CRX K-AWD Rally-X Car Build

[Jalisurr]

Hey Folks,

Figured I'd start documenting my other project a bit while I'm waiting on some machining delays on the Fiero project.

Background - I had been competing in the BC Rally-X championship with my 2013 Subaru STI Hatch. Unfortunately it had an engine failure partway through the 2022 season. Instead of having the engine rebuilt and installed, I decided to sell it off and build a new project. I set about researching what was the lightest (closed, street legal) car with the shortest wheelbase I could find which either came AWD or could be swapped to AWD, and had readily available parts and support in the aftermarket to build. Preference for a naturally aspirated motor as turbo lag is tough to drive around on tight rally-x courses.

The plan:
- 2nd generation (88-91) Honda CRX. Stock weight around 2100lbs, 90" wheelbase.
- K24A2 from an Acura TSX. 2.4L 4Cyl with over 200hp naturally aspirated in stock form, relatively torquey and plenty of headroom for mods. This is a well trodden path for this chassis with plenty of support
- 5 speed AWD k series transmission from a 2nd generation CR-V
- CR-V Rear diff. As stock these had a cool but bad for racing dual pump awd on demand system. The plan will be to lock the diff to the driveshaft and put a freelander style viscous coupler on the driveshaft to give it full time awd. This is a pretty common setup in the Honda drag racing world.
- Torsen diffs front and rear
- Hydraulic cutting brakes (individual control of braking left/right rear wheels - this is what all the top rally-x guys are doing)
- Rally-x suspension - I've had good luck with Flatout suspension on my Subaru so I'll stick with them.

The candidate:

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I picked up this 1989 CRX Si with just a hair over 400,000km on it which I was tipped off to by another member of the local racing scene. It had been sitting in a friend of his' gravel lot for several years and he was willing to let it go for a good deal. I checked it out and it was pretty much perfect for my needs. The interior was old but not trashed, the body was rough but only cosmetically, and most importantly the chassis itself was as rust free as I could hope for (plenty of rust on the fenders and rockers though). It needed a quick brake bleed, a fresh set of tires swapped on, a battery, new gas, and some coaxing on the first start, but I was able to drive it the ~40 minutes home. Then the fun begins!

[Jalisurr]

First step - clean the car of all the grime and moss that was building up

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There were a bunch of quick maintenance items that needed to be done so I took care of those in the first couple months:
- New struts for the hatch
- New hinges to replace the rusty hatch hinges
- Plugs/Wires/Distributor Cap to make the stock D16 engine run smoother
- Valve cover gasket to stop the (worst) oil leak
- Replaced a bunch of lightbulbs, and the turn signal housings in the front bumper
- Reinstall sun visors and various trim pieces
- Remove the spaghetti of aftermarket stereo wiring, the head unit, and all the speakers

The first major upgrade for the car was the installation of new suspension. I've had good (event-winning) results with Flatout's GR40 line on my Subaru so when I saw they made them in Honda fitment as well it was an easy decision. They're relatively inexpensive and simple for rally-x suspension with external reservoirs and helper springs, with single adjustment in rebound only. Spring rates I went with after discussing with them are 225lb/in front and 175lb/in rear. Slightly softer in the front and stiffer in the rear than the stock 250/150 springs for better rotation and forward weight transfer under braking. I would have gone even softer in the front if I weren't going to be adding some weight with the new engine and transmission combo.

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Replacing the rear suspension also ended up requiring replacing the lower control arms as the stock bushings were totally seized. These will get replaced again with the AWD parts going into the back so I just picked up the cheapest ones I could get quickly for now which happened to be an extremely blingy gold.

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In the front I also refreshed the worn out ball joints and tie rod ends, and got the car a fresh alignment. Then I tossed on a set of used RE-71R tires in 205/50r15. Next stop will be to test it all out at an autocross

[Jalisurr]

Autocross day! For this I set the ride height as low as the coilovers would go (which ends up being about the same as stock ride height) and cranked the rebound stiffness up to 16 clicks front and 14 rear (of 18). The car is certainly a bit softly sprung for tarmac use but that's not the goal, I really just want to check handling balance. The car handled great, with plenty of rotation on lift-off or braking and minimal understeer. The unassisted steering was a bit of a wrestle through the quick transitions but with the relatively skinny tires not a huge deal.

