Tag Archive 'fuel economy'

Jul 30 2008

CRX D15Z1 (Civic VX) Fuel Economy Swap Guide

Since I knew what a Civic VX and d15z1 was I’ve always wanted to toss one of the swaps in my car. I never really had any money and was trying to look out for some sort of local deal, but in the end I’d saved up some money and figured I’d just go for a JDM swap. It’d come with all the sensors and wire harness and a bunch of junk I figured I’d end up spending for anyway, so I went ahead on bought the damn thing from a Canadian importer for $520 USD, shipping included.

Thing came in about 3 days (all the way across the continent and to my door), and I was ready to get started. I knew all the basics and honestly didn’t even look at anything online before starting the swap. Just figured I’d go ahead and do it and see what came up. Anyway, I intend this page to be a guide for those looking at the swap that can already do stuff like undo bolts and then put them back where they came from. This was my first engine swap, and it went fine, so I’m not going to bother with how to swap the engine as much as I’m going to discuss the specifics of this swap.

Why did I do it?

The short of it is that I wanted better fuel economy, and I knew this was going to be the most efficient engine I could get. The d15z1 has both vtec-e and lean burn, and is smashing good with my HF transmission.

Also, as you can see from this image, my gas mileage has sucked recently due to a doomed CX head swap. It was really sucking, and the car had horrible power to booth. Nowadays, I’m up in the 60s, with hoop dreams of fuel economy up in the 70s. Right now I’m just sitting on the 3rd tank, and I’m hoping to keep it up above 60 mpg consistently, though the numbers seem a little wonky just halfway through this tank…but that’s not important.

Anyway, the d15z1 swap was pretty cheap, maintained stock power, and promised much better fuel economy, so I went for it. I would’ve gone for an even smaller engine if I could get one, but it’s not exactly easy to find a working insight swap just laying around.

What did I have done beforehand?

Previous DPFI -> MPFI and and OBD0 -> OBD1 swaps left me in a decent position to get this done without having to rewire everything myself.

I did the obd1 rewiring myself, but in hindsight, having bought a conversion harness probably would’ve been a good idea. It’s not that it was hard to just chop my old plugs off, but it’s kind of messy now.

Also, when I did the dizzy swap I went with obd0 plugs since I got a dizzy with no plugs, and even though rewiring the dizzy was really easy, i would’ve saved 30 minutes if I’d thought ahead and used the obd1 plugs from the git go.

So, moral of this story (and more things you’ll learn later): think ahead!

What didn’t I have done beforehand (or what should you know)?

The fuel line on the VX is weird. You can see it in the picture, but it’s got to run around the EGR, neither my stock DX nor the replacement CX fuel line I’d been running would fit properly for the new, egr enabled engine.

I spliced to lines together to get it up and running at first, but I ended up spending 80 bucks for the damn thing from majestic honda, so try and find one in advance, but be warned that they’re hard to find.

The EGR Control Box is really just a bunch of crap, and is kind of hard to find. Since it’s on the firewall of the car it won’t come with the engine, and there aren’t many running around. Try to get one from someone who has swapped out a vx engine, I ended up spending 50 bucks on one cuz I needed it fast. Here’s what it looks like and the parts diagram:

ECU pins are a pain, and you’re going to need more for the VX swap. I only needed a few, but I bought some VX plugs anyway for about 10 bucks shipped. I had to wait a few days to finish my ecu wiring, so I’d wish I’d done it in advance.

The driver side engine mount that connects to the block is different from the EG civics to the EF civics, so you’ll need to swap it out. I forgot to do it until the engine was in there, and then I couldn’t get the crank pulley bolt off (easy solution, drove to my old shop and did it there), but you’ll need to remember that and know that you’ll need to notch the timing belt cover a bit for the new (old) mount. It’s hard to see in the picture, but you’ll see what I mean when you do it yourself.

Don’t forget how annoying the shift linkage pin can be. To tell you the truth, I just dropped the linkage with the engine and didn’t mess with the pin. After my last experiences with that, I figured this way was easier.

Don’t forget to be prepared to buy a new o2 sensor. They break easily. I got mine here and had good luck without paying 3-400 from honda (wasn’t cheap though).

JDM Engine Note: As you can see, the JDM catalytic converter has a second o2 sensor on it down near the bottom. You don’t need to worry about that but to leave it in or plug it so you’re not leaking exhaust.

Anyway, on to the swap!

So, how do I stick a d15z1 in my CRX?

Don’t forget this, first of all:

Pulling the engine

It’s seemingly simple! Just don’t let me forget anything! (NOTE: I’m not going to number the steps, that seems a little too arbitrary since I don’t plan on making them uniform difficulty or importance).

Safety, as always, is a priority. If you’re going to be doing this kind of work, make sure you have a proper jack, proper stands, and know where to jack up the car safely.

Anyway, the first step to anything like this is to disconnect your battery. With that out of the way, I just started stripping stuff off. Intake, wires, all sorts of stuff. I just disconnected everything I could besides the mounts.

