N52>e30 Build Thread for the Sophisticated Gentleman

[Mazdayasna]

Very clever play with the not-a-sump! Looking forward to reading future updates. I recently bought an E82 128i and have really fallen in love with the N52.

[hubcapboy]

There's a ton of controversy about how the factory engine arms work and how you should treat the magnesium block on the n52 discussion thread. I'll summarize some of it and my decisions here... you may come to different conclusions. As much as I can, I use "motor mount" to mean the flexible suspension between the engine and subframe, and "engine arm" to mean the piece that bolts to the engine block and transfers loads tot he top of the motor mount.

-The engine block is magnesium, and is generally isolated from steel parts by using rubber, plastic, or aluminum intermediate parts and gaskets. This is due to some concern that direct contact with the dissimilar metals will cause corrosion to the magnesium. I knew a little bit about this coming in... and for a start it didn't make sense that if the engine block was grounded to the rest of the electrical system, why it would make any difference at all whether the metals were in direct contact. Galvanic corrosion is electrical/chemical, and will happen any time two metals are conducting and exposed to the same continuous electrolyte to complete the circuit. If I had to guess, this would never be a concern if this engine weren't exposed to the elements, particularly salty winter roads. The countermeasures that BMW took in the assembly of the engine seem to me to just distribute the effects and if possible move corrosion away from surfaces that need to separate for surface... such as threaded fasteners, the oil pan, and ancillary brackets. The factory oil pan for an N52 manual is painted steel, and the gasket is detailed with a flange to stop salt water from making a short bridge between the materials... but there's aluminum pan bolts that will certainly scratch off the paint on the pan enough to make an electrical connection, and they thread straight into the magnesium. Building the engine arms out of aluminum to match the factory arms wasn't just vastly more difficult for me, it was unnecessary because there's going to be steel in the ground path eventually. A lot of it. The whole car. For my engine arms, I'm using an aluminum washer to give me a gap from the block and to prevent direct contact, and I'm painting my steel bracket.

-The bolts on this engine, wherever they engage magnesium, are aluminum. This is probably both to reduce weight and minimize the corrosion where a bolt needs to move eventually. The most important thing to know about these bolts is that YOU CAN ONLY USE THEM ONCE. This is not a joke, this is not a suggestion. Normal steel bolts are torqued, which is a measurement of how much force is applied to the bolt and at what distance, and translates to a tension in the bolt which holds the components together. In typical steel bolts (any of the ones that aren't labelled DO NOT RE-USE) this tension does not exceed the elastic limit of the bolt. The tension stretches the bolt, and when you remove the bolt it goes right back to its original length. These aluminum bolts, every single one on the engine that engages magnesium, are torque-to-yield. In the service manual, you'll see a torque, and then an angle. The torque gives you a starting point, but the angle prescribes an amount that you need to stretch the bolt beyond it's elastic limit. This plastic deformation means that you have a very predictable tension in the bolt after this procedure... but after it's removed it will not go back to its original length. If you try and repeat this process on the same bolt (after removing and re-installing) there's a very high chance the bolt will break. I tested this on four used engine-arm-to-block bolts, the big ones, and every single one broke about halfway through the specified angle. DO NOT RE-USE ALUMINUM FASTENERS ON THIS ENGINE.

-The mechanism for how the factory brackets transfer load is not really known... we haven't talked to the BMW engineers who designed them. Anecdotally, one of the bosses on the arm is rebated so that it "pushes" onto the engine block nub. It's a very shallow interface, and it's in cast aluminum. I think this is just for ease of assembly. I don't believe that these bolts see much shear force since they are torque-to-yield. Usually this type of connection is designed to be slip-critical, where the tension in the bolt is used to create friction between the mating surfaces, and that coefficient of friction along with the bolt tension is enough to resist the anticipated forces. I ran my aluminum washers over some rough sand paper to give myself some confidence there. There are also engine arms for this engine which only use 3 bolts (I believe the z4) so as long as we're sensible about placement, a bracket with four bolts will be adequate. The last thing to know about how the statics of these engine arms work is that the shape of the arm has absolutely nothing to do with how the load is distributed between the bolts on the engine block, provided that the bracket is sufficiently stiff (and in the directions we'd be worried about, mine are). The only factors in distribution of load are the direction, magnitude, and location of the force applied to the bolt group from the motor mount. The arm is a black box.

