N52 Swap Discussion

[nando]

the 3.07 should work fine with the 3-stage. I run the stock 3.15 in my 330i (actually, it might be a 3.07, I'd have to check) - lots of people rant and rave about the 3.64 or whatever from the automatics, but, meh. It feels like it has torque for days, I rarely downshift to pass anyone. I feel like all shorter gearing would accomplish is more shifting and a buzzier highway drive. Also, I never turn the A/C off. I just leave it on "Auto" and let it do it's thing. Never seems to be an issue.

My E30 is more of the fun car though, and the gearing on the ix sort of is what it is (short). So for me, having power higher up with a higher redline is a huge bonus.

I think either is fine, as long as you know what you're looking for. if the 3.07(?) in a 330i is enjoyable (which weighs like 3400lbs), the same thing in an itty bitty E30 is going to be a riot.

Oh, don't worry about weight without the trans. If it was easy, that'd be cool. But looking at the weights in the ETK, plus what was already posted before - I feel pretty confident that it's going to end up between 326-330lbs, which is lighter than my M20 by a good stretch.

[Eric]

My ambition for weight was 4 cylinder weight. It looks like we're within 30-40 lbs of an M42. I'll take it. That means we're probably on-par with an S14 as well. If you don't need AC, you're there.

I'd put money on the S14/G265 combo weighing more than the M42/G240 combo.

[LukeJ]

If you look at your picture of the 'bore sighted' engine block..... And look at the concentricity of the main caps...

It looks to me like the front of your engine is 'tilted' toward the right side of the car. If you move the front of the motor to the left, using the right side mount as a pivot point, you may get closer to that " alleged one inch " dimension on your left side mount.

You may be in the right spot, it just may be that the crankshaft is not parallel to the frame rails.

[hubcapboy]

I picked up engine arm Rev 1 pieces on Thursday. The plates against the block and against the motor mount are 1/4", the rest of the webs and gussets are 3/16. I'm going to start with the starboard side because it went perfectly (ominous). I fitted the upper stiffeners to the motor mount plate and the web and tacked them in place, set the plate on the motor mount and rotated the web until it made continuous contact with the plate on the engine, tacked that, and then fitted the lower stiffeners. Here it is from the above-front:



This is from the front, but the underside:



and this is the bracket in place after going back and filleting one side:



Basically no complaints about this side. I didn't have the relationship between the upper and lower stiffener established (because it depended on the thickness of the material) but now I can trace one side of this and the upper and lower stiffeners can "slot into" the web. There's no great way of locating this perfectly on the engine plate at the weird angle, but I have a spare engine plate and motor mount plate to create a fixture for this so it can be recreated if we need to without disassembling my car.

The port side went almost as well. Almost. I was a little too attached to the arm being the same width as the motor mount plate:



Similar to the other side, the motor mount side is pretty nailed down geometry. The vertical webs match up to the motor mount plate, and the flat web matches up with the corner. I'd kinda figured that this was going to be close, but it ended up being some grinding to clear the bolt. To actually be able to feed the bolt? Might not be possible. Luckily my brother was here and asked me why I hadn't made it wider. duuuuuuh. There was also some grinding to get the vertical webs pulled back a little so the flat web was touching. I didn't quite get that right. Both easily fixable, and this'll do for now. After easing back those two areas I dropped the web against the engine plate and tacked it in place, then pulled it off and filleted one side:

[hubcapboy]

Here's that bracket bolted back in place:



The red squiggle is the vertical web that needs to come over. This just means my square plate on the motor mount becomes a little rectangle. Super easy to move that over 3/4" and have tons of room. I don't have enough bolts for all the holes right now anyway (since I now have six on this side) and the one in the bottom left needs to be cleaned with a tap before it'll go in any further on either block.

Here's how they relate to each other. This photo isn't particularly aligned with anything, and the shadows and fillets make everything look weird, but pulling a line across the image is looks like the rear side of the arms aligns pretty cleanly (which they should)



LukeJ once again has me on my toes more than the rest of you... so everyone else better catch up looking for mistakes. the boresighting is... yea. super rough. I don't think the output shaft of the trans is aligned with the crankshaft anyway, so there's going to be an offset. I thought it was a cool shot and was reality-checking the declination angle.

I *don't* and *didn't* have a great way of nailing down alignment with the chassis... the chassis rails taper inwards here, so centered between them is meaningful, but they're not useful for much else. The alignment was done with the transmission attached, and centering the shifter in the tunnel port, So my control is that the shifter is centered and the e90 motor mounts holes were equal distance to the frame rails on each side (each of these probably to about 1/8"). I still don't have a great check for this not being skewed in the car because the block is leaned over, but here's a straight edge along the bores with a speed square against the radiator:

The radiator here was pushed up tight against the firewall and the speed square is just nudging it.

[LukeJ]

I wasn't pointing out a 'mistake' as much as giving a possible reason why your 'otherwise good' engine placement still doesn't completely jive with other documented instances.

If the motor was pivoted, then the bolt would be more in the center of your left mount arm

[hubcapboy]

True, but the shifter would be about 2” to the right and I wouldn’t be able to select 5th or 6th...

There’s no denying that what you’re modeling reproduces CWLO’s relationship between the motor mount and the two bolts on the block. I’m just pretty sure that my block is straight, and I don’t have a reason to move it back that far. I’m honestly curious whether the z4 mounts would have just worked for me. Maybe I’ll find out that I’m miscalculating my radiator clearance.

[LukeJ]

These are all the reasons why I started with the stock mount, captured it's actual geometry, and then only changed what 'needed' to be changed. As I currently understand it.

You have a lot of variables going on here.

I just don't want to see you get too far past this point and then discover there are other issues.

On the other hand, if you continue as is, and you're able to accomplish everything you want and end up with a great car that gives you minimal problems. Then I'm rooting for it.

[LukeJ]

As far as measurement goes.

Are you able to measure from the back of the block to the subframe on both sides?

I'd think having the block square to the subframe would be better than square to the radiator.

I realize I've got no 'street cred' here. I just showed up yesterday and put myself in the conversation.

I have been lurking for the last year or so, whatever that's worth.

Mostly though, I have 20 years of precision measurement and machining under my belt. So that's where I'm 'coming from' in my comments.

[LukeJ]

This is what I see when I look at this picture. Sorry I wasn't able to freehand the lines straighter.

[hubcapboy]

No, you’re helping. Trust me.

can someone weigh in with whether the crank is truly on the centerline? I guess even if it’s offset, it should be straight.

tomorrow I’ll make a plug for the front and rear main seal with a center to measure to, and I’ll get a distance to the frame rails on each side.

do we know that the frame rails are symmetrical over the centerline?

[LukeJ]

You could run a string down the bores in the 3 or 9 o'clock position. Tape it to the front and get it to where it just touches the back bore.

Run the string out to the CSB and see if there is a noticeable angle. Like a horizontal plumb bob.

[hubcapboy]

The only reason I didn’t go that far when I was bore-sighting is I’ve heard a rumor that there’s an offset between the crank and the output from the transmission. So the CSB may not actually be concentric with the crank...

[nando]

I'm pretty sure it's centered. It's not like BMW (in the past anyway) to do something so ugly. I'd have to dig out my G260 to check for sure, but based on the transfercase alone, I feel pretty confident it isn't offset from the crank centerline.

[hubcapboy]

I would think the same thing, but the CSB is offset... So the car isn’t symmetrical...