Choosing Wire Gauge/size For Engine Looms?

[welshpug 1,661]

As per title, wondering if anyone can point me in the right direction for what gauge/size wire I need to use for each particular application when building my own loom, I have an S40 loom and plug, a set of crimper wire cutters and a fair understanding of engine wiring.

 

It would be to run an XU10J4RS engine in a Citroen ZX.

 

I know the injectors and coils would need larger wire from relays before splitting to each individual component, then a smaller wire from thereon, which guess would be sufficient for most sensors as well, bar the crank sensor that uses a 3 wire shielded cable.

 

The engine does have a camshaft sensor and a knock sensor, I know the S40 is only capable of semi sequential injection+wasted spark, so the cam sensor doesnt need to be added, but what about the knock?

 

Further on what do people use to cover and protect the wiring? heat shrink all the way or only on the joins and something else on the longer runs?

 

Any input and links much appreciated, I have used SimtekUk before for a few multiplugs doing wiring conversions and repairs, but never a full loom, also know of VWP Polevolt, RS and maplin etc.

[Weser 30]

When I did the 12v install in my camper I found these sort of websites handy:

http://www.offroaders.com/tech/12-volt-wire-gauge-amps.htm

Google 12v wire required for others

Dont know if it helps but I was doing more power stuff not signals a lot of the time your not going to have to worry about too much current.

 

Farnell is a great site for connectors of all sorts.

 

I found:

http://www.the12voltshop.co.uk/Shop/

pretty good for some automotive spec cable. However they only do red and black and I sure you will want a few other cables if you are doing a whole loom.

 

Hopefully you find something useful

[Alan_M 66 1 Cars]

I'm sure someone off here mentioned that you can get a generic loom (but adaptable for other systems) for a MegaSquirt ECU for very good money. Decent connectors and all the wiring is numbered.

 

That's the route I plan to take (when I get round to it!).

[Tom Fenton 1,542]

I use 1.5mm to coils and injectors, 1mm to sensors. Most sensors are better if you use twisted pair, lockwire pliers come in handy for this.

 

Sleeving wise I use a combination of nylon braid, heatshrink, and convoluted tubing.

 

I always use Vehicle Wiring Products.

[brumster 135 1 Cars]

I did my recent build with stuff from VWP; they get my thumbs up too.

[welshpug 1,661]

great thanks for the pointers guys, I'll get measuring later and see how much wire I'll need

 

I guess VWP etc do the shielded wire I'd need for the TDC sensor?

[pugpete1108 62 1 Cars]

great thanks for the pointers guys, I'll get measuring later and see how much wire I'll need

 

I guess VWP etc do the shielded wire I'd need for the TDC sensor?

 

i got some shielded cable for my sensor from maplins as i dont think vwp sell it?.

 

i used 1mm all round for my loom apart from the main earths and feed to the coil which i do believe i used 2.5 mm maybe?? i also used this for the main switched live to the relay board

i just went on ebay and bought a 25m roll of black 1mm cable and that was enough for the managment loom

 

and as said twist all sensor cables as pairs.

 

hth

[GLPoomobile 958]

What's the story with the twisted pairs for sensors? Why is it recommended?

 

And at risk of sounding like a total spaz, what exactly is meant by twisted pair? Is it just a pair of wires, joined at both ends and then twisted along the length?

Edited September 6, 2011 by GLPoomobile

[welshpug 1,661]

just a pair of wires twisted together, not sure specifically why though.

 

just quickly calculating how much wire I'd need and rough costs, looks like I'd need about £25 of wire, plus about £30 of plugs!

 

wonder how much someone would charge for a loom....

[Tom Fenton 1,542]

Your costs are way low, you will spend far more than that.

[Alastairh 47]

1mm is more than enough for your sensors. Personally i would use 0.5mm / 16/0.2.

 

Al

[welshpug 1,661]

ok, just thinking about the 12v+ feed from a relay to the injectors and coil, on most looms I've worked on they have a single wire to each set then split to 4 nearer each component, would this wire need to be larger?

