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Acura-Powered Honda Civic/CRX

layout by Joe Rogers

The following notes cover aspects of swapping the engine and drivetrain from a 1987 Acura Integra into a 1987 Honda CRX Si. Also covered are various other bits of information on compatibility between the two models. Both cars have 5-spd. manual transmissions, and are US models in stock form.

NOTE: All standard liability disclaimers apply here; I, Wes Grammer, will not assume responsibility for anyone's individual use of this information, nor for any damages incurred through its use.

1. The 1.6L 16-valve DOHC engine in the 86-'89 Acura Integra is essentially the same engine Honda installed in Japanese and European versions of the first-generation ( 84-'87) Honda CRXs. Therefore, the swap is a natural one since the car was designed for this engine. I also verified that this swap had actually been done by others (CRE Performance, Barre, MA; King Honda Motorsports, WI).

2. It should be possible to convert a CRX 1.5 DX (carbureted) model; however, as both the Si and the Integra are fuel-injected, a significant number of additional Si/Integra parts would be needed , such as an Si wiring harness, ECU, electric fuel pump, fuel lines and filter, exhaust system, and other sensors for the fuel-injection system not included with the new engine. Nevertheless, it should be possible, since (other than the above) the DX and Si are pretty much the same. I would *not* recommend converting the CRX HF - the suspension, brakes, electrical system, and most everything else is different, and would need to be upgraded to take the extra weight and power of the Integra drivetrain.

3. The following items from the Integra were *required* for the swap:

  1. 1.6L engine, incl. manifolds
  2. 5-speed transaxle, including axle shaft extension & bearing
  3. Left and right axles, new axle shaft nuts
  4. Rear engine mount bracket
  5. Transmission mount
  6. Wheel hubs
  7. Air cleaner-to-throttle body hose, w/clamps
  8. Upper radiator hose

4. The following items are *optional*, depending on your preference:

  1. 23mm aftermarket torsion bars (if using Civic) crossmember), to handle extra weight
  2. Integra front crossmember, w/torsion arms (required for) power steering)
  3. Integra steering rack (for power steering)
  4. Integra ECU (needed if Integra fuel-injection control box) is used)
  5. Integra fuel-injection control box (if Integra ECU is) used)

5. Since the Integra is about 400 pounds heavier than the Civic, it is equipped with power steering from the factory. The combined extra weight in the Integra engine and driveline add approx. 100 lbs. to the CRX; however, the steering effort is only a little higher than before, and so the power steering system is really not needed. Still, the extra weight does affect the handling noticeably, and the front suspension will bottom out under hard cornering unless larger, stiffer torsion bars are installed to compensate. This is the approach I took in my car.

If you just *have* to have power steering, the entire front crossmember and power steering rack from the Integra will bolt into a CRX. This approach has other advantages: the Integra crossmember has larger torsion bars, a larger sway bar, and is stiffer (and heavier), which keeps the body from flexing, improving handling. I don't know how the suspension geometry is affected by this swap; King Motorsports has gone this route on one of their cars, and would be a good source of additional information.

6. Two components need to be modified for everything to fit: the Integra hubs and the Civic front engine mount. The modification to the engine mount is minor - it needs a notch cut out of it to clear the cylinder head of the Integra engine. The Integra hubs need to be machined to properly fit the Civic front spindles. The work can easily be done on a metal lathe; a sketch showing the details follows these notes. To date, I have not experienced any problems resulting from these modifications, and to the best of my knowledge and belief they are safe. As for the bearings, both cars use the same one, so there is no problem there.

As for the remainder of the mechanical connections, everything fit perfectly, and access is no worse than the stock engine. I did not re-install the air conditioning system, and don't know if this part would present difficulty, but I don't believe so. The alternators appear to be the same (I used my old one), and the clutch cable, exhaust header pipe, and shift linkage mated right up (I did notice a shift in positions on the gearshift lever - neutral is about where 2nd and 4th gear used to be. It was a little strange at first, but I quickly got used to it).

The only mechanical problem I had was the throttle cable - its end was too short to easily fit where the Integra cable had gone. I slotted the holes on cable mounting bracket, and eventually got it to work.

7. I was told by CRE Performance that I would also need to take a small section out of the underside of the hood, over the Integra motor's timing belt cover. For some reason, this turned out not to be necessary in my installation; it might be something that is model-year dependent. I did later notice a spot under the hood where things had obviously been rubbing, but that was all. There was no vibration, and the hood closed easily without force, just like before.

