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163 Posts
Discussion Starter · #1 ·
This thread is a WIP. **All that is left now is to finish the wiring pinouts**

About the Swap
This thread is about putting a D16Y5 VTEC-E engine, harness, and ECU into a 1988 CRX DX*, retaining the original transmission and exhaust. I converted the CRX to OBD2, including the ability to use an OBD2 scan tool just like you would on any 1996+ passenger vehicle. I did a little bit of restoration, but the body work and interior remain largely as they were when purchased. The main contribution here will be showing how to wire the one-piece OBD2 harness to the CRX dash harness, something you will probably not find anywhere else.

*The previous owner had swapped in an OBD0 JDM D15B. Many times throughout this thread I refer to the JDM D15B as a D16A6 or it's parts as those from an Si.

This is all backstory so skip to the next section if you're not interested. :zzz:

My friend had a late nineties Mazda Mirage. Not a bad car, but it was beat to hell and had never had any maintenance done to it. The driver's door had a peculiar scratch along it's side that looked like a bear had clawed it. I fixed a belt squeal on it, but any time she'd ask me for any more help I'd tell her to buy a Honda. Other brands are put together stupidly, are harder to work on, and they just don't have the reliability, fuel economy and performance of a Honda.

At some point in time we started talking about getting her a CRX. She's only 5ft tall and I think she saw it as a cute little car that was sized for her. :bounce: CRX's aren't seen too commonly anymore, but any time she'd spot one on the road, she'd take a pic and text it to me. I spotted a real nice red one with the personalized plate "SIANARA". I knew the guy would never sell. There's a clean white one near my house that an old guy drives. At her work there's a super clean yellow one. I doubt either of those guys would part with them either. There's usually a couple for sale locally, but they're completely modded to crap and in horrible condition, missing parts that are very difficult to find.

Eventually one popped up for $1200 looking fairly stock and complete but sold "AS-IS AS-IS". It was a white DX with some huge ****ty wheels, drag tires on front and cheap ones on back. It looked to have a D16A6 head swap and ****ty MPFI hack job running on a chipped P28. It had some masking tape on the drivers door glass to cover an inch gap. There was a dent on the driver's door and fender, and it was missing the rear interior. The tops of the door panels were pitted and there were stickers on the back bumper. The title was clear and there was no rust. The seller was a drag racer with another CRX so I wondered if he had used this one as a parts car, but his drag CRX was completely stripped so it's not likely. I judged it to be a good starting point if the price was right. She talked him down to $800, we jump started it and drove it to my place.

It ran good but blew a lot of white smoke which I assumed to be an improperly done head gasket. When she got the title it turned out to be a salvage which was disappointing but not a deal breaker. I found a D16Y5 at a junkyard in Denver for a good price, so we rented a van and made a road trip. I had them drop the engine on a big tire and we brought it back. Then I began gathering up info and wiring diagrams. I also began scouring junkyards for missing and broken parts.

Engine Choice
The D16Y5 came in the 96-00 Civic HX. It's a lean burn, VTEC-E engine, nearly identical in appearance to the D16Y8 except for the presence of EGR and a cat converter directly on the exhaust manifold. If you take the valve cover off, you can see the roller rockers unique to only this and the D15Z1 (Civic VX) engines. VTEC-E differs from VTEC in that it switches from 12 valves to 16 around 3000 RPM, affecting the intake side only.

D16Y5 Swapped CRX vs Stock HX
The 96-00 Civic HX has power steering and AC, weighs 420lbs more than the CRX, has a larger surface area and higher coefficient of drag (difference of .02). It has larger 14 inch rims (which favors taller gearing), and each rim is about 5lbs less than the CRX's. Based on the positives I estimated that the HX engine in the CRX should gain about 7mpg. I don't know how much the negatives (heavier rims, shorter gearing) will detract from that.

The end result of a D16Y5 swapped CRX should be comparable power and acceleration to the Si, and fuel economy comparable to the HF. If the Civic HX gets around 40mpg, a CRHX should be able to achieve 45-50.

