Thread: Air flow meters

I was talking to a land rover nut the other day & he informs me that the mesh before the airflow meter is just another filter (just in case) is this correct????????

NO
The mesh is there to align and average the airflow so that the sensor gets a set proportion of the air flow entering the MAF.

I read a tech article long ago ( by Bosch AFAIR) where it was stated that the mesh should be removed only if there is at least 300MM of straight tube entering the MAF.
The belief/myth that it is an extra filter is the result of wishful thinking, and an article by julian Edgar in Autospeed that he got better airflow by removing it, without him realising its true function.
Regards Philip A

Originally Posted by PhilipA

NO
The mesh is there to align and average the airflow so that the sensor gets a set proportion of the air flow entering the MAF.

I read a tech article long ago ( by Bosch AFAIR) where it was stated that the mesh should be removed only if there is at least 300MM of straight tube entering the MAF.
The belief/myth that it is an extra filter is the result of wishful thinking, and an article by julian Edgar in Autospeed that he got better airflow by removing it, without him realising its true function.
Regards Philip A

To second that, I had a 90 model dropped in here as the local mechanics couldn't get it to run right. Had a duel battery set up and the feed horn cut off the air filter housing to make it harder for the MAF. We discovered by lengthening the feed to the Hot wire it came good. On a closer investigation I then noticed the mesh was gone!

The mesh on mine fell off so I chucked it. Never noticed any changes. That was at least 1 year ago.

The mesh on mine fell off so I chucked it. Never noticed any changes. That was at least 1 year ago.

Well logic would suggest that at high flow the amount of air at the outside of the curve would be greater than the amount on the inside of the curve.

So the MAF would probably underread and the mixture be leaner than with the mesh. So you may lose power as the AF ratio would be less than planned.
But with the age and state of most sensors and injectors in these old cars, you may be better off and get better economy.LOL

But the mesh is not just a pretty face, it is there for a purpose.

Regards Philip A

The mesh does nothing it just stops crapola getting in your engine

As for making it a smoother flow thats not really true the air has to make a 90 degree turn inside the maf to go through the wholes so making it a lamina flow is pointless

The experts may disagree

The mesh on the MAF is used to smooth out airflow to ensure the sensors have the best chance of a steady reading. It is not used for measuring the air flow per se. In situations where owners use oiled-gauze air filters, it is possible for excess oil to coat the MAF sensor and skew its readings. Indeed, General Motors has issued a Technical Service Bulletin, indicating problems from rough idle all the way to possible transmission damage resulting from the contaminated sensors. To clean the delicate MAF sensor components, a specific MAF or Electronics Cleaner should be used, not carburetor or brake cleaner.

This from Wikipaedia . It is not necessarily correct as it reflects the views of the poster, But it is a reference that supports my recollection of other more authoritative sources so I will use it. LOL

Funnily enough the Book on Bosch Injection that I have, written by the Chairman of the Technical Committee of the SAE, Charles Probst, calls them "protective screens"
Regards Philip A

Originally Posted by steve_35

The mesh does nothing it just stops crapola getting in your engine


The experts may disagree

Surely that is what the air filter is for?

Originally Posted by steve_35

As for making it a smoother flow thats not really true the air has to make a 90 degree turn inside the maf to go through the wholes so making it a lamina flow is pointless

The experts may disagree

I think it is possibly to make sure there is the same mass of air equally distributed across the entire cross section of the air flow meter. That means that the small amount that goes through the sensor part is a true indication of the entire amount of air passing through.