Jul 30 2008

CRX D15Z1 (Civic VX) Fuel Economy Swap Guide

Published by Benjamin Jones at 2:39 pm under Ecomodding,Gas Mileage,Swaps

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.

21 responses so far

21 Responses to “CRX D15Z1 (Civic VX) Fuel Economy Swap Guide”

  1. [...] posted my swap guide on my site: crxMPG – Gas mileage never looked so good

  2. Ndenon 30 Jul 2008 at 10:16 pm

    sweet ! nice pics but some of the wiring scans (2nd & 3rd) are fuzzy. awesome bro. my back to vx swap with 49state ecu is done but i’ve 2 or 3 more steps before she is dialed in. man wish i had that oem cat ! (kudos) Outstanding mileage too ! what rims/tires u rollin on SVOboy? how about ur intake, and exhaust piping diameter /muffler ? again appreciate ur posting this !

  3. Jon Steffenon 07 Aug 2008 at 6:42 am

    YOU ARE THE MAN. I am starting this swap as well, first I did research, now i’m aquiring parts and then i’ll do the swap. Trouble i’m finding is getting the motor. I’ve done numerous b series d series CRX EF EG EK DA DC swaps before, but then I started reading up on the d15z1. I almost bought an HX motor swap before I heard of the d15z1, (thank god I didn’t). I have a spare crx with no motor so my friend and I are on a quest to get 60mpg like you.

    Ever hear of light pressure turbo’ing? Saab uses this as a way to get better fuel economy out of small engines. If i ever get the VX CRX swap done, I may try this LPT thing to get even better MPG. Food for thought.

    Great write-up!!! :)

  4. Benjamin Joneson 07 Aug 2008 at 12:58 pm

    Nden -

    Hey man, I sent you a PM on ecomodder about the cat, I have another, ;) . I’ve got VX rims an yokohama tires (forget which ones, but they’ve been great). The intake and exhaust is all stock crx stuff (except the vx intake arm).

    Jon -

    Thanks for the nice words. I bought my engine from an importer. They didn’t have it listed on their site, but I heard through backchannels they had them (they’re out of stock now though), so it might be worth it to just call up an importer and ask. I’ve heard of LPT, but I only think it would benefit over the z1 if you did it on the insight 1l engine or something. That way you’re reduce the engine size but be able to dial up the power with the turbo.

    Thanks guys,

  5. [...] Engine swap! __________________ crxMPG | Benjamin FT Jones | CollegeVegan ——————————EcoModder Gear—————————— Window clings | Support EM | Shirts [...]

  6. [...] sir, different car, but check this out: crxMPG – Gas mileage never looked so good

  7. Richardon 06 Sep 2008 at 12:35 pm


    I’m considering swaping a vx motor into a 95 Del Sol. The Del Sol currently has the stock dx motor and trans, and I’m averaging 40 – 41 MPG. I would really like to be getting about 50 MPG.

    If I do the vx swap I’m thinking about using a HX transmission instead of the vx trans. I’m a little worried that the Del Sol’s weight of 2300+ might be to much for the tall 3.25 vx gearing. Plus I intend to keep the AC.

    What do you think about transmission options?

  8. Benjamin Joneson 10 Sep 2008 at 8:12 am

    Eh, that’s not too heavy. You can go with the HX tranny if you want but I don’t think you’d find that the vx/cx tranny is that much of a burden.

  9. [...] this summer I swapped a new engine into my CRX, which quickly bumped up my mileage quite a bit. Nowadays, with a little ecodriving, it’s [...]

  10. Cedon 05 Oct 2008 at 2:15 pm

    Nice work, you’ve inspired me to pickup a beater crx and attempt this sway.
    Did you have to do any type of modification to the axles? Did the axles bolt right into place from the vx tranny? Is it possible to re-use the crx transmission?

  11. Benjamin Joneson 05 Oct 2008 at 3:37 pm

    Hey Ced -

    You’ll actually need to use the CRX tranny. Just make sure you match 89-91 stuff with 89-91 stuff or 88 stuff with 88 stuff and you’ll be fine.

    Good luck!


  12. Cedon 06 Oct 2008 at 10:33 pm

    Is the crx tranny 4 speed? If so, I might wanna go with a complete d15z1 swap, motor, tranny, ecu, axles, hub, clutch cylinder, wiring harness, cluster, etc.