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I finished mid pack which isn't surprising given the far from optimized for tarmac state of the vehicle. It spun an inside front tire pretty easily with the open diff, and it also blew a LOT of oil smoke, the valve seals on the ol D16 are definitely toasted but I'll just keep topping it up until that engine comes out rather than going through the trouble of fixing it properly.

Overall a successful day! Here's the onboard of my best run

https://youtu.be/mzKdiJvgl9k?si=ay7N8d8ZofFQlXH0

[eHoward]

Looks good!

I had a dx crx in college. It was a lot of fun.

Looking forward to seeing your build.

[The Dark Side of Will]

I was conjecturing about exactly such a build a few years back! I was thinking of the 6 speed, which would have to be sourced from overseas. I didn't know there was a k-series 5 speed CRV before that.

Rock and roll, mang!

[Shaun41178(2)]

Always liked those and with a K it will fly

[Jalisurr]

I was conjecturing about exactly such a build a few years back! I was thinking of the 6 speed, which would have to be sourced from overseas. I didn't know there was a k-series 5 speed CRV before that.

Rock and roll, mang!

Yeah, 2nd and 3rd generation CR-Vs (2001-2011) as well as all years of Honda element came with a K24 and a 5 speed transmission with the AWD transfer case. Conveniently, if down the line I decide I want more gears, the 6 speed stack from a TSX will drop into the 5 speed case, and there are lots of aftermarket gearsets available.

The rear differential is also from a CRV (any year up to 2011 will work) or Element. 06+ cars got a better stock system that engages faster with ramp clutches, but I'm going to be ditching that mechanism entirely so I picked up a used 2001 CRV diff for cheap

[Jalisurr]

My next undertaking after the suspension shakedown was the most important of all - make the car look cool! But really, it was going to take some time to collect all the parts for the drivetrain swap and there was a lot of body work to do.

Most of the work was stripping the old (very thin!) paint down, discovering rust spots (many), and either sanding down minor spots or treating bad spots before applying rust paint as protection below my finishing color. I did some minimal bondo-ing over the rear fenders - there had previously been an excessively thick layer. This car needs to survive Canadian winter rallies and all the road salt that entails. A healthy application of fluid film into all the areas I didn't have direct access to will also help with that. It became obvious in this process that this car has had a few different people attempt rust repairs on it with various levels of competence in the past. Thankfully once again it seems the undercoating has done its job and kept the primary structure and suspension mounts of the car clean and rust-free. I sanded down a couple test spots to further verify and they were perfect.

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My paint of choice for this car was Tropical Turquoise plasti-dip from the beltline up, and black bedliner from the beltline down. I chose these because they are easy to apply over imperfect surfaces, and easy to touch up the inevitable gravel impacts without sanding down panels again.

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I'm leaving the hood as it came for now - it'll be getting replaced with a fiberglass hood to clear the new engine

[Jalisurr]

(Some of this is slightly out of order in the order I'm posting it vs the order it was done, but I figured I'd group similar things together)

Equally important to paintwork is accessories! I sourced an aftermarket roof spoiler as well as an EDM (european, not dance music) rear spoiler. I got a good deal on the EDM spoiler as it had had some kind of large wing mounted to it in the past, so there were indents and holes on both sides from the pedestals. I cleaned that up as best I could and filled the holes with some black panel bond I had left over from the Fiero.

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I also pulled out the stock (nonfunctional) sunroof mechanism and replaced it with a tinted polycarbonate panel from Y&S shields. Saved 26 pounds right up on top of the roof. I used some generic rubber weatherstripping and plenty of waterproof adhesive to ensure it doesn't leak. It's held up to a car wash without dripping so I think that was a success.

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Finally, I also picked up some RokBLokz universal mud flaps (they don't make anything in CRX fitment! Shocking!) and rigged up some simple brackets to mount them up. At stock ride height they're around 3" from the ground - the car will be getting lifted 1-2" so this should be about the right height.

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The end result looks much more rally car from the back. Still need to do something with the front but I've got ideas.