That screen in the MAF, filers, and such...

[Racer X]

So, my MAF screen is missing. Has been since I bought the car. I've always noticed that it tended to surge under acceleration, but something happened last night that's making me wonder now...

At ROTB, before I ran on the track I replaced my K&N with a Fram paper filter, because my K&N was uber soiled. I dropped the Fram in, and there was no real performance difference, but it was a little more responsive. This was a week ago. Yesterday, I finally cleaned and oiled my K&N, installed it, and OMG WTF my car feels like it has 20 more HP than it did. Before with the paper it pulled hard, now with the cleaned K&N it pulls like a scared dog. From what I understand, a K&N shouldn't make that much of a difference over paper. Then I remembered reading once that the MAF screen removed can cause some drivability issues. Now, the K&N has a screen similar to that MAF screen, whereas the paper filter had nada.

What are your thoughts on the MAF screen, and performance difference between a paper and a K&N filter? And while I'm at it, where I can get that screen from (like, what other cars)?

 

[Ishodu]

That screen is really only on the MAF for protection of a large particle. Such as the bolts that hold the MAF on the upper air box lid.

 

[bmcreider]

I also heard the MAF screen does something to the air flow to the sensor, but I do not know if that's credible...

Some ricer know it all friend of mine decided he would take it out while my car was in his garage, to "open it up some more" well I noticed a bumpy idle afterwards lol...so I'd say MAF Screen is there for more than just bolts.

 

[Ace]

Hamal i have an extra MAF with a screen on it if you want it...ill bring it to the next breakfast....

 

[SASHO91]

i had taken mine out for awhile when i was running the fram filters... didnt notice anything...
so i put it back in.
But since i have been running my K&N, i havent tried it....
but i would rather keep it on there.... just for reassurance... (sp)
i might pull it off one night just to see how it does... just for the **** of it.

 

[DHMag]

fuel and air atomization is its key element.

 

[SHO SPD]

I took mine out. I dont notice any difference in performance. No strange idle or anything either.

 

[Racer X]

Hamal i have an extra MAF with a screen on it if you want it...ill bring it to the next breakfast....

Chris, done deal.

I swapped the Fram back in for ***** and giggles, and the car does seem more sluggish. With the K&N, there's definitely some more get up and go.

 

[Racer X]

*Update*

Before I begin, this is what happened on MY 92. The same might not happen on YOUR car. Your mileage may vary, and all that good ish.

I installed the MAF screen this weekend, and immediately... and I mean immediately, I noticed a difference! My car has torque!! Tons more than I've ever known about, either, since this screen has been gone since before I owned the car. The throttle is much more responsive, with no tendency to surge or bog like it used to at all kinds of weird times.

So, in my case, the missing screen did significanty degrage the performance of my car!

Now, if you'll excuse me... I have some cars to find on the mean streets of Yonkers.

 

[F-22 Raptor SHO]

fuel and air atomization is its key element.

Think of the screen as a polarized lens for the air that enters your intake. It provides some bit of normalization of the air before it goes thru the maze of the intake.

The GMC denali has a screen that is more of a giant honeycomb. They claim it serves as a flash arrestor. No worries about that with the SHO.

Its nice to have a screen in for other reasons. Ask Huntervf what he thinks about screens. He is the only one I know that shot peened his piston for more hp. It wasnt intentional, but its why I use blue loctite on my maf nuts now.

 

[Redskull]

Alright, I guess I need some clarification here: I always thought that the screen in the MAF was the most important thing, i.e. without it it wouldn't be able to measure any of the air. The gist I get from this thread is that it doesn't do much except keep large **** from flying in? From the service manual:

"The Mass Air Flow (MAF) sensor is located between the air cleaner and the throttle body. The MAF sensor uses a hot wire sensing element to measure the amount of air entering the engine. Air passing over the hot wire casuses it to cool. The MAF sensor then outputs an analog voltage signal to the PCM to determine the intake air mass. The PCM will then calculate the required fuel injector pulsewidth in order to provide the desires air/fuel ratio."

Doesn't this mean without the 'hot wire sensing element' (mesh screen), you car has no idea how much air you get? Or am I all screwed up?

alan

 

[Rockledge]

The hot wire sensing element is not the screen. The "sensing element" refers to one of the small filaments that are a part of the sensor assembly.

 

[Redskull]

then what could cause such a difference in Racer X's as opposed to others with no effect?

 

[Axianator]

then what could cause such a difference in Racer X's as opposed to others with no effect?

While there are a few factors that could come into play in Hamal's case, it basically boils down to:

Factory screen on MAF = more uniform airflow into the MAF housing
Uniform airflow over the MAF sensor = improved air-mass sampling and load metering
Improved load metering = changes in commanded timing and fuel delivery
Changes in timing and fuel delivery = changes in throttle response and overall power

 

[SHOZ123]

AFAIK Ford does not use the screen on any of the newer MAFs. I think it is only a precaution to keep the nuts from the air filter box out. If the MAF needs a screen to improve the flow it is a badly designed MAF.

And fuel atomization is nothing but Tornado talk......

 

[Axianator]

AFAIK Ford does not use the screen on any of the newer MAFs. I think it is only a precaution to keep the nuts from the air filter box out. If the MAF needs a screen to improve the flow it is a badly designed MAF.

While I agree 100% with what you're saying, Paul, one has to remember that back when this MAF was first introduced in the '89 model year (for both SHOs and Mustangs alike), mass air flow technoloy was in it's infancy for Ford, with both of these cars being the first models from the company that would sport such a technology. That said, I wouldn't doubt for a second that while the primary purpose of the 55mm MAF's screen was for safety, it ended up producing the aforemention side benefit in airflow characteristics that have been noted by Hamal and others while toying with their MAFs.

Bottom line is that, as you and I both know, MAFs are very sensitive to changes in the position and direction or airflow into their housings. Not only that, but MAF design and technology have both come a long way in the 16 years since the SHO was originally introduced. What may be considered a crappy or inefficient design today may have been the best thing on the market at the time (not that I'm praising the 55's design by any means).

And fuel atomization is nothing but Tornado talk......

Bah! Who needs a Tornado when you have a magnetized fuel rail?

 

[Rockledge]

While I agree 100% with what you're saying, Paul, one has to remember that back when this MAF was first introduced in the '89 model year (for both SHOs and Mustangs alike), mass air flow technoloy was in it's infancy for Ford, with both of these cars being the first models from the company that would sport such a technology.... MAF design and technology have both come a long way in the 16 years since the SHO was originally introduced. What may be considered a crappy or inefficient design today may have been the best thing on the market at the time (not that I'm praising the 55's design by any means).

I'm thinking maybe that's one of the reasons why the early Ford MAF systems required a BARO sensor...because that type of data had to be more precisely measured on account of the early MAF systems (and EEC systems in general) not yet being up to the task of handling it properly.

Would you agree with that hypothesis?

 

[Racer X]

Speaking of the Baro sensor....

Anyone know the test procedure offhand?

 

[Rockledge]

Speaking of the Baro sensor....

Anyone know the test procedure offhand?

I think you can probably put a vacuum pump/gauge on the vent port and then measure the frequency as you increase and decrease the pressure:

http://fordfuelinjection.com/index.php?p=32

 

[Racer X]

Frequency? What?!! You mean I have to go out and track down a friggin osicilloscope to test this damn thing?