Engine Swap
OK, this is the cool motor-head part, this site is not called www.CRXKSwap.com for nothing. The motor, that is what makes it all go, and go it does. There are a variety of eligible K series engines that are swap candidates, what you choose depends on your budget and what your prejudices and end needs are, or at least what you think they are at the time. Our goal, and part of my personal prejudice, is to go with an all motor setup. No turbo, no supercharger (although the Rotrex is very intriguing and if we were to go forced induction, I think that's where the future lies), and high reliability. We don't want to be fixing things every weekend. We did not consider the K24, as it is taller and will only fit with a large hole in the hood and, besides the K24A2 from the TSX, they are not performance oriented engines, at least without some forced induction. So here are the options:
| Engine | Vehicle | Compression | HP@RPM | TQ@RPM | Trans/LSD |
|---|---|---|---|---|---|
| K20A | ITR/CTR (non-USDM) | 11.5:1 | 220@8000 | 152@7000 | 6spd/Yes |
| K20A2 | RSX S | 11.0:1 | 200@7400 | 142@6000 | 6spd/No |
| K20A3 | RSX/Si | 9.8:1 | 160@6500 | 141@4000 | 5spd/no |
| K20Z3 | '06+ Si | 11.0:1 | 197@7800 | 139@6000 | 6spd/Yes |
One would conclude that the K20A3 is a bit poopy, especially with a 5 speed and not "real" VTEC, so scratch that. The K20Z3 was introduced in the '06 Civic so they are not as readily available. Furthermore, this engine has an electronic throttle body and complicates the ECU setup and in fact, I am not aware of anyone who has done a swap with it in a CRX. That pretty much leaves the K20A2 and the K2OA. The K20A is the clear performance winner with 10% more HP and another 10 lb-ft of torque. But probably even more important is the limited slip differential. With a car as light as the CRX, you better find a way to put that power to the ground and LSD will certainly help. It will also moderate the torque steer, something you will definitely see in a 200HP+ 2000lb front wheel drive car. The down side is the K20A is considerably more expensive, about 2K, than a K20A2. The K20A was not used in any USDM cars, so you need to go to a reputable dealer who imports the engines, used of course. When you buy one, you really have no idea of what the mileage is, and the importers simply estimate it from the year of manufacture and the supposed inspection system in Japan that discourages keeping high mileage cars. In any case, everyone will claim between 10-35K miles, which is nothing for a Honda engine.
Needless to say we went with the K20A. we bought ours from JHPUSA.com after some research and the impression they were a reputable dealer from reading around and talking to them. I will say, the engine/tranny we got was really clean and certainly looks low mileage. There was some minor damage to a few sensors and some scraps and scratchs as these things get knocked around in shipping. The K20A was made available in the ITR and the Civic and most dealers don't distinguish. They are the identical motors, although you will see some slightly different specs in HP but I think this is due to the intake/manifold/exhaust setup on the different cars. Most dealers include the engine, tranny, harness, ECU, shifter and cables. Unfortunately, the Civic version uses a different shifter box and cables than the ITR and although you can adapt either one, we preferred the tunnel mount shifter of the ITR vs the dash mount style of the Civic. The engine we got had the Civic type shifter, although the tranny codes indicate the engine was from an ITR, who knows? I suspect the dealer threw in the shifter and cables from the Civic with the ITR engine. In any case, after running the motor for the past 9 months I can say it runs like a charm, burns no oil, and kicks butt!
One of the beautiful things is that with 110HP per liter stock, you get an engine with performance that surpasses almost any production engine in the world without forced induction (the new Porche GT3 barely ekes it out at 115HP per liter). Many car companies are happy to make even 100HP per liter with turbo or supercharging. Put on top of that Honda designed this engine to go 150K miles easily, and you've got a rock solid, reliable, kick butt motor. We were not going to touch the internals and the performance modifications were limited to headers, intake, and the necessary ECU tune. With this setup we got about 217WHP on the dyno, which was a little off as our RPM calibration was a bit low so it was probably more like 220+. This corresponds to around 250BHP or 125HP per liter on a stock engine!!! Holy Mackerel!! (Yes! we beat the GT3.) And remember, the key here is power to weight ratio, and the CRX is no heavy weight. That's about 8.4 lbs per HP assuming 2100 lbs. Compare this to other performance cars on the market, here is a great site with many modern cars Power to Weight ratio (Power to Weight).