 

I'm guessing only marginally as there's only going to be two of each component drawing at any one time, but I'm unsure how much larger to go if I say 1.5mm for the injectors+coil, dooing this way would cut the size of the loom down a bit.

[welshpug 1,661]

Your costs are way low, you will spend far more than that.

 

I'm planning to put my ecu in the standard ecu box on the back of the battery box, and the relays in the standard relay box whihc is next to the battery, and is also where the main multiplug for the engine loom to car loom is situated, so my wire lengths are probably significantly shorter than most 205's so I would imagine thats where the cost is a lot lower.

 

Really is quite a nice engine loom to work on in the ZX, not like a 205 where it snakes all over the place and goes through bulkheads etc!

[welshpug 1,661]

excuse the shoddy night time phone pic and photobucket editing skillz, but this pic illustrates the routing of the loom.

 

[stu8v 68 1 Cars]

Twisted pairs cut down on interference.

[sport1901966 8]

I'm in the process of doing the same and really can't find anywhere recommending wire sizes with enough confidence that I'm happy to base my loom on them. I decided to measure the wires on an old 1.9 8v ECU. The table below shows my findings -

Edited September 8, 2011 by sport1901966

[welshpug 1,661]

Excellent gives a decent starting point.

 

I've actuallty dropped Martin at MEF Motorsport an email to see if he could supply all the stuff I need to make it all up, I know he makes up looms for DTA ecu's.

[HERMAN 33]

I have sent you a pm about sheilded cable

On a different note if there is anybody who runs a garage they could get an account with a company called holger Christensen http://www.hcdk.com/default.aspx?id=995 they suppliy vwp most of there items but you have to have a business account as they will not deal direct to the public they are a big company that supplier the auto electric industry. They are very cheap if you are willing to jump through hoops to open a account and they are bassed in Nottingham.

Neil

[jackherer 543]

holger Christensen http://www.hcdk.com/default.aspx?id=995

 

I was in communication with them about replacement pins for the two under dash multiplugs. They would only sell me a minimum order of 500,000 because it would have meant a whole batch being made as demand was so low. I ended up getting them from Farnell, its very hard to find things like that in their catalogue/website but ultimately worth the effort.

[Sandy 191]

Go to the right source Meirion, Polevolt. Neil Talbot that runs it is a friend of mine and extremely experienced at doing these looms, can advise you on all of it. He supplies Raychem 55 crank cable, best I've found for the S40. Use 0.5 for all sensors and coil/injector returns (S40 pins can only really take 0.5mm for a neat crimp), use 1mm for power to coilpack and injector groups. I use heatshrink in favour of mesh, if mesh gets oil on it, you'll never get it clean, gets awful! Conduit good for bulk sections, but untidy for small stuff.

[gtmotorsport 0]

Must catch you soon in regard looms, as you know I am more industrial!

 

Going to go the Raychem route purely because I have a been given bits and bobs over recent years from contractors, etc I have worked with. Does help that I knew what it was in the first place to come by it.

 

 

[JoshGti 8]

Welshpug, if it helps (or havent already got it sorted) ive got about 2m of excess sheilded wire laying around in a bag that i cut out of the motronic loom i fitted to my car? Not actually doing much so you could probly have it for pennies of me if needed.

[welshpug 1,661]

thanks for the offer, Herman sorted a length of cable for me

 

tempted to just get the emerald loom that's in the for sale section but I dont need the plug

[pugpete1108 62 1 Cars]

been busy lately with sorting my loom out (entire loom for the car )

 

i added some multi plugs i cut out of the 405 loom i had in the loft to make it easier to remove refit the different sections of the loom if needs be.

 

i have seperated the managment loom out on its own and i needed around 50 connections to do this, now my bl**dy fingers are sore from all the soldering and twisting wire etc

 

im just hoping it all still works when i put it back in the car.

[welshpug 1,661]

well i've done this once before on this car and it still works

 

need to find a round multiplug ideally off another petrol ZX so I can start my loom