Reposted here, from my original posting on a GN list.



Please, read this fully before just jumping in and removing your MAF screens or updating your systems. The following is a short version of lots of info., and related items. First off, the intake tract is made up of every little component from the intake valve clear thru to the air filter. For this simple little bit of data I'm just looking at one small element of it.
While air flow is of critical importance to an engine, the metering of fuel to that column of air is what makes the power. Any engine is just the some of it's parts, and each component must be matched, to all the others. If you want to get into making changes, then you MUST understand ALL the ramifications. Not some, all. As per my normal petulant self, I want to stress that HP is a function of knowledge, and that knowledge is only
beneficial when executed in a proper tuning route.

Now for the News:
At 28" of water,

A LS1 MAF with screen, will flow 747 CFM
without screen, 800 CFM
A LT1 MAF with screen, will flow 637 CFM
without screen, 730 CFM
A GN MAF with screen, will flow 583 CFM
without screen, 660 CFM

In the case of the LS1 you might go owww, ohhh, that's 50 CFM, or a 7% change. Knowing that for every 1% reduction in intake restriction, you can generate 2% more HP you might go yepeee, 14% more HP. But, that's not the case, Unless your MAF is located at the TB, and your not using any other intake tract ducting (ie no turbo)(and that if removed, the actual transistion is 0% restrictive). But, it is an indication that there is
room for improvement.

As per an old post by Mike Pitts, and a new Hot Rod Mag article, there is some HP to be gained in removing the MAF. Both seem to have shown about 30HP.

The trouble with just removing the screen is that it throws the MAFs calibration completely out the window. If you're doing your own chips, then you can tune things properly and get things right again. But, be prepared for a real learning process.

If you're seriously thinking of wanting to get this right, I'd suggest you go thru the old procedures of getting 128s across the board, and then base lining your WOT performance. Then once that's PERFECT. Then remove the screen, and start over. And by start over, I mean start with your virgin bin file, and then table by table rebuild your scalers and MAF tables till you again get your 128s, and then start working on your WOT stuff.

Again, improper use of this info., WILL melt your motor down. Diligent testing, note taking, and patience is mandatory. All changes need to be made one step at a time.

It also might be an advantage to pick up a spare MAF, and then swap MAFs/chips while trying to get this right.

For related reading, please peruse:
http://www.gnttype.org/techarea/engine/mafrelocate.html

If you really want to understand the scalers, and MAF tables, an ecm bench is an excellent learning tool.

YMMV,
FWIW,
Bruce
87 Black Car, looks kinda stock <g>.

 

Bruce,

I have read many times that you should *not* adjust the MAF scalar tables.

So I took that advice seriously and never touched the tables during the tune.

I was able to achieve 128 course blms and the int were right around 128 through all the cell.

I used my WB for WOT tuning.

Am I still missing something? All my adjustments were made with the injector pulsewidths. I was amazed at how close I could get them with just that one parameter.

I did however adjust the MAF tables for idle so my previous statement about never touching them was not entirely true. But the idle area was the only on I touched.

As stated before, Am I still missing out by not tuning the MAF tables.

Thanks. Great info.

 

If your running a Stock MAF there should be no NEED to alter the Scalers, and Tables.
You ahead of 99% of the class by using a WB, so you're in the area of being far more accurate then blindly guessing about what's goind on.
Now there is a stage II to all this, that I'm still gathering notes and experimenting with.


Now with the above is with the ASSUMPTION that we're still talking about cars well within the design parameters of the system. After all this is DIY PROM.

Now as you get to non computer oriented cams, and manifolding there are other issues. And if you read my Final Answer, you have a slight insight to where I'm going with this.

Carefully read and reread the TPI board posting about the Magazine article. Then the final answer and then this post.

Then you'll maybe see what been left out of all this todate.

The Chase is Afoot........
Bruce

 

hmmm

 

It's getting hard to figure where to post this stuff anymore, there are so many threads running.
But,

While I've menetioned the Scalers, and Table entries, and that when you change the Scalers, you change the LV8 calc.
In getting to the fine edge of things, when you change the LV8 cals., that throw off everything related to LV8s. While, if you haven't changed things too much you might be OK, but if you get in there and really get the MAF stuff right from an AFR point of view, you might have a real chore getting the MAF filtering, and LV8 limits and parameters all back to correct levels.

I've revised my earlier thoughts:

If you reduce the MAFs restriction to about 0, and then recalibrate it correctly, there is no performance difference from MAP to MAF. The only real difference is the 8" of intake tract length.

 

vs. a k&n on the tb?

 

vs. a 2.5" pipe restriction as now you can have whatever size tubing you want going wherever you want

 

Hi Grumpy this link is dead. Would you have any of the info in another thread on the GN boards??? I have looked here through DYI but have not came across anything. Thanks, Jay

 

On Turbobuicks.com there was a thread that had the actual flow vs reported MAF readings, of a GN MAF.

Just as another lil comment. While with the stock small plenum things are too bad, but with the larger the plenum, the larger the intial MAF error is, ie, when you open the throttle since, part of the airflow is just going to correct the vacuum level in the plenum, rather then thru the engine. So there is a false rich, and depending on combo maybe just enough to correct for AE, or cause a serious flat spot off idle.