I've read posts on adding HP by removing the screen. Personally I feel this is a load of crap, but that's just my opinion. What's yours??

 

It is not going to be much of a difference if that is all you do. However, look at the screen and if you scrunch all the wires of the screen together you can see how much air it blocks the intake...a far portion. As long as you have a good filter there really is no reason for them.

 

You need a third choice "Don't do it...it will screw up the readings to the ECM".

 

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"it will screw up the readings to the ECM".
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You know, there may be a lot of truth in that. I only thought you could mess stuff up if you hurt the MAF wire. However, now that you said that, my car just puked on me and the GM shop said I the computer is messed up. Now, that that clicks together, hindsight tells me to leave the stupid MAF alone!

 

If you cut the screens you MUST recalibrate the MAF scalar tables in the eprom. The wire is going to produce a different reading due to the different airflow characteristiecs when you remove the wire.

 

Do you think my eprom can still be reprogrammed to fix my problem or is the damage already done?

 

If you take the time to do it yourself, yes. If you want to buy one, no....they won't know what your readings are.

Cheaper than buying a new MAF and then you can do other tuning too!

 

IMO the MAF scalar tables are hard to tune and pretty much impossible to get right (At least when I tried). Your better off going to speed density if you are willing to burn your own chips, that’s what I did.

 

I voted no because thats just the way it is.

And that, is 1 of the best sig pictures I have ever seen, LOL. :rockon: :sillylol:

 

Trust me, owning these cars you know GM designers do some short-minded boneheaded things that don't make sense and could have been avoided0with a little attention when they were designing these cars. The MAF screens, however, don't fall in the category. They are there for a good reason and should not be removed not only because its not going to yield any gain but it can damage the MAF sensor itself and make the car not run right. The screens help even out and regulate the air flowing through the maf body so that the sensor wire doesn't get a screwed reading (sort of like the strainer tip on your faucet) but it protects the wire as well. Anyone who owns a tpi car knows the MAF is a fragile unit and if that wire is damaged, you're sh%t out of luck for $200. There are legit "free" mods out there but the MAF screen "trick" falls in the same boat as the throttle body bypass and those IAT relocator kits.

 

I wouldn't do it. Look at the price of a new MAF and then just spend that money on something good. :-)

 

What really boneheaded things are you talking about. While I don't think the design guys walk on water they did a pretty decent job. Do not confuse bad engineering with cost. While these cars suffer from component quality problems every so-called mod I have tried has a counterproductive side. All in all the engineers working for the car companies are among the best in thier fields.

 

I didn't want to go there. But if people are concerned about an "intake restriction", your suggestion is right.

Since you have tuned both, I am curious of your opinion on tuning SD? My opinion is that it is "initially" more time consuming to tune the VE tables, but once done it results in a better tune. But I've spent far more time tuning "spark" to get my tune optimal than fuel, so it really doesn't matter which system you use (if you want an optimal tune), they will ultimately take the same amount of time.

 

My opinion is in the archives. Lacking any other serious modifications, I wouldn't recommend it.

On a 305 engine, there will be no appreciable gains. On a stock 350, there will be no appreciable gains. On a modded 350, you may see some gain at WOT if the fuel delivery has been altered. The theoretical airflow of a 350 is 550 CFM at 5,000 RPM. The TPI system starts becoming restrictive at 5,000 RPM, so the design of the MAF is adequate for a stock engine. At partial throttle with no screens, things can go really badly for you.

 

I Agree with RedFirebirds statement. I believe the designers put it there for a reason. Its obviously not a filter to keep debris away from the center thermistor. The air goes through a filter before it even hits the MAF. Besides that what sort of filter would that screen make, the only thing it's going to filter is a tree branch or leaf and we're not going to get anything like that coming through the intake. I believe the screne is there to help remove turbulance of the incoming air and by removing the screen your going to cause more harm than good. I think sometimes people get carried away when trying to add more power and start looking for everyway to increase air intake and removeing restrictions, but fail to realize that somethings are there for a reason.

The only complaint I've heard about the MAF sensor is the self cleaning mode that the computer performs on it. I've heard that this can cause the thermistor to prematurely burn out.

 

I disagree completely. The screens will not remove turbulance, they induce turbulance. And I have been running the same "moded" MAF for 15 years and it has not caused a single problem. And when the stock 305 was still in the car it didn't increase power (not noticably that is) But it did dramatically increase throttle response, especially at part throttle .

 

I stick by my claim that a MAF sensor screen removes turbulance from the incoming air. The only sensor that I know of that actually induces turbulance is the Vortex Air Flow sensor and even this sensor removes the turbulance from the incoming air and then reintroduces it at another stage of the sensor. I'm almost positive it has the same type screen on the front of it also. At the middle of the sensor it has a triangle shaped bar running across the middle which deflects the air into the inside walls of the tube, generating the turbulance.

 

Alright, I got the details about my car. The reparable GM shop said my computer was f*cked up. However, they also told me it already had an aftermarket chip in it, which is weird considering there were no mods exept smog pump removal before I got the car.