Curb Weight
1988 CRX DX MT 1922lbs
96-00 HX MT avg 2341lbs
decrease of 419lbs, estimated .9mpg per 100lbs (3.77 mpg gain)

Coefficient of Drag
1988 CRX .30
96-00 HX .32
decrease of .02

Transmission Gearing (CRX DX trans used in this swap)
1988 CRX DX 3.250, 1.894, 1.259, 0.937, 0.771, final 3.888 Rims 13" (2800RPM @ 70mph), Rims 14" (3000RPM @ 70mph)
96-00 HX 3.250, 1.782, 1.172, 0.909, 0.702, final 3.722 Rims 14" (2500RPM @ 70mph)
retaining the CRX DX transmission favors acceleration over fuel economy, even more so when used with 14 inch rims

Fuel Economy
1988 CRX DX 29 city, 35 highway
96-00 HX 33 city, 41 highway
These are the conservative #'s

Power Output
D15B2 92hp @ 6000RPM, 88ft/lbs @ 4700RPM, compression 9.2:1
D16A6 108hp @ 5600RPM, 100ft/lbs @ 4800RPM, compression 9.1:1
D16Y5 115hp @ 5600RPM, 104ft/lbs @ 4500RPM, compression 9.4:1
+7hp, +4ft/lbs over the Si, +13hp, +6ft/lbs over the DX

Convert to OBD2
I decided right from the start to swap over the complete engine, harness, ECU and smog equipment. I wanted the reliability and credibility of doing it this way. I didn't want a questionable tune on a chipped ECU. I wanted the factory ECU complete with an OBD2 port and a diagnostic port that could be jumpered manually.

Any mechanic in the future should be able to service this car. If there's a problem or if it fails emissions, they wont have to question the tune or the wiring. All the parts should be stock and referenced from either an HX or a CRX.

One problem with doing an OBD2 conversion is that you wont find any help online. All my searches turned up posters on various forums fervently rejecting the idea outright and recommending an OBD1 conversion with a chipped ECU. When people on forums don't know the answer, they attack the question and the poster. Having been in the game for a while I'm at a point where if I don't know the answer, no one else does either. For this reason, when I did run into trouble, I opted not to ask.

References (not primary sources) ... oefficient ... 26279.html

163 Posts
Discussion Starter · #2 ·
Restoration / Fixes

Tape residue is a [female dog] to get off but at least it had kept the interior dry.

I determined that the problem was that they had put a 90-91 (door mounted seatbelt) door glass on this 88-89. Both windows are shown so you can see how different they are.

One of the first things I do whenever I buy a car with an aftermarket stereo is pull it out and gawk at the horrible hack job someone always does on the harness. Hint* duct tape isn't an electric insulator - it conducts. Masking tape is no better, nor is simply twisting wires together.

Some solder and heat shrink will do. This is my standard of work, however, I might have left it alone if it was at least a professionally done crimp job like what you will have done at Best Buy. Note that I put a few pieces of tape to hold the wires together after I took this pretty picture.

These are some random bits I picked up that were needed for restoration or for the swap. I didn't end up using the OBD2 charcoal canister. I went through several iterations before settling on the original canister. More about that later. The splash guards were from a hatchback since no CRXs were available for months on end. They don't fit perfectly but they're close enough. The throttle cable is from an EK (D16Y8 or D16Y5).

Heat shields, splash guards, engine mounts, and things like that aren't important to a lot of people but they play an important function in the drivability, cleanliness, and performance of the car. I can feel a difference on the highway when the splash guards are missing and it shows in the fuel economy. The engine rocks hard with throttle input without the front mount.

The alternator and bracket were missing from the junkyard engine but they were easy enough to find now that EKs are so common.

I ran new 12 gauge speaker wires and wires for doorlock actuators. By far the easiest way to do this is to remove the fenders or at least remove the wheels and splash guards.

I sold the super-wide spray-painted wheels for $100 to some guy that was very eager to buy them. Maybe they were something rare, who knows? Maybe not? Everybody's taste in wheels is different, but there was no way I was going to buy tires for them and have her struggling with manual steering. I thought HX wheels would be appropriate, but she really liked these Integra webs I had on my GSR and the tires were pretty new.

163 Posts
Discussion Starter · #3 ·
Engine Removal
I put this part off for a while because from this point on, the car would be immobile. I felt pretty confident in the info I had gathered but there's always a risk that there will be a problem or your wiring documentation could be wrong. One day I came home from work and there was still plenty of daylight left (sun doesn't set here until 10pm in the summer), it was a beautiful day, so I poured a Jack and Coke and yanked the motor out. I opted to do it outside because the engine hoist would hit the damn heater ducting in the garage. Besides that, there were lots of people in the neighborhood outside and I thought it would be funny. My roommates would be coming home from work, looking over and asking "what - the - fuck". :shock: :cookoo:

When I pull a motor, I remove the hood, radiator and T bracket. It's often a good idea to remove the throttle body to preserve the TPS and MAP sensors.

