E34 M50b20 to M50b25 ?

Post Tue Feb 12, 2008 8:41 pm

What needs changing for this engine swap ?

engine and ecu
gear box ? different ratios ?
prop ?
exhaust ?

It's a mates car and i'm not sure which year('93 ?) it is but i've heard there's single and double VANOS engines ? Which is best and are they interchangable ?

Post Tue Feb 12, 2008 9:41 pm

swop like for like Andy

use the B25 box, ECU and MAf etc, same as dropping an M20B20 for a B25

Final drive will be V low on th e b20 iirc

Zausts are samey same iirc, ETK will show all common parts for the two.

Post Wed Feb 13, 2008 10:22 am

Or you could use the 520i fly, crutch and box - it's strong enough tbh, a mate has run a 2.8 through a 316i Compact box. It will go very, very well on the 520i diff.

Post Wed Feb 13, 2008 6:44 pm

Cheers guys

Post Wed Feb 13, 2008 7:13 pm

Looking at the ETK the exhaust gasket from the manifold to front/kat section is the same but the b25 has bigger diameter clamps and metal O-ring seals in the rest of the system so it's a bigger bore on the b25 but the b20 system might bolt up OK to the b25 manifolds ? Probobly not the best long term solution to carry on with the smaller exhaust on a b25 lump but it will get the car mobile again for a bit ?

The exhaust manifolds are the same as well.

Just looked at the prop for both and it's a different part number and length, one's 1624mm, the other 1661mm.