7A differences

[Toby_Unna]

Does anyone know the differences between the 20V engines used in B3 onward Coupes?

I have a 1990 CQ with the earlier engine management, and am considering putting a different engine in because I can't seem to make this one run properly. The engine I'm looking at is from a later Coupe, which looks subtly different (ICV in a different location for example.)

Is this going to be a straightforward swap assuming I get the ECU, loom etc, or is it not feasible (for example, are the speed/reference sensors on the gearbox bellhousing in the same positions?)

Cheers for any and all help!

[mcandmar]

All you need to do is change the intake manifold over, the only difference on the engine was the idle valve plumbing, throttle body and exhaust manifold.

[Toby_Unna]

great, thanks for that!

[stiglet]

What he said ^^^

There is no difference in the engine itself other than the tubular manifold. Seems like a lot of hassle to go to to solve a problem. You will have to take the dash out for a start just to get to the wiring loom.

But to answer your question, yes it will work. You won't have to take the whole engine out though if you just want to change to the later management. You will just need to change the inlet manifold so you can change the ICV position, and the throttle body TPS is different too. You may as well change to the tubby exhaust manifold as well.

Does that answer your question?

[Toby_Unna]

That's useful, thanks. A switch to a different management system as you've suggested will certainly rule a lot of potential problems out!

Is the loom a pain to change then? I'm used to old BMWs where the engine loom is self contained including the ECU, and plugs into the car loom at the firewall...

[stiglet]

Yes it's a real Bi*atch! You have to take out the dash. It's quite difficult on the engine side too, as the battery is in the way where it goes through the bulkhead.

It's a sure way to solve your problem though.

[Error404]

Cut a 3" hole in the bottom of the battery try