Mine is ported and I was wondering if anyone has ever flowed one somehow to see what the difference in flow was so I can give my computer a more accurate reading of the actual amount of air going into it before I try to mess with the AFR...

 

In general, you increase the MAF tables about 20% over stock to get the amount of air flow when it is ported/polished. The exact amount will probably vary on the quality of the porting, but 20% seems to work pretty well on my ported/polished MAF.

 

Do a search in LT1 Tech for a post from about 2 months ago.
There was some good info in some of the later pages about air flow capabilities of the LT1 maf sensor.
IMHO, you're going to be fighting an uphill battle with the ported maf sensor and I would suggest you find a stock one since it is not a restriction until you're making some serious horsepower.

 

I have a stock one but for now ide just like to get it tuned as it is I dont think it was really polished very well and the edges where the wing was cut out is a lil rough so ill say 15%. So basically add 15% to the MAF calibration tables?

 

Don't touch the MAF tables. Stay with the stock MAF if you can.
If you add even 10% to the MAF tables the car will run rich and will get bad gas mileage. Proven through experience.

 

I messed up my last post I meant to say I have a stock one I could put on but it has a ported one on there at the moment, also I have a quick ? about the timing above someone said teh stock timing at WOT, im assuming 95 and 100 MAP, was 37-39 above 4k I only see 35-36 at 95 and 33 at 100, is there anything I can do to the timing above 4k rpm to make any sorr of improvement Ive already added 3 degrees to the whole table below 4k rpm just as an initial experiment, as for the fuel at WOT if I set the % change to 0% the AFR is around 12.7:1 which would only have any serious benefit in the higher rpms where it begins to richen up, is it that easy of a fix or is there more to it than that? Oh also in the open loop AFR table it was suggested to me to add 3 or 4 across the board to help gas milage after startup before it goes into closed loop, this also seems like a pretty crude way of doing things but maybe it works any comments on any of this stuff? Thanks for the help so far!

 

MAdwolf, i am going to be making about 525 FWHP with my 383 stroker. I am running 12.3:1 compression, my cam specs are 260/260 duration @ .050 lift, 110 LSA, .617 lift. My MAF sensor is completely ported and polished and the little black braces are cut off too. This was done previous to my engine being rebuilt. We are almost ready to put this thing on the bench Dyno and I am working on a base tune to fire it up with. I noticed you said to leave the MAF tables STOCK. IS that just in his case? Or should I leave mine stock too ?

 

Ported MAFs usually behave very erratically on widebands. One pull you can get an AFR curve, then the next pull it would be slightly different on the same program. I'd recommend trying a stock, unmolested MAF first. It should still be OK for your application.

 

What about the grannatelli MAf sensors? Also saw an 85mm ZO6 MAF sensor that was adapted for use with the lt1 somehow. So dont even descreen the stock one either?

 

Stock, non ported, non descreened MAF is what you want. Both Granatelli and the Z06 conversion MAFs are junk in my opinion.

 

Grannatelli MAFs are junk for the one main reason that no one knows what the calibration is. Using a ZO6 85mm MAF is a viable conversion and does work well in my opinion (for what thats worth ) But the key to making the ZO6 85mm MAF work is getting the table correct. It took me several interations to get it right and to get the trims working well.

I have 2 cars running now with the ZO6 MAF sensors, one with a CC306 cam and the other with a GM 847 cam. Both cars are running well the CC306 cammed car is running 11.80s now all motor and just bolt ons and ported heads.

 

I have no problems with my ported/polished MAF. Didn't have any problems even when I did not have my MAF tables adjusted, either, or after I adjusted them for 20% increase. In my opinion, you just have to get the tables right, or it will not run correctly (especially in the case of the Z06 MAF conversion). I do not recommend a Granallti MAF, since they are suppose to already have the tables adjusted in the signal sent to the PCM, causing more problems than fixing them. I still believe that those people who have problems with a ported/polished/descreened MAF have somehow damaged the sensors on the MAF when they modified it. I've never had problems with mine in over 2 years, and most of the guys in my area with the MAF modified don't have any problems either. Anyway you go though, make sure you get the tables as perfect as you can (of course, this is easiest with the stock MAF).

 

Well I got my car back running again and I leaned out the AFR some in the higher rpms where it seems to get really rich but I was wondering if its safe to do with the ported maf since madwolf says you dont always get a consistant AFR which means it could go leaner than I want, I could swap a stock MAF sensor on as we speak but would rather not go through the trouble since have a hard time getting it to seal with my ram air box if I dont need to.

 

If you don't want to have to worry about it, put the stock maf that you have on the car and return the tables back to stock.
You're trying to change too many things at once and you could run into trouble.

Yeah, I said that in another post. Are you datalogging anything, or are you just going by what is in your timing map?
The computer does add timing at different rpm at wot.
Up to 3500rpm you'll see an additional 2 degrees, 4000 and 4500 an additional 3 degrees, and above that an additional 4 degrees.
Log a run, you'll see.

 

I am logging runs but I didnt know it added timing on top of what is on the tables... thats good to know lol. Thanks