Ryan,
i don't know if this helps or not, but I found this a minute ago
Quote:
|
Originally Posted by StevenD57
FYI, a group of folks from the tuner23 mailing list have developed some alterations to the P-series and LA3 ECU's using the EEC Tuner and the PCMX software to convert vane air meter systems to be able to directly use hot wire mass air meters.
The reason this is necessary is as follows:
The stock VAM system uses the voltage signal from the amount the air door is open (that is a measure of the pressure drop across the vane door or volume of air passing through the meter) along with the barometric air pressure signal from the BAP unit and the air temperature signal from the VAT to calculate mass air flow.
Unfortunately the maximum air flow the turbo 2.3L EEC-IV was originally designed for is either approx. 280 cfm or approx. 360 cfm depending on the model or year of the system. Most modified car particularly ones with upgraded turbos are far exceeding these figures. Once this maximum flow rate is exceeded the vane air door is fully open and the system is no longer able to effectively meter the correct amount of fuel for this additional air flow through the system. Even with the assistance of the EEC Tuner it then becomes very difficult to correctly tune the A/F ratio in the upper rpm ranges where this condition exists. This condition is fairly recognizable since the resulting A/F curve as shown on a dyno data-logged with a wide band O2 system is very distinctive to a trained eye.
The code change eliminates the calculation mentioned above and then the VAF transfer table is altered to match the flow verses voltage output table values for the hot wire mass air unit to be used. At that point it becomes in effect a MAF transfer table. The hot wire mass air meters used in this operation (represented by the size and calibration of the meter) are chosen to size them for the expected max air flow of the engine/turbo combonation while still keeping the output voltage signal within the range the ECU can deal with (a max of a little less than 5 volts on our ECU's).
With this conversion it becomes possible to tune the A/F ratio to a safe level through-out the operational range of the engine/turbo combonation.
The hot wire mass air conversion using the EEC Tuner can even be done with cheap used hot wire mass air meters from junkyards. The main criteria is that the flow (kg/hr) verses voltage output table for the meter has to be available so it can be entered into the VAF/MAF transfer table. Mine is done with a nice 75mm MAF unit from Pro-M and I'm very happy with the results.
All or most of the bin and resource definition files (rdt) for use with the PCMX software are available in the files section of the tuner23 mailing list plus some additional documentation and wiring diagrams. That way it is easy for others to duplicate this modification.
|