This was the first time I took a good look at the motor. I assumed it was the original block with an A6 head plopped down. I nearly shat when I noticed it was an OBD0 JDM D15B. I quickly took down the Craigslist ad I had posted for $20. This motor is worth saving even if I don't currently have a car to use it on.

163 Posts
Discussion Starter · #4 ·
Engine Install

It's a little bit awkward rolling an engine out across a pitted driveway this way, especially while holding a collins glass in one hand. This was one of the moments a roommate got home, paused, asked what the hell she's looking at, then tentatively offered to help.

I declined.

Use a piece of cardboard to protect the bumper from the bottle jack. We're not animals.

I helped my other roommate pick out the HX a few months prior. Given enough time, everyone I know will be driving an 80's-90's Hondas.

This is the realization of my goal of having a 98 Civic engine in an 88 CRX without anyone ever questioning whether it's stock. Not the cops, not a mechanic, not the emissions tech - only the girl that checks the oil and coolant and drives it to work everyday knows any better and that's only because I told her. Even now she doesn't quite get it :rofl:

Magnecor Plug Wires
The spark plug wires you're looking at are Magnecor. These are not gimmick wires like Nology. They're about the same price as the OEM and NGK wires everyone in the Honda community insists on, and those would be my recommended wires as well - if Magnecor didn't exist. Magnecor are built technically superior, but more importantly, they never need replacement. Also, they (just barely) fit into the original spark plug holders.

Magnecor, you should sponsor me for posting this. I need a set for my GSR.

163 Posts
Discussion Starter · #5 ·
Conversion Issues
There are some minor problems with putting a 1998 Civic engine into a 1988 CRX. None of them are particularly difficult to overcome but this is where many people cut corners possibly because they just don't know any better.

Cable Transmission / Front Engine Mount
Absolutely the most important physical aspect of putting a 92+ engine into a 4th generation Civic/CRX is to use a 4th gen cable trans. Cable to hydro conversion kits are an unnecessary complication. Some designs perform suboptimally and are prone to failure. A front engine mount adapter is often sold separately and will cause added vibration.

Some people may disagree with me but it seems like a no-brainer. Your original trans has the front mount provision and is already cable. It has three of the four engine mounts total. If you want different gearing, swap the gears into your transmission case. If you want a low mileage trans, rebuild your existing one. Save the expense of buying a hydro trans, cable to hydro conversion kit and front engine mount adapter.

One bad thing about mismatching the engine and transmission across different generations is that neither flywheel cover will fit. Many people say this is okay and I've never had a problem, but it's something that bothers me and perhaps I will get some sheet metal and attempt to make my own.

MAP Sensor
The CRX has a firewall-mounted MAP sensor while the later D Series engines have them on top of the throttle body. You can remove the CRX's original MAP as it wont be used.

IAT placement

Sixth generation D-Series Civic's have the IAT in the intake tube, while earlier Civic's have it in the intake manifold. I drilled a hole into the CRX DX air tube for the OBD2 IAT. I used a step bit so that it has a very strong, air-tight pressure fit. I chose this location because the harness reached without needing modification and I was trying to avoid fouling the sensor with crap that sometimes burps out of the breather hose. Perhaps unsuccessfully but it can be pulled out and wiped easily enough.

The IAT had to be sourced from the junkyard since the intake tube wasn't supplied with the junkyard engine. I opted to use an OBD2 sensor because the plug fit the engine harness. You could wire the the OBD0 IAT to the OBD2 harness if you wanted to.

Neither Intake Tubes fit

The throttle body placement is different between the D16A6 and D16Y5 / D16Y8. Neither intake will fit perfectly, but the CRX D15B2 intake is pretty close. I trimmed the DX airbox lid at an angle so that it would mate up to the intake tube's new position. It fits remarkably well with only a little bit of unnatural tension on it. Scroll to the pic of the finished swap to see it fully installed.

The D16A6 and D16Y5/Y8 intake hoses are too short.

Breather Hose diameter mismatch between Valve Cover and Intake Tube

I used a pipe cutter to cut a nipple off the Breather heater line so that I could stick the nipple into the intake tube. Then I put a clamp on the protrusion from the intake tube around the nipple, as well as on the hose end. The hose is just barely large enough diameter to be forced over the output on the valve cover.

