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Old 01-18-2008, 09:03 AM   #1
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CRX mods

Okay - with a CRX on the horizon, here are the proposed mods - and I'd love feedback on any of them that you've had experience with.

1) SuperMID - will acquire shortly. Definite first mod once I get the CRX and the SuperMID. I do need instructions for the CRX if anyone can help.
2) Likely to need an HF ECU. Is there a way I can get it (or the existing one) chipped for even better FE than HF stock?
3) Taller gearing in tranny. The CRX that's on the horizon isn't an HF, so will work with my mechanic on an HF-style transmission that will enable better mileage especially in 4th and 5th. He's got the experience to re-gear properly. If it's doable, I might go with a 6-speed transmission.
4) Weight mods: many various mods, ranging from nearly free to expensive like a carbon-fiber hood
5) Custom pulleys - basically slightly larger pulleys on alternator, water pump, get racing pulleys for better weight while I'm at it.
6) Quick-release removable passenger seat
7) Removable aero rear wheel panels
8) VX tires (or better), VX wheels
9) Remove antenna, possible windshield mounted panel
10) 195 degree thermostat
11) Amsoil
12) Bosch +4 plugs (can use advice on this one - not sure how well they perform on Hondas
13) Camera & LCD for side mirror removal
14) Plastic or composite fuel tank like the Insight - can use help finding this if anyone knows where to get this

Any other mods you've done to a CRX for great FE would be appreciated as well.
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Old 01-18-2008, 10:08 AM   #2
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Ummm, is there any specific reason you aren't buying an HF version? This would save you some work...
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Old 01-18-2008, 07:28 PM   #3
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I think putting an HF ECU on a DX or other CRX would not work very well. The HF engine has alot different cam timing then a DX would and a DX would probably run like crap with an HF ECU.

You would need to swap the HF head and intake manifold to make this work and even then I'm not sure how well this would work. The HF head is an 8 valve with 2 valve reliefs in the center of the pistons, and the 16 valve pistons have 4 valve reliefs in the corners.

If you are serious about good FE and can't find an actual HF, I'd recommend swapping the entire engine/transmission/ECU from an HF, or even better, an HF transmission and VX engine/ECU.
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Old 01-18-2008, 08:26 PM   #4
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I think putting an HF ECU on a DX or other CRX would not work very well. The HF engine has alot different cam timing then a DX would and a DX would probably run like crap with an HF ECU.

You would need to swap the HF head and intake manifold to make this work and even then I'm not sure how well this would work. The HF head is an 8 valve with 2 valve reliefs in the center of the pistons, and the 16 valve pistons have 4 valve reliefs in the corners.
You actually can't even use an HF ECU in a CRX DX - not without modifications, that is. The DX has throttle body injection, whereas the HF has mutiport injection. If the CRX is an SI, this will be less of a problem. BUT, the HF has an EGR valve. And the SI doesn't. In fact, it doen't even have provisions for one. In either case, it would be necessary to swap an HF intake manifold to use an HF ECU. And, in the case of the DX, an HF/SI distributer as well as some wiring mods would be required. But even here, you would run into problems. Specifically, the HF manifold has MUCH smaller runners than the ports on the DX/SI head. This would certainly result in less efficient operation.

An alternative would be swapping an HF head on a DX bottom end. Honestly, I am not sure this would work without changing pistons, as the HF head is a 8 valve head, while the DX/SI head is a 16 valve head. On the other hand, the Civic CX uses an 8 valve head on a bottom end with pistons that have valve reliefs for a 16 valve head. So it MAY be possible. But you would REALLY want to check this out before doing it. Don't come to me if you end up bending valves. Because you were warned.

Given all these issues, I have to agree with the others here. If fuel economy is what you want, you are better off just buying an HF than trying to mod a DX/SI to get the same thing. Not only has everyhing been done for you in terms of the motor. But the car is also MUCH lighter than DX/SI models of the same year. If you can't find an HF OR have a specific CRX already in mind (which it sounds like you do), I also agree that either a full HF swap OR a D15Z1 swap would be the best way to go. It would also likely also be the cheapest, as B-series engine swappers are willing to virtually give away entire HF and VX powertrains. Mixing and matching parts, on the other hand, is going to require that you buy these parts in the first place. This ALONE could easily end up costing more than picking up a complete drivetrain from a swapper. After that, you would have to spend money on the gaskets and other odds and ends required to put the motor together. And to to it off, the resulting motor may not pass smog where you live.

As for the transmission, I would recommend just going with a full HF transmission, Regearing is going to be MUCH, MUCH more expsnive than just getting a perfectly good used HF transmission from either the local pick-a-part or an engine swapper. I would oly consider gear swapping if you do ALOT of driving in town, wheregears 1-3 on the HF transmission basically REALLY suck. Six speed? I don't know about this one. But I think that a six speed was available in 1988-1991 Civic wagons. Bascally, it had a super-low first gear. Whether this could be modified to give you a better transmission for normal driving is something I really don't know.
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Old 01-18-2008, 10:35 PM   #5
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Great - then HF tranny & engine it is, along with apparently the proper wiring harness. I'll start looking on those. There are supposed to be 2 Honda yards near Huntington, WV that my 2nd mechanic knows about - should be easy enough. Thanks for saving me a lot of work on that one.

