Honda Car Forum

I have an 88 honda crx hf with a good bit of modification done to the engine, exhaust, and fuel system. My engine is capable of 7000 rpm's but due to the stock HF computer the rev limiter I can only go to 5200 rpm's I had an MSD ignition, but it kept frying distributors so I removed it. I would like to know if I can replace the stock OBD1 HF ECU for an OBD 1 SI ECU without having to modify the wiring?The CRX HF comes from the factory with an OBD 1 ECU. The question is will any wiring change?The HF also comes with multi-port fuel injection. As far as my modifications are concerned:The cylinder head is ported, It has double valve springs, and titanium keepers,I have a 1.6L intake manifold and throttle body. Short ram cold air intake.Walbro 255 lph ( liter per hour ) fuel pump that gives me 62 psi of fuel at the fuel rail. I also have a full coilover suspension and 17 inch AXIS alloy racing wheels.I also have D/C headers and 2.25inch exhaust all the back to to the muffler, which is 2.5 inches in and 3.5 inches out.I appreciate the info. Will the Si Transmission bolt up to the 1.5L motor?Are the older Si computers OBD 0 or are all SI computers OBD 1 ?Is the gearing the same in the older SI tranny as the 92 and up?

Short answer NO. Just convert your engine to OBD1 and get a hondata reflash and have them disable the rev limiter. Problem solved. If you don't know how to convert yours to OBD1 google it...

ok first.. it doesnt have 'a good bit of modification' if your still in dual point. you need to convert it to multi point if you want to run an si ecu. search honda-tech.com. you need a manifold, injectors, distributor, little wiring ect

Your 1988 CRX did NOT come with OBD1 stock. Yes you may have MPFI but it is still "OBD0", unless someone before you converted it. You would need to convert the wiring to OBD1 to use an OBD1 ECU. A 88-91 SI ECU will plug right into your HF since it is already MPFI. If you got rid of the long geared HF transmission and swap in a shorter geared 88-91SI transmission you will be a lot happier since you are running 17" rims. Yes, the 88-91 SI trans will bolt right on to your motor and into your car. The spline count on the transmission input shaft may be different. (use the clutch disc that matches the SI trans.) I think you HF axles will work with the SI trans too. Swapping in a Si trans. will significantly improve your acceleration especially with 17" rims.(SI final drive=4.25) (HF final drive=2.954 49st. or 3.250 Ca.)The 88-91 SI ECU's are all "OBD0", only the 92-95 Civics are OBD1. The gearing in the 88-91 SI transmissions and the 92-95 SI/EX transmissions are the same. (The ex has the same final drive and 1st-4th but 5th gear is a little longer) The 92-95 uses a hydraulic set up to engage/disengage the clutch and the way it mounts to the car is different. If you want to use a 92-95 transmission in your car you need to buy this>>>>http://hasport.com/shop/product_info...ducts_id=171If you want to run a OBD1 ECU you need this>>>>http://rywire.com/store/obd0-obd1-co...cd27a2eae89and what is listed on the page.The major benefits of OBD1 is going to be when you get to the point where you want to tune the ECU for your setup (especially if you go turbo or high compression) or if you have plans to swap in a newer motor. The benefits of using the 92-95 transmission is they are newer, easier to find and they have a stronger diff. pin. If you like your car the way it is and just want a little more, go for the 88-91 SI ECU (the rev limiter is 6500). And get a 88-91 si transmission.

The HF ecu is OBD0, not OBD1. OBD1 started in 1992 for most Hondas (excluding the NSX). But to answer your questions, no, you're going to have to modify the wiring no matter what. At the very least, you're going to have to buy an OBD0 to OBD1 conversion harness, to be able to plug in the Si ecu. Yes, the Si transmission will bolt up to your engine. However, it depends on what Si transmission you're talking about. If you're talking about the OBD1 '92-'95 Si transmission, then you'll also need to buy a cable to hydro conversion kit. The '92+ Civics have hydraulic transmissions, while the '91 or older Civics have the cable transmissions. They all bolt up together, but it depends more on the car you have.