I've heard references made to gutting the maf. sensor. I have only seen a picture of this from Lingenfelter. Obviously the screens are removed, I've already done this to my new maf.

So I'm guessing gutting it means grinding out the heat sinks? I'm also guessing there is probably a significant performance increase, because of the high rate of airflow through the maf. But what's the downside (there always is one)

 

uh, no. gutting means getting rid of the screen.

the heat sinks are a major part in the funtion of the MAF.

 

The fins were added by gm after a couple of sensors failed in death valley testing. In my opinion minimal gain is had by removing fins. The cfm gain is minimal. Screens are the biggest restriction. Remove fins if you wish but I do not recommend it. Others may.

 

When I removed the end screens I went the extra yard and cut out the five heat sink fins too.

The only caution is to cover the ends of the sensor tube with duct tape before you start cutting the fins. When finished with the cutting, clean out all debris before removing the duct tape.

 

I have not had any experience with the MAF on the L98 motors, but on the LT motors, there is a huge metal fin like thing that diverts air to the MAF sensors. I bought a spare on ebay and gutted that one. I took out both the screen and the fins. I noticed an increase on the butt-o-meter, but it is minimal to say the least. Not bad for a free mod though.

I would recommend getting an extra one just in case something goes wrong, or the sensor breaks over time. The screens are put in place to catch any debris that may get past the filter. the wire sensor of the MAF is very small and extremely fragile so patience and a smooth touch is very necessary.

 

The Butt/Meter never lies, but it does tend to exageration ..
I've got 3 maf's. 1 Granatelli high perf. doesn't work !

Taking out the screens, if stuff gets by the K&N filter ..
it's not gonna be big enough to screw up the maf.

I'm not a rocket scientist, "but" there are a different set of factors
that come into play at higher air velocity, vs. low speed aerodynamics,
which I know a little bit more about from my Hang Gliding days, and low speed aerodynamic studies.

One thing I'm curious, if anyone has data as to the actual speed of the air flowing through the maf. which could help to determine the parasidic drag of the heat sinks in the maf. Like jet engine design, mach 1 breakthroughs .. Seems to me, from what I've heard so far in performance development .. Getting the air to flow efficiently is The priority in the development of engine performance ..

 

I don't know about the velocity of the air going through the maf, but if it helps, here are some flow bench numbers for the stock maf and the 2 different extents you can gut it to.

Stock: 529 cfm
Screens removed: 711 cfm
Screens removed, heat sinks ground away: 750 cfm

These numbers come from Motorbooks' How to Tune and Modify your Chevrolet Fuel Injection book.

IMO, removal of the screens may be worth it, if for nothing else, simplicity of the mod and the possible gain. You're not ever going to feel the results of it and probably won't see anything at the track. I made back to back runs at the track with and then without the screens and I saw no difference. Consistently, the car runs no different. I even repeated this when the old maf failed. This is on a stock motor, though, with only bolt on stuff done to it. The story could be different now with my new motor.

The good news is that in the 3 different cars I've de-screened the maf on, and all the ones I've driven other than my own, there was no loss of driveability or throttle response and no surging, as some have claimed.

The stock, screened maf flows towards the limit of what an average 350 can pull. The majority of the mod is from the screen removal. Unless you're scratching for every fraction of hp, I don't think the heat sinks are worth removing.

Chris

 

The intake ports in stock Corvette #113 heads will flow about 195cfm and the stock TPI intake will flow about 200cfm.

More importantly here a 240chp L98 requires 340cfm at peak HP. You can measure the ID of your MAF, and do the math to get air velocity.

Assuming the MAF has a 3.5" ID the max air velocity would be about 85 ft/sec, if my math is right.

That's pretty slow compared with runner velocity which can get to over 300 ft/sec. BTW, I've read that ideal head port velocity is in the neighborhood of 1/2 Mach 1.

I don't know that the issue with screens & heat sinks is so much a matter of parasitic drag but rather reduction in crossection:
529cfm-stock L98 MAF
711cfm-descreened MAF
750cfm-fully modified (heat sink fins gone too) MAF
(RE: "Insider Hints", TPIS)

 

Everyone is into ridges these day's. AFR says that is why their heads flow better and golfers put dents in their gulf ***** to make them fly further,
All I know is with TTS I check the engine on a regular basis and with the screen in the hp and voltage spikes are steady.
With the maf screen out I see voltage and hp spikes, which would jerk the car but the hp drops off shortly after so I realy don't see any gain that lasts.