Other Hose size mismatches
You'll need a longer and slightly smaller diameter hose to go between the fpr and the fuel tank return line behind the driver's side strut tower. The y5/y8 fuel pressure regular has a smaller diameter hose fitting than the 88-91 Civic. The charcoal canister hose goes to an inline one-way valve and on to the nipple in the center of the intake manifold. The brake booster vacuum hose needs to be shortened about an inch.


Charcoal Canister

The 1997 OBD2 Charcoal Canister (electrically controlled) requires a pressure sensor in the fuel tank that the CRX doesn't have. The design of the OBD2 canister varies by year and jurisdiction but only a passive system will work in the CRX. After contemplating cutting the fuel tank and fitting the pressure sensor, I opted to stick with the CRX's original system. I think that there wasn't quite enough room for the OBD2 canister on the CRX's firewall anyway.

Leaving the OBD2 harness's purge control solenoid plug unplugged doesn't cause any issues. If you scan the OBD2 port, it will report an error but it will never light up the CEL on the gauge cluster or change the way the engine runs.

D16Y5's Exhaust Manifold / Cat Converter combo

This VTEC-E valve cover is actually from a 94-95 Honda Civic VX and never appeared on the D16Y5. I thought it was a nice way to highlight this particular swap.

Despite what you see here, I recommend having the exhaust manifold and downpipe installed to the engine when dropping it in. It's a hassle squeezing it between the front lower crossmember after the fact.

To get the total emissions low enough to meet the federal standard on their lean-burn engines, Honda opted to put the catalytic converter right onto the exhaust manifold. This helps the cat converter to reach and maintain operating temperature, but doesn't much affect the emissions sample taken at your required emissions testing. In other words, you'll pass the test using the CRX's original cat converter, exhaust manifold, and downpipe.

I care about emissions and global warming. I have a son and also I just give a crap. If that in any way changes your opinion of me or my thread, hit your browser's back button. Sorry you read this far into this thread :cry:

I contemplated using both cat converters. It would theoretically run cleaner, but not in practice and it certainly wouldn't warrant the increased complexity and maintenance cost. It's quite possible that the D16Y5's cat converter wouldn't fit in front of the radiator. I can't remember testing that. Ultimately I decided that using the CRX's original exhaust was the best solution. The car passes emissions with the low numbers Hondas are to be admired for.

Water Neck angle doesn't match Radiator

I swapped over the D16A6's water neck so that I could reuse the stock CRX's upper radiator hose.

Clutch Cable bracket mount on Valve Cover

The original clutch cable bracket mounting location is gone with the old engine, but doubling up on the throttle cable bracket works suitably well.

DX Throttle Cable too long, Si too short

The left cable is from a 96-00 Civic EX / HX, D16Y5 / D16Y8 and that's the one you'll need to use. The cable on the right is from a 88 CRX Si. The DX DPFI cable is stupid-long (not shown).

The EK cable is still a little too short to fit the adjustment bracket on the manifold, but you can trim most of the rubber bumper off the pedal side and then it will be right in the center of the adjustment range. Leave a thin ring of rubber to fit the nipple shaped end of the plastic tab and keep it flush to the flat metal end of the cable.

Gauge Cluster requires cable VSS
The CRX's speedometer requires a cable vehicle speed sensor, while the Civic HX uses an electronic one. It turns out you can just leave the electric plug on the OBD2 harness unused without any ill effects. The OBD2 ECU gets the VSS signal from the speedometer.

OBD2 ECU requires rear O2 Sensor

OBD2 emissions require a second O2 sensor after the catalytic converter that compares the oxygen reading to the first O2 sensor to verify that the cat converter is working. If you don't have it, you'll get a solid CEL on the dash. Unfortunately, the CRX exhaust doesn't have a bung after the cat converter. You could find an OBD2 cat that will fit, or you could do what I did and have the bung added. I took a piece of sheet metal and cut out a plug bracket like you find all over the engine, and bolted it to a steering rack bolt.

You can use a four wire O2 sensor from just about any Honda from this era. I got mine off a 94-97 Accord as it is easy to access. The threads often strip though, and an O2 sensor tool is pretty much required.

The second problem is that the HX harness has the rear O2 sensor plug near the exhaust manifold where the cat converter is on that particular engine. You can't use an EX harness because it has a four-wire O2 sensor plug (HX is wideband) and doesn't have a plug for EGR. The easy solution is to go to the junkyard and cut male and female O2 sensor plugs (sensor side and harness side) to make an extension harness.

