MAF porting

[BrdWAtti2d]

Well I'm in a discussion on another forum about MAF porting. Another user is saying that it will screw with A/F ratio in a negative manner. Back up a few weeks. I pulled my MAF just to clean it up a bit, took it apart and polished the heck out of it, I've seen no difference in performance. That really wasn't the point of doing it. It's ugly and I just wanted it to look a bit better. I have a hard time believing that smoothing a 5" section of the intake is going to have much of an impact. Unless I'm way off base here the purpose of the MAF is to meter air. So, 1 liter per second of air at 80 degrees through a smooth tube would be the same as 1 liter per second of air at 80 degrees through a rough tube. It's been a while since I was in high school but I'm pretty sure the laws of physics haven't changed. Thoughts from the brain trust?

[Joe 1320]

Smoothing things up doesn't hurt. Polishing doesn't affect much of anything. Porting a MAF and ditching the screen was done way back before programming was available in order to lean out a factory rich condition. GM puts a slightly rich mixture at WOT as a little added protection against parts carnage. Of course this isn't the best A/F ratio for power, so the MAF work was a bandaid. Now if the Maf and it's intake pipe are poorly designed, it can be a bottleneck. On a stockish LT-1, it's not the MAF that needs work.

[BrdWAtti2d]

Thanks for the reply Joe. So the only time this "might" affect things is if you remove the center post and de-screen? Sorry If I'm being a pita here but I'm just trying to understand how this works. I'm assuming the little wires in the MAF measure the speed of the air moving over the wires and in turn caluclates the volume of air in conjunction with the intake air temp to adjust for density? So if you removed the center post the volume of air moving through the MAF would be incorrectly calculated? How does de-screening effect this? It doesn't effect the way the MAF calculates air volume, it would only offer greater flow and less turbulance? Not saying I'm going to do either of these things, just trying to educate myself.

[FTA1995]

If you ever plan on using the MAF for closed loop tuning in the future, I suggest you leave it alone. The benefit isn't all that great; if you believe you're getting an overly rich running condition, you should fix that first before making any judgment calls on modifying working components.

[Injuneer]

The MAF sensor works by heating the wires to a specific number of degrees above the incoming air temperature, then measuring the power required to generate that temperature, using a Wheatstone bridge circuit. Knowing the power input to the wires (= the heat loss to the air), and knowing the specific heat of air (BTU/#/degree-F) the MAF can calculate the MASS (not volume) air flow. The PCM needs to know how many pounds (mass) of air is entering the engine, so it can squirt the correct pounds (mass) of fuel required to achieve the target air(mass)/fuel(mass) ratio.

What you have in effect is a hot wire anemometer.

But.... the wires are only heating the tiny mass of air that is touching them, so the meter calibration has to be based on an assumption of how closely the velocity of the air past the wires represents the velocity of air across the total open area of the meter. That's why the screen is there - to make the velocity across the open area as uniform as possible. Remove the screen, or the divider wall, and the velocity distribution across the open area is no longer uniform (unless the inlet ductwork is extremely symetrical = 2002 Z06) and the factory calibration is no longer valid.

Leave it alone.

[BrdWAtti2d]

Thanks Fred, wasn't planing on doing any modifications to it, just wanted to understand how it worked and how someone's modifications might affect it. That makes it very clear. Thanks again for your usual in depth explanation.