madlowmazda
+1y
I probably would not have even thought about the stock harness and computer from the cars until I realized some important features of the EFI systems of the cars.
1) The car computer fueling algorithm relies heavily on the air flow meter to inject fuel. Basically the more the door opens- the more fuel it provides. So it doesn't care what kind of engine is behind the throttle body- it has no way of knowing either! Just as long as there is a sealed connection between the throttle body and the air flow meter- it's happy! Obviously you would have to have a four cylinder engine behind that throttle body, but still - it will run- and run well it does! The engines in these cars are basically the same as the trucks- just missing a few valves!
2) The car efi system uses a vacuum advanced distributor- same as our carbed trucks- YES, something that can be reused!
3) The car EFI harness is very simple due to it's simple nature of mainly using the air flow meter as it's main input. The harness is not cluttered with emission junk.
4) The car EFI harness is not completely tangled into the rest of the vehicle wiring harness- and this is important! Basically it has ECU plugs, and goes out to the engine and only has one plug that connects with the vehicle harness- one that matters at least. AND THIS PLUG HAPPENS TO BE THE EXACT SAME PLUG AS A MAZDA TRUCK! The wires in this plug are almost identical to the ones in the truck- all that is required is moving the wires in the connector to get them to match the truck! The plug I am speaking of is called X11 in the truck and X10 in the car- if you were looking at the mazda wiring diagram. It is a big white plug- most of you are probably familar with it if you have ever installed a weber carb and decided to get rid of the factory feedback carb computer and wiring harness after the installation of the Weber. This plug is behind the truck glove box- behind the blower motor squirrel cage. It contains the wiper harness as well. From this plug I get power for the EFI computer system, can send tach signal to the cluster from the EFI system, obtain clutch pedal position to send to the EFI computer, and get a/c on signal, and I think something else- I'll have to look it's been a minute since I did this.
I have got SEVEN of these upper plenums made so far- and they are all spoken for right now. 3 are staying with me. Rowdy=Brad is getting one, Orangemazdab2000=Kevin is getting one, and two more of my local mazda buddies are getting one each.
I would like to post the wiring schematic that I have created to modify the car EFI harness to plug into the truck harness. I have done 4 harnesses already. I have it all written down- I just need to get it so other people besides me can understand it.
Midnightmike- someday you might want to read over this thread if you get another mazda truck and want to fuel inject it.