ECU loom - can anyone tell me why this won't work?

[Mister Towed]

Hi everyone, I'm thinking of building a one off special using a classic chassis, a hand laid body and a modern alloy motor for added lightness.

I'm looking at the Rover 25/45 or Ford Puma for the engine which will be coupled to an RX8 gearbox http://www.p9cyoplates.co.uk/products It also looks like it's cheaper to buy a complete car than just a motor, so I'll have the whole thing running before I start, so at least I'll know for sure it worked before I started messing with it.

I'm trying to find information about wiring up the ECU's on t'internet, but all I keep coming across is people spending £2-3k on throttle bodies, bike carbs and aftermarket ignition systems only to find they have to pay a specialist another grand to get it running right.

So, I'm thinking, why not reuse the complete loom from the donor car? Why couldn't I just strip out the entire loom, complete with battery, fuse boxes, ECU's, ignition barrel and all, thin out/blank off the redundant circuits and plop the whole thing into my chassis so the engine plugs and plays exactly as it did in the donor?

Anyone out there with any experience or knowledge of doing this?

All help gratefully received.

[Paul L]

Mr T - Obviously, I know nothing.

But there are a lot of clever people over on 'Rods 'n' Sods' that might be able to help.

They have a technical section where you could post this question.

In the mean time, I've added a few links below to some of their 'Garage' builds.

They include wiring up Lexus, BMW & Jaguar engines into various cars/trucks.
( Not all in great detail, but one has links to further info. )

http://www.rodsnsods.co.uk/forum/gar...s-86457/page20

http://www.rodsnsods.co.uk/forum/gar...w-121129/page6

http://www.rodsnsods.co.uk/forum/garage/m-o-5073/page66

Originally Posted by Mister Towed

… So, I'm thinking, why not reuse the complete loom from the donor car? Why couldn't I just strip out the entire loom, complete with battery, fuse boxes, ECU's, ignition barrel and all, thin out/blank off the redundant circuits and plop the whole thing into my chassis so the engine plugs and plays exactly as it did in the donor? ...

Based on these builds, your logic is sound, especially if you start with a complete car.

It seems you really need to watch out for all the circuits linked to the alarm/immobiliser (door locks, etc.).

The guy using the Jaguar engine seemed to start the engine each time he removed something to see if it still worked.

So, by a process of elimination, you are left with all of the key bits of wiring loom you need.

Hope that helps, Paul.

PS
Does this mean you are not building a SWB 250?

[landmannnn]

I've done both.....

Wiring from scratch - allows you to make it simple. The main problems are that it takes a lot of time and is really expensive. The cable is bad enough, but automotive quality connectors are far from cheap. I think Ispent a good £500.

Bodying the existing loom - assuming you keep the main components in the same place it is plain sailing.
The problems arise when you move things, so for example the heater might be a few inches from the original location. You will end up adding a few inches of wire with butt connectors.(or solder/heatshrink) You have now introduced a potential failure point with inevitably the wrong colour coding. All a recipe for a rainy day breakdown.

Personally, next time I will do a hybrid. Take the original loom, decide what it is going to do and strip it right back just to do those functions, even to the point of removing all the shrouding. Re-wrap it and create a brand new loom for everything else.

Just my experience.

Joe Lucas, Prince of Darkness

[Mister Towed]

Thank you Paul and Landmannn, some sound advice there.

It sounds like excellent advice to disconnect each of the circuits I don't need while the engine is still in the donor then start it to see if the circuit was essential, I'll definitely do that. I'll also check the Rods 'n' sods site to crib any more ideas.

It's also nice to hear from someone who's actually used a donor loom and believes it's a workable idea.

Oh, and to answer your question Paul, yes I will still be building a 250SWB as a daily driver, but I'm retiring in nine months and am looking to scratch build a car to my own design too, just to keep my hand in, you understand

[Paul L]

Originally Posted by Mister Towed

... I will still be building a 250SWB as a daily driver... and am looking to scratch build a car to my own design too...

Excellent, two build threads to look forward too.

Would you like some links to some 'scratch' build threads?

Cheers, Paul.

[Mister Towed]

Originally Posted by Paul L

Would you like some links to some 'scratch' build threads?

Cheers, Paul.

...but of course!

[Paul L]

As if by magic…

I've posted linked to these two South African build's before:

This shows how a 3D buck was built for a metal body shell.

http://www.rodsnsods.co.uk/forum/gar...dy-buck-313330

This is the same technique being used for a fibreglass body shell.

http://www.rodsnsods.co.uk/forum/gar...-project-83285

I've also mentioned this guy whose original project was lost in a fire, but his new project uses 1:1 scale plans and a wire frame.

http://www.ffcars.com/forums/120-fac...d-page-11.html

This build also uses a wire frame to shape body work & a combination of other car parts.

http://www.rodsnsods.co.uk/forum/gar...uilt-car-49948

Or how about a basic buck made by scaling up a toy car.

http://www.ffcars.com/forums/146-oth...ing-shape.html

Finally, the next two builds are a masterclass in fibreglass work.

http://www.rodsnsods.co.uk/forum/garage/jays-223105

http://www.rodsnsods.co.uk/forum/gar...w-model-119210

Enjoy, Paul.

[NeilF355]

Originally Posted by Paul L

As if by magic…

I've posted linked to these two South African build's before:

This shows how a 3D buck was built for a metal body shell.

http://www.rodsnsods.co.uk/forum/gar...dy-buck-313330

This is the same technique being used for a fibreglass body shell.

http://www.rodsnsods.co.uk/forum/gar...-project-83285

Hi Paul
I have been watching those builds by Petrolheasdsa and JoseOSI in more detail here
http://www.madmechanics.com/forum/bu...a-project.html

http://www.madmechanics.com/forum/bu...body-buck.html

Well worth a look if anyone has a bit of time to spare. Mind you their budgets must be colossal!
Neil

[Mister Towed]

Colossal budget you say? Gulp...

Thanks for posting those links guys, I shall read them with interest.

[froggyman]

Interesting build ideas MrT. Look forward to see how this progresses. I have just stripped the interior out of a Z3 in order to simplify the wiring for a 250SWB build and the loom is like an elephants trunk, unlike the grass snake in a Vitesse! Dilema time. Do I start pulling it out or leave it be? Maybe the answer is to rip it out and fit a new loom along with a Vitesse engine. Simples. Why are newer cars so complex in the electrical dept?

[Mister Towed]

Got to agree that old cars are far simpler in the electrics department, but the march of progress is inevitable I suppose.

Good luck stripping out the masses of electric string in your Z3 donor, I'll be doing the same in about a year's time if all goes to plan.

[MartinClan]

The engine wiring loom complete with coonectors for ecu, snsors and relays was self contined in the BMW donor I used for thr Marlin. To make it go all one needed was power.

I also reused the donor fuse/relay box and the main loom. However I did spend about 3 months stripping out everything I didnt need. About 75% of it as I recall. There is abig advantage keeping all the standard wire colours and sizes.

Robin

[WorldClassAccident]

Nothing to worry about with the Z3 wiring. Just unplug stuff one thing at a time and trace the wires back




Then just tape the unused wires together and hide up behind the dashboard somewhere.

:-)

[Mister Towed]

Thanks MartinClan, it's very reassuring to know that someone has already done it.

Thanks WCA, your Z3 wiring picture is very, um, reassuring...