MAF Conversion

Most 80's and some early 90's BMW's used a Bosch vane air flow (VAF) meter to measure the volume of incoming air. The VAF uses a vane (or flapper) in the flow path of the incoming air connected to a variable resistance track to give the ECU a signal. The flapper and the small rectangular port it rides in causes a huge restriction. On my VAF meter, it caused a pressure drop of 4" of Hg at 300 CFM according to the flow bench info.

A Mass Air Flow (MAF) meter is a cylinder with a small heated wire element in it. The voltage (or current, I can't remember) required to keep it heated varies directly with the mass of air passing through the cylinder. The cylinder presents very little restriction to the air flow compared to a vane meter. This gives you the power gain. To over simplify things, an engine is essentially an air pump: more air in means more air out, which means more power.

How does a MAF meter and its linear voltage signal work with an ECU looking for a divergent (curved) voltage signal of a VAF meter? Custom calibration and a black box. The MAF conversion is calibrated with the black box to give a signal identical to what the VAF meter gave for the same air flow. This means NO TUNING by you! No air/fuel mixture meter is required. There are trim pots on the black box to allow for up to a 40% larger injector if required in the future. The other MAF conversion out there (Split Second) has four trim knobs which must be set using an air/fuel meter and lots of trial and error. The advantage of the Split Second unit is its flexibility. It can be moved from your BMW to your Porsche without recalibrating the MAF meter. Although, if you have more than one car that you want to convert to MAF, you can probably afford two conversions.

 

MAF Conversions

 

 Pros

 Cons

 Split Second

 Flexiblity - Can be moved to another car without recalibration

 Difficult initial setup (4 different knobs)

Expensive > $1000 with air filter

Requires air/fuel mixture meter

 Modern Performance

 No setup - calibrated to your VAF meter

Inexpensive - < $550 with cone filter

No mixture meter required

 Must be calibrated to VAF of a new car

They have done a calibration for the VAF for my '88 535is which has a part number ending in 027 (I think). It is used on E28 and E34 535's as well as some 6 and 7 series. They may have a calibration for other VAF's. If not, you will have to send a VAF of the same part # as yours for calibration.

Ask for Nick Mannarino mp23ccSPAMSUCKS@aol.com at Modern Performance in West Long branch, NJ. (732) 222-3679. Don't forget to remove the spam reference from the address.

Oh, yeah, this thing adds some kick. I lent it to someone for two weeks and was dying. I did not realize how much it did for my car until I had to go without it.

 

Ed

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