Grim Reaper

You made a half dozen duplicate posts on "Tables for Ported MAF" with absolutely no post. I have deleted them and left just this post. Please explain what you want to know? Simply posting a a "Title" with no post will not get you many responses.

I8AStang

Sorry, the network here at the university messed up when I hit send, I did have a question. THanks for leaving it so I could ask.
I was wondering if anyone has calibration tables for the ported maf, and also if anyone has experience tuning for one. The reason I removed fins/screens in the first place is I feel I will be maxing it out. When I called tpis, they said it just leans it out approximately the amount you want, but the more I think about it the less I believe them. I've even thought about buying that wells unit everyone talks about, and just compensating after the tables are maxed. I am taking the car to the dyno, but I want it to be fairly close before I take it. Just to let you know, the car belongs to my dad, and is a vortec headed tpi 383 we are installing in a 71 cutlass convertible. From dyno sheets I've seen of simalar engines, it will need approx 280g/s of air (I have calculated this 3 different ways, and come up within 10g/s of 280 everytime). By the way, I'm new to this board and find it very useful. Even if nobody has a table, if anyone has done it and has experience on how it affected its calibration (not if it broke or didn't make the car faster) I would appreciate it. Thanks

Grumpy

If your maxing the MAF out then you need to change over to a MAP system.
Unless you consider yourself as good as GM I doubt your going to remove the screens and get the cal right.

No comment,
look at one of their chips and get back to me about what they're doing. or they think they know.

Just do it right it's sooooo much easier.
Or leave it alone.

Just that simple.

formula5

I am in the process of learning the maf tables in great detail.When I am done,I will write an article on maf.There seems to be a lack of information on maf systems.I have done some radical things with the maf tables to see how it effects the engine.But I am going to wait to release my finding until my research is complete.

I8AStang

I really don't understand your opinion on not doing it right by staying maf. I don't see much difference between compensating on the upper end of the table to obtain a good a/f ratio, and altering VE tables as you would in speed density to do the same thing(yes, I do know you have the BLM's to help you out, but wot on a dyno those don't apply, unless I don't unerstand how the car is using them). I do kinda wish I didn't port the thing, as I would only max it out around wot and after 4500rpms. I don't think it would be hard to get right, if the calibration was right until I ran out of table. Thanks agian for the replies.

formula5

Last time I checked gm uses maf as thier primary form of engine management.They have used maf always.Besides a few years gm used the ill fated sd.I will send you some info via email that might help, I8Astang.Maf does seem to have a bad rap round here.

Grim Reaper

Oh oh. Wait until Grumpy explains how some of his LT1 friends (the later LT1s use both MAF and SD) have found they get more power by setting their PCM to use "SD only". I'd love to explain more, but I will let Grumpy.

Craig Moates

Arm-wrestle, anyone?

I'm still a firm believer that the MAF system can be set up with a bypass system to give you any performance ceiling you want which, if it's calibrated via MAF tables properly, will give very little error. So you lie about the injector sizing? The innocent ECM never suspects a thing. Think about it.

Bottom line is when you cut out your 'fins' and remove your screens you are making a pseudo-bypass system. I did the calculations based on my own experience, and you're talking about a SIGNIFICANT deviation from the factory calibration. The RIGHT way to do it would seem to be to go ahead and take the darn MAF off and really calibrate it. Have access to a flowbency and a DVM? That'd do it. Just tube up a MAF and run it. Have access to a WTM flow meter or something? Good. Better yet, wha you could do...

Here's an idea: Set up two MAF units in series with pipe in between. Hook up two DVMs, one to each MAF, and a power supply, and then hook up a shop-vac to one end of the two-MAF assembly. You could go ahead and record the DVM readings of the two MAF assemblies in series independently or simultaneously. By doing this, you will identify the voltage -vs- voltage characteristics of the two MAFs compared to one another. Since you know the 'stock' MAF voltage-vs-flow relation from the stock MAF scalar tables, you thus know the 'modded' MAF voltage-vs-flow relation and can correct your MAF scalar tables accordingly.

By the way, one MAF is stock (the 'control' you're using to calibrate flow) and the other is heavily ported and/or has a bypass pipe. I don't know that a shop vac will move enough air, may need something else. And the relative goodness of seal of the shop vac with the array is varied manually to move from SCFM=0 to full-scale. Of course, once you move beyond the range of the stock you'll be extrapolating. And since you will need to fudge the SCFM numbers in the table 'low' below 255, and will only be interested in capturing the 'shape' of the voltage -vs- SCFM curve of the modded system, you'll have to fudge your FI sizing low accordingly by a linear factor.

Make sense? Thought not. It will work though. Although I don't know how you capture effects like backwash pulsations and the sort. I'd talked about this before, and while I have yet to do it in this particular system, I've done it many times before in related applications of liquid and gas flow metering. Anything can be used as an accurate meter of flowrate if it's calibrated and referenced proerly. And if you lie once, just use another lie to cover it up. The net effect will be the truth.

I'm still pressed to understand how (save feedback info on the EG composition) MAP, where you guesstimate volumetric air delivery efficiency, can be more repeatable from system-to-system than MAF. We're talking a total lack of experience here, however.

Nonsense I'm sure. Slap me down please. Now would be preferred.

formula5

I'll just say"maf is the black sheep."

I8AStang

I do have access to a flowbench, for some reason I thought it was more complex than a simple voltage signal. The thing is I'm just barely going to max it out(the table), so I'm thinking the Wells unit would have been a better option for me. It has been my experience that one form of engine management set up properly can duplicate the performance of any other(provide there isn't some ceiling as is imposed by the factory maf). I'm just personally fond of MAF because I think being able to directly measure air coming into the engine is easier. I've even looked into running MAF for our university FSAE car (we can not run speed density, only n alpha due to the fact it is a modified crotch rocket engine). I guess attempting to tune that thing on the dyno with the Haltech was sorta a turn off. The people at Motec couldn't seem to understand why I would want to run MAF. Oh, wait that's a different subject all together. Either way, I don't think I will be maxing it out much, but a table would be great. If all I need is a flowbench and DMM, I think I can do that. Thanks