: Before undertaking this type of swap, one must understand all elements of tool use; equipment, chemical, and tool safety, and know enough about mechanics to solve peculiar problems and their resulting chaos. A background that includes machining, welding, metal fabrication, electrical, and physics will save a lot of money. There is no guarantee that this will work for you. You are on your own if you do this to your car and it does not work. Nor is there any promise or guarantee that this will work at all. However, it does for me, but, as you will see, it is definitely not
plug and play.
However, if you attempt this and have any questions, I welcome them.
This project regards only the 1985 Honda CRX HF and the 1992 Honda Civic VX. Other years of Honda vehicles may differ from what was used here. There are probably other ways of doing some or all of what was done in this project, however, this method works for me. -soletek-
Why do this? In Nov. '91 I purchased a 1992 Honda Civic VX VTEC-E --wonderful mileage, great handling + comfort. Went fast, too. A car to love.
That car was destroyed in an accident after three years of driving; commuting about 150 miles per day. For a few years the focus was on my muscle cars, then when I looked to replace it, all VXs I found were overpriced or junk. I began thinking that a really interesting alternative would be a lighter car with the VX VTEC-E drive train. Suddenly an original CA 1500 1985 CRX HF showed up online. It came home with me. A year earlier I had purchased a VX engine, CX tranny, and all parts that I figured were necessary for this swap.
After completing the standard tune-up on the HF, adding a new radiator and rebuilt cylinder head with porting and polishing, it appeared to run so well that it was driven for a year before the head gasket blew. It had been burning 1 qt. of oil per thousand miles. At that point, it seemed like a good time to start the planned project.
A baseline average of 51.7-highway mpg had been established with the tired old HF (340,000 + miles). Its engine was advertised with 58 horsepower, the VX with 92 horsepower. That difference made me very anxious to drive the finished car for the first time in order to measure the change in performance and mpg. Though patience is a virtue (one I do not possess), this change has taken a very long time and many alterations requiring extreme attention to detail for reverse engineering of wiring harnesses (engine, under dash, and chassis). Little did I know what I was getting myself into!
Major Components Used
: 1985 Honda CRX HF carbureted car; 1992 Honda Civic VX D15Z1 engine; 1992 CX Transmission; 1992 CA L00 ECU; and a 1995 LX under-dash wiring harness.
Prep for install
: As usual with a geriatric vehicle, a complete suspension overhaul was required: replaced steering rack, tie rod ends, radius arms, lower control arm bushings, struts, upgraded to 27.5 mm torsion bars in front, Eibach springs on rear corrected spring rate, switched to VX wheels all around, new Yokohama 175/75/13 LRR high mileage tires were already on the car.
Removal of HF engine/tranny
: Using a carbureted HF involved the removal of a family size pasta bowl of vacuum hoses which required knowledge of what they all did in case it was necessary to retain some for the future. After that, I began to wonder if I wanted to deal with this at all. When the engine and tranny were on the shop floor, the realization struck that that engine would never go back in the car. Now it was VX or crusher.
: The car on the lift and a tranny jack to hold up the VX engine/CX tranny combo proved that they fit better than the original HF engine/tranny combo. The VX engine is slightly tighter front-to-back, but much lower in the engine compartment than the HF was. The tranny jack allows tilt in two axes as well as the ability to lift and lower to set the initial most important step of axle alignment. Once the placement and tilt of the engine were correct, all measurements and fabrication of new motor mounts was possible.
: This was accomplished by using the factory CRX HF rubber mounts attached to the chassis, and VX steel mounts attached to the engine/transmission on the right front and center rear. This made grafting of those components possible, leaving only the left front metal portion to be fabricated. Then came the left front HF rubber mount connected to fabricated aluminum brackets attached to the same location on the side of the engine where the HF mounted. In addition, the VX mounts in the center of the timing cover.
