After having a conversation w/ an AEM tuner yesterday about MAF restrcition, I decided to test how restrictive, if any at all, the stock MAF is.

I decided to use my 500whp+ car as the testing reference since I still use the stock MAF. My car has the stock airbox w/ stock air filter w/ 15,000miles on it. I figure if there was any airflow restriction, it would show up on my car.

I hooked up a vacuum hose to the intake pipe that is between the turbo and the stock air box and ran it inside the car to my vacuum gauge. I then proceed out and start doing some 3rd-4th gear pulls. If the MAF is restrictive, then I would see some vacuum in the intake tube.

First pull at 23psi, showed no vacuum

Second pull at 28 psi, showed no vacuum

Third pull at 32+psi, showed no vacuum.

There you have it. No vacuum means no restriction.

 

As I would have thought the stock MAF is not very restrictive at this air flow. However it can only read up to 3000 hz. After this it doesnt see additional airflow. This seems to me to be the only downfall in using the stock MAF.

 

You pushed me over the hill. I'm ditching my K&N Typhoon and going back to stock airbox. I'm tired of the ****ty driveability, especially since it doesn't flow any more air. Thanks for the info.

 

I don't know how many hz I am at, but according to my XEDE, I am at 95% of its reading ability at 34psi. My RX6 turbo moves around 60-65lbs/min of air.

 

Thank you for this test, I was planning the same thing. 1 question...what filter are you using?

 

Where did you get that information? I'm curious.

 

I thought that it flowed more air but the MAF could not see it...

 

true^, the evo9 can read higher frequencies but same sensor

 

Yes a MAF is restictive, but the big problem with it is its ability to read mass quantities of air coming into the engine. The voltage just gets to high and it no longer can determine the load on the engine.

 

The 3000 hz limit was something that I heard somewhere. It may not be correct. I dont know this first hand.

I have seen 2750 hz on a friends car, my pockerlogger showed 53 lbs/min at this karman reading. Thats all the data I have collected myself.

Brian

 

Stock OEM filter w/ 15,000 miles on it.

 

Okay, the MAF itself is not restrictive, at least not at the power levels most people are at. The issue with the MAF is at very high airflow, it reads INCONSISTENTLY, as long as it reads correctly, and your happy with how its working and your tune works with your mods, then there is no reason to change it.

I run a blowthrough aftermarket MAF, but honestly, speed density or a blowthrough MAF are somewhat unecessary unless your having ALOT of difficulty getting the car to run okay with the stock MAF. IMHO I think most of the people who want to dump the MAF are interested in running VTA BOV's..

I found the best drivability was with the stock MAF, but in my case, I had alot of difficulty getting consistent part throttle higher boost tuning, that was my reason for it.. But I still occasionally go back to the stock MAF to make comparisons.

And the stock airbox is not a restriction until your making quite a bit of power.

The MAF will read over 2800hz, though I have never personally see it go higher.

I don't know how good this test is though, since a restriction may not necessarily manifest itself as a vacuum in the airbox, you would have to measure it after the MAF in the intake pipe before the turbo.. But turbulence may be significant without being a measurable level of vacuum..

 

Jack,
For my particular setup (see below) do you think a GM 3.5" maf would be a good idea in lieu of the stock one?

 

It depends.. What I mean is, if you log the MAF frequency on several runs, and you just cannot repeat the same curve, or you get dropouts in the signal, or it jumps around what seems randomly, or vibration/noise from the engine are frustrating the sensor, then yes, upgrading to a different MAF would make sense, if you can repeat the curve then you can tune with it, and it isn't picking up loud noises or vibrations, then its not necessary. Make sense? My problem was with part throttle performance and tuning, I could not consistently reproduce the MAF curve at those conditions and therefore had a hell of a time tuning the car safely without being very very conservative.

 

I used a port in the intake pipe that is after the MAF.