Question on 525i swap.

Post Thu Jul 16, 2009 3:25 am

I have a 1988 525i with a m20b25. I have 1986 320i with a m20b20 with a getdrag 240. Will the 1988 directly swap into the 320i? Will the wiriing harness work along with all other electronics and cooling system? Thank you.

Post Thu Jul 16, 2009 6:44 am

Yes.
Use the wiring loom from your 320i,you should be able to swap the chip from the 525's motronic to your ECU.
There may be minor differences in the cooling system hose layout and possibly the water pump may be different.Once again,use your 320 bits.The 320 radiator will be fine,as well.
You may find that the car is undergeared,a swap to a 3.91 or 3.73 diff will help.

Post Thu Jul 16, 2009 9:49 am

It it's a pre-facelift 320i then it will be Jetronic rather than Motronic won't it? I thought that these two systems were incompatible or at least some modifications would be required to the 320's engine loom?

Post Thu Jul 16, 2009 2:32 pm

clarko74 wrote:It it's a pre-facelift 320i then it will be Jetronic rather than Motronic won't it? I thought that these two systems were incompatible or at least some modifications would be required to the 320's engine loom?

Good point,I was suggesting using the original car's engine loom on the basis that it was motronic,and that if the 525i has it's ECU under the bonnet in the same place as an M50 version it will be too short to comfortably reach under the dash.
In this senario,a facelift engine loom would be the easiest option.
But in general principle,the swap is on,things like the sump and oil pick-up will be in the correct place,it's just the detail that will require sorting.