Megasquirt loom advice

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sowen
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Megasquirt loom advice

Post by sowen »

I'm just making a start making the new wiring loom for my Megasquirt installation and wondered what advice anyone has for making them? I'm not an electrical expert, usually I've used crappy red and blue crimps which look a mess doing wiring jobs. I've bought a few extra amp superseal connectors for joining the loom to the car etc in trying to make a more respectable and reliable job of it!

I've got a decent amp crimp tool for the crimped ends, it's more of the holding together and sealing of the loom, and how to run the injector wires from one wire on each bank to connect to all four injectors?

I was thinking of soldering some extra wires to reach each of the four injectors either side, unless someone has a better idea, and use some heatshrink and insulation tape to hold the wires together in the loom, then cover it with convoluted tubing like the hotwire looms are done.


1972 Rover 2000TC M16 turbo
1975 Land Rover OM606 diesel
1984 Rover SD1 3500 Megasquirt powered

DaveEFI
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Post by DaveEFI »

MS V3 PCB has two output pins per injector driver so four in all. So I split those at a convenient point in the loom. (the reason for two pins per output is one can't handle the maximum load the drivers can sink.) Did the same with the +12v feeds to the injectors.

I'm not a lover of those pre-insulated red blue and yellow crimps. If you make one using the correct crimp tool then remove the insulation, the crimp looks awful.
A proper crimp grips the wires all the way round to make a gas tight seal. Simply squashing it flat will work - but isn't so long lived. The best type is the heart shaped one

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sowen
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Post by sowen »

That's the tool I've got, found it in the bottom of a drawer at work!

I've got 8 individual wires already crimped into the injector plugs for the 12v feeds, should be plenty long enough to reach far enough away from the engine to somehow join together and run a fused supply to them.

What I can't decide on is how to run the two wires I already have from the loom for each bank to connect to each of the four injectors either side. Either I'm going to split the primary loom wire into four individual wires at one point, or have them joined individually near each injector similar to how the schematic diagrams show?

I'm waiting on a few reels of heatshrink to come through the post so plan on cutting some 1" lengths of that to bind the basic loom together every 4-5 inches rather than wrapping it in insulating tape.
1972 Rover 2000TC M16 turbo
1975 Land Rover OM606 diesel
1984 Rover SD1 3500 Megasquirt powered

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Post by DaveEFI »

Doesn't much matter where in the loom you do the splits - but I'd stagger them to avoid having a bulge in one place. I ran the pair from each injector back to fairly close to where the loom goes through the bulkhead - my theory being it would make it easier to alter the loom for sequential if I ever decide to go down that route.

As regards making the actual split, my preferred method is to have one injector direct from one of each of the four pins on the MS connector and splice in the second one where convenient. I remove about an inch of insulation only from the first wire, separate the wire strands into two groups, thread the second wire through, twist and solder. Then heat shrink.

Incidentally, Lucas grouped the injectors as left and right bank. In theory, there's a better way. Can't swear it is better, but my feeling is it gives a slightly better idle and low speed torque.

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sowen
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Post by sowen »

I like the idea of chasing the firing order, and I'm at the point of being able to incorporate that into the loom. Having the loom split closer to the ecu than the engine is an idea, and as you say if I was to upgrade to sequential further down the line in theory less hassle on the engine side.

When I did my first Megajolt loom that was soldered and heatshrunk to join the various parts, and the joins staggered as you say. I've had to extend it and trim it bac so it's just EDIS so am also considering remaking it to match the Megasquirt loom now.

I'll have a look at joining the wires as you say, means I'll probably have to buy another couple of coloured reels of wire and wait for them to come through the post!
1972 Rover 2000TC M16 turbo
1975 Land Rover OM606 diesel
1984 Rover SD1 3500 Megasquirt powered

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Post by DaveEFI »

My preferred way is to use a hotwire loom as the donor - the actual cable on those seems to survive very well and not suffer from insulation cracking like the thicker walled cable used on the flapper. I can then stick (in the main) to factory wiring colours. Even the likes of Vehicle Wiring Products doesn't stock the entire range of colours - and buying all new costs a fortune anyway.
This does, of course, mean fitting a DB37 connector to it. Which I prefer to starting with a generic MS loom.