The shop also told me my year of car, '86, has had a history of computers that go bad, not relating to the MAF screen removal.

I think that Morley's testimony of 15 years w/o the screens seems to be pretty hard proof that it doesn't mess too much with the computer. It is just us unforntante ones with very old possibly faulty computers.

 

And from my eprom burning experience (and 27+ years of working with computers and Assembly Language), I can most assuredly tell you the MAF reading WILL change if you cut the screens. AND if you don't RECALIBRATE the MAF Scalar Tables within the eprom (which is something only the most experienced of eprom tuners should do), you will affect the ECM.

A lot of guys with SD will tell you that they've made modifications to their cars WITHOUT modifying their eprom and tell you their cars run without any problems.

However, running "without any problems" doesn't mean it is "optimal" or "properly tuned". GM has built a lot of "tolerance" into their calibrations because GM doesn't want warranty claims. GM designed the eprom to work just as well for the guy with a brand-new car as the guy with 250,000 miles. But the eprom is far from optimal for either.

That is why I have shaved .5 seconds when my car was basically stock with eprom tuning. FYI, my car "ran without any problems", but when I got into tuning, I was running "pig rich" and wasting gas. Now, I gained .5 seconds AND my gas mileage increased to US 30 MPGs (before I decided to make further mods).

"Without any problems" doesn't mean it's right.

 

Again wisdom and experience puts the young, impressionable mind in its place. I respect that.

-xmind2006

"little piece of irony there in my screen name"

 

Ok, basic aeronautics and aerodynamics, putting ANY kind of obstruction into an other wise unrestricted air flow will induce turbulance and restrict flow. nuff said.

I never claimed that my MAF readings didn't change at all when I removed the screens. I said it didn't cause any problems with the MAF. The car drove no differently other than a crisper throttle response, and it got 26 MPG in the mountains of northern PA.

From all I have read and gotten through conversations with "experianced" GM mechanics and tuners, the screens were put in as a last ditch effort to protect that expensive little flow meter in case of catastrophic failure of either the air filters or the ducting behind them.

Glen, I am not arguing that the ECM won't see a change with the maf screens gone, rather that the programming within the ECM is lenient enough that it has no effect on performance or operation of the engine. And 15 years ago you could monitor what the ECM was seeing but not do a damn thing about it, the tools didn't exist for your average person to change the programming in their ECM. So in that time frame "running without a problem" was "running right", since it still fell within the factorty parameters.

 

no offense here, but all the guys who are serious about tuning proms say pulling the screen out is detrimental to the calibration, whereas all the guys who don't mess with computers say it's alright. i'm inclined to believe the guys who have "been there, done that"....

just this past weekend, I installed 24lb injectors in my 91 5.7. I coudln't immediately reburn a chip with the injector constant changed. Did it still run? yup. Did the check engine light come on? nope. Did it feel like it was running fine? yup. but when i got around to redoing the chip with the injector constant bumped to 24 (instead of 22), i noticed that it smoothed out a bit more and seemed a bit crisper. and that's not even a 10% difference. so yes, there is a TON of leeway where the engine will still start, run, accelerate, pass smog and not set a check engine light, but that doesn't mean it's optimimum. I bet glens' car ran just fine before he started tuning the prom, so what does that mean about how it runs now when it's 1/2 sec quicker in the quarter? food for thought.

and i think fluid flow characteristics (air can be characterized as a fluid really can't be summed up in "common sense" ways, it's just not that simple. for example, several tests have shown HP increases by adding a muffler to a straight pipe system. it makes no "common sense", because the muffler is an obstruction, but the tests seem to indicate that at least sometimes, the obstruction helps.

 

That wasn't "common sense" I posted, it was fluid dynamics, the most basic of fluid dynamics.

 

How can you tell me that the installation of that screen was a last ditch effort to protect the temp sensor?? The air thats passing through the MAF has already been filtered, the only thing that screen is going to stop is a freaking tree branch. What it sounds like to me what your saying is that they installed it for the absent minded consumer, the one who neglects to change out his filter, or even better the one who takes out the old and forgets to put a new one in its place!! Besides that how can you say the screen induces turbulances. The incoming air is already turbulant, is it suppose to generate turbulance in already turbulant air??

 

That rational of "why the screens exist" is a new/interesting one. The one I have heard is that the screens "equalizes" the air flow more evenly across the wire. Without the screens, the air will tend to move slower on the sides and faster in the middle.

I think it was Bruce (Grumpy) that posted this finding a while back. He had done a lot of testing of the MAF (with and without screens) and I believe it was Bruce that first posted the fact that the readings changed and why (when the screens are removed).

You are correct that "eprom burning" is a recent event for us "little guys". The best we could do was monitor with our scan tools and hope to compensate with a mechanical method (fuel pressure/adj. base timing) trying to correct the "worst area" of the powerband/rpm range without affecting other areas too much.

