Fuel injection to SU carb swap

[sblake01]

So you gave up on the EFI?

[iestyn.lewis]

Hi - I have (most of) the parts to go ahead with this on an 83 ZX. Your excellent writeup raised 2 points -

- Are you sure the ECU has anything to do with ignition timing on a non-turbo 83 car? I know in a turbo car it does, but I thought the non-turbo was purely mechanical and vacuum controlled. I wasn't planning on having to get a new distributor/ignition module...

- I think the ECU also controls power to the high pressure FI fuel pump - any suggestions on the best power source for the low-pressure electric pump?

I have a spare P79 head on which I'm going to mount the SU intake, carbs and a stock 280zx exhaust manifold with EGR plugged. My plan is then just to unhook the harness and AFM, unbolt the FI exhaust manifold from the header tube, and pull the stock head, manifolds and all. Then swap in my new head with the carb setup. Pull the EFI harness, but leave the ECU in place.

This way I can easily go back to FI just by swapping the other head back in. I hadn't thought about the fuel pump and ignition module needing ECU input though. Thanks for any help anyone can give.

[Arne]

Ignition module on the '83 should be the E12-93 with three terminals, a pair at the top and a single on one side. The single side terminal is the one that gets a signal from the ECU.

Two options for that - either replace with an E12-80 module, or I've heard that if you simply provide the side terminal with 12v (switched with the ignition) you should be OK.

You'll want a relay and fuse/breaker protected circuit for the pump, ideally switched with both ignition and oil pressure for safety. Should be fairly simple to wire that up, no different than adding an electric pump to an early 240Z.

[iestyn.lewis]

Thanks! Also just found this thread, which explains the distributor issue. I had no idea...

http://www.classiczcars.com/forums/showthread.php?p=289835

[fattyjay22]

great thread guys! its helping alot! Quick question though, what are you doing with all the old efi wiring, ecu, etc? I really dont want to swap and then have all those dang wires hanging around my engine bay looking like crap!

Oh BTW i am doing a 72 SU swap into my 76 280z with l28 and p90

Edited July 10, 2009 by fattyjay22

[Arne]

Unplug it from the main harness and remove it.

[fattyjay22]

ah what a beautiful sight!

Cool so it does just unplug. I will have to go take a look at it. I was hoping i didnt have to cut and tape, or tear half the dash apart to get to it all!

[Arne]

The car I did had the injection from an '83 in it, so the details may be different from yours. But I still think it should be unplugable.

[ROCKNHARD]

have a diegrinder or something standing by if you plan to use the iron exhaust manifold from ZX injection engine. i had to do some VERY minor trimming of the exhaust manifold flange to fit my 71 su carbs and manifolds with 82 iron exhaust. didn't use the 71 exhaust manifold because the collector bolts were frozen. fuelie exhaust collector or downpipe from ZX will also have serious clearance issues in early Z. i had major frame and tension rod interference. kind of an experiment. i plan to correct this before finishing out my ebay.

[Shade133]

i know this thread is kind of old. but i had a question that was left un answered.

here in arizona you have to emissions test all cars 1966 and older..

and as some of you might know mine is failing horribly with high hydrocarbons.

and here in arizona if you look at my post in the help me section they only test HC and CO

at load and idle.

so im assuming it will be really easy for me to get it running clean enough with carbs.

my question is. is my assumption true?

i need it to pass with 250 or less HC at load and IDLE

and 1.50% CO at load and 2.00%CO at idle.

possible?

also i would like to know a ball park range of how much doing this conversion would cost.

Edited July 13, 2010 by Shade133

[78zcar_blue]

I am in the process of converting from EFI to SU's on a 78 280Z, my question what about the control relays for the fuel pump? I changed the fuel pump to the Mazda carb style, I wanted to know will the control relay and fuel pump work as before without the EFI wiring? or will I have to rewire the relay or something else, Thanks in advance for your help. By the way everything is hooked up carbs, choke cables ect, just the fuel pump is not functioning.

[raminduction]

Hello Arne, Thanks for the info on the FI to SU convert. I wasn't too concerned about the carbs. It was the "brain" and the wiring that bothered me. I didn't want all this stuff "laying about" in the car and needed to know if the entire mess could be disconnected and put in a plastic bag with the worn out FI system. I'm converting a '75 to carbs and using my original early '71 carb setup on it. Tired of fighting FI, especially after realizing that fixing it up would cost more than the convert. Any other info? m