320i to 325i ecu question...

[kingwajuk]

Hi folks,

I've just brought a 320i cab and I'm looking to drop in a m20b25 in soon however Im alittle confused about which ecu to use.

As my car is a 1993 it comes with a cat and lambda sensor and from what I've been told I can keep the m20b20 loom to run the m20b25 as its the same loom?

my question is that do I have to use a ecu from a 325i that has as cat? or can I use a non cat ecu to run the car as its a 1993 il need to have the cat and lambda for the mot and stuff.

[kingwajuk]

forgot to say that il be using a facelift m20b25...

[StuBeeDoo]

If the engine comes from a pre-'92 car - and you can prove it - you don't need to run with a cat.

[kingwajuk]

what do you mean by "prove it" ? I just thought it would be easier if i kept the loom which is already in the car and just stuck in a new chip or ecu..

[StuBeeDoo]

If you can provide documentary evidence of the build date of the engine, and/or the registration date of the car it was originally fitted in, then providing it was before 01:01:1992 you don't need to run a cat. IIRC, the E30 ECU doesn't need to have the o2 sensor plugged-in. All E30s from '88 on were "cat prepared". In practice this just meant that to run with a cat, all you had to do was fit a cat and o2 sensor and plug the sensor in to the loom (the plug's there, under the battery tray, on all "cat prepared" E30s).
In practice, this means having the original V5, or getting a letter of confirmation from BMW GB, so that come MOT time you can give the tester the conformation and the car won't be cat-tested.

[kingwajuk]

im with you now! I'l get a copy of the v5 off my mate as I'l be taking his engine.

[Speedtouch]

You can keep the existing 320i ECU and just pop a 325i chip in it (they are identical apart from the label on the lid).

[kingwajuk]

I'l be intouch over the next week or so for a chip then...

[StuBeeDoo]

im with you now! I'l get a copy of the v5 off my mate as I'l be taking his engine.

Not sure if a copy is any good, as it's an "official" document.
I'm sure someone else here who has done an engine swap will know though.
Try asking Daimlerman on here. You can tell him I sent you.

[Brianmoooore]

MOT test requirements are apparently simpler than that. Your modified car is not a standard model, and as such, doesn't appear on 'the list'. Go to here: http://www.motuk.co.uk/manual_730.htm and open the first pdf flowchart near the bottom of the page,