Miata MX-5 VAF problem solved We had a peculiar requirement recently.
There was this Mazda Miata 1.6 which came withh a Vane type Airflow meter (also called as the Variable Air Flow meter or VAF). This type of unit has a flap in the path of the airflow and generates a voltage depending on how much open it is. This is used by the ECU to adjust fuelling. The VAF unit also incorporates a sensor for intake air temperature and also a switch to operate the fuel pump when there is airflow.
The unit had the following problems:
1. The unit had worn out and was giving intermittent problems.
2. Since the vane was in the path of the airflow, it was causing a restriction and reducing the airflow to the engine.
In order to resolve this problem, we resorted to the following:
1. Fitted a MAP sensor to the manifold.
2. Removed the original intake air temperature sensor and fitted it directly.
3. Fitted a Unichip Q+
4. Connected the fuel pump relay to the Unichip.
Before removing the VAF, we fitted the MAp sensor and correlated the VAF voltage with the MAP voltage. Thereafter, using the Unichip's MAF-MAP conversion feature, we simulated the VAF voltage based on the MAP voltage. This voltage was fed to the ECU which continued to think that the voltage it is getting is from the VAF.
The Inlet air temperature sensor was directly connected to the ECU, so no modification to the ecu input there.
The Unichip was programmed to operate the fuel pump whenever the engine was cranked.
This way, we got to replacing the restrictive VAF sensor with a MAP sensor and still have the main ECU functioning normally.
Due to the lower restriction in the intake, the airflow improved.
Since had the Unichip in place, we also remapped the fuelling and timing.
End result - a more driveable and reliable car ! |