A different swap. The PhY-49 MPG build!

  • Thread starter Thread starter phyregod
  • Start date Start date
  • Replies Replies 24
  • Views Views 7K

We may earn a small commission from affiliate links and paid advertisements. Terms


My RSX-S was totaled out via water damage, and I need a new commute vehicle. I shopped many RSX-Ss, and found none that I was happy with. Mine was quite the gem. Ever suffering from my CRX addiction, I've relapsed again. I commute 200 miles a day, so I figured I could feed my addiction and save $$$ doing it. Enter the PhY-49 build. a Y-49 1990 CRX Si hypermiler. The aim is 65+ mpg on a 75mph commute in a comfortable, quiet car.

How? A Civic VX lean burn engine mated to a HF transmission. Lowered a bit with hard tires, some tasteful aero mods and light weight reduction. Full interior, sound, sound deadening. Weight will come in the form of lighter wheels, suspension, tires, etc.

Enter the project car:
A JDM front end Y-49 Si. Roof already skinned with a DX skin (sun roof delete) may be a re-do from my donor if exploratory surgery reveals a hack job. B18a1swapped with matching manual trans. Slammed egay coil overs and stock struts. Extra Rice. And yes, those are curb feelers. probably going to undo the JDM front end swap. Anyone want to trade a USDM Y-49 front end for it??

She looks clean in pictures! But it is actually rough all over.

The Swap: 1994 Civic VX Lean Burn Engine!
VX motor.jpg

Ordered up with as much oem stuff as I could. Stock AC, Alt, shift linkage, Axles? wiring, etc. Came with ebay header installed. Ugh.

Neuspeed Sport springs
KYB STR.T shocks (Oranges)
Aluminum hats, Energy suspension Spring isolators and all new oem bushings and whatnots.

Because everything on the Phy-49 is missing, broken, spray painted, or effed up, Enter the Donor. A '91 HF. Don't call me an animal. Although this is a bone stock HF, it is non running, and salvage titled. This little gem is going to save me about $1600 in restoration parts. Picked her up for $650. I was sad all the way home knowing this car is, sooner or later, headed to the crusher.

This will be a LONG build. Taking my time with it. Sourcing bits and pieces as I go. I have all the big pieces. Just need the million little bits to make it all go together, and the million hours to get it done. Aiming for a perfect stock interior and an OEM looking swap.
This combo will easily achieve 65mpg with careful driving. Achieving lean burn at 65mpg while cruising 75mph is going to take some form of dark magic.

Quick question.. 94 Civic VX engine to 91 CRX HF trans, I'm solid with a 91 Crx Si clutch, pressure plate, flywheel and throw out bearing, correct? I can't seem to find what clutch people used in these swaps. Don't want the HF clutch. Can't find a definitive answer.. Eco swaps are harder to research given their rarity. I don't even have a complete parts list yet!
Last edited:
I found the same info. What concerns me is people say the vx flywheel is 15 pounds and has a smaller surface area.

HF is smaller as well, and designed to hold 57?hp. The VX is 92hp and I'd rather err on the side of durability. The Si clutch is rated at 108?.. Perfect. Except the fly is 3 pounds heavier. I know for a fact the Si clutch will work with the HF, just muddy on the VX. If anything is a millimeter off, it'll be a nightmare. I'm 98% certain the si clutch is perfect. Just looking for that last 2%.
For highway, the weighted flywheel may actually help keep momentum up. city, the lighter will improve milegage as it's less mass to spin.

but really, we're talking about .1mpg on 100 miles probably
I'm not so concerned about weight as I am dimensions and bolt patterns. Lighter and heavier have their advantages and disadvantages.. For an mpg rig, none are significant enough to do much of anything, as B said.. Just need to be 100% positive it fits before I order a shiny new paper weight.
My search told me that the VX and EX flywheels are the same part number. At least same part number when trying to purchase one today (hondapartscheap.com). I figure that means they're the same bolt pattern. And since D16Z6 motor with D16a6 trans is commonly done....I think you're good to go.
I just cross referenced Exedy's site again. Exedy clutch and flywheel part numbers from the 94 VX and '91 HX are the same.

The first time I looked it up, I searched the clutch kit part numbers.. They have different "clutch kit" part numbers because of the throw out bearing being different for the Cable/Hydro trans. That threw me for a loop. I just saw different part numbers and went hunting for info instead of digging deeper.

So to put it out on the internets, To mate a Civic 92-95 VX Engine to a 90-91 CRX HF Cable transmission, use a '91 CRX Si clutch kit and flywheel.
Last edited:
Finally off work, had a chance to unwrap my VX motor.

This is a "clean, strong running motor with un-cut wiring harness, fuel lines, vacuum lines, all sensors" from Beaver's Honda Car Salvage 9455 Smith Rd, Kannapolis, NC 28081.
image1 (1).JPG image1.JPG image2.JPG image3.JPG image4.JPG image4 (1).JPG image3 (1).JPG image1 (2).JPG image2 (1).JPG

I've contacted them calling complete and total BS. Awaiting a reply. Blown head gasket and front and rear mains is not "Running good".
Last edited:
Ok, Called Beaver's. They agreed to refund $200 for an engine gasket set and they are shipping me a new EGR system. These were my terms and they apologized and happily agreed. No fighting or BS. Aside from shipping a bleeding engine marked "clean", they have agreed to make it right. I'll update if they don't. Good people so far.
Hopefully that's good enough for the fix. ie, if it was leaking all this time, what wear damage could have taken place inside?
I'm assuming the inside looks exactly like the outside. I'm going to use that $200+ cash to buy a full rebuild kit. Have the machine work done and build a fresh, new motor out of it. It'll be much better than a used motor and I don't mind the extra coin. I'm going to put a gazillion miles on this thing. They sold me the long block for $405, (spent an additional $400 on alt, AC compressor, axles, shipping, etc.) so now I'm in the long block for $205 If all goes according to plan I'll have a new motor for $800ish.