About regearing - I am actually likely to do a full tranny rebuild and redo all 5 gears. 5th will be for lots of freeway miles - so better FE at the cost of a little power, which this really won't need.

Yes - VERY specific reasons for getting this CRX (although with luck I may end up with a couple plus parts cars eventually). Entire history is completely known to me. There is a little sentimentality as well, it does come into play on occasion. But I've driven or been driven in this for more than a third of this vehicle's life - and it's one specific owner - she babied the vehicle with the exception of letting it sit for so long.

Plus there's the zero and I mean ZERO rust on the vehicle - California - Los Angeles & Sacramento. Interior is not perfect but I know every quirk of the vehicle, which is a major plus. It's never NOT been to a Honda dealer except to Goodyear once for tires & brakes - haven't found an HF with zero rust and all Honda maintenance yet.

The sway bar setup in the DX even though it costs weight does help as it's some of the little extra safety in the vehicle. Compromise.

What I'd like is an early 88 HF with the older style seatbelts and the new style hatch ideally - will probably spend a couple years finding one without rust, so this will work as an excellent project car in the meantime, too.

Since I plan on putting over a quarter million miles on the vehicle in the next couple years - any money put into the vehicle will average out to pennies in the long haul.

Okay - other suggestions besides an HF motor & tranny?
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Old 01-18-2008, 11:41 PM   #6
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Other suggestions? First of all, full wiring harness swaps are NEVER a good idea when swapping engines. This is DEFINITELY the hard way of doing things. As any Honda engine swapper will tell you, it is MUCH, MUCH, MUCH easier to modify your existing harness to run the motor that you wish to swap in there. Also, you might try going with a D15Z1 rather than an HF motor (D15B6) if yu can find one. The D15Z1 will give you better mileage AND an extra 30HP. But, like the HF motor, you should be able to find one for next to nothing.
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Old 01-19-2008, 03:10 PM   #7
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"An alternative would be swapping an HF head on a DX bottom end. Honestly, I am not sure this would work without changing pistons, as the HF head is a 8 valve head, while the DX/SI head is a 16 valve head. On the other hand, the Civic CX uses an 8 valve head on a bottom end with pistons that have valve reliefs for a 16 valve head. So it MAY be possible. But you would REALLY want to check this out before doing it. Don't come to me if you end up bending valves. Because you were warned."

I have a DX block in mine with the HF head except mines was a HF to start with. The valves line up perfectly with two of the four valve reliefs. In fact a 1992 CX has the same 8 valve head PM-8 on the DX block.

Word of warning about the HF motor though. Honda no longer makes the pistons for the 8 valve motor so I bet they are not making the rods either. If you go that way you better be sure you get a good condition used motor. There are no JDM motors like that.

If I did mine again it would be a VRX for sure with the VX VTEC-E motor
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Old 01-19-2008, 05:51 PM   #8
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Word of warning about the HF motor though. Honda no longer makes the pistons for the 8 valve motor so I bet they are not making the rods either. If you go that way you better be sure you get a good condition used motor. There are no JDM motors like that.
The HF rods do indeed have a different part number than the DX rods. But that doesn't mean that DX rods WON'T work, although you might want to check on that. Sometimes, Honda just uses different part numbers for the same part. For instance. the Integra LS and CR-V both use the same timing belts. But the part number is different for both. On the other hand, it is possible that HF piston might use a different diameter pin, which would require a different rod. In this case, a DX rod with a DX piston would probably work. On the other hand, NOTHING might be compatible. For this reason, it would certainly be best to get a good-running motor. This way, by the time it conks out, you will have gotten your money's worth from it and probably won't care if you can't rebuild it.
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Old 01-19-2008, 10:13 PM   #9
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I see a lot about the D15Z1 swaps but am missing something important. What did it come out of? Why is it better mileage plus HP over the HF? I definitely want to do this right, and I know someone modified a CRX to get 85 MPG - so I know I'm on the right track on this one.

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Other suggestions? First of all, full wiring harness swaps are NEVER a good idea when swapping engines. This is DEFINITELY the hard way of doing things. As any Honda engine swapper will tell you, it is MUCH, MUCH, MUCH easier to modify your existing harness to run the motor that you wish to swap in there. Also, you might try going with a D15Z1 rather than an HF motor (D15B6) if yu can find one. The D15Z1 will give you better mileage AND an extra 30HP. But, like the HF motor, you should be able to find one for next to nothing.
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Old 01-19-2008, 10:15 PM   #10
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I have thought about this - can't find enough info on weight, etc. to figure out the whys of it all. I have thought about a VRX - VX motor, rims & tires, specially geared tranny. Anyone seen this done - ideas on what I'd be in for? I know I'd have to get a VX but one with a good motor but rustbucket might work.

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If I did mine again it would be a VRX for sure with the VX VTEC-E motor
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