Driver's Side Engine Mount

The mount on the timing belt side of the motor was different, so I swapped over the one from the old motor. Then the timing belt cover wouldn't fit, so I had to do a little bit of careful trimming. I cut it so that you can't tell it was cut and there are no gaps for crud to get all over the belts and pulleys inside.

163 Posts
Discussion Starter · #6 ·
More Backstory

This was my driveway at the end of Fall, 2013. The CRX took a backseat to a $600 Accord that I got so that I could leave it in San Diego for my Gramma to use and so I wouldn't have to rent a car when I'm there. I did a ton of maintenance to it and my older brother rebuilt the auto transmission, but at a bare minimum the only things it needed were a new muffler and axle. The axle kept popping out on the previous owner because the teeth had been worn off the inboard end due to improper installation.

I had been making steady progress on the CRX, then I got hung up on one part of the wiring (main relay) and everything came to a grinding halt. Winter hit, and I went idle. I'm native to San Diego where it never drops below 65F. I'm solar powered. In the real winters that I experience here, I've found that I go into a type of hibernation: alcohol, house parties, video games.

With some wheel dollies I was able to cram the CRX in for the winter, but it was a tight fit.

It was around this time that the project's owner got into a car wreck in her Mirage. Some idiot totaled her car, but she wasn't hurt and she got more money from the insurance company than she would have if she had tried to sell it. I decided to loan her my GSR until I could get past the roadblock I was at with the CRX.

An STi with a tow hitch makes one hell of a tow vehicle. It's easy to forget the CRX is even there.

The CRX sat for a bit (months), and then the landlord's son decided to take the property over and throw us out. It was a dark time, but soon the sun began to exert its influence and thaw out my frozen motivation.

This is the CRX in the Spring of 2014. I hadn't looked at it for about six months, then the temp climbed above 50 degrees, and within fifteen minutes I had found the hangup. Probing the main relay, scratching my head, opening harnesses and tracing out wires by hand was all it took.

163 Posts
Discussion Starter · #7 ·
Reference Diagrams

These are the pinouts for the CRX's ECU harness. I found several inconsistencies. There are others floating around the internet but none were any more correct than this one.

This is the green dash harness plug near the ECU on the OBD2 engine harness.

163 Posts
Discussion Starter · #8 ·
Civics 88 to 95 - including the CRX - have two separate harnesses, one for the engine that plugs in at the strut towers, and one from the strut towers to the ECU that is hardwired to your car's dash. 96-00 D-Series Civics use a one piece engine harness to the ECU. It connects to the dash harness by way of a green plug near the ECU plugs, and a plug on the driver's side strut tower. The wires in these plugs do not match up straight across to the CRX's strut tower plugs.

Determine what wires you need
What this means is that the majority of the harness is self-contained. Most sensors etc go directly to the ECU and you don't need to concern yourself with them. The wires you need to hook up are the ones that go to the car. Your instrument gauges, back up lights, AC button, main relay, brake light, clutch switch, electronic load detector, and power from the fuse boxes. That's not so bad, is it?

Pull the passenger side strut tower harness through the firewall back to the ECU plugs snipping as few wires as possible (two go to the under dash fuse box). Then probe each wire in the driver's side harness and look for continuity at either the ECU plugs or the instrument cluster plugs. Label each wire with masking tape as you go. Now cross reference each wire to the OBD2 dash plugs. Some OBD0 wires have no cross reference. On the other hand, the OBD2 engine has some connections that don't correspond to the CRX (such as VTEC). Cut the unused CRX wires at both ends and repurpose them for the missing OBD2 engine wires instead of running new wires.

This is the complete OBD2 engine harness. No cuts or splices are made to it. The metal bracket and rubber bushing where it passes through the firewall should be removed. Any other brackets and holders should be removed as well.

Due to inaccurate and vague documentation, I decided to go to the junkyard and rip out a dash harness from a manual trans EK. To get it out, I had to cut it in half unfortunately. Many wire color/stripe combinations are repeated, but to match them up from one side of the cut to the other, I noted the silver dots. There are several green/black wires for instance, but one will have one silver dot repeated about every inch, another will have two.

Finding what plug near the fusebox the wire terminates at still doesn't tell you much. From there I used my roommate's HX as a reference. The wires that had me guessing turned out to be for the fuel tank pressure sensor and air conditioning. Some wires are marked online as "Auto trans" which is completely false, most notably the backup light switch.

There's a grey rectangular case securing all the wires underneath the pedals. You cut the tape and then pry it open carefully not to damage it to the point it wont snap back together.