8. The Integra engine can use all of the CRX Si fuel-injection system components (including the ECU) without any changes. Remove the Integra engine harness, and replace it with the one from the Si. The vacuum lines from the two external control boxes need to be connected to the same corresponding locations on the new engine (a service manual might help here!). This is by far the easiest way to go; the only drawback is that redline is higher in the Integra (7500 RPM vs. 7000 in the Si), and the CRX's ECU will shut off the fuel at lower revs.

9. For the truly insane, the complete Integra fuel-injection system (ECU and all) can be installed into the CRX. I should know, I did it. The problem is that while 95% of the wiring is the same, there are a significant number of changes that need to be made. Unlike the setup in (8), the Integra engine harness is retained, along with the Integra control box (there's just one), and the two CRX control boxes and MAP sensor are discarded. The Integra control box mounts perfectly on the firewall next to the fuel filter; Honda has already provided you a pair of perfectly spaced tapped holes (one is the mounting hole for the old MAP sensor, the other is an unused one covered with back tape). The Integra ECU replaces the one in the CRX - it plugs right in and bolts down where the old one went, under the passenger seat. The required changes in system wiring are given below (Important Note: These changes pertain to the 1987 model year ONLY, and are not known to work for other years):

  1. Make the following changes on the engine harness connector (CRX side), C-138:
    1. Exchange positions of wires (Y/G), (G/Bl)
    2. Exchange positions of wires (Y), (Y/R)

  2. Connect Integra MAP sensor (C-66, Control Box) to CRX harness (C-143):
    1. Connect (R) to (R)
    2. Connect (W) to (W/R)
    3. Connect (G) to (Br/W)

  3. Connect solenoid valves in Control Box (C-65) to CRX harness (C-110, old control box connector):
    1. Connect (Bl/Y) to (Bl/Y)
    2. Connect (R/W) to (R/W)
    3. Connect (W/Y) to (Y)

  4. Add a 6th pin (center row, under (R) wire) to engine harness connector C-27 (CRX side); wire it to (G/W) on C-110 (Idle Control Solenoid Valve).

Additional notes: The Integra does not have an IMA sensor like the one in the Si system - the harness connector that went to this sensor is left open. Also, the Idle Control valve in the Integra is a continuously-variable type, rather than a simple solenoid as in the CRX. These differences makes the Integra and CRX ECUs incompatible with the each other's systems.

There are only a few advantages with going this route, instead of the simple approach in (8). The first is that the engine control system is transferred over completely; everything is guaranteed to run exactly as it did in the Integra. The other is the higher rev. limit (7500 RPM), important if you plan to race your car. Aside from the wiring changes, it is also a very clean-looking setup, with fewer hoses and external doodads than in the Si.

10. Notes on brake system compatibility/upgrade:

  1. The Integra front rotors and calipers will bolt up to the Civic spindle. However, piston diameter is larger, which might cause problems with brake balance in the hydraulic system. CRE Performance recommends using the 88 Civic/CRX DX or Si calipers; they have the same piston diameter as the 84-'87 caliper, but use a larger pad and will work fine with the Integra front rotors, which are larger. I haven't verified this on my own (yet).

  2. The rear brakes can be upgraded to disks by swapping in the Integra rear axle. A side benefit is a larger rear sway bar. I've been told that the Civic axle tube is retained, and the rest of the stuff swapped over. The stock master cylinder and proportioning valves can be retained, as can the original parking brake - supposedly it all fits. More information can be obtained from CRE Performance, the source of all this information. This swap was also mentioned in an issue of Hot Rod magazine (yes, I was astonished too); unfortunately, I can't remember which one, but it was in the section where they answered technical questions from readers.

  3. It is a big hassle to mess with any other part of the brake system.

11. Final note: I have driven my Integra-powered CRX for about 10,000 miles now, and so far I haven't had a bit of trouble related to the swap, except that my very old and tired radiator couldn't keep up with the new engine's heat output. I now have a new radiator, and things are running cool again. In the performance department, it is a lot quicker than stock; the top end is truly awesome. In addition, the gearbox has a slightly lower final drive ratio and closer spacing between the gears, which makes it even more fun to drive. The Integra uses a slightly wider tire than the CRX Si (195/60HR14), which will make the Civic speedometer read about 2% higher than the actual road speed.

Many thanks to Chuck of CRE Performance, Barre, MA, for providing much of the information on mechanical interchangeability and the required modifications, and for providing me with some of the parts I used for the swap.

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