Unusual T/A

If you remove the maf screen You WILL run leaner regardless of what anyone has to say. More air equals leaner condition right? If you remove it and run too lean that equals detonation (knock retard) and an obvious loss of timing. If this does happen you can either buy another maf with the screen, or buy a translator. I would leave it alone until you find out what your air/fuel ratio is currently. If you really want more power just buy a translator and tune it. The stock maf is just fine.. Leave it alone..

unit213

Unusual T/A

Where does your info comes from? Personal experience or is it just theory? I'm just curious since many of us here have done it and have not had any problems. Removing the screen doesn't necessarily mean you'll be getting more air either. It's there to straighten out flow from the factory baffle. The airflow is straight with an aftermarket lid.

Dave Carney

</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by camaro_ls1:
<strong> Where does your info comes from? Personal experience or is it just theory? </strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">I know! I know! <img border="0" title="" alt="[Big Grin]" src="gr_grin.gif" />

Why would pcm not add more fuel if it saw 02 readings getting lean? <img border="0" title="" alt="[Smile]" src="gr_stretch.gif" />

StalkerLS1

I descreened my 2000 when I bought it used and got nothing but ping city at 5k RPM and up. Too bad my screen was destroyed taking it out so as silly as it sounds I made my own Screen.

Home-Made MAF Screen Pic

It's just a temporary fix as I plan to get a MAFT but it definitely solved the problem as all the pinging is completely GONE.

Unusual T/A

</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by camaro_ls1:
<strong> Unusual T/A

Where does your info comes from? Personal experience or is it just theory? I'm just curious since many of us here have done it and have not had any problems. Removing the screen doesn't necessarily mean you'll be getting more air either. It's there to straighten out flow from the factory baffle. The airflow is straight with an aftermarket lid. </strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">It comes from experience on my last two cars, via autotap readings and on the dyno via wideband. If you have a big screen in the way blocking all the air flow, then removing it would hence make more air right?? More air equals leaner ehh?? All cars are differen't I'm trying to give my info to this guy so he can decide if he wants to do it or not. Personally I would just buy some maf ends and leave the stock unit alone.. like I said every car is different, some cars run better some hate it..

Unusual T/A

</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by Dave Carney:
<strong> </font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by camaro_ls1:
<strong> Where does your info comes from? Personal experience or is it just theory? </strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">I know! I know! <img border="0" title="" alt="[Big Grin]" src="gr_grin.gif" />

Why would pcm not add more fuel if it saw 02 readings getting lean? <img border="0" title="" alt="[Smile]" src="gr_stretch.gif" /> </strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">I have no clue...... Why do our cars detonate? Why do we need to tune our cars after headers/cam installs? Why don't you do a search and then you will see that there are a lot of people who had problems descreening the maf? You will also find that some people have better luck with descreening it too.. <img border="0" title="" alt="[Big Grin]" src="gr_grin.gif" />

Colonel

"If you remove the maf screen You WILL run leaner regardless of what anyone has to say. More air equals leaner condition right?

Well, not exactly. More air entering the engine WITHOUT more fuel entering the engine equals a leaner mixture. More air registers at the MAF and at the O2 sensors. The result (after learning) is the same mixture. If what you were saying is true then ANY intake OR exhaust modification might lean the mixture. As we all know, that's simply not the case.

Also, just because you remove the screen doesn't necessarily mean that more air will enter your engine. There has to be a demand (there can be other greater restrictions.)

...And even if it does lean your mixture just a little bit (which I've seen no good evidence that it does despite having done it myself on several different vehicles) this would be a GOOD thing in most cases, as the mixture is normally on the rich side from the factory.

Colonel

"Why don't you do a search and then you will see that there are a lot of people who had problems descreening the maf? You will also find that some people have better luck with descreening it too.."

I think you'll also see that the positive reports outweigh the negative ones by at least 50-1.

