ok red i have one last question if i put the maf part inside a larger tube for instance from 2 in maf to a three in tube what happenes to the other inch of open space in the intake?
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He was refering to the DIAMETER of the MAF tube, not the length of it.

If you did change the diamter of the MAF tube you would cause it's readings to be low. MAFS are calibrated for the diameter tube they are in. If you put a maf in a 5" tube, it would read WAY low!

 

i was talking about the diameter also but thanx anyway

 

Random got it...

The MAF sensor works by air cooling a small heated filament. A tube with a smaller diameter forces more air past that little heated filament inside, which cools it faster. A tube with a larger diameter would allow to go around the filament, which causes it to cool more slowly.

The net result is, the exact same MAF filament inside a larger diameter tube will read less air because of the lesser cooling. The stock computer will see this lesser reading and inject less fuel, so you end up running lean (very lean depending on how much different the tube is)

Also consider, the area of a circle grows exponentially with diameter. A 2.5" tube has a cross-sectional area of 4.91 inches... But a 3" tube has a cross-sectional area of just below 7.1 inches. We only increased the diameter of the tube by 1/2 an inch, but the area jumped by 2.2 inches. That's quite a change for the stock ECU to correct for.

Oversized MAF sensors are typically built in conjunction with oversized injectors, or are tuned with a different correction factor to begin with. I suggest you do not mess with it.

-Red-

 

Actually, if you wanted to try an expensive experiment, you could do this...

Given: The stock MAF sensor is 2.25 inches in diameter. The stock injectors are rated at 245cc/min.

Change: Replace the stock MAF tube with one that is 2.75 inches in diameter. Replace the stock injectors with ones that are rated at 370cc/min.

Theory: Replacing the stock MAF tube with one that is 1/2 inch bigger results in a MAF that can theoretically flow 49.4% more air at the same electrical output (3.976" vs 5.940" cross-sectional area). This theory is flawed however, because the filament itself impedes flow and I cannot account for what it does to maximum volumetric capacity of the MAF tube. There are also things I'm not figuring, such as texture of the tube wall and actual MAF sensor calibration.

Caveat: Doing this should hypothetically allow you to run a larger MAF without running lean and with "less" constriction in the intake system. The problem is, increasing your intake size from 2.25" to 2.75" is never going to make enough power to use all those 370cc/min injectors -- you will need substantially larger modifications to actually USE all the airflow the modified MAF can see. At that point, you're better off using a piggyback or other method of fuel control.

-Red-

 

That's what the guy I talked to told me to do he said make sure that I use the same injecters that came with the MAF that I had!

Does the elantra 1.8 have the same injecters as the 2.0 tibby? They share the same MAF as far as I know!

 

"Use the same injectors as the MAF's original car" doesn't really hold true. All MAF sensors are NOT created equal.

You can have two identically-sized MAF sensors (both 80mm) and blow the exact same amount of air through each at the exact same temperature. One might read 1.5 volts, the other might read 2.8 volts. Same size, same air, same temperature but TWO different outputs.

MAF sensors are not linear in output either. Our MAF sensor may send 1 volt when it sees 8lbs/min of air flow, but at 16lbs/min of airflow it sends 3.6 volts. The air doubled, but the voltage didn't...

What it actually comes down to is the ECU that was in the car originally. The ECU knows 100% that "This much voltage = this much air = this much fuel I have to spray". If you change the MAF so that the same amount of air reports less voltage, you confuse the ECU. The simple answer is "well duh, just change injectors". The problem is, MAF sensors come in lots of different calibrations. You can't do that.

The best way to oversize a MAF is to buy one specifically built for your car. Own a Mustang? There's gazillions of options for bigger MAF units.

For those people who are not lucky enough to have aftermarket MAF sensors, the absolute best way is to modify your stock sensor. And the only REASON you would want to modify your stock sensor is if you are approaching the limits of what it can read already.

Unless you're making better than 200HP at the tires, you aren't there yet.

-Red-

 

Ok red you know everything about tibby stuff but what about us accent guys? My MAF is so small it will fit inside your MAF The accent is limited by there stock units the next best thing is to upgrade to the tibby elantra unit! SO besides my SAFC is switching to the same style injecters going to help the lean problem that occurs from the switch!

 

Ok now wait, how do you KNOW the MAF is the constriction? What else have you done to the car? Ported the head? Installed cams? Had the intake manifold bored out? Throttle body?

What makes you so sure your MAF is holding you back?

As for fixing your lean problem, use your AFC, that's what it's there for. Adjust fuel UP across the band. Go to a dyno shop and get it tuned right, because you don't want to screw it up. An AFC on a MAF-equipped car will solve a lot of fuel problems if you have it tuned right.

-Red-

 

OK dude don't blow a gasket!! lol

It's not that the MAF is a restriction but the fact that it will be when my turbo is put on!

Whats the chance that we can put one of those speed density controlers on the car to eliminate the MAF all together? I think that is what it is called?