Converting 3 plug to 4 plug ?

discopotato03 · Post by **discopotato03** » Sun Oct 14, 2007 8:49 pm

Hi all , I need to know if the 4 plug harness and computer are easy to fit inside a 3 plug RX Turbo sedan . Does it all plug in under the dash or is it a nightmare ?

I have to go this way because the Spider EA82T's throttle turns in the opposite direction to the std type TPS so it needs to be the 4 plug MAF system all the way .

Cheers A .

Suby Wan Kenobi · Post by **Suby Wan Kenobi** » Sun Oct 14, 2007 11:10 pm

You can rewire the plug for the TPS so it will read backwards and drill new holes for mounting it. You will also need to get a spider manifold throttle cable. The wires to the bypass air control also need to be made longer and you will need a Vac source for the dizzy too

discopotato03 · Post by **discopotato03** » Mon Oct 15, 2007 7:43 am

Are you saying that its possible to run a Spider EA82T with the 3 plug system by adapting a 3 plug TPS (swap closed and open throttle switch wires) and fitting the mechanical + vac distributor ?
Thats makes sense I suppose to get it in and running .

What I was asking was how hard/easy is it to change the computer/loom inside the car from 3 plug to 4 plug . In other words can one system be unplugged up under the dash and be exchanged easily ? What I don't yet know is what else the loom plugs to inside the car other than the computer itself . Obviously the loom has to find power and fuel pump relays but not sure if this is inside or outside the car in an L series . I'd rather have parts of two looms than pull the complete dash out if possible .

Cheers A .

Suby Wan Kenobi · Post by **Suby Wan Kenobi** » Mon Oct 15, 2007 12:08 pm

As far as plug and play i under the dash, that bit isnt so straight forward. You will need to run a different plug for the AFM a set of sensor wires to the dizzy and change the dizzy you will also need an ignitor to go with the coil and the knock sensor wire comes in from the engine loom not from the short dizzy loom. The ECU plugs are different so you have to rewire those. You would be best to pull the 3 plug harness out and swap it for the 4 plug and be done with it.

timmo · Post by **timmo** » Mon Oct 15, 2007 4:55 pm

and from a physical approach I guess that means pulling the dashboard out and taking off the front fenders!

timmo

Gannon · Post by **Gannon** » Mon Oct 15, 2007 4:59 pm

There are too many differences between the 3plug and 4 plug wiring systems to simply swap plugs.

The 4 plug TPS contains a potentiometer and a switch that is closed only at idle.

The 3 plug TPS is 2 switches, one closes at idle and the other closes at WOT. there is no potentiometer on the 3plug system

Search the usmb, i think someone there refit a 3plug TPS to a spider manifold

discopotato03 · Post by **discopotato03** » Mon Oct 15, 2007 7:41 pm

From the top . What I want to do is fit an Aus spec Vortex EA82T complete with its engine loom . I will have all the ignition etc bits like coil ignitor CAS MAF etc and its ECU . What I want to know is how difficult it will be to fit a 4 plug RX Turbo loom inside the car itself . From digging through Vortex and L series manuals I believe the Turbo Vortex engine loom should plug to the L loom that runs under the drivers side gard and into the car in front of the drivers door .
Today I was looking at a mostly stripped 3 plug turbo 2wd Vortex and it looked reasonably straightforward even though its loom runs to the rear parcel shelf under which the ECU lives er lived .

So to round up I want an ALL 4 plug system the body/dash side being late RX-T and the engine bay side being Turbo Vortex Arachnid .

The original question should have read is it difficult to swap out a 3 plug ECU/dash loom for the 4 plug ECU/dash loom .

Cheers A .

Suby Wan Kenobi · Post by **Suby Wan Kenobi** » Mon Oct 15, 2007 10:56 pm

The original question should have read is it difficult to swap out a 3 plug ECU/dash loom for the 4 plug ECU/dash loom .

Cheers A .

It wont be an easy straight forward swap but can be done.

Another alternative would be to lay a stripped down harness of the 4 plug over the 3 plug setup.

Which ever option you choose it wont be a plug the later ECU in and turn the key.

Gannon · Post by **Gannon** » Tue Oct 16, 2007 4:59 pm

If you have your heart set on a 4plug system, go buy a 88 or later touring wagon, make sure it has MPFI.

Thats what i did and it worked a treat, everything plugged in.
But my car was a 92, which means it had the later wiring system.

Your RX on the other hand is of the earlier system and some plugs mightn't match up.

Are you sure that you cant fit a 3plug TPS to your spider manifold, that by far is gonna be the easiest option.

steptoe · Post by **steptoe** » Tue Oct 16, 2007 11:25 pm

Been looking at this for myself. Brumberty likens Subies as a bit like lego as it all bolts together. This time the spidey throttle body mount studs are not the same pattern as the standard efi throttle body so are not easily interchangeable. Spidey is larger throttle inside diameter. Gees, ain't it a bloody cavern inside those spiders!!? My wiring has been interfered with and may have been modified to suit - find Fury as it may have been his work.

YouTube · Post by **El_Freddo** » Wed Oct 17, 2007 10:49 am

Wiring is always messy.

I've changed my carbie 88 wagon to run an MPFI. I took an MPFI loom from a 91 wagon and replaced all the wiring til the back seat with this. The rear of the car has the original wiring that splices into the MPFI loom. In hind sight it would have been easier to swap the entire loom over to avoid the headache of splicing.

There are plenty of leone MPFI's out there, just gotta find one.

With the late RX style dash, you'll have to replace the entire thing as there are switches that mount differently and you'll also need the steering wheel stalk switches.

As for the Vortex loom, if you can get that loom to be route'd around the car as it should be in an L i don't see why it wouldn't work. The L's wiring passes through the front right guard, the vortex wiring goes through the centre (or near) of the fire wall. If there's enough length in the wiring to place the ECU were it is on an L i don't see why it can't be done (if you're going to splice it to replace the 3 plug ECU and engine wiring.)

Clear as mud?

Bennie

discopotato03 · Post by **discopotato03** » Thu Oct 18, 2007 12:52 pm

The wrecker I haunt had one and I went back for that section of loom but the car was gone . Grrrrrr .

I remember now that I have a stripped 4 plug loom in the cave but don't remember if its Vortex or RX turbo - the length will give it away .

All I want to change is enough wiring to run the 4 plug computer and engine . Once the computer is plugged in to all the engines sensors all it needs is ignition switch power supply to the ECU and FP relays and it should run . Actually Ign switched power to the ignition system would be handy too . Other than a suitable tacho signal feed thats about all there is to it .

A .

discopotato03 · Post by **discopotato03** » Sat Oct 20, 2007 7:41 am

No time to do more than look ATM , my 4 plug body loom is mostly tagged and from a Vortex - has air suspension wiring .

Next week will look in manuals and see if I can isolate just the engine to computer and tacho wiring . I really hope L and Vortex engine to body loom plugs are the same but not a biggy provided I can identify the essential wires . I do have a std manifold engine loom but can't remember if its 3 or 4 plug kind and its big round connectors are different .

More later , cheers A .