DX to HF conversion
 

I am seeking information on swapping an '89 CRX HF engine into an '88 DX Hatch. Need to know how to match computer, injection and engine harness if we don't have all the HF parts. Will an OBD-0 computer from an Si control the HF injection? Can we use an engine harness from an Si? How much mileage will we lose if we use the DX dual point injection? Any input will be appreciated, especially from someone who has done this conversion. We have traded for a 500 miles since rebuild HF engine and transmission and are determined to build my son-in-law a high mileage school car, but need help with the electronic match-up.

Thanks, Jesse

Re: DX to HF conversion (miniwhl)
 

88-91 crx and civics are fairly the same.
mounts, motor and transmission, vacuum lines, harness plugs [tps, injectors, etc] and throttle/clutch cable. so:

yes you can use an si ecu.
yes its better to use an si harness. [including the resistor box]

try not to use a dual point harness for a multi, youll end up hacking the harness and more problems. the si harness is all you should really need for that swap. but im not sure if you need to swap your hubs to hf/si ones, to use hf/si axles.

someone correct me if im wrong.

Re: DX to HF conversion (kojack_0)
 

Thanks Kojack

We do have the HF axles. The main concern we have is electrical. Will the DX fuel pump provide enough pressure for the multi-point HF injection?

Jesse

Re: DX to HF conversion (miniwhl)
 

i believe so.

if you feel its not good enough upgrade to a new/er or use hf ones.

hmmm. do you also have a cabin harness off an si?
cause i believe the si engine has 3 plug and and dual point has 2.
[im talking about where the engine harness meets the cabin harness, next to the underhood fuse box]

Re: DX to HF conversion (miniwhl)
 

you cannot use the HF or Si engine harness in the DX car unless you swap out the complete cabin harness also, which is not an easy job - just use the DX engine harness and make the DPFI to MPFI wiring changes to it - just the same as if you were putting a D16A6 Si engine in it - you will need to add wiring for the EGR on the HF engine and you will need the EGR components that are on the firewall of the HF - use the HF ECU as the Si ECU is going to make it run too rich - you don't need the HF axles - you use the DX axles - the HF axles won't fit the DX hubs - the fuel pumps are all the same

Re: DX to HF conversion (kojack_0)
 

Do you mean the harness which goes from the ECU to the firewall? Is there another cabin harness besides this one? I have always used an Si body for swaps and have never addressed this issue (besides which, I generally pay some younger person to do the squirming under the dash, I'm 63, but still love the Honda Hot Rod)

Thanks

Re: DX to HF conversion (miniwhl)
 

mainly from the ECU to the engine bay - much easier to do the DPFI to MPFI wiring changes, which just consist of changing the distributor connector, adding the injector sub-harness and resistor box along with 2 wires from the ECU to the engine and moving a couple of wires at the ECU - takes about 2 hours to do it right and have it look like it came from the factory - you would have the additional wiring for the EGR which you wouldn't normally have on the DPFI to MPFI

Re: DX to HF conversion (jlicrx)
 

Thanks,
This is the first I've heard of the EGR issue. Thanks for the tip about the harnesses. I believe we have the axle situation resolved, with HF inner joints and Si outers. We think the body has Si brakes and hubs, because it has been converted to disc rears, and we think it has the larger Si fronts, as well, because 13" wheels won't fit over the calipers. It's always a puzzle to work on cars which have been modified by someone else before you get them, but at $300 for the body with a JDM d15 Si engine and Si transmission sitting in the rear cargo area, it was too good to pass up. We traded the d15 for the HF setup, but have limited access to the rest of the HF parts.
Your kind help is very much appreciated.

Re: DX to HF conversion (miniwhl)
 

all of the axles are the same on the transmission end - only the hub end is different - if you have HF hubs, you use HF axles and it doesn't matter what the transmission is, as long as it isn't a ZC - if you have DX/Si hubs, you use DX/Si axles and it doesn't matter what the transmission is, as long as it isn't a ZC - if 13" wheels don't fit the front, it does not have Si on the front - it has either Civic EX or Integra knuckles/hubs, which still doesn't affect axles