1.3 Motronic Up-Grade & 2.7i How To

[madformx5]

If you use a 2.7 crank in a 2.5 block with the 2.5 long rods and custom pistons where can I buy the pistons. I have a 1990 325is so I don't have to do the converson.

[madformx5]

Really great and informative thread.

[kenika65]

Thanks and for you question...

Why do you want to build a 2.7?

Is your motor in need of a rebuild?

Or does it run great and you just want it faster?

[madformx5]

I have a car without an engine and I know where I can get a free 2.7 and a cheap 2.5.

[kenika65]

Humm sounds like a lot of work...

What is your budget?

[GOOBER]

Awesome thread! I've got an '88 seta and was looking for some cheap performance gains! Currently the car is running like shit but I think it has to do with a bad ecu. Question: If I get all the "i" parts does it matter what year it's off of? Can I use and early head off an '85 or does it have to be later?

[nando]

there is no '85 i motor.

you can use any head/intake etc off an M20B25. I would be looking for parts off an 89 or later though, the earlier cars came with 153 ecus which aren't very reliable and lack any aftermarket. I believe you can use your existing harness and sensors, but you will need the AFM off an i motor.

[GOOBER]

I was gonna look for a later ecu the 173, I found an '88 "i" car though with pretty much everything I would need.

[Ruffian]

I don't think I've seen this thread before...good contributions all around.

My 327i is a high compression eta euro block with the 731 head and a port matched eta intake. I've toyed with the idea of upgrading the motronic, but i'm leaning toward the "not broke, don't fix it" school, and I run a mechanical distributor with vacuum advanced timing. It would be fun to get it on a dyno, then swap in the motronic upgrade and "i" intake, fuel delivery and spark management to see if there's any change worth noting.

[kenika65]

Goober just throw the 173ecu.

Then find and build up an i head, port and polish and throw it and an i intake on there and your good to go.

But you can put the 173ecu in and be done if you want just remember you only have single valve springs so dont cry when you break one holding rpms over 6k.

any pics of your seta?

[GOOBER]

Yeah I've actually sourced all the parts for like 400 bucks! It's gonna have the "i" intake, head, throttle body, afm, and the 173ecu with a mark d chip - which I'm getting from a friend (got 17lb injectors too). Should haul eta ass when I'm done.

Kind of in pieces at the moment because I'm doing a full suspension overhaul as well as a bumper swap but here's what it looked like over the summer when I first got it.

[Mike]

Anybody know if the front balancers have different trigger marks, for super e, and I's? I am hearing that the pulley size is different, but how about the crank referencing? My 2.8 seems like the ignition is off, but am not really sure. I am running an I balancer on it with a new reference sensor. Realoem confirms they are indeed different part numbers.

[morerevsm3]

just completed 327is conversion on my 86 325e, only problem is tacho doesn't work.
I used 731 head and cam, plus all the conversion parts from classifed section here on REVS (http://www.r3vlimited.com/board/showthread.php?t=126308), 02 sensor doesn't work either, runs like a pig when warm, so disconnected it, racing the car next weekend, will be interesting to see how it compares to the 325i race cars

[Holland]

Correct me if I'm wrong, But can't you use a M52 crank to make it a 2.8?

[euromk2]

Love that intake manifold. Where is that manifold from?