VX engine swap

[StorminMatt]

Originally Posted by bobski

Unfortuantely, all of the two-stage VTEC D15Bs are OBD-2 engines.

On the other hand, if the motor is JDM and pre-1999, the ECU is actually more OBDI than OBDII - at least when it comes to wiring it up in an earlier car. Yes, the plugs are OBDII plugs. But it does't use all the extra OBDII sensors. In other words, although the ECU pinout is different from an OBDI ECU, it is no more difficult to wire up.

[maxxgraphix]

That's it?
http://mymiata.paladinmicro.com/Miata4-WireO2.htm?
A 4 wire O2 is nothing more than a 12V and a couple grounds?

I'm suspecting a bad O2 in my motor, hence the low MPG.

1992VX - You'll need to get a P08 ECU or a chipped P28 to make your car run right. Also get the schematics for wiring. The VX will have everything you need under the hood. Just need to know which ones.

[GasSavers_bobski]

Originally Posted by maxxgraphix

A 4 wire O2 is nothing more than a 12V and a couple grounds?

1-wire sensor: 0-1 volt signal, grounds through the sensor body, relies on exhaust heat
2-wire sensor: 0-1 volt signal, grounds through a dedicated ground wire, relies on exhaust heat
3-wire sensor: 0-1 volt signal, grounds through the sensor body, 2 wires for heater
4-wire sensor: 0-1 volt signal, grounds through a dedicated ground wire, 2 wires for heater

In the case of OBD-1 Hondas, you use the same 1-wire O2 signal wire for the 4-wire signal and the signal ground gets run to the sensor ground wire that the TPS and temperature sensors use. One of the heater wires gets ignition switched 12V+ (can also be found in the engine harness) and the remaining wire gets grounded through the ECU's heater control connection. So the heater doesn't strictly get switched on with the ignition - the ECU has control over it. What criteria it uses for switching the heater on and off, I'm not sure.

[maxxgraphix]

I don't think the P08 ECU has the ability to control the O2 heater. It's now wired as on when the key is on. Over all the engine runs smoother and an odd hesitation at cruising speed is also gone.

I'll guess we'll wait and see what happens next. For now I'm happy since I believe my MPG will increase to where it should be. I feel it's a pain to get a P28 and program it when I already have the right ECU.