: The engine came from a trusted recycling business in Sacramento. After it was installed and running, it received a tune-up, new (not rebuilt) distributor, plugs, wires, valve adjustment, oil and filter change. With all the extreme wiring modifications it was heart-in-mouth at the start up. The engine did not respond the first time but all the lights worked and the ECU responded as it was supposed to. The problem (not easily found because of all the mods) was the ICM being faulty. After replacement, the ignition key turned and the engine did not even crank. It just started running! What a shock, it took a few seconds to register that there was no problem. That was a real high.
: There are numerous changes that must be made to accommodate the computer-controlled engine and monitored transmission. There is no way around using a compatible transmission with the VSS (vehicle speed sensor). The ECU requires the VSS input to operate the engine's VTEC-E feature (to understand the importance of this, please refer to: pps 5-4 through 5-7 in the 1995 Civic Service Manual; published by Honda Motor Co., Ltd.; Printed in U.S.A.; part #61SR303.) In addition, the HF transmission has no vehicle speed sensor, and has a cable driven speedometer. I haven't found an after-market conversion kit, if you do let me know. [Now one could create a small gearbox with multi-ratioed, exactly timed gearing to fit between the cable and the ECU at a high dollar cost in both time and machined components. But why? Just put in a transmission that already fits.] The VX/CX transmissions are geared properly for the VX engine and fit the HF axles as well as having VSS. The Honda factory engineers knew what they were doing.
The CX is much tighter and firmer feeling than the HF transmission was.
The shift linkage
: The shift rod attaches almost identically to the CX transmission as to the HF, no change required. The extension rod related to the VX is on the opposite side. By manufacturing of a new extension rod bracket and mounting it on the left side of the shift rod, it works just as the HF originally did.
: The 1985 HF instrument cluster had no MIL (malfunction indicator light). Therefore, an upgrade to the LX cluster was my choice as it was new, cheap, and in a local junkyard.
: The HF had a cable operated mechanical clutch; the VX has a hydraulic clutch. Fortunately there is now available a mechanical to hydraulic clutch conversion kit. It is installed on the lower radiator support per manufacturer's instructions. What does not come with the kit is a -3 steel-braided line that must be routed to the slave cylinder. After fabrication of a mounting bracket the installation is pretty tidy. The car shifts very smoothly.
: The water neck out of the cylinder head was replaced by one machined from aluminum, complete with air-bleed. The redirection of the neck allowed use of the HF upper radiator hose. The HF lower radiator hose fits the VX with the removal of about 3/4" on the lower end. The HF radiator fan is too thick and the fan motor hits the transmission, so it was replaced with a thin fan from Summit Racing that draws the same amperage but displaces twice the volume of air. It is very quiet and runs for almost no time because it cools the engine so quickly. Next to be fabricated was an aluminum fan shroud with a 100% interface with the HF radiator.
: The carbureted HF has a mechanical fuel pump; the VX uses an in-tank electric fuel pump. So to compromise, a 1987 CRX Si fuel tank was installed, and an electric Mallory fuel pump from Summit is externally mounted. The HF fuel tank held 10 gallons; the Si holds 12 gallons -- Great! If the completed project only gets 60 mpg, it will go 720 miles on one tank of gas.
The HF had two vapor return lines and one fuel line; the VX has one vapor return line and two fuel lines. By replacing one vapor return line of 1/8" with a stainless steel fuel line 3/8", and reusing the 5/16" fuel line as the fuel return line from the fuel pressure regulator to the fuel tank, the problem was solved.
The exhaust system
: By carefully cutting off all flanges and counterparts from the HF exhaust system they could be reused for the new VX exhaust. The VX CAT is bolted directly to the VX exhaust manifold as it was on the HF. Running from it is 1 1/2" mandrel bent tubing. That runs to the ball gasket flange, then steps up to 2" tubing for about a three inch run, then steps up to 2 1/2" mandrel bent tubing through to the muffler. This removes backpressure and will increase performance as well as gas mileage. The sound is a low-throated rumble somewhat like a Porsche.
: Mileage purists might find air conditioning expendable. The women in my life do not. ('Nuff said.)