Seriously, think about it. Increase the airflow (I'm humoring you here), what happens? The MAF reports a slightly higher load and the mixture is returned to normal (if this wasn't the case then any change in density altitude would throw off the mixture for as long as the DA was different, which of coures, certainly isn't the case.) If the O2s read something other than stoic during closed loop, the Ltrims will change to compensate. Stoic mixture is returned. All is well. <img border="0" title="" alt="[Smile]" src="gr_stretch.gif" />

StalkerLS1

</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by Colonel:
<strong> "Why don't you do a search and then you will see that there are a lot of people who had problems descreening the maf? You will also find that some people have better luck with descreening it too.."

I think you'll also see that the positive reports outweigh the negative ones by at least 50-1.

Seriously, think about it. Increase the airflow (I'm humoring you here), what happens? The MAF reports a slightly higher load and the mixture is returned to normal (if this wasn't the case then any change in density altitude would throw off the mixture for as long as the DA was different, which of coures, certainly isn't the case.) If the O2s read something other than stoic during closed loop, the Ltrims will change to compensate. Stoic mixture is returned. All is well. <img border="0" title="" alt="[Smile]" src="gr_stretch.gif" /> </strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">I'll be the first to confess I'm not an expert in this area but since were just sorta brainstorming here..

Isn't what your saying here Colonel true for part throttle driving only? Isn't the LT Fuel tables, etc ignored at WOT? I assumed the WOT Fuel Tables were a little more hard coded..

I'm probably talking out my A$$ though.. <img border="0" title="" alt="[Razz]" src="gr_images/icons/tongue.gif" /> Time to go read up!

StalkerLS1

Okay here's a little more info I dug up.

Under normal driving, yes the PCM will make short term fuel corrections (Integrator) to maintain 14.7:1 A/F Ratio. If the computer sees that it is always making the same correction with the short term values - say adding fuel - after a while it will make a "long term correction" or "block learn". This means that a new correction factor is actually stored in the PCM so that it can be used over and over again in future calculations.
If the long term correction or block learn value is right, the short term or integrator corrections will become smaller, and again start to vary slightly rich and slightly lean, with the average equal to 14.7:1.

WOT However.. everything Above is thrown OUT THE WINDOW!

Once the throttle exceeds about 70-75% open, the PCM no longer responds to the O2 sensors. The O2 sensors are dropped out of the "loop", and the PCM enters "enrichment" mode.

It targets a new, richer A/F ratio, that is better suited to high power, rather than good gas mileage. The system then operates as described in the first section, simply measuring the air flows and putting in what it thinks is the correct amount of fuel. There is no "feedback" from the O2 sensors to tell the PCM it is making the correct calculation, and the short term corrections, or "Integrators", are locked at their neutral value of 128. The long term corrections (block learns) may or may not be used in "enrichment" mode. It appears that if the PCM was using the BLM's to add fuel (BLM's greater than 128), the PCM will use the Cell 15 BLM's for enrichment mode. If the PCM was using the BLM's to subtract fuel (BLM's under 128), the PCM will use Cell 18, and lock the BLM's at 128 also.

All that said.. I know my car pings bad with the MAF Screen removed, despite giving it months to learn and make a permanent correction which it never did. Putting the Ghetto MAF Screen in and no more pinging..

Lastyrss

Great post Brian..... <img border="0" alt="[cheers]" title="" src="graemlins/gr_cheers.gif" />

Fast Eddie's 02 T/A vert.

I descreened mine 7000 mi. ago on my brand new car.I don't have any problems at all,runs perfect.

It's a free mod......you have to do it!!

Colonel

Ahhh, good post, yes. But what he doesn't realize is that although O2 readings aren't directly used during WOT (no big secret there), open loop fuel settings are infact based on what the PCM learns while it is in closed loop.

