When you change the engine from OBII to OBDI.

1. How hard is it. (for a person with no electrical knowledge)
2. How cost effecient is it. (what else is involved other than a OBI ECU, and wiring)
3. What happens to all the sensers and **** which are on the OBDII motor. (junked ?)

 

Do a search on questions like this before you ask them. All you need to convert your 99 Si to OBD1 is a conversion harness and ECU.

1) Not very hard, you unplug your stock ECU, plug in the jumper harness, plug in the OBD1 ECU.
2) Very cost efficient ($150-200 for the harness, $100-200 for the ECU, $15-75 for the chip, or you could go Hondata). You can't reprogram OBD2 ecus, so this is a good alternative.
3) The obd2 sensors remain on the motor, the obd1 ecu just doesn't read any input from them.

 

wow so i can switch back and forth whenever i choose. (for emmisions)


Thanks for the help

 

If you're engine is modified enough to the point where you would need (or benifit a lot) to use a Hondata or a chipped ECU, then using the OBD2 ECU is not going to help you pass emissions.

The OBD2 ECU will not run your modifided engine properly, and you will probably have even worse emissions.

 

Yes, my 99 CX with b18c5 was run with an obd1 p28 ecu and a conversion harness. but i always had the option of unplugging the conversion harness and plugging in my 00 Si ECU (ITR ECU was immobilized). Both worked fine, but my p28 had a skunk2 chip so it changed air/fuel maps, decreased vtec crossover, and increased fuel cut.

 

how do you know when its worth to do the conversion.

I mean i know if i get I/H/E and cams it would be a waist to concet to obdI