Getting Ready
With the K20A in hand, we started the work on the engine swap. The engine, transmission and drive train were removed along with radiator, front cross member, front suspension (in preparation for rebuild). All bracing, headlights, relays were stripped and the electrical harnesses were pulled into the cabin. Basically we had a naked engine bay. We used the Hasport mounts which requires the battery tray and passenger side engine mount removal. You also need to relocate the brake proportioning valve. We needl not go into too much detail here as there is already some good resources that discuss this as well as the info in the Hasport manual. So I will just give a basic overview and dive into details where we did things differently.
After stripping the engine bay and removing the mount and battery tray, you need to weld in the Hasport engine mount on the passenger side. We then cleaned up and prepped the bay for paint and primed and painted the bay our WR Blue. Once this was done we were ready to drop the engine in, but not before some prep work and minor mods. First we decided to upgrade the clutch and flywheel. We went with a Fidanza light weight aluminum flywheel with a replaceable steel face. Lighter flywheel allows the engine to rev quicker and gives a bit of a HP gain. As it turns out, the K20A already has a lightened steel flywheel, leave it to Honda, so we didn't gain that much. We also used a Fidanza 3.2 Kevlar clutch and pressure plate which has some grip but is very streetable. In general we like the setup.
Another issue with this swap is the interference of the alternator. First the idler pully sticks up to high for the hood to close (actually even without this problem the engine is too high for the stock hood) and second, the altenator interferes with the right headlight mount which needs to be cut. To avoid these problems you can delete the power steering pump (which you don't need) and the AC compressor (I hope you weren't thinking you could keep the AC) and relocate the alternator down low where the AC compressor was. Karcepts makes a relocate kit that makes this a simple bolt in operation and is shown below. The rear engine mount gets removed and the front cross member and radius rods are removed. Again, due to interference issues most people choose to replace the front cross member with an after market traction bar. We choose the Full-Race bar which uses spherical bearing radius rods. The installation will require removal of the radiator mounting brackets and some sheet metal trimming. You can also remove the stock exhaust manifold from the engine as it will not fit and you will have to find some suitable headers. Finally, follow the Hasport instructions and bolt up the motor mounts and install the clutch adapter. The K20 uses a hydraulic actuated clutch but the CRX uses a mechanically actuated clutch via a cable. The Hasport adapter allows the use of the mechanical clutch pedal and cable, it works quite well and has a good feel. You will also have to perform some cutting/bending on the rear sub frame cross member to clear the engine on the drivers side and possible the headers on the passenger side. More detail is given in the previous references.
At this point you are ready to put the engine in. The easy way is from the bottom with a lift, but who has a lift, we don't. It is a tight squeeze, but in my case, I had dropped the entire suspension including the rear cross member so it was a bit easier. We did this because one of the bolts on the sub frame was frozen so we had to drop the cross member. When we were all ready to go we rented the lift (again) carefully dropped the engine in, it is tight, but amazingly all fits. The mounts are bolted up as described by Hasport. in our case since we had dropped the rear sub frame we could test fit it to see where it had to be altered to clear the motor. We then bolted it in along with the rear engine mount. Note that with the Hasport kit there are only 3 motor mounts and the front mount is not used. This is possible because unlike the stock soft rubber mounts, which are designed to isolate engine vibrations, the Hasport mounts use stiff polyurethane bushings eliminating the need of a 4th mount, but also eliminating any thought of a smooth engine experience. But than, that's not why we do this swap, so quit bitching. You can specify the stiffness of the bushings as "Street", "Race", and "Extreme Race". Mine are "Street" and they are stiff, but I guess if you have a 500HP K20 you might need stiffer.
