LS1LT1 Forum banner
21 - 28 of 28 Posts

·
Registered
Joined
·
214 Posts
Wish I would have known this before I de-screened, port and polished mine.

+1. I have three ends, 1 fully opened, ported and polished, 1 descreened and 1 stock. While ported one sounds the best at WOT, but the idle quality was scary all over the place when the engine warmed up, even the descreened unit had a less than perfect idle, so I have the stock ends with the screen, IMO best for my setup and it didn't cost me $400 to learn the lesson.
 

·
Registered
Joined
·
1,605 Posts
This topic comes up quite often.

TPIS says it's the way to go.

Byran at PCMFORLESS asks, on the data sheet, whether the MAF has been descreened or not. So apparently it does make a difference in how he re-programs the PCM.

I ran across a GM HIGH TECH PERFORMANCE mag article (Jan 2008) where eleven LT1 'F' body cars, all with various bolt-ons, competed. The quickest 3 or 4 had de-screened MAFs. Now, there may be other differences that account for them being the quickest, but it least those 3 or 4 guys believe in the benefit a de-screened MAF provided them.

You may be able to find the whole article on-line; it's entitled "TOP DOGS, BOTTOM BUCKS".

I once read that the LT1s are tuned rich from the factory, so de-screening the MAF may lean out the WOT A/F ratio that could result in quicker times. I guess the best way to find out is to do back to backs.

Jake

West Point ROCKS! Nation's TOP COLLEGE per Forbes Magazine!! Graduation Day Parade 20 May 2010!!!
 

·
Registered
Joined
·
6,381 Posts
All you have to do is compare your MAP reading at WOT to the barometric pressure your scanner reads. If they are essentially the same, there is no intake plumbing or filter restriction and therefore no MAF restriction. If there was, your MAP could not reach BARO. Any other HP increases would be just tuning. As I recall, GM uses the same MAF on the 502 RamJet big block. All this other crap is propaganda.
 
G

·
We need to think of the MAF sensor for what it is: a sensor. We don't try to "upgrade" the MAP sensor, the IAT sensor, or anything else. It's supposed to sense something, it's calibrated. We wouldn't port out our thermostats so that they could flow better, would we?
People actually do all 3. People who go from NA applications who go to boosted applications have to change their 1 bar MAP sensors to a 2 or 3 bar Map sensors. The car wouldn't run worth a damn if they didn't upgrade it. Also people modify the IAT by either putting in a resistor in the connector to make the PCM think that its cooler air coming in to increase timing. People also modify their IAT by relocating it further away from the engine bay to get a proper reading rather than having it heat soak by sitting in the engine bay. And last but certaintly not least.. People have drilled holes all throughout their thermostats to have water flow through them earlier. I have seen this done with a brand new thermostat.

Just throwing that out there :thumbsup:
 

·
Registered
Joined
·
977 Posts
I guess you told me! :) I know about the MAP sensor changes (I've helped do a 2-bar MAP SD tune for someone), but I meant modifying the existing one. We don't mess with its calibration or else the engine wouldn't run proeprly. That was my point with modifying the MAF sensor without correcting its calibration. I feel the IAT resistor mod is a hack, and I don't believe it has any effect on timing on '94-'95, but I agree that moving it so it correctly measures incoming air is a good idea. I've got to say I'm surprised to hear of the t-stat mod, never heard of that one before! So I stand corrected there. But it does seem like a hack when a person can just get a lower-temperature model.

But hopefully my point about the MAF was not lost even if my comparisons don't hold up 100%.
 

·
Registered
Joined
·
1,605 Posts
I recall reading on the 'Golen Engines' website not to use any other MAF than the stock one. No details were given as to why, it was merely an emphatic statement.

Now, if we have confidence in and respect for Golen Engines, their reasoning certainly bears examination as to the basis they relied on to make such a statement.

Modifying the stock MAF is a different issue though. Many, many guys do it and TPIS and others have flowed modified MAFs and found, after modification, they do, in fact, increase air flow into the engine. Whether the engine needs and can take advantage of the additional airflow is yet another issue.

The wrinkle is, that if the engine's current configuration doesn't require the additional airflow that a modified MAF supplies, no or little power increase will be seen. However, we must remember that the MAF was designed by GM for a set of specifications that the factory engine has when it leaves the assembly line.

So then, what happens when we begin modifying our engines - as most of us do - to create HP and Torque far exceeding what the factory had considered? It stands to reason that modifying certain parts of the engine are called for in order to meet that higher power goal. Common sense should be in control here.

As as basic, core example, merely having the programming of the stock PCM re-programmed on a totally stock engine shows an increase in power. Why? Because GM was faced with several variables and requirements which had to be met in order to make the car/engine pass all the Federal requirements and standards. Things such as C.A.F.E. and Gas-Guzzler Tax are two examples.

Buyers tend to prefer smooth idling, quiet exhaust, higher gas maleage cars; they sell more cars when they're manufactured that way. It's only after we get our hands on them that many of the design features go out the window.

My position is that to make an over-all, blanket condemnation of modifying the MAF isn't supportable. It's not a one-size-fits-all situation. It depends on the particular engine and the goals.

Just my view.

Jake

West Point ROCKS! Nation's TOP COLLEGE per Forbes Magazine!! Graduation Day Parade 20 May 2010!!!
 

·
Registered
Joined
·
618 Posts
jake i think ya hit the nail on the head, this is what i gather from it. a after market maf is more presice and sends feed back faster than a stock one however the factory computers can't benifit because the can't procces the information any faster than one the stock maf sends and on descreening the maf , don't do it enless you have a after market cai. the factory boxes make a lot of turbulance and mess with it, have heard the slp cai that has 2 tubes that go into one will mess with also. ram air cars are usally ok aslong as running a high flow filter. and yes your car will show a leaner afr after the descreening and or porting because more air is coming in and that is what happens when fuel is not added in to compensate for the more air. now if you need a little tuning for more air incoming depend on how much air your moving overall like a fairly stock car should compisate for it self, how ever if heavily modified car and moving a lot of air across the maf it might have to be retuned to comensate.
 
21 - 28 of 28 Posts
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top