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[FTA1995]

okay guys,
I've got a new idea;
I would like to write new, accurate to the part flow tables for my MAF to the pcm to organize things a bit for the motor swap in about 6 months.

Heres the deal:
I've got the dreaded granatelli open flow "upgrade" which everyone knows does not line up proportionately with the stock closed ended and screened MAF.

I can not find any information linked to any successful modification to what I'm trying to do here.... I'm wondering if I need to get a few devices set up to send a set amount of air mass through at any given time while measuring the frequency output of the MAF at given mass flow ratings, and then attempting to build a appropriately proportionate table. It's going to be difficult to do it that way, especially considering the dynamic changes in flow through different velocities without the screen.

It's going to be way to hard to switch to speed density since the weather is so crazy around my area, I have run sped density before, but I've run into a few problems in certain conditions severe enough to make me desire otherwise....

To summarize; I would like the increased flow benefits while maintaining an accurate air metering for tuning the right way.

Ideas? Anyone tried this themselves?

[Injuneer]

You would have to set up the MAF in the suction side of a head flow bench, and install the actual inlet ducting you plan to use, on both side of the MAF sensor. The ducting will have a significant effect on the calibration of a sensor without the screen.

The flow bench would allow you to control volume air flow rate, but your sensor needs to be calibrated for mass air flow. That's simply a matter of recording the pressure and temperature for each volume flow rate and converting it to mass flow using the perfect gas law..... pretty much what the "density" portion of speed-density does.

There are online plans for a "do-it-yourself" flow bench, using a shop vac.

The less complex alternative would be to simply by a new factory sensor, with the screen intact.

[FTA1995]

Flow bench sounds like a good idea.
Of course switching to the delco maf is a simple solution, but it would seem that the screen system would keep the CFM up but potential velocity down.

[Injuneer]

"keep the CFM up but potential velocity down" doesn't really make sense if you think about it. Since the meter has a fixed cross-section area, the velocity has to go up proportional to the CFM.

The objective of the screen is to provide a uniform velocity across the open area of the meter, so that the tiny portion of air hitting the thin film resistor is representative of the amount of air passing any other point on the cross-sectional area. That's why removing the screen ruins the calibration. The flow velocity distribution across the open area is no longer uniform. The uniform flow also helps reduce pressure loss through the sensor.

[FTA1995]

right, but i'm thinking about the minute resistance from the support for the thermistors. Yes, the screen forces an even parallel flow laterally across the sensor, but i don't believe that removing the screen would increase the flow rating. I made a crude drawing to make sure we're talking about the same thing here. the first one is with screens, the bottom two are both without screens and generally speaking have much more turbulent flows. I'm also not really taking cavitation pockets into effect because I'm already thinking way too far into this.the bottom right would be a variating pressure pattern decreasing as you get closer to the outer diameter of the housing.