I say this is why companies like TPIS were able to sell a lot of those "Magnum Level 1 and 2" eproms. Those were the ones designed for "basically stock engines with minimal/no modifications" other than AFPR, relocated IAT/MAT and cut-out/modified MAFs. It's probably the reason they recommended it as one of the "freebie/cheapie" mods in their "Insider Hints". They knew that you'd need a modified eprom later to get "optimal performance". Without cutting the screens, you really didn't need their eprom.

 

So my question is, if removing the screens is not a good idea, why does TPIS advise doing it to gain better flow characteristics?

 

Study aerodynamics, you'll understand what I am talking about.

 

This is just my oppinion of the screen and it sounds to me that your trying to base you oppinion against mine without providing anything to back it up. So far you have failed to convince me. Like I've said before I still believe the screen is there to even out the flow of air coming in so that the thermistor can get a better reading. There is no way that they would put something like this in as a safe guard. How often does an air filter fall apart and get sucked into the engine ( NEVER ), How often does the plastic ducting fall apart ( NEVER ). If something like this ever did happen there's a 99.9% chance that it was the fault of the person working on it.

Look at some of the claims of some of these aftermarket air filters that are out their some claim to help smooth out the incoming air. Isn't an airfilter a restriction?? I never claim that the screen on the MAF wasn't a restriction, of course it is. I claim that it helps to smooth out the air by removing some of the turbulance. And for the most part I feel it was put there to allow the thermistor to get a better reading. The computer uses this reading when determining A/F adjustments.

 

As I said earlier, to buy their expensive eproms (so it will now be properly tuned).

But let me answer with another question, why does TPIS advocate the relocated MAT/IAT sensor? It does NOTHING for the fuel calibration on a MAF car (that's what the MAF sensor is for) AND totally screws up the fuel calibration on an SD car (you need a new eprom for a relocated IAT/MAT to work properly on SD).

Just because a company sells something doesn't make it good. Look at the "Tornado". I guess P.T. Barum was right.

 

GEEZ! CHILDREN!

Ok, the screens in the MAF create turbulence. I've said it a million times, I'll say it again. You want proof you can read about fluid dynamics or I can post another lengthy article about it here although I dont much feel like wasting my time with resident experts that have never studied the material (many names mentioned above included). Period.

Ok, the screens attempt to create equal average velocity vectors across the entire cross section of the MAF. I've said it before (and I said it first), I've said it a million times, and I'll say it again. Period.

Ok, about the 'calibration' problems. Know what comes into play here? Significance. Does it affect the readings? Yes. It is significant to screw things up? IMO, no. The MAF itself isnt accurate enough in what it reads to make enough of a difference where the ECM cannot compensate for any problems the screen removal may cause. Its my opinion and always has been that if the BLM's are not maxed at one end of the scale or the other, the ecm is plenty capable of fixing things based on o2 readings. Thats what the o2 is there for, otherwise you wouldnt need it. Where problems in fueling come in are transition areas, and thats where the MAF is at its worst anyway, so a little variance is going to make no difference with such terrible accuracy to begin with. Theres a huge difference between accuracy and precision, I think everyone should go look those two terms up, analyze what they are dealing with, and see if what you are doing matters in the grand scheme of things or not. Period.

The screens on the MAF on my 86 were removed at 29k miles in 1988 by the previous owner of my car. At 130k in 1996, it was still fine, still got decent mileage, didnt exhibit any driveability problems, and I dont think the screen removal hurt it any. Do you want to remove the screens? Ask yourself the following:

Do you need the 5hp it might provide? (This is a guess, it may be less, may be more. In any case, its a paltry difference.)
Can you take them out without screwing up your MAF? Keep in mind half of the people who think they are capable find themselves on a trip to the local parts store.
Can you reprogram the prom, if you really want to make sure all your settings are 100% ideal (as ideal as they can be anyway)?

If you answer no to any of those, you answered the question of removing the screens or not. If you really feel like doing it anyway, by all means treat it like a cracked piece of crystal that you dont want to break, ok?

 

if ur gonna cut the screens, cut the one after the maf.. its not nearly as important as the first one. except maybe for backfire protecion??

 

Would you put one of those tornando peices of crap in your intake? Whats the difference between that and maf screens.
Taking them out is pure luck in result. Sometimes it helps, sometimes it hurts. These cars aren't perfect from the factory. usually they are rich. If we remove the maf screens we get faster air to the outside and away from the sensor. Combine that with less restrictions and we get more air flow to the engine. However the maf sensor may not pick up on the outisde air due to its more central location. On a stock(rich) engine the maf thinks a little less air is going in then reality and doesn't add as much fuel and your rich condition becomes less. Although the o2 sensor is going to change it to whatever it likes in the end anyway.

But who really is only going to gut the maf and do ZERO other mods. I say its a crap shoot. I would have no problems doing it myself.
My friend has a bone stock 350tpi with maf and flowmaster. His maf is gutted and it runs fine.
my .02 cents