 

http://www.gmtips.com/3rd-degree/dox...maf-screen.htm

Stroked with MR/SR headers and all, meybe have something to gain.
Stock motor (ie, air foil, mufflers, cut lid, that sort of crap) - won't do a damn thing.

 

Getting rid of the screens gets you and additonal 650-750CFM of air flow, but you are also taking a chance of getting debris in there if you have a crappy air cleaner element, especially if you have a cut out lid. Those wires in the MAF are super tiny, and it doesn't take anything to break them.
You won't notice any "Seat of the pants" performance gains by removing the screens, but your overall MPG will come up a little bit.
I would advise keeping a spare MAF in the car, just in case something happens to the modified one while you are on a cruise.
I speak from personal experience!

 

Thanks for posting those numbers.
Thats a huge difference in the volume of airflow. Fuzzy math says that's about a 30% increase in airflow volume. I believe there are other factors to consider besides only the volume of the flow.

Such as parasidic drag of the screens, which in turn totally turbulate the air flowing through the screens, as the analagy of the golf ball where the dimpled surface turbulates the boundary layer reducing the drag of the ball. Unlike the golf ball the screens have no positive effect, only 30% increase in drag, and reducing the actual crossection of the sensor.

But it seems to me the most negative part is the turbulation and disruption of the airflow through the maf. High speed aerodynamics always seem to be dependant on very clean airflow.

As for a stock motor there may be some gain, maybe not. But I believe my 355ci. W/Trick flow heads,/headers & free/flow exhaust will out/flow the capabilities of the stock maf. I also have the 52mil. BBK.TB., Although I am limited by the flow of the TPI. there is a gigantic spike in Torque at 3400rpm, by 3800rpm it has increased 200ft. lbs., that has to require some serious air/flow. I'm still undecided as to which way to go with the TPI, even going with larger runners would probably have a negative effect, as it would decrease pressure and slow the flow down. For now I'll stick with the TPI and stock runners, unless someone can clearly show a superior/cost/effective alternative. I won't sacrifice Torque for HP.

 

You know for all of this I'm thinking I'll just stick with my speed density setup.

My experience though has been that no harm will come from removing the screens on the MAF. Anything that manages to get through the air filter that is going to be big enough and moving fast enough to damage the MAF is going to do some further damage down the line anyway.

I've heard more stories of the MAF being taken out by K&N filter oil than I ever have heard of one being taken out be debries. Hell one of my friends never ran an air filter he said that "oh it'll just get burned anyway." Many spun bearings later his MAF is still good.

 

Before anyone flames me, let me say that I am just posting this because it is a good read. Use the info as you see fit.

http://www.gmtips.com/3rd-degree/dox...maf-screen.htm

 

That is a good article! It's always good to hear as many sides to issue as possible. I have a racer/lady friend who having had her new motor built and raced a couple times, lost one of her nuts, (for the air cleaner cover) in the pits, at ButtonWillow Race track. After it promply blew up, Wendell (my mech.) found it inside the motor! (By the way she has an F Body) I suppose the point is, watch your nuts, when your fooling around in the pits.

Seems to me the point's made in this analysis are mostly applicable to a stock setup & stock prom. As my prom was dyno/calibrated with no screens in the sensor. I still don't believe anything big enough is going to get by the air filter, unless of course you forget where you left one of your nuts, not something most Guys are gonna do ..

 

My Granatelli works just fine on my '96 (no screen) and I removed the screen off my wife's Olds and her gas mileage increased by almost 2 MPG (not scientific, but it keeps her happy).

 

I removed the screens and fins on my '87Pontiac MAF with 383. The engine never missed a beat. Now I have an '88 Corvette and removed the screen and fins again. car runs fine. I think the fins are just for running in Death Valley. Seriously...ultra hot air. I live in Cal where the summers get to around 108-110 for about a month. I drive the car everyday. No issues with the MAF at all.

The fin removal will give slightly more air flow volume. Put Duct tape on inside of MAF to protect body on both outer sides of fins from scratches. Put it in a vise to hold it still, and use a hack saw. No problems.