Long story short, real life experience shows that time and time and time again, both closed loop and open loop fuel/air mixtures are eventually restored after screen removal. Try it. Test it. You will see and agree. <img border="0" title="" alt="[Smile]" src="gr_stretch.gif" />

Colonel

...And again, if this were not the case, those at high altitudes would find their WOT mixture WAY on the rich side (they don't.) Those in cold weather would find their mixtures WAY on the lean side (they don't either.) These two examples meaning all else being equal (we're simply talking about a difference in density altitude.) More air in equals a leaner mixture while less air equals a richer mixture? Right? But alas, we all know that these are not the cases at all. Only one thing can explain that...There IS compensation taking place over the long haul, both during closed loop and open loop. <img border="0" title="" alt="[Smile]" src="gr_stretch.gif" />

StalkerLS1

</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by Colonel:
<strong> ...And again, if this were not the case, those at high altitudes would find their WOT mixture WAY on the rich side (they don't.) Those in cold weather would find their mixtures WAY on the lean side (they don't either.) These two examples meaning all else being equal (we're simply talking about a difference in density altitude.) More air in equals a leaner mixture while less air equals a richer mixture? Right? But alas, we all know that these are not the cases at all. Only one thing can explain that...There IS compensation taking place over the long haul, both during closed loop and open loop. <img border="0" title="" alt="[Smile]" src="gr_stretch.gif" /> </strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">Colonel,

What your describing above is a function of the Map and Bar Sensors. If you shipped your car from one location at or below sea level to a location that's way above sea level your bar/Map sensors will go to work and account for this to maintain 14.7:1 A/F Ratio. You won't have to drive around waiting for your Long Term Fuel Corrections to fix this.

I would agree with you that open loop fuel settings are infact based on what the PCM learns while it is in closed loop. Still though, you can't deny that a lot of people despite the above have lean conditions with descreening / Porting the MAF.

It's just a theroy but perhaps the timing advance is based off some MAF Data in which case is simply adding way more timing at WOT than some of us can get away with. ??

It makes no sense to me either but apparently the MAF is in some way the very heart and soul of our ability to alter the A/F Ratio. Just look at the MAFT unit. What is it actually doing here? Fooling the Maf into thinking there's more/less air entering the Engine? If the PCM has the ability to learn and correct then wouldn't the MAFT be a temporary fix?

-Brian.

Apox

If i was to descreen the MAF could i buy like a hypertech programmer to fix the badtiming?

Colonel

"Still though, you can't deny that a lot of people despite the above have lean conditions with descreening / Porting the MAF."

Wait a minute. You're getting into porting the MAF now. That's a TOTALLY different story as you're altering the reported load to the PCM which is not the case with descreening (and also why your fuel/air is not affected.)

I gave a good explanation not long back as to why a MAFT works. See if you can find it. I think it'll help you.

And no, I've not seen where people have caused pinging problems by descreening (porting, yes.) Speak up if you're out there. It's been over 4 years into this game and I haven't heard from you yet. <img border="0" title="" alt="[Smile]" src="gr_stretch.gif" />

unit213

I do have pinging with my descreened MAF, BUT it's not a result of removing the screen. That may be the case with others who've removed theirs.

Colonel

</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by Apox:
<strong> If i was to descreen the MAF could i buy like a hypertech programmer to fix the badtiming? </strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">That's not a good reason to buy a HPP3. It's so called "Power Tuning" usually causes a power loss. It leans the mixture (often too far) and increases the timing advance (often too much at some RPMs under some loads.)

Descreening a MAF will neither significantly effect your WOT mixture or timing advance. Porting the MAF will.

How much timing advance are you getting now? If it's very low it's most likely caused by knock retard. Get rid of that and you timing advance will look MUCH better.

Gary Z

Colonel, Brian,

This is the most interesting and informative discussion that I have yet discovered on this valuable site. Thanks to both of you for your efforts.

The lesson for the rest of us should be that one of the best ways to learn is to ask questions that will get the experts into a pissing contest. <img border="0" alt="[punch]" title="" src="graemlins/gr_punch.gif" />

-Gary