I have a 1988 Honda CRX Si with a 1st gen B16a swap. It's running a PR3 ECU via a conversion harness I bought off of Ebay which allows me to run the VTEC solonoid, oil pressure, dual O2 sensors and Knock Sensor.
I want to go ODB 1 so I can run a Hondata 4b. I've tried researching the internet on what's actually needed for this conversion but haven't found one good write up with everything included.

This is what I've come up with:

1) ODB1 ECU (P28 seems to be the most recommended)
2) ODB0 to ODB1 Conversion Harness
3) ODB1 Grey plug distributor
4) 4 wire O2 sensor
5) Something on injectors - wither ODB1 injectors or a wiring change
6) Engine Conversion harness which allows connecting ODB1 distributor, O2 sensor and injectors to ODB0 harness

There might be other items or points I'm missing...

Blurex contributed a good write up recently on the Hondata forum but pictures are desperately needed for clarification:

http://hondata.com/bb/viewtopic.php?t=177&highlight=

Come on guys...I know a bunch of you have gone through this. Help out a fellow user with no where to get an experienced person (I'm in Puerto Rico). I'm sure a lot of us will benefit. If I can't do this than I'll probably skip ODB 1 and get a ZDYNE Gold ECU.

Thanks!
Raul

 

For the injectors you can either just take out the resistance box on for your stock injectors or you can run high impedance (OBD1/OBD2) ones. For the distributor just get a VTEC one that is OBD1/OBD2. I just wrote up a wiring diagram yesterday so I have to finish it up before I start making a harness for my friend's 88 CRX. Is there a reason why you wanna run 4b?? STOCK B16 and boost maybe???

 

you have it pretty much covered, except you're missing the VSS sensor, you need the electronic one and would need to jimmy-rig the instrument cluster similar to the 92-93 integra

greg

 

JDMspec...

I'm thinking 4b since my motor is built and I want to go turbo for Xmas

Cheetah...

VSS Sensor - is this for the speedometer and RPM gauges? IF so, I just dropped in the mechanical one of of my original CRX engine. I fit the B16 and is working great.

 

You need the electronic one to report speed to the ECU...

 

Cheetah...

Can you give me more info on rigging electronic VSS to the CRX cluster and also sending the signal to the ODB1 ECU?

 

i don't think you need to change out distributors. a distributor is a distributor. unless there is some sensor inside an obd1/2 dizzy that doesn't exist in a pre-obd dizzy, this doesn't make sense to me. I am running an obd1 ecu in my car with an obd2 motor and dizzy and things work fine.

can someone expand on this idea for me?

 

A friend wanted to do this...we were lazy(even though he had a mechanic that used to be a stereo installer, so he knew wiring), so we bought an adapter harness from Kenji, made it simple and easy.

Austin

 

You do need to change the dist. because of the crank position sensor is different.

I just completed this conversion in an 89 CRX/B16. Made an adapter, 92-93 GSR dist, wide band O2, AEM EMS.

The injectors work fine using low impendance/resistor box. If you remove the resistor box, you will need to swap to high impedance injectors too. The box is required with the low impedance injectors, or you will fry the ECU.

I found for the money, the AEM was a better value than the Hondata.

On the P28 as the recommended ECU if you go Hondata, they are more available, but do not have the knock sensor (something that I value).

Your choices for ECUs with knock are P72, P61, P30.

Good Luck.

-Jim

 

i do the lazy man way out, I put the 94+ GSR or Type R cluster int he CRX, fits in there like it belongs for the CRX and 88-91 Civics. If not you have to use the 92-93 gsr clock on the cluster to trigger cycle for ecu to recognize, btw, wcu only needs speed input for vtec if you use a vafc or other vtec controller this will not be needed.

the obd0 distributor has 2 teeth less on the cyk sensor than the later obd1 dohc-vtec distributors.

even with kenji or locash harness conversions you need to change distributors or there is be an offbeat and car won;t run up to part, i.e. wrong ecu map will trigger at each rpm cycle.

greg

 

Yes you are right OBD1/OBD2 internals are the same but nonOBD is different... nonOBD fires at a different pulse rate than the newer systems and is not compatible with the OBD1/OBD2 computers.

 

seems lik you guys pretty much covered it, but i will add another source for a conversion harness. I got my harness from jason (turbo_ek@yahoo.com). It cost me $160 shipped, which is MUCH less than the harnesses from locash. I'm very happy with the harness and wiring it all up was pretty simple too. good luck!