The HF had factory air. The VX also has an a/c compressor with it. It is installed in the factory VX location (belts and tensioners are all applicable). The VX compressor clutch, condenser fan, cooling fan, and blower motor relays coupled with the HF heating and air conditioning control switches were reused. An air conditioning specialist must modify the high-pressure and low-pressure compressor hoses so they work with the existing HF hoses. The reason for this: They take special crimped-on fittings and must be mounted and clocked in the 'as fit' position.
: This is BY FAR
the most complex, mind bending, portion of this project.
Due to the many unknown factors, redundancy seemed important, so the following parts were acquired in preparation for the job: 1) '95 VX engine harness (complete); 1) '95 LX under-dash harness (complete except for ABS under-hood extension segment purposely cut off, '85 CRX has no ABS); 1) '94 CX under-dash harness (not complete because some bonehead cut the harness off at the main relay); 3 under-dash fuse boxes; 2 under-hood fuse relay boxes; 2 sets of condenser fan and a/c compressor clutch relays and diodes; 1) '95 LX instrument cluster.
It was necessary along the way to purchase: 1985 Honda CRX Service Manual; 1993, '94, and '95 Honda Electrical Trouble Shooting Guides; 1995 Civic Service Manual; I already owned the 1992 Civic Service Manual on CD which was missing the two most important pages (The ones relating to the LAF sensor connecting to the ECU.)
The reason to use so many manuals was, predominantly, because this is a CA car and there were two versions of the car sold here, both smog legal. (The '92 - '93 five-wire non lean-burn version, and the late '93 - '95 four-wire non lean-burn version.) In addition there was the '92 - '95 federal five-wire lean-burn version. Having acquired all three ECUs, the plan is to run tests on the smog analyzer to find out the truth behind the emission output of each one. This will take time because of the need to drive the vehicle with each version for gas mileage results, as well. The findings will be reported on Gassavers. (Note: The engine harness is wired with the 4 pin and 8 pin connectors to facilitate a quick change from the four-wire to the five-wire LAF sensor to allow easy testing.
It was always clear that the ECU inputs and outputs are mandatory for the system to work correctly. In CA all emissions components must be operable. For example: Fuel injection air box; emissions control box (D15Z1, only); 16 lb. Radiator cap to replace the HF 13 lb. cap, etc.
Starting with the '94 and '95 harnesses, the entire casing was stripped off, including all wires and plug-ins that would not be used: The '85 CRX has no ABS, SRS, cruise control, rear windshield wiper, rear window defogger, power windows, power door locks, or moon-roof. To maintain the '85 CRX heater and A/C controls the '95 harness connectors were removed with the wires left intact for future use. The process started with the wires that were connected directly to the ECU then tracing Pin A1 and everything it connected to followed by tracing each additional wire in alphanumeric order connecting to the ECU for the D15Z1 engine.
Completing that portion, allowed following up on the other required componentry, such as: combination switch (headlights, parking lights, hazard, turn signals, intermittent wipers, windshield washer, mist function); ignition switch, horn, dash light dimmer, a/c, dome lights, clock, cigarette lighter, blower motor, blower fan, mode control motor, recirculation control motor, and many, many other satellite components. The externally mounted electric fuel pump required a newly added power wire and ground.
It was surprising that just as many wires were removed from the '85 CRX harness as were installed with the altered '95 harness that utilized an integrated control unit. The HF had multiple control units spread throughout the dash. All the wires leading to and from the units, and the units were removed.
It is a joy to report that all systems kept are functioning properly (including: key in ignition warning buzzer; seatbelt light/buzzer, intermittent wipers with automatic park function, hatch open warning light, and all others).
Though this seems very detailed, it is vague, as will be discovered on commencing this project. As stated at the beginning: When questions arise feel free to ask.
: Though it was complex and difficult, it has been some of the greatest fun I have had doing automotive projects. Look for interior modifications, aerodynamic changes, ECU comparisons, and further gas mileage reports in the future. -soletek-
For pictures go to the link below:
To enlarge the pictures: Double click on the first picture on the front of the album, then use the arrows to the upper right to move through the set. The title/explaination is across from the green arrows on the far left.
Additional ECU and gas mileage testing information:
CRX VX Mileage Experiments