    Would it have been easier for you to just attempt a complete swap? It seems to me that everyone on the gassavers.org decided to keep the crx transmission. My plan is to remove every possible panel inside the vehicle, redo w/ fiberglass resin, and weld in a few pipes to withstand a collision (I’ve heard too many death stories with crx owners).

    Thanks for all your help once again.

  13. Benjamin Joneson 08 Oct 2008 at 5:50 pm

    Ced -

    It’s a 5 speed hf tranny, you can’t use the vx tranny without heavy modifications (which is pointless).

    Also, you can’t just swap in the EG wiring harness. I have an integra cluster, but that doesn’t really have anything to do with the engine swap. Also, you shouldn’t need to change axles.

    Safe driving > random tubes, but more safety to ya!


  14. Matton 04 Nov 2008 at 9:01 pm

    I should note that it is actually not very difficult to use a VX transmission in a CRX. Hasport actually makes a conversion kit (which includes a clutch actuator) that allows this swap to be done quite easily. The only catch, of course, is the cost of the kit itself (a few hundred dollars). But it might be worthwhile for some, given the fact that the newer transmissions are probably going to be in better condition.

    Also, if you want to stick with the HF transmission, you can buy a driver side mount from Hasport for the VX motor. This mount works with the two-bolt 1992-1995 driver side bracket on the motor. Unlike using the 1988-1991 bracket and mount, the mount will sit straight in the car. Also, you will not need to cut the timing belt cover OR leave it with an open hole below the bracket, as is the case if you use the 1988-1991 mount and bracket. Of course, this mount does cost $129. So you may or may not think it is worthwhile to use it.

    One more thing. There is a MUCH easier way to deal with the fuel line than trying to splice things together. Simply bend the line at the fuel filter end instead. This can be done by wrapping the banjo fitting up to the bend in paper towels, sticking it into a sufficiently large steel pipe, and putting some muscle into it (just don’t pull on the hose itself). Within seconds, it will just bolt onto the fuel filter like the stock Civic/CRX line.

  15. Scotton 16 May 2009 at 11:18 am

    Yep you guys are going in the right direction i have had my 1992 vx hatch for a few years now and love it.. Didnt really know what a had at first but i knew it was kinda special after filling up the tank and checking the gas millage when i first got it. Everything is stock now besides my big ass air intake which i highly recommend to reduce restiction on your engine so it can flow air in better at very low rpm’s. Im currently getting right above 40 mpg in the city of spokane even when i get on the throttle and get up to speed. Ive got 60 mpg on the highway but its a easy 50 mpg on a below normal day. When i finish college and get a good job i plan on getting the k20a type r swap with a shit load of turbo boost so i can smoke corvettes and what not with my little 2094 pound honda.. But dont worry guys im going to keep my b15z1 close by so i can make hybrids jelouse again. Well enjoy your projects i know i will..

  16. [...] If by off chance you land yourself a lemon with a shot engine, you can always do a VX swap – it’s easy! This may be too extreme for you, but if an engine swap is not out of the question for you, try to [...]

  17. [...] free to check out my swap page for VX questions, and ask me anything else that comes to mind: crxMPG – Gas mileage never looked so good CRX D15Z1 (Civic VX) Fuel Economy Swap Guide Of course now that I look at the site I realize it’s been hacked annoyingly… [...]

  18. Gus Joneson 05 Dec 2010 at 8:57 am

    Question: Wouldn’t swapping in a 1.3L engine, from a first generation HF, be better? The first gen (1.3L) was carbureted. I would think, that swapping in the 1.3L block coupled with the 1.5L fuel injection would be…very, very interesting! Especially since the first generation HF was rumored to get about 60 m.p.g. in stock (i.e. carbureted) form. What do you think?

  19. Benjamin Joneson 05 Dec 2010 at 8:11 pm

    Hi Gus,

    You could do that, but it seems like a lot of work. The 1.3l engine block is not an easy swap in itself.

    I ended up swapping in a 1st gen insight drivetrain, so I’m happy with that now :p

  20. Jon Steffenon 20 Mar 2012 at 3:10 pm

    Wait! you ended up swapping a 1st gen insight drivetrain into your crx Ben?

  21. Benjamin Joneson 12 Apr 2012 at 5:37 pm

    Yep, that is correct. Though I didn’t have time to properly finish things up before I moved out of the country.

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