 

hmmm I just did the conversion in my crx two weeks ago and didn't do anything to the vss. The vss in the 88-91's is in the instrument cluster and is pulsed by the speedometer. The pulse goes to the pin on the stock ecu and through the conversion harness should go to the pin on the obd-1 ecu. I don't see the need for conversion. My vtec works, I have no codes, and my speedometer works.

You need to change distributors because the pulse wheel inside the obd-0 distributor has 16 teeth on it and the obd-1 distributor has 24 teeth. Without changing the distributor the ecu will have the wrong reference for where the crankshaft is in its rotation.

Wether you keep the resistor box or not depends on what type of injectors you will be using. If you are using peak and hold injectors (low impedance) you keep the resistor box in place. If you are using saturated injectors (high impedance) the resistor box has to be removed. There is no real reason to remove the resistor box and convert to saturated injectors. Most aftermarket injectors are peak and hold and will require the resistor box if upgrading. Saturated injectors can be purchased in large flow ratings but the cost is much more than the peak and hold counterpart.

JHill- Have you had a chance to play with the wideband and aem ems together? I have been having a reoccuring problem where my ems reads the incorrect voltage from the wideband and therefor the ems can't accurately convert the voltage reading into an a/f ratio. If you have fixed this problem I and a few others who have either a hondata 4b or the ems in our 88-91's would be very interested in how you wired it all up.

7rrivera7- You can use the 4b on your pr3 ecu and not convert to obd-1 but you will still have problems with having two o2 sensors and problems datalogging a/f ratios. Even if you convert to obd-1 you will have a difficult time datalogging the correct a/f ratios because something about the 88-91 wiring creates a big ground loop that effects the voltage that is read by the ecu. Have you considered zdyne? Speedphreak loves his, although it doesn't have a datalogging feature.


[Modified by racerxadam, 7:11 PM 11/15/2002]

 

Yep, I have no probs either.


[Modified by Jeff C, 8:00 PM 11/15/2002]

 

I have not had VSS problems either, which I attributed to using the AEM.

On the wideband question, yes I did get it to work. The scale had to be changed in the AEMPro software to match the output graph (voltage/AFR). The one that comes preloaded in the software is nowhere close to being right for the FJO that I am using. The AEM now reads very close to what the FJO display is reading.

 

I realize that the output graph has to be changed to match the output from the fjo controller. did you use the exact values from fjo? who's conversion harness did you use and if you made your own do you have the pinout information? How do you have the outputs from the fjo wired to the aem? In other words, what pin does the + output from the fjo go to and where does the - output go? I have tried a bunch of configurations and have had zero success. This is very exciting to know that someone doesn't have this problem. There are a few other board members who are also having the same problems as I am. I need details.


[Modified by racerxadam, 8:25 PM 11/15/2002]

 

OH OK, I guess I didn't get your question.

I carefully extrapolated the values from the FJO chart, and compared them with the numbers that JR from AEM has on their forum. They are good.

I made my own ECU harness adapter, PITA! I would buy one if I was going to do it again. The FJO has four wires, keyed power, sensor ground, sensor input and ground. Both the grounds went to chassis, and the keyed power went to just that, and finally the sensor wire went to the AEM ECU pin D14 in the 30-1000 unit.

The pinouts for the harness were time consuming and are several pages of special notes, but I could compile something together now that I have it all out again.

HTH,
-Jim

 

When I wanted to convert to obd1 I couldn't find any link/information regarding the conversion. Here's my pin-out's...might be easier to understand for some.

http://www.boosted.org/ecu/COMPLETE.txt

I have the same problem as my wideband voltage being off that racerx and jhill had. Need to try grounding wideband signal ground to the chasis....Hondata says to make sure you DONT..and wire signal ground to o2 ecu signal ground. hrm.

 

Heres what I did

OBD2 VTEC Dist with plugs repinned using OBD 1 plug (OBD1 dist works as well)
4 wire 02 sensor
custom made harness
VSS is mechnical and eveything works fine, no codes on both p28 mugen ecu and Hondata

For resistors, I have RC440 sat injectors so I opted not use the resistor box (cut it out) For sake of simplicty, you can use the OBD0 injectors and keep the resistor box. If you want to use OBD1/OBD2 injectors, then the resistor box needs to go.