I'd not do the injector 'looping' within the injector Junior Timer connector. No point - and makes it much more difficult to get lengths correct.
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sowen
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Post by sowen »

I have the long loom for the Megasquirt and am trying to stick with the colours from that loom and the schematic rather than try to keep to the oem hotwire loom colours. For the most part there is more than enough wire already there, it's just the additional wires to join the 8 injectors, which from my basic experience of making electrical items work can become a raging mess very easily!

My first idea for the joining the injectors was to solder the joins about 2-3 inches away from the connectors to allow for the wires to reach down into the main loom as it passes along the fuel rail bosses, I want to avoid looping as you say.

As I've already begun with the main 12v feeds to the injectors with approximately 1m of wire on each, I can do something similar with the MS loom wire, splitting that deep in the loom the running the 8 individual wires up to the manifold and injectors.

I've been thinking of buying a fuse box specially, as I will now have the MS ecu, injectors (x2?), fuel pump, edis, knock detector and lambda, which could make some of the power feed wiring easier to plumb in.
1972 Rover 2000TC M16 turbo
1975 Land Rover OM606 diesel
1984 Rover SD1 3500 Megasquirt powered

DaveEFI
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Post by DaveEFI »

There's lots of ways to skin a cat, as they say. I really just followed how Lucas did it on my EFI. Including keeping the EFI power feed separate from the ignition. Although Lucas may have just done this because the ignition was standard across the range and the EFI added on.
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sowen
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Post by sowen »

Yes, plenty of options, and plenty of right and wrong ways to do them!

I'd like to keep the additional looms I'm putting in completely seperate from the original car loom, in case it ever goes back to factory standard and for reliability with cutting up an existing old loom. I consider the EDIS to be entirely standalone from the Megasquirt so am keeping that independant apart from sharing the same power supply and a multiplug between the module and MS ecu so they can talk to eachother.

In it's present state the EDIS is fully operational with input from the MS for the advance curve, and fueling on the hotwire. As basically as I can go it's being done one step at a time making sure the engine is running and the car as usable as possible at all times.
1972 Rover 2000TC M16 turbo
1975 Land Rover OM606 diesel
1984 Rover SD1 3500 Megasquirt powered

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richardpope50
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Post by richardpope50 »

Speaking from experience, I suggest you follow the official MS wiring diagram for earthing 100%. There are no ifs nor buts on this as the one I initially followed from my supplier was wrong.

PM me for a link on this if you want.
Richard.
Dax Rush 5.0l TVR V8, EFI with Megasquirt ECU and wasted spark, Racelogic Traction Control and Quaife LSD ....... Now nut and bolt restoring a TR6

sowen
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Post by sowen »

Yes I'm following the earths as close as I can to the supplied schematics which match up with most of the other schematic diagrams I've found on the subject. I have some spare black wire to use, and will do the sensors after the injectors have been finalised.

It's really the bits that the schematics don't detail which I guess is open to interpretation and personal preference/experience, for which I have very little in wiring.
1972 Rover 2000TC M16 turbo
1975 Land Rover OM606 diesel
1984 Rover SD1 3500 Megasquirt powered

DaveEFI
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Post by DaveEFI »

sowen wrote:Yes, plenty of options, and plenty of right and wrong ways to do them!

I'd like to keep the additional looms I'm putting in completely seperate from the original car loom, in case it ever goes back to factory standard and for reliability with cutting up an existing old loom. I consider the EDIS to be entirely standalone from the Megasquirt so am keeping that independant apart from sharing the same power supply and a multiplug between the module and MS ecu so they can talk to eachother.

In it's present state the EDIS is fully operational with input from the MS for the advance curve, and fueling on the hotwire. As basically as I can go it's being done one step at a time making sure the engine is running and the car as usable as possible at all times.
Think you're going about it in exactly the right way. And if you've got EDIS triggering MS reliably, that's half the battle. Loads of problems are down to MS not getting a reliable tach signal.

My general rule of thumb is not to use a connector where one isn't essential. Wire never gives problems - connectors can.
Dave
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sowen
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Post by sowen »

The dizzy is still triggering the efi and tacho, I've been rained off and not had any time this last week to run a wire from the MS loom to the efi trigger and try it out yet, but that's tomorrows plan.

Part of the reason for going for the long loom was as you say, less connections as I'm sure there will always be something that isn't long enough! I'm leaving a coil of the main loom off the ecu in the dashboard just in case I ever take the MS off and put it in another vehicle. It's far easier to shorten wires than it is to lengthen them!
1972 Rover 2000TC M16 turbo
1975 Land Rover OM606 diesel
1984 Rover SD1 3500 Megasquirt powered

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