N52 Swap Discussion

[hubcapboy]

Both the Z4 and the X3 have a pin 13 to a 5A power, while the 330i does not. It’s on the top left of the diagram. This is probably only relevant to me because I’m looking at my e90 Bentley while I’m sitting in the car and everyone else is using the TIS correct for the module.

I think that might have been my historical excitement over bolt-on brackets. In retrospect I was just celebrating that the bracket for the ZF in the 330i (22316760303) puts the trans mounts in the same location as the getrag 420G, which has cast-in ears. If I'd built a crossmember from the 330i transmission mount locations it would have ended up looking very similar to the Bayside piece, but that approach is an adapter for the e30 pan to bring the mount points back to the 420G location, and an adapter for the ZF to bring the ears back to the 420G location... which is under the guibo and the shift linkage... on a car that doesn't have a 420G involved at all, and an engine which never game with a 420G (I don't think). The approach here just adapts the chassis to the transmission we're using.

[nando]

Both the Z4 and the X3 have a pin 13 to a 5A power, while the 330i does not. It’s on the top left of the diagram. This is probably only relevant to me because I’m looking at my e90 Bentley while I’m sitting in the car and everyone else is using the TIS correct for the module.

yeah, it does the same thing. the difference is the CAS is supplying 12v on the E90, and it's coming from somewhere else on the E83/E85. It just activates the module.

On the E30 you'd probably use the original FP relay to trigger pin 13, and whatever powers the pump itself on the E30 to pin 1, and the E30 FP ground wire to pin 2. The pump then gets wired directly to the EKP. I assume you can leave pin12 disconnected, since of course the E30 doesn't have a K-CAN bus. :)

What's interesting is if you look at the terminal descriptions (15 and 30), they are consistent all the way from the time of the E30 to these newer cars.

[hubcapboy]

I’m confused by your reference to whatever powers the pump... the fuel pump relay on the e30 is in the box on the left fender... don’t we have a full amperage, ignition switched supply from there to the pump? I was expecting to connect both pin 1 and 13 to the e30 fuel pump’s power.

In the meantime... I bought a Z4 propeller shaft for the price of the guibo at the transmission, which I needed anyway. There are apparently ways of using a z4 front shaft, e36 m3 automatic rear shaft, and a reversed e30 center support bearing to make this work. The 318ti swap mentions that it’s an auto front shaft, CWLO just said Z4 front shaft, so I bought an auto and it’s way too short. Like, 3” too short. I have a full propellor shaft from an automatic e30, so unless someone talks me out of it my plan is to do the same as Forcedfirebird did on his 6 speed swap and just make a front shaft out of the two fronts I have (by measuring my length and taking it to a driveline ship to be sectioned welded and rebalanced)

Unless someone else has an amazing idea, this seems like a reasonable way of consuming plentiful and cheap e30 auto shafts. The shaft OD is different by 0.2mm...

[nando]

Yeah, sorry, that wasn't clear - that's what I meant. It seems complicated but it's really not.

[hubcapboy]

https://www.wolfetechfab.com/shop

is this what I think it is?

[nando]

those could work. Not sure if N54 mounts are the same as N52, but they probably are. You should also be careful bolting pure steel mounts directly to the magnesium.. but maybe you can put a plastic sheet or something between them to keep galvanic corrosion from happening. Also, you will still need to use aluminum bolts.

Funny enough, we did the flash for that Garagaholic N54.

[hubcapboy]

Fingers crossed you’ll be able to say that about mine before long! My DME’s should be on your doorstep ;)

I don’t have a reason to use those mounts... I think I have everything on track to put my own together, and I want to use the more modern hydraulic motor mounts. I have aluminum washers to space the plates away from the block... and I believe the aluminum bolts are one-time use so I’ll get a new set for the final install. Photos soon ;)

[nando]

Yeah, they came yesterday. :)

[LukeJ]

Be careful using aluminum washers to space the steel plates away from the block.

The BMW mounts utilize a boss in the bedplate that captivates the mount and makes side movement impossible.

I would be worried about trusting three aluminum bolts that were side loaded.

Just trying to be helpful.

Thanks for your progress and updates.

[hubcapboy]

Luke makes an incredibly good point... but it’s only one of the four bolt faces that are countersunk on each arm... (the brackets shown above only caught three, in certainly planning on using four like them factory arms)

I’ll think on that pretty hard.

I expected that interface to just be for assembly but there’s certainly some capacity to it... although I’m not sure if the shear strength of the outside rim of that cast aluminum piece has significantly more strength than the four bolts.

With torque-to-yield bolts I expect the connection to be slip-critical (the capacity coming from the pretensioning of the bolts pressing the surfaces together and never engaging the bolt in shear) but it’s certainly worth some thinking. At the VERY least you’ve talked me into roughing up the washers...

[LukeJ]

The 'countersink' or counterbore is machined to the same plane as the other faces.

The main thing is this feature allows for 'zero' movement so the bolts only have to be in tension. I suppose it could rotate and shear the bolts....

Perhaps if an aluminum ring is made to mimic this feature, it could be captured in a counterbore prepared on the steel plate?

[hubcapboy]

like I said... you’ve got me thinking about it hard. The faces on the block, and thus all four milled faces including the bored one, are coplanar, like you say.

The bolts are significantly undersized for the holes in the arms, and they’re also almost fully threaded. It’s unlikely that there was ever an expectation that they were the shear capacity, or the threads would be excluded (and the shank would pass into the block with a sunk thread)

Its not the case that the recess makes it impossible to move... that interface still has a capacity.

Like you say, if only one location is recessed it’s going to rotate, particularly since on side they picked the location with the most eccentricity (it’s the opposite corner from the motor mount).

I’m pretty confident that the shear resistance in the original design was a slip critical condition. The tension on the bolts creates enough friction that the shear capacity just the friction between the faces. I think the aluminum washers probably reproduces this close enough.

The bolt holes in my plate are oversized the same amount as the original arms... in a condition where we expect the arm to rotate around the recessed mount, the first bolt to engage would have to resist all the shear... I think the recessed location on the arm is just an assembly side so the arm, fastener, and tool aren’t three things to hold... but I’m still listening if you can talk me out of it.

If all four were socketed, I’d have no confidence in the flat plate and washers.

[nando]

I'd agree with that assessment. aluminum bolts are not going to be very good at shear. BMW would have added shear keys if needed to all 4 locations - I think that recess is likely for assembly, probably to "key" it so only the right part can go in with the right orientation.

[LukeJ]

In order for the mount to 'rotate', your drivetrain would have to rotate relative to the frame. Like end over end. Probably not going to happen.

That boss prevents any movement on the shear plane. Without movement, shear is impossible.

I've got a set of Z4 (E85) mount arms sitting here. I've looked at other N52 mount arms. If you look closely, the boss is in a different location for each model's mount arms. Also, depending on which block/bedplate you have, only one location per side is finish machined to accept the boss feature. EDIT: I went and looked again, there is more than one location on each side of the engine.


The bolts are in the locations that can accept the counterbore feature.

I'm rooting for your success, but I'm going to try to do it a different way.

[LukeJ]

Also, let me say from an engineering/machining standpoint. They only need one boss feature to accomplish the goal. If they were to make more than one feature, the tolerances would have to be super exact (true position) on both the mount and the block in order for things to fit and assemble properly. A couple .001" either way and you'd have some sort of interference fit or the boss' wouldn't line up exactly.