Once I had a bunch of random junk off, I drained all the fluids and removed the coolant hoses from the engine.

I decided to remove the A/C at the same time I did the swap (I know, I know, it was leaking anyway and I just didn’t care), so I had to pull that out. Normally you’d need to empty the system, so you’d have to take it to a shop and have them do it. Shouldn’t cost too much, really. The a/c hoses normally require some big wrenches, but since I don’t own them I just used two vice grips and the came apart fine.

After pulling the a/c compressor and the hoses, I realized I needed to get rid of the stuff in the bumper and in front of the radiator. I pulled the bumper and removed everything off the front (with the intention of sliding the engine under, anyway), and pulled both the radiator and the a/c junk. Under the dash there is a clamp and some bolts, which allows you to pull out the a/c stuff, remove it from the case, and toss the case back in.

On the radiator I got rid of the stuff you see in red. The one fan is for the a/c and the hoses are a/c or automatic transmission related.

Next up is the axles. Took off the shock forks and then I undid the lca using the stick-a-1/2″-pry-bar-between-the-lca-and-the-knuckle-while-lifting-the-knuckle-then-lowering-it-down-and-jumping-on-the-studs-until-it-popped-method. I’ve always done it this way, and there may be a better way, but I like this. From there I just pulled back the axles and hoped they wouldn’t get in the way.

So, by this time you should have everything nominal removed besides the mounts, however, life will be easier if you remove the alternator and a/c compressor. It’ll prolly be easier without the intake or exhaust manifolds as well. Before I removed the engine I pretty much had it stripped down to a long block.

No, for the actual removal I had everything off the front of the car I could get off, including the front crossmember. Before actually dropping the engine, I lowered the car as close as I could to the ground the slipped a jack under there. I removed the transmission mount first, gave it some support with the jack, did the driveside mount, and lowered the engine completely. I did this alone and it wasn’t too hard, so *shrug*

Then I jacked the car up as high as I could and slipped the engine out under the front of the car.

Sticking the new engine back in

Hopefully I didn’t forget anything about pulling the engine, because we’re about to put the new engine back in.

The first thing to figure out is how you’re going to move the engine around. This image is not a joke, it worked for me:

There’s not much I can say here but do everything in reverse. I put the new engine in with all the manifolds and alternator on, so it was a bit tighter of a fit. Either way, be sure to put the driver side mount on the engine first and cut the timing belt cover to fit.

Once the engine is in, before you start hooking stuff up, make sure to put new fluids in the engine and the transmission, don’t want to forget that. From there I hooked up the cooling system and left off the radiator cap so I wouldn’t forget that either.

Anyway, after all the basic stuff is done, you start to get into a few annoying things. On the back of the DX block was the coolant temp sensor, in the shape of two single male/female prong plugs. I had to chop them off and solder on the z1 plug so that I could hook it up on the thermostat. I’m told the sensor isn’t polar, so it doesn’t matter how you solder up the plugs.

Also, on the back of the JDM intake manifold there is no spot for the purge solenoid, so you need to tap into some manifold vacuum and put that in and tie wrap it to something.

Hopefully you have the distributor wired up, but if not, follow these diagrams to switch around your wiring to get on the obd1 vtec distributor. Similarly, if you don’t have obd0 to obd1 ecu wiring then you’re gonna need to figure that out. I can’t give you much help there, but either buy a harness or just chop plugs and wire. Here are some pinouts, have fun.

Here’s where it gets to start customized. You’ll need to follow this to wire up your o2 sensor. I ran both the power and the ground straight back to the ecu just to be sure. I’ll talk about troubleshooting the o2 sensor here in a bit. The o2 sensor plug has 7 wires, and looks exactly like an obd1 distributor plug, in case you’re trying to find it.

The next thing you need to do is wire up stuff like the egr, egr control solenoid, vtec pressure switch, and vtec pressure sensor. That’s pretty damn easy, just follow these diagrams.

Other than that and the purge control solenoid, I don’t know what else is custom about this swap. Just make sure everything is together, all your fluids are in, and you don’t have wires flailing around. Go ahead and start it up! You should be done.

If not, I’ll have some o2 sensor troubleshooting (code 41).

O2 sensor troubleshooting

The internet way to fix such an issue is to check your wiring until you’re confounding about the solution and then to buy a new sensor. The real way is to follow these instructions I’ve taken from the 92-95 civic manual. You’ll need a digital multimeter, but it’s well worth it, I should say.


Well, my engine swap is done and good and hopefully yours will be done as well. I think this chart speaks for itself (7-18-08 being the first fill after the swap):

The first spike into the 50s you see is after my auto to manual swap, the following dip is after my misguided head swap, and the current spike into the 60s is the d15z1 goodness at work. If you’ve done or plan on doing this swap, drop a comment.

Also, if you have any questions or things I left out, just leave it in the comments and I’ll fix it up.

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