Car is a 1991 CRX DX. Performance is not a goal, just needs to be a roller. I pulled the head off the old motor and found it was pretty much wore out every which way and needing a big rebuild. Needed a cheap motor and I found this Dual Carb thing.

How do I keep the carbs on the JDM motor and make it work with what I have for wiring/electronics? Would I even need an ECU if it were carbs? I'm thinking all the engine management goes out the window with the DPFI. What about fuel delivery, would the pump be any different?

I searched all over the forum. There are many threads about upgrading from carbs to MPFI but nothing from DPFI to carbs.

 

As for fuel, I believe there is a mechanical fuel pump that attaches to the cylinder head.

As for spark, you'll still need some sort of computer. Personally, I'd try to track down the ecu for your motor and wire it up as per OEM diagrams, but you could also possibly go with MSD or something.

 

I'm just basing this off of carb'd motorcycles I have had in the past where there is no computer whatsoever. I'm thinking as long as you have juice to the distributor its going to have spark.

Doesn't the computer just control the spark based on feedback from the engine management sensors that I can't use anymore?

 

The twin carb models where a PGM-Dual carb setup. They had an ECU.

The fuel pump is different, although i don't remember how. I didn't think the distributors were different though.

Enjoy them though, i had them on my old civic. They sound great.

 

the distributor has vacuum advance for the ignition timing - the fuel pump is on the back of the head next to the distributor - the carbs have a ton of vacuum lines - i don't know what they do or how you would find out where they all go - you wouldn't need the ECU if the carbs don't have some kind of electronic feedback - we run dual Weber carbs on a DOHC ZC and don't have a ECU - we have swapped a few of the dual carb D15Bs into the ED DPFI cars and just used the intake manifold and distributor from the DPFI - had to make a block-off plate to cover the fuel pump hole

 

ECU might have been for the choke then?

This was my old civ:



I never really did any work on it. It also looks like all the vacuum lines head to that black box on the right side of the engine bay.

 

The generic thing to do with vacuum lines is to just block them all off and see what you have.

What about powering the distributor? Probably just plug it in the harness and it should go, because I'm thinking its on the ignition switch and has nothing to do with the ECU?

I guess what I'll do is just drop it in, block all the vacuum lines, hook up the starter and the distributor and figure out what the hell I am going to do about fuel delivery and let it rip.

 

The dist has 2 wires correct one is black and yellow and one is blue. The blue is out for tach and the black yellow is power for coil and internal ignition module. Just run a keyed ignition power to the dist and presto spark.
As for vacuum lines etc... The carbs are essentially the same as 1983-1986 honda prelude. find a service manual or one of these at the junk yard and start tracing.

 

Thanks

I solved the fuel issue. I'm leaving the in tank electric one on a loop and splitting it off to the mechanical one. Now I won't have a problem getting fuel from the tank and there will always be a ready supply at the mechanical pump.

 

as stated you won't need an ecu. The carbs are not easily adjusted so you might want to think about webers down the road they are cake to adjust and give you options for the choke, either manual choke, water choke or electric choke.

 

cant you just use the intake manifold, etc off the old motor? just delete the carbs all together

 

It would swap over but I have DPFI and the carbs actually make more power. I'm not interested in going MPFI, so......

 

that's what I was wondering as well, but if you are interested in power, there is a simple and free dual carb mod you can do, you can find it on http://www.4guk.co.uk/forum/

 

Why would you want to do that?!