Thread: Whats this OBD control?

Originally Posted by ytt105

I'm looking for a kit for my 2000 4.6 P38.

A couple of the overseas sellers are talking about OBD control of the computer via the petrol fuel trims.

I presume the others use the O2 sensor to control the mixture, though an Aussie kit I'm looking at seems to only use a pressure input.

Whats the best?

All VI kits use the petrol injection signals as their main input. The O2 sensor is for reference only. The map between the petrol and lpg is fixed by programming after installation. Then if the petrol ecu sees inaccurate mixtures from the O2 sensor and corrects the petrol signals, the gas ones follow by the map. What OBD input does is fine adjust the map by reading the fuel trims on the obd2 port, so there is less variation between petrol signals on gas and petrol signals on petrol.

For all this to work you need obd2 readings the gas ecu will recocnise. I have not been able to get these on a D2 or P38 as yet. It's not a big deal for something as old as a P38, it's much more needed on newer vehicles where the ecu flings up engine malfunction lights at the drop of a hat.

As for what's best, I suggest you shop for what you can get solid local support for, if you shop on price you may be very disappointed.