In order to have unrestricted access I deemed it prudent to pull the cotter pin and just let the gas pedal dangle. A lot of times, pulling more parts out than necessary is faster than leaving it together and working around it.

I left the split loom that goes over the center tunnel intact since it's easy to pull a wire on one side and see it move on the other.

At this point the wiring splits in different directions with some of it going out to the driver's side strut tower plug, some heading toward the main relay, and some going to the gauge cluster. That covers all the wires we care about at least.

THIS IS WHAT HELD THIS PROJECT UP FOR AN ENTIRE WINTER. Inside the blue tape is an oem main relay splice found on DPFI cars only, and not documented anywhere. This little splice causes a neat problem where the engine continues running with the key removed! Especially fun when gasoline is shooting everywhere due to a hose clamp on the fpr being overlooked! Oh, and here's a hint: the engine doesn't stall when you disconnect the battery!

On DPFI cars, the fuel injectors and fuel pump are both on the latched side of the main relay. You have to cut this connection and separate them so that the ECU can deactivate the main relay at will. Main relays on MPFI cars are wired the same as EK's and every other '90s Honda I looked at (Accord, Integra, Prelude, etc).

Here is the driver's strut tower plug. Originally I thought that I would adapt it to the OBD2 harness's strut tower plug to it, but as it turns out, none of the wires apply. Most of the wires were removed. Some were repurposed.

I got a female driver's strut tower plug from the junkyard to make it easy to probe wires.

As you can see in the finished product, the original strut tower harness isn't involved at all. The dash side of the OBD2 harness came from the junkyard. I cut the wires as long as I could reasonably get to. Running these wires through the firewall cleanly was difficult.

These are the CRX's passenger side strut tower plugs unplugged and removed from the brackets. The bracket isn't reused.

I pulled the split loom off to separate out a couple wires that had to be snipped so that the harness could go through the firewall.

After cutting a couple wires to the fuse box and removing the split loom, the CRX passenger side strut tower harness was pulled through the firewall for dissection. Then the OBD2 harness was ran through the firewall, along with some wires reconnecting to the fusebox (ECU power and ELD). I slid split loom over the wires to keep them secure, but held off on the electrical tape until the project was completed.

As I confirmed each wire, I temporarily connected it, tested it at the ECU or cluster, then soldered and heat shrank it. Some wires were labeled on each end to be reused rather than running a new wire from the ECU all the way out of the firewall.

This is the original CRX ECU harness, hacked up for a ****ty MPFI conversion. Some extra wires were run to an OBD1 conversion harness that was connected to a chipped p28. These plug connectors would be removed from the car, but I kept them intact until the last moment so that I could more easily identify what the wires were for. All of the OBD0 pinouts I found online had errors, so every wire was verified by hand.

At this point I was probing every wire, and in many cases, literally pulling wires out of the split loom and physically following them to their conclusion. In blue there's an OBD2 jumper harness that I could strip and hook up test connections without ever violating the OBD2 engine harness. In the end it wasn't useful for this project.

Everything was coming together here. You can see that the two-pin service check connector is wired up, as well as the OBD2 diagnostic port. Once the engine was running, it was useful to hook up a scanner and see if any sensors still needed to be hooked up.

This is the finished product, all wires connected and secured. The original ECU harness plugs are completely gone, as well as each of the original strut tower plugs. Unused wires were completely removed from the harness.

The CRX is now effectively OBD2. Any OBD2 engine could be dropped in and plugged up. It's not easily reversible - to convert back to OBD0 you'd have to get another dash harness.

OBD2 diagnostics are fully functional, and you can jumper the SCS to set the ignition timing or manually read the trouble codes.

Here you can see the black harness bracket and the blue connector. I scavenged these off junkyard EKs to use to secure the engine harness so it doesn't rub under vibration. On EKs, the perfect bracket is down near the battery tray right where the harness comes out of the firewall, held on by a 10mm bolt.

These plugs are left unused. Just ziptie them up and hide them. This is the power steering pressure sensor plug, the electric speed sensor plug, and a plug for the charcoal canister purge valve.

163 Posts
Discussion Starter · #9 ·
This is the CRX on borrowed HX rims. I took these pics to try and convince the owner but she didn't think the expense was justified. It looks great with the Integra webs anyway. Other than the rims, this is the finished project.

As far as the exterior restoration goes, all I did was change the rims, remove the stickers on the back bumper, change the door glass, replace the missing fender bumper, replace the missing splash guards, and pry out the dent in the fender.

