sacermors

Okay so i did alot of research on the mpfi swap and got that all covered in my mind, then i saw that boomslang sells an OBD0 dpfi to OBD1 mpfi harness adapter. have searched and cant find an answer to what may seem like a stupid question but this is my first Honda project. Question is why would i want to convert to OBD1? And second question is when i look up the obd1 jazz its vague and just states to get an obd1 distributor, 4 wire O2 and ecu that will run the setup. Havent been able to find specifics...

I have a 1991 Civic Hatchback Std. DPFI i knew what to get for a basic mpfi swap but what cars can i scavenge for parts to also do the obd1 since the conversion harness covers wiring for both i really just need to know if i need a specific intake a specific distributor and which ecu i would need.

sorry for long post just been searching for a while and couldnt find d15b1 specifics.

HondaPartsHero

Most people convert to OBD1 because of its tuneablility and ease of finding OBD1 ECU especially those that have VTEC equipped (P28 being the most popular).

If you are planning on running the D15B1 the closest ECU will be the P06 ECU from the 92-95 DX/LX Civic. For this ECU and engine and pretty much any other OBD1 conversion you'll need the following:

-OBD1 ECU (dependent on your engine)
-OBD1 distributor (dependent on your engine)
-4 wire oxygen sensor


Wiring for this conversion (all of these can be rewired or adapters for ease of install):

-OBD0-1 ECU adapter
-OBD0-1 distributor adapter
-add additional 3 wires to add a 4 02 sensor
-fan switch wiring will have to be moved from the back of the block to the thermostat location of the OBD1 engine
-OBD1 injector clips (if you have an Si/EX model you can reuse your injectors and keep the resistor box)
-you also may have to add VTEC, knock sensor or IAB wiring depending on the engine and ECU you use

On top of this you'll have to convert from DPFI to MPFI. The FAQ in the EF subforum or Hybrid forum will have DIY's for this.

Alternatively you can go to a place like Rywire and buy an DPFI-MPFI OBD1 conversion harness and bypass all the wiring altogether.

sacermors

Thanks for the reply! I'm assuming most people don't keep the d15b1 because it's not as easy finding obd1 swap info for it as the mpfi swap. I'm glad you spoke up because this is the first I've seen of the fan switch wiring also.

HondaPartsHero

As far as the D15B1 you'll have to use another intake manifold as well as the D15B1 uses a dual injector system and you'll need a MPFI style. You can use pretty much any manifold from 92up for D series or an 88-91 D16A6 (Si or EX) but the 92up will have the correct injectors.

bgdriver

If you want to keep obd0, you need:
Chipped pm6 ecu with Turboedit
88-91 distributor
88-00 MPFI intake manifold

Turboedit's newer versions are quite powerful

sacermors

Thanks for info guys. So to do mpfi and obd1 at the same time id need a 92+civic mpfi intake manifold and fuel rail, distributor, 4 wire O2, ecu and the various plugs for said items. No resistor box because of obd1 injectors, then just wire it all up and hope for the best yeah?

HondaPartsHero

Yep

4drEF

i'm curious as to why you would require a chipped ECU.

acmoc

Because the factory chip that holds the basemap is not re-writeable.
You remove that chip, solder in a socket and buy a rewriteable chip that you can plug and unplug.


Take the car to a turboedit tuner and he can plug it into his burner and tune, adjust the parameters for air, fuel, etc.

Or you can buy a burner yourself, download the software and diy it

I found a seller who sells socketed pm6 ecus( 88-91 crx si) with a rewriteable chip and oem basemap on it.
I ordered that and just need to find a tuner.

4drEF

^ I understand how to chip and what TurboEdit is, but I do not understand why you recommend a chipped ECU for this DPFI to MPFI conversion.
What's wrong with running a stock PM6 on this setup?

acmoc

I thought he mentioned he wanted to tune it, without converting to obd1.

sacermors

alright so one last question guys. to just do the mpfi conversion i see 99% of the write ups say to use the Si parts. Well im headed to my local pull a part and ive looked up the three here in Georgia and they dont list whether the vehicles are the Si model. If i cant find an Si which cars can i use to just do the mpfi swap not including obd1? I assume the Si was the only model that had the mpfi parts for 88-91?

HondaPartsHero

88-91 EX, 88-91 CRX HF, 88-91 RT4WD civic wagons

sacermors

"HondaPartsHero" for sure. Thanks! They have very few 88-91 listed as is so i figured an Si would be nearly impossible here. I've yet to see a legit Si 4th gen period. In person. I loved the idea of getting this car because of how rare it is around here but now im seeing that it's not going to be so easy finding anything local. Also got my new eacv (iacv) in but im not too sure itll work right on the mpfi. Looks very similar but the hose fittings arent the same orientation. I've been trying to get the car running as smoothly as possible before the swap.

bgdriver

Because I didn't consider the fact that nearly stock Hondas still exist.

4drEF

Do some searching. You aren't limited to 4th gen - you can use newer year intake manifolds and still keep it OBD0. Some will be a little trickier than others so do a little research first.

acmoc

You can use a manifold from a d16z6 which is a newer model civic.
People say it performs better as well.
Has longer runners
Only issue is the support bracket doesn't line up, the fuel return line is a different size on the Fuel pressure regulator, and it doesn't have a mount for one connector that the ef models has, but it affects nothing and you just zip toe it out of the way.
You won't get a check engine light.

Also, the fuel injectors are different than the mpfi crx civics.


You could piece it together I imagine so you have the best manifold.

That1guyinvegas

Would you be able to pull similar preformance out of the chipped pm6 with the newer intake (wiring isn't an issue, long story) say with a sleeved and bored to 78mm D16a6 (jdm)? I do believe there is an OBD0 vtec head?

Matt8314

The onky OBD0 VTEC head is the 1G JDM B16A head. There was never a D-series OBD0 VTEC head ever.

As far as using a chipped PM6 vs OBDI, you should in theory be able to get as much power with a properly tuned OBD0 ECU. However, it is going to be harder to find someone who can tune it. Also, OBDI has other advantages vs OBD0. For instance, gas mileage will be better due to the better electronics and four wire oxygen sensor. Plus, it just seems to run better. To me anyway, OBDI ECUs just seem to make for a smoother running car.

That1guyinvegas

Thank you, always like learning something new