How a MAF works

[MTCFORUM]

A MAF measures Mass Air Flow. That is the mass of the air flowing into the engine.

There are two small wires inside the MAF that get an electric current ran across them. As the current flows the wires heat up and as the wires heat up, the resistance changes. The MAF has circuitry inside it to measure this change in resistance across the two hot wires.

The more air that flows across the hot wires the cooler the wires get and the more the resistance changes, hence more air flow. If it is a high density day, then there is more air density and thus more cooling so more air density is automatically compensated for. The same is true for altitude. The lower air density does not cool the wires off as much so it measures less air flow.

Now, here is why you should NEVER have a K&N filter on your car. The oil from the filter migrates into the MAF and onto the hot wire. The wire is now insulated and will measure less air flow than what's really flowing into the engine, thus shifting the engine lean, this is bad.

While I'm K&N bashing, I have another point. Let's give you a rag to cover your mouth. Then I want you to run around with the rag over your mouth and breath through it. Now, let's do the same thing but this time I'm going to put oil on the rag. Which way do you think you will breath better? We have a few knowledgable medical people here, answer that question.

I have NEVER seen a K&N filter gain power over a paper filter if the dimensions of the filter are the same.

To make the insulation worse, once oil gets on the hot wire, it will now collect more dirt, thus insulating the wire even more.

Have you cleaned your MAF lately?

jerry

[MTCFORUM]

The talk about the oil from the K&N filter really has me thinking about crud being built up on my sensor so I will clean it with the electrical parts cleaner spray when I get the car back from the body shop and re-install my C&L\K&N mass air.

I went and looked at my mass air stuff that I have stored in a plastic bag for safe keeping until the car returns from the body shop and the oil dripping from the thing seems like the thing was maybe over treated with the oil. There were literally drips of oil all over the rubber part that are from the filter element. I cleaned all the oil off of the rubber parts of the filter last night and tonight there are more drips again. Last night when I cleaned the C&L tube that the sensor mounts to with an alcohol coated Q tip, it did come out pretty filthy so my sensor must be even more crusty. Maybe this will help the idle problem I've been having but I still want to get Mr. Wizard to re-burn my chip or do the in car calibration to the EEC.

Does anybody think the seemingly excessive drippings of oil from the filter element onto the rubber parts of the filter is a sign the thing was over treated with oil or is it supposed to be that coated with oil?

thanks

[MTCFORUM]

Steve, if there is noticeable oil coming off the filter, then most likely your MAF wires are covered in it. This is not good. If you still have stock MAF screws, you'll need a tamperproof T-20 to remove them, you can get one of these at any reliable hardware store (no not HomeDepot).

I don't care what K&N says, oil is bad and a filter should never be oiled. They are essentially making a poor filter, from a filtration particle standpoint, to get less pressure drop across the filter, then using the oil as a means for filtering the incoming air. Funny how they are about the only company that has you oil the filter.

If you look at a Mark, from an air flow standpoint, there is about 5-8 RWHP to be gained from a better induction system prior to the throttle body. The air meter is about 1/2 of this contribution. So, if you improve the ability of the motor to get air in, you will gain some power.

jerry

[MTCFORUM]

Which aftermarket filter out there doesn't have oil on them... I keep reading about how all these non-K@N filters can be re-oiled with K@N stuff, which leads me to beleive they also have oil....

anyone have any recomendations??

thanks for the info Jerry... I noticed a lil Oil on my MAF wires a while back and didn't think much of it

BK

[MTCFORUM]

What is the best thing to clean the MAF with???

This might explain the check engine light that comes on every few month in our 98 GT car?? Lean condition triggers itself every now and then and we dont know why? Ever since the install of a COLD AIR KIT with a big OILY K&N filter.

Also as already asked what other filter can I use? A K&N came with my blower kit also... I imagine sticky oil cannot be good for impellers and bearings over time either?

[MTCFORUM]

Cleaning MAF wires 101. <A HREF="http://www.tccoa.com/articles/intake/mafclean.html" TARGET="_blank">http://www.tccoa.com/articles/intake/mafclean.html</a>

[MTCFORUM]

I've been using K&N filters on carburated and speed density equipped cars/boats for years now with no problems. Paper and foam filters on these same cars/boats were nothing but trouble.

Paper filters are wax impregnated paper that clogs too fast for daily use while foam, well, foam filters fine when used with sticky air filter oil but foam is just too restrictive. I'd rather spritz some trichlor on the MAF every so often than have to use paper or foam.

While I can see your point with K&N oiled filters on a MAF equipped engine I still need to ask, what is the alternative air filter medium? I'm always interested in seeing different points of view and learning from them.

[MTCFORUM]

What is the result of high humidity to the MAF reading? Do the O2 sensors correct the MAF?

[MTCFORUM]

There are other types of MAF meters which are not effected by oil of a K&N. A friend of mine's Porsche 928 uses a 'barn door' MAF. It has a mechanical mechanism, which is deflected by the air moving past it. Down side is that they cost more and have parts which can wear out.

[MTCFORUM]

Wouldn't that make it a speed-density setup and not a MAF?

[MTCFORUM]

THat would be a VAF, Vain Air Flow setup like the probe

Josh

[MTCFORUM]

<IMG SRC="http://www.students.tut.fi/~hezekiel/pic/kjet.gif" BORDER="0">
Barn-Door is old technology which was used by Bosch. Not really something you'd use over a hot wire MAF.<BR><BR>
[Modified by JohnE, 9:49 PM 5/1/2002]

[MTCFORUM]

Ran one of these for &gt;170k miles on an Audi-engined Porsche, and it was flawless, except for the injectors getting leaky around 100k. Massive fuel filter, and all bets are off if dirt or water gets into there. Needs approx 65 psi fuel pressure.