Swapping a 4.5 into a 4.2

[N4 FTW]

Hi Chaps

I have managed to source a 4.5 to replace my crank snapped 4.2 with, I just had a quick question about the exhausts. If I use the 4.5 manifolds that the engine comes with, will they mate up to my decats and back box I have at the moment?

Or will I need some jiggery pokery to make it fit?

Cheers!

[FUBAR]

Ask M3John as he did this

[mikesr]

The 4.5 and 4.2 centre pipes and the cats are different lengths. I think the 4.5 may be a larger diameter as well.

I replaced the centre pipes on my 4.2. The first set were for a 4.2 and didn't fit. It turns out I have a 4.5 exhaust system fitted. IIRC the 4.2 pipes are about an inch shorter than the 4.5.

[Tafford]

The only difference I found was the length of the cats / centre pipes - the 4.5's cats are shorter by about an inch and the pipes are therefore an inch longer. The diamters seem to be all the same from the manifolds back. I've got 4.5 cats fitted to a 4.2 and managed to get the 4.2 centre pipes to fit by extending them with a sleeve at the back box.

[amazon]

I have a 4.2 with a 4.5 back box - sleeved to fit - as I recall it was an easy fit (I wasn't actually doing it of course, but I was watching)

[Byker28i]

Any issues with the wiring/ECU. I'm guessing the mapping won't be the same?

[N4 FTW]

Thanks chaps.

The mapping is ok, I have the ecu to swap out too it was more the exhaust I had in mind, I'm sure I'll find out soon enough on that side of things