M90

[Bert Poliakoff]

Well after 14years it is running. The motor, an M90, was built using 10:1 pistons and we are thinking with the head being surfaced it might be 10.5:1. It has been ported and port matched and I am running a 284 cam re ground by Schneider Cams in San Diego. The AFM has been bored out approximately 2mm Though my car still needs work to finish it, I am driving it with a dog leg and 3:07 diff. I only have about 120 miles on it and am keeping the revs no more than 4K.What I am observing is it is fast but doesn't really come alive until its gets on the cam at about 2500 revs. I am running a stock 002 ECU and we haven't decided if I will change to Motronic 1.3 or maybe one of Don's stand alones, but that will come later once it is complete. Oh, and I am running a 2". Billy Boat exhaust system It really rumbles at idle and makes a great noise as the revs go up. A throw back to younger years starting with flathead Fords. I will post a UTube in the next week for so. And as soon as it gets some miles on it, I will get it on a dyno and post the results

 

[sfdon]

Watch your timing and ambient temperature.

 

[shanon]

Once broken it, you will love the 4-6k range (ie: sound!). Cue evil villain laugh.

 

[bluecoupe30!]

like this......

 

[Markos]

Oh, and I am running a 2". Billy Boat exhaust system It really rumbles at idol and makes a great noise as the revs go up.

Congrats on the motor. Let us know what you think of your dogleg, particularly in traffic.

Any particular reason why you went with a 2” exhaust. That seems more appropriate for a sub 200hp 4cyl car. A 2” exhaust is just 51mm in diameter. A factory 3.0CS exhaust is 60mm, and a 2800CS is still larger at 55mm.

 

[sfdon]

Note the Stahl headers are 38mm/1.5” EACH

 

[bavbob]

Bert, congrads on this build I have been watching from afar for how many years? Exciting!

 

[Bert Poliakoff]

Congrats on the motor. Let us know what you think of your dogleg, particularly in traffic.

Any particular reason why you went with a 2” exhaust. That seems more appropriate for a sub 200hp 4cyl car. A 2” exhaust is just 51mm in diameter. A factory 3.0CS exhaust is 60mm, and a 2800CS is still larger at 55mm.

Well to start with, My car is an early E24. Therefore when I say 2" that is on each pipe. As to the dogleg, that has been an experience. I only drove my car 20 miles before tearing it down to the shell. This was/is my first adventure into old BMWs so in all candor I didn't know what to expect, but once I figured out down shifting and first don't like each other, things went fine.The first time I tried it I thought I had blown the gear box. So now that I understand that facet of the trans, it is actually fine in traffic. Drove it 20 miles today to a C&C event and I am getting more relaxed with it. Since it is a ground up restoration. I am not fully trusting the car and am waiting for all the bugaboos to show up. So far only two relays and an axle that wasn't properly torqued that came loose, Luckily no damage underneath. As to Don's comment, the car is Motrtronic 1.0 so no timing issues there. The car barely gets warm, but I am driving around without the hood on. Hopefully the gauge is good One day I will get into why I had to rebuild the motor a second time after it only ran 20 minutes on the first go around

 

[boonies]

Well to start with, My car is an early E24. Therefore when I say 2" that is on each pipe. As to the dogleg, that has been an experience. I only drove my car 20 miles before tearing it down to the shell. This was/is my first adventure into old BMWs so in all candor I didn't know what to expect, but once I figured out down shifting and first don't like each other, things went fine.The first time I tried it I thought I had blown the gear box. So now that I understand that facet of the trans, it is actually fine in traffic. Drove it 20 miles today to a C&C event and I am getting more relaxed with it. Since it is a ground up restoration. I am not fully trusting the car and am waiting for all the bugaboos to show up. So far only two relays and an axle that wasn't properly torqued that came loose, Luckily no damage underneath. As to Don's comment, the car is Motrtronic 1.0 so no timing issues there. The car barely gets warm, but I am driving around without the hood on. Hopefully the gauge is good One day I will get into why I had to rebuild the motor a second time after it only ran 20 minutes on the first go around

First drivers are exciting and nerve wracking for sure. Looking forward to hearing about the reason for the second rebuild…obviously not a pleasant story.

 

[Bert Poliakoff]

First drivers are exciting and nerve wracking for sure. Looking forward to hearing about the reason for the second rebuild…obviously not a pleasant story.

