | Yes | 19.9 | 325 | ||||
| Yes | Yes | Yes | Yes | 19.9 | 325 | ||||
| Yes | Yes | Yes | 19.9 | 370 | |||||
| Yes | Yes | Yes | Yes | 19.9 | 320 | ||||
| Yes | Yes | Yes | Yes | 19.9 | 338 | ||||
| Yes | Yes | Yes | Yes | 19.9 | 400 | ||||
| Yes | 19.9 | 411 | |||||||
| Yes | Yes | 19.9 | 394 | ||||||
Analysing The Results
There are some super interesting measurements in the table and I think they missed some key findings in the video, which is fair enough, given the setting.
Standards
Before getting in to the results, how much is 19.9 inches of H20 in PSI/BAR?
0.7 PSI or 0.05 BAR.
In other words, with a 0.7 PSI/0.05 BAR restriction, the CFM numbers tell us how much the flow varies by.
Analysis
To me, on the surface, 0.7 PSI seems a tiny amount.
And yet, there is a massive 25% difference in airflow between the lowest and highest numbers (325 vs 411CFM).
This may seem like there is huge potential for extra horsepower but if the engine cannot consume 325CFM at max power, the extra flow is irrelevant.
The flow measurements are only relevant if the engine can consume 411CFM but is only getting 325CFM because of a restriction. But again, I think we have to be careful here.
If this was actually the case, that the engine wanted 411CFM, it probably would not be only getting 325CFM.
Why?
Because a 411CFM demand would increase the vacuum on the 325CFM setup, which would pull more air through the 325CFM setup meaning more than 325CFM flow.
There are formulas which can tell us how much the vacuum is and how much flow we would actually get but I’m not getting in to that here.
Also, I think there is a simpler way at looking the situation. In a perfect world (excluding pulse tuning), in a normally aspirated engine, at the back of the inlet valve, we have ambient pressure.
If we have say a 0.7 PSI restriction, this would mean a 4.7% loss in power. So while I said above, 0.7 PSI seems tiny, on an NA engine, it’s quite big.
Coming Back On-Piste
Coming back to the original question, is a MAF sensor a restriction?
In this case, on this flow bench, with the components they were using, absolutely.
I think in the video they say that the compressor is the restriction and that it’s pointless looking at other things (bigger air filter) if you don’t take care of weakest link first.
Elephant
And while the size of the compressor (I think they look at the compressor inlet diameter) does have an effect, I think they missed the elephant in the room.
With the small compressor housing they did a couple of tests which showed little difference in flow. But in among those tests was a test without the MAF and without the MAF housing there was a huge improvement in flow. Flow increased by 13% without the MAF housing (325CFM vs 370CFM).
Larger Compressor Housing
Yes, swapping to a larger compressor housing upped the flow at lot vs all the small compressor numbers, except against the deleted MAF number.
Small housing, without MAF – 370CFM
Large housing without MAF – 411CFM
A 10.5% difference.
Quite a lot but the MAF housing on it’s own gained 13%, a bigger difference than the larger compressor, and MAF housings are much cheaper than bigger compressors……..
Anamolies
There is a big anamoly in the test. With the big compressor housing, with and without MAF the difference in flow is small. I’m not sure why, I presume because the MAF housing used with the larger compressor was bigger but I can’t be sure.
Conclusion – Is A MAF Sensor Restrictive?
Is a MAF sensor a restriction?
Depends on the power you are making, the internal diameter of the MAF you are using and the type of screen that the MAF uses.
Finding Out
The easiest way to find out is the measure the vacuum after your MAF sensor and compare this to the vacuum before the MAF sensor.
Power Loss
How much power are you losing due to a restrictive MAF?
For NA engine divide the pressure drop by ambient pressure and multiply by your horsepower.
For turbo engines it’s harder to quantify because the turbo will make the boost you tell it to, boost targets ignore compressor inlet pressure/vacuum.
Having said that a restriction at the compressor inlet will force the turbo to work harder to achieve the boost target. A turbo working harder is a bigger exhaust restriction which will cost power. Depending on turbo size the higher boost might also make the turbo less efficient (if the pressure ratio pushes the turbo off an efficiency island) which means more heat, which means less oxygen mass so even though the turbo meets the boost target, the air is carrying less oxygen than it would it if the compressor inlet vacuum was less.
In short, turbo engines benefit also. Less restriction means more power from the same boost pressure.