The huge ride height and wheel gap made me question if these were the correct springs for the car. Apparently Honda intended these for intense offroading.

1,452 Posts
Can I simply say I love you for this?

My 88 so has a y8 that I'm really hoping I can convert to a y5, possibly with the HF trans.

One of the biggest hang ups is the obd2 conversion. I've only seen this done once before and the person had major issues with the ecu.

Job well done my friend I will be making several hard copies of your reference diagrams for later use.

Any mpg numbers for us yet?

163 Posts
Discussion Starter · #13 ·
Thanks! It's encouraging when people show interest in your thread. This one requires a lot of time and effort. The longest and most important part will be translating my wiring notes over and that has yet to come.

Hold off on printing anything out just yet. Those diagrams are there to help organize my thoughts, but they may end up getting removed. They weren't as helpful as I anticipated. They were only a starting point. There are a lot of variations between years and trims. On top of that, some of the pinouts are simply incorrect but not in a way that has mattered for most conversions. I'll be drawing up my own, most likely in table form.

There's no reason to have any ECU problems*. I can understand though. The information just isn't out there. The Helms doesn't have the level of detail we need. I had to physically trace wires out by hand. That means getting sacrificial harnesses at the junkyard for both the Civic HX and the CRX, cutting open all the loom and following each wire to its conclusion and each splice's conclusion. The splice off the main relay on DPFI engines-only held me up for months. It isn't documented but it should never matter unless you're doing something like this.

*The one ECU problem I have is the fuel tank pressure sensor, but it doesn't cause a CEL so I deemed it not worth fixing and outside of the scope of this project for the owner's needs.

I finished this project early in the Spring 2014 and turned the car over. The only problems she's had have been with the security kill switch (my fault), the tie rod ends wearing out, and the battery being too weak for winter starts. The engine conversion has been 100%, no CEL's, not even for the rear O2 sensor!

I have to say that I'm immensely disappointed not to have MPG numbers to report. She has a hard time understanding how to get them. Also, she doesn't often fill the tank up all the way. To get an accurate reading, you need at least two consecutive readings. On a car that gets great mileage but also isn't driven much, it can take about two months to even use two tanks of gas!!

I don't think it gets as much mileage as I anticipated though. It could be because she's new to driving stick and like most drivers, drives in a way that wastes gas. I'm also unsure of whether it has the original trans or one that must have came with the D15B. I know how to tell but I'll have to drive it myself. I hope to be able to work something out where I can drive it for a while and get a reading, because that was my main interest in putting this project together.
*edit - it has the original DX trans. Just under 3000RPM @ 70mph and 3500 RPM @ 80mph

One thing I can confidently report is that this thing hauls ass. The HX's VTEC-E, paired with a normally geared trans on a lightweight CRX allows it to really get up and go.

She's bringing the car back so I can replace the shift shaft seal. I need to remember to take some more pics for this thread.

** notes for me **
Closeup of the breather hose
Front engine mount
Final Charcoal Canister hose layout
Lack of Flywheel Cover (engine / trans mismatch)
Find Timing Belt Cover pics?
Find Cluster Harness pics?
Next to my CRX?

163 Posts
Discussion Starter · #15 ·
Not in this case. Converting to OBD1 would mean buying a conversion harness to get something I really don't want. I'd probably make my own conversion harness to save the car owner some money. But then if I'm going to do that, why not convert to OBD2 and run the correct ECU for the engine?

I really wanted to keep this project as stock as possible since the owner doesn't know anything about cars and since I wont be around to fix it down the road. I set this up so she has the OBD2 scan port, a fully functional CEL, and the two-pin ECU jumper harness. Also, she may be moving to California. It would most likely get BAR'd as-is. If they want to be strict about it then she'd just have to get a fuel pressure sensor welded into her gas tank and throw the Civic HX's charcoal canister on the firewall, put the exhaust manifold/cat on there, and it'd be 100% legit.

Has the ECU chipping community downloaded the real, actual tune from OBD2 ECU's? Even if they have, I know they don't have all the correct fuel and ignition trim tables. EGR? The only way to get this engine running optimally is with the stock tune. I can street tune a car for drivability, but I'm not going to sit there and datalog/flash, datalog/flash... I need real-time tuning. I'm used to the AEM EMS. Even then, I just don't have sophisticated instrumentation, let alone the time and patience to get it all dialed in like OEM. AFR with a wideband, sure, but not timing, VTEC crossover, EGR, Ignition timing based on crank fluctuation...

