Thought I’d make this to clear up a few questions that seem to get asked weekly. Plenty of people want to throw a different engine in their car from the same family but not necessarily the same model of age i.e. putting a 106 GTI engine into a 1.1 mk1 Saxo. So this thread should answer most of the questions that spring up asking about which looms fit which cars etc. I will no doubt miss things out so feel free to ask or to correct me if you see something amiss. I’m only going to speak about what I have personally come across and will try and give rough ages etc.
Please note this only covers petrol engines from S2 106 & Saxo I will update this with more photos as soon as I can get hold of some. No companies or services will be mentioned to keep things legit.
Basics
ECU's
There are
THREE types of ECU configuration used, these are:
1. Single plug, 2 rows -> the least common although you will find them, they are the same layout as what you may find in S1 106 and some AX models. I’ve seen these in S reg Saxo VTR’s
2. Single plug, 3 rows -> This is the common Mk1 ECU this is also seen in S2 106's quite a lot. Most Mk1 Saxo's use these aside from early ones.
3. Three plugs -> Later Mk2 ECU's again found in S2 106's, usually 2001 onwards.
Chassis Plugs
There are
4 types of chassis plug configurations.
1. Small Single Plug - Mk1 Saxos and some early Mk2 models use this type
2. Large Single Plug/Early Pin Layout - Some early Mk2 models use this
3. Large Single Plug/Late Pin Layout - Again some early Mk2 models use this but this is the mainly seen from 2001 onwards & also later S2 106's
4. Small Twin Plug - This is found in early S2 106's
Possible Loom Combinations
1. Combining ECU No.1 & chassis plug No.1 - Early Mk1 single plug looms.
2. Combining ECU No.2 & chassis plug No.1 - Late, most common single plug looms
3. Combining ECU No.2 & chassis plug No.2 - Early Mk2 Saxo's are found with this it’s the first type of crossover loom
4 -Combining ECU No.3 & chassis plug No.2 - Again Early Mk2 Saxo's are found with this it’s the second type of crossover loom
5 - Combining ECU No.3 & chassis plug No.3 - Common 3 plug loom found in later Mk2 Saxo's and later S2 106's
6 - Combining ECU No.2 & chassis plug No.4 - Found in earlier S2 106's
So they're the 6 main types of loom, hopefully now you can have a quick glance at your ECU to find out which type it is then you can un-plug your chassis plug and have a check of which type you have. Doing this means you can identify which loom you have.
When doing a conversion you need to ensure you have the same loom as your car if you want it to plug straight in and work. Please don’t be caught out with the early and late pin layouts on the larger chassis plug. A late crossover loom (number 3) WILL fit into a later Mk2 model but it WILL NOT run as the pins are in the incorrect places.
Looms number 3 & 4 can be mixed; therefore if you have a Mk2 Saxo with single plug ECU & loom No.3, you can install a 3 plug engine with loom No.4
Choice's
So now you have identified what loom you have and what loom you need, you may well find that you can’t find the loom you need. In this case there are a few options to you.
1. It is possible to swap the necessary sensors in a 3 plug engine to those of a single plug engine, this means you can mix and match loom/ECU configurations with the actual engine. You will still need to find the correct loom to fit you chassis plug however.
2. You buy a whole car and change the interior loom, therefore if you take the interior loom and the engine loom from any car if can be fit into whatever model you like. (Providing you stay 106/106 or Saxo/Saxo otherwise you will have to change other interior items.) If you buy a donor car and are not to keen on wiring this option is good as it means you need no outside 'specialist' help and the job can be done in a day.
3. You get a loom spliced, a spliced loom is basically a loom that has the chassis plug changed to your required plug. For example you can use an early Mk1 engine with ECU No.2, and change the chassis plug from No.1 to No.3. Or you can take an early S2 106 loom and engine and change the chassis plug to that of a late Mk2 3 plug Saxo. This option allows you to buy any engine/ECU/loom and fit it to your car without buying any other parts (in terms of wiring.) Downsides to this are that the process is quite specialist and it does require you usually sending off your cars loom and the loom from the new engine.
(photos stolen from various members so cheers
)