B35 ECU compatible with a B34?

[Zacm829]

Can the B34 engine run correctly off of an B35 Ecu. What are the pros and cons to this? I put the B34 in my E30 and need to get it running. Thanks

[ElGuappo]

Yes, it will run just fine.
You have less sensors to worry about since the b35 harness has fewer connections (are you asking about just plugging a 179ECU in instead of an 059?)

I would AT LEAST do the Super E harness upgrade first. The later Motronic is FAR superior.

[wkohler]

You cannot just plug a 179 into a B34 harness. If you notice, the 179 has 3 rows of pins while the 059 has two. You would need to convert to Motronic 1.3 to run the 179. This requires a different harness (325i harness will work), the toothed balancer, crank position sensor, and some other bits.

[Brad D.]

It should run pretty well but you will need to install some of the b35 specific equipment to make it work. You will have to install the trigger wheel from the b35 and as mentioned you will have to install the correct wiring harness. See my m30b35 FAQ for more information.

[Zacm829]

So what are my other options to quickly get this thing running? B34 harness splicing into the E30? How hard would it be to upgrade the B35 parts? prices? thanks in advance

[Kyle in NO]

You can wire an E30 Super E or '87 year-model 325i harness onto your B34, along with the B35 crank hub and sensor. You can plug the B35 ECU into that and have her running in an afternoon.

[RonW]

Does the B35 have a cold start valve? If not, does that mean you should disable the CSV on the B34 if you do the retrofit to the B35 ECU?

[wkohler]

You can wire an E30 Super E or '87 year-model 325i harness onto your B34, along with the B35 crank hub and sensor. You can plug the B35 ECU into that and have her running in an afternoon.

Why couldn't you use the 325i harness which is made for the E30?

[mooseheadm5]

Does the B35 have a cold start valve? If not, does that mean you should disable the CSV on the B34 if you do the retrofit to the B35 ECU?

You wouldn't really need to disable it per se. Just don't hook a fuel line to it. There is no plug on the 528e super eta harness or the super eta 325e or any 325i harness.

[Kyle in NO]

Why couldn't you use the 325i harness which is made for the E30?

Because the injectors are farther apart on the M30, and the 88-92 325i harness molds the injectors plugs into a big-ol hunk of plastic, so you can't stretch the wires out to reach the M30 squirters. The 87 325i and Super E harnesses are identical, and they have individual injector plugs like the ETA and B34 harness.

[wkohler]