Well, now that you ask here is the horror show. I had the motor rebuilt by one of the supposed best shops in town Went to put the final torque on the head and found out I got it back with a stripped out head bolt hole. Pulled the head to true cert it and then found out the pistons were measured wrong and stuck out above the block. Got an extra thick head gasket from BMW. Closed it up and the motor was running fine so we took it out for a test drive. The oil pressure light came on so back to the garage and we dropped the pan and found the oil pump literally disintegrated. The idiot at the machine shop said mine was still good when I asked him to put in new one The timing chain sprockets were totally worn and the chains well stretched as well. The garbage from the oil pump took out the cylinder walls, all bearings and the crank it self, as well as the cam bearings but the pistons were still good so I sold those as once rebored I would need new pistons.So original $3500 was out the window and make room for the next $4800. the motor is right, now. The shop that did #2 rebuild was this nasty looking radiator shop with a machine shop in the rear. I was put off a bit when I saw it but my friend who went over everything mechanical in the car, said to trust them and let them do it. So I did and now have a good motor with good oil pressure. I guess you get what you pay for.

 

[boonies]

Wow…glad you got is squared away, but…what a shame. Have to wonder why shops take on work they clearly cant handle.

 

[Klassic]

Very nice upgrade.
Regarding ECU, I think you're heading in the right direction going for an aftermarket unit. I know its a few bucks to get installed, but it is a major piece of the puzzle that often gets short changed in an upgrade such as yours. By getting a good dyno tune you are going to get the best performance across the rev range. Better control over running temp, and control over detonation.
And, if you can, get it done right away as using it with an approximate tune is potentially damaging (e.g bore wash etc).
"Your get what you pay for"

 

[sfdon]

The moment you changed your pistons and compression - you began your timing issue.

You cannot keep the original timing map and increase your compression ratio while
driving a car designed in Northern Europe in the 70's in that town you call Phoenix
where the temp will be 96* on Saturday and " The highest recorded temperature in Munich is 97.0°F"

You have too much timing and too hot of weather. Think of the poor little pistons getting eaten up....

 

[paul]

Well after 14years it is running. The motor, an M90, was built using 10:1 pistons and we are thinking with the head being surfaced it might be 10.5:1. It has been ported and port matched and I am running a 284 cam re ground by Schneider Cams in San Diego. The AFM has been bored out approximately 2mm Though my car still needs work to finish it, I am driving it with a dog leg and 3:07 diff. I only have about 120 miles on it and am keeping the revs no more than 4K.What I am observing is it is fast but doesn't really come alive until its gets on the cam at about 2500 revs. I am running a stock 002 ECU and we haven't decided if I will change to Motronic 1.3 or maybe one of Don's stand alones, but that will come later once it is complete. Oh, and I am running a 2". Billy Boat exhaust system It really rumbles at idle and makes a great noise as the revs go up. A throw back to younger years starting with flathead Fords. I will post a UTube in the next week for so. And as soon as it gets some miles on it, I will get it on a dyno and post the results

I had a 1:3.07 diff behind my M90 engine.....was not happy with it so changed to a 1:.2.45.......far better driving (just my opinion) The 3.07 was more suited to Motorway driving....very long in the legs. 110 kph @ 1800 rpm in 5th gear if I remember.

 

[JFENG]

110 kph @ 1800 rpm in 5th gear

Paul, I suspect you had the OD 5spd. Bert has the close ratio box where his 5th is equivalent to your 4th gear.

Bert, it the motor broken in yet? Any more driving impressions
John

 

[paul]

Yes I meant to say current diff is 1:3.45 not 2.45......my GBox 5th gear is .813:1..........4th in my GBox is 1:1..........very happy with it.

 

[Bert Poliakoff]

Congrats on the motor. Let us know what you think of your dogleg, particularly in traffic.

Any particular reason why you went with a 2” exhaust. That seems more appropriate for a sub 200hp 4cyl car. A 2” exhaust is just 51mm in diameter. A factory 3.0CS exhaust is 60mm, and a 2800CS is still larger at 55mm.

I went with the stock down pipes, I believe they were stock, and are 2" where they went into the resonators and kept 2" all the way back.I am running M90 exhaust manifolds that have been port matched

 

[Bert Poliakoff]

Paul, I suspect you had the OD 5spd. Bert has the close ratio box where his 5th is equivalent to your 4th gear.

Bert, it the motor broken in yet? Any more driving impressions
John

Only 20-30 miles a week so far. I don't fully trust it yet so I don't venture too far from home. I won't get on the dyno until I have at least 6-700 miles on it. However, I can say with certainty it likes to get up on the cam. 2500++seems to be where it likes to be Been driving it without brake lights which we finally got working this weekend. It was scary driving it that way as I am not so sure people understand hand signals anymore
As to rpms on the freeway, with the dogleg and 3:07 it looks like I am turning about 25-2700 RPM at 120 klicks. I am running a 260kph speedo so I just use 65% when converting. I am not sure how close that is but it appears to be in the ball park

 

[JFENG]

25-2700 RPM at 120 klicks.

Perfect for Highway cruising. Good luck the motor