When you get your car dyno-tuned they'll do the WOT tuning, but I didn't choose a D16Y5 to try and make the car fast. Most places don't even have load-bearing dyno's to do the street tuning. Don't forget they charge by the hour.

People don't realize how much the D series changed from OBD1 to OBD2. The Y8 is very very different than the Z6, even though a Z6 tune will run the Y8. Even an Accord or Integra ECU will run a Y8, B6, Z6, Z1, so that's not saying much. I've tried it. Optimally? Not even close. It's not worth running a Y5 if you're not running it optimally. You're better off getting a Z6 and running the stock map.

You can tell how different the sixth gen single cams are from the fifth gen and earlier by how much less ignition timing advance they run. The less timing required, the more efficient the head design. Not to mention the giant plenum on the Y8. The sixth gen was tuned physically and electronically for better drivability. Better take-off from a stop. The Z6 was squeezed for max peak hp.

Didn't mean the tone to appear contentious here. Just vomiting out my train of thought :biggrin: Your question contributed something I wanted to add to the thread. Hope I answered it. Thanks!

414 Posts
This is awesome. I often wondered about running an obd2 ecu in an older car since I'm a fan of making a swapped engine run right with a factory tune, but never knew if there'd be annoying issues or couldn't find a good enough reason to justify it.

I can see why you used the stock ecu in this case, really seems like the best choice for the lean burn engine especially if she wants mpg over performance

163 Posts
Discussion Starter · #17 ·
Yeah, it's no cakewalk but once I post up all the info it will be more accessible to people. My fear right now is forgetting anything or not having it documented well enough in my notes. It's been a little over a year since I did this. I would love to do another car and make revisions if necessary, but the plan for my Si is just to put the D15Z1 out of my VX into it. (Then I'll get my GSR back from San Diego, swap the motor and my Type R trans into it, and put a non VTEC into the GSR and sell it or give it away to family.)

I thought I would simply wire the CRX's passenger side strut tower harness to the OBD2 harness's green plug, and the CRX's driver's side strut tower harness to the OBD2 harness's driver's strut tower plug. I thought that many of the CRX's ECU harness wires would go directly to the OBD2 ECU harness. I was completely wrong about everything.

I pulled both strut tower harnesses into the car all the way to the ECU harness, chopped them off, chopped off the ECU plugs, and ran a couple wires back out to the engine bay (ignition and starter wires need to go out the driver's side, as well as a handful for the OBD2 harness's driver's strut tower plug, and a couple wires need to go to the under-hood fusebox). On the OBD2 harness you have two plug harnesses that need to be wired up to the CRX, the driver's strut tower plug and the green plug near the ECU. Many of these wires go to the cluster by way of the chopped wires, and the rest go to the dash harness. On DPFI cars, one wire splice to the main relay has to be altered. No splices are made into the OBD2 harness.

This process is not reversible, unless you count replacing the entire dash harness. You could easily swap out the OBD2 harness for another one though, even an OBD2 two piece.

I see you're in Ogden. That's pretty close to where we found the CRX.

414 Posts
Putting an LS into a gsr? I wonder how well that'll sell. I actually considered the same thing. There was a gsr sedan shell with minimum rust for dirt cheap, a friend was willing to sell his trans for dirt cheap, just needed to find a decent engine and ecu. Could've had a running non vtec gsr for well under $1k for a quick flip, passed on it since I figured people won't be interested.

The wiring sounds like a pain, I'm sure there's obd0-obd2 jumpers around. Maybe.

Now I know why there's not as many nice crx's left in utah, they all escaped this salt trap to different states haha

163 Posts
Discussion Starter · #19 ·
I'll just sell it as an Integra. Lots of people don't know the difference. I've come across many people with GSRs not even know what that meant (used to do car audio, then later emissions). Nobody wants to pay the premium for a GSR. They just don't care. Much easier to sell it cheaper as a normal car.

There aren't OBD0 to OBD2 jumpers. All the wires you need aren't there. It would have to be a type of harness extending to both strut tower harnesses and the ECU. That will never happen. The only solution is to pull the strut tower harnesses into the car, cut the plugs off, and rewire the sucker.

I have never considered wiring a pain. I was comfortable with wiring long before I was comfortable with the physical part of a swap. Now it's all cake. Next I'm going to teach myself to rebuild transmissions. Not sure if I will ever venture into engine internals.
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