-There's tons of speculation about whether there's a factory engine arm that would work when combined with a different factory motor mount, or a motor mount re-drilled into a different location in the subframe, or a factory engine arm with some straightforward modification. I hadn't welded aluminum, don't trust welding of cast aluminum in this application, and didn't really have any way of testing every engine arm in my mock-up. I can say definitively that e9x arms would not be a good starting point, because the motor mount locations are out over the control arm ball joints for our car... the arms are just too wide. I still have a spare subframe and the loose engine block, so if anyone wants to see how a set of arms relates to the E30 subframe, send them my way.

OK. Here's my engine arms.

The factory engine arm is cast aluminum, and it's a pretty gossamer construction. You can see one rebated mating surface on the top right of the picture here, but all of the mating surfaces on the bracket and along the side of the block are flush. Cutting and realigning this bracket would be possible, if you could get over the challenges with welding cast aluminum, but I'd want to insert a plate between the two halves to do this, and you'd have to know the plane that you needed to move the bracket in advance. These brackets are now wheel chocks:



There are six mounting bolt pickups on each side of the block. I started off by taking a rubbing of these, scanning them, and cutting plates to match the "front four" and "rear four" on each side. I didn't know at this point where it would make sense for my arms to attach. The five holes in the middle were just in case I needed a later reference between an "arm part" and a "plate part," and thier location ended up pretty much meaningless. My goal was to design arms that defined their own geometry (slotted together with tabs or assembled with bolts, and could then be welded) but I wasn't successful. The final arms need to be assembled in a jig.



On the port side of the engine which is the "high" side of the block, I bolted my new e46 motor mount to the modified seat you can see in the early engine bay posts, and dropped a thick square plate the same size as the motor mount on the stud. I started mocking up arm shapes for the front and rear engine plate locations (you can see all six potential bolt locations here... if it's a bolt location that hasn't been used, they are tapped from the factory but I found that you'll want to chase it with a tap to clean up the threads that have had gunk in them for as long as your engine is old)



I used a ton of 3/16" craft plywood, hot glue, and paper templates, and learned that an arm that goes to the rear plate location will inevitably conflict with the steering linkage, and an arm that goes to the front location will end up being a very awkward shape, and will obscure the installation of at least the bottom bolt in the center. Mounting with three bolts at this odd angle wasn't ideal. If I was going to run the arm straight over to the block, it was going to be very close to the center two bolts, probably spanning them, and a four bolt plate would have been awkward. I went back and re-drew a 6 bolt plate and some of the pieces I'd templated out of plywood, and this was the first iteration I tested. The markup here is showing how I need to widen the arm to clear the bottom bolt (I wasn't sure if I was going to be able to warp the bracket to clear).



After making that adjustment, here's the final port-side arm being assembled in a jig that was created from the first attempt. These jigs aren't great, but I have the original prototype engine arms stored in them, so I can always make a new set.



We've assembled two pairs of engine arms from these patterns and both engines plopped right into place.

[hubcapboy]

A very similar and boring process started on the starboard side. The bolt locations made a lot more sense on this side with respect to the motor mount, and this side was pretty easy to template.



I think these are @hoveringuy's fingers up top holding the cut-back factory manifolds while I muttered about how there was plenty of room to turn a front bank exhaust back over the engine arm... worst case maybe I'd scallop the top of it for a little more clearance... while he muttered back about how the factory manifolds suck and I was making a huge mistake. It was incredibly nice to be able to set the head on and off, mount the mainfolds, etc to check this stuff without having to lift the whole engine and transmission in and out.


I still think this early design is better if you aren't going to bother with the headers, but the header development came together at about the same time, so a revision to the starboard engine arm pushed the arm itself forward to wrap around the ideal routing for the front back collector



I don't have a great shot of that bracket holding the mock-up block in place, but this is what it looks like leaning over the fender from above with the engine away from you, and the lowest hole picking up the motor mount stud:



and here's both prototype brackets in the jigs with the final designs set to the side. These got a few coats of epoxy paint and sat around for a few months while I started on other components... but you might see either of these painted or unpainted in later photos holding one or other engine up while I worked on something else.



With these new arms bolted to the mock-up block and one more fixture to define how the engine rotates around the mounts, I was able to unbolt and grind off the fixtures for the not-a-sump... leaving me with the mock-up block sitting under the hood supported on engine arms and motor mounts, with clear space below to start looking at oil pans.

[hubcapboy]

Very clever play with the not-a-sump! Looking forward to reading future updates. I recently bought an E82 128i and have really fallen in love with the N52.

Every time my brother comes over to sip a beer and look at the car he shrugs and says "you know you can buy this engine in a 1 series... right?"

[hubcapboy]

OIL CONTROL

If you haven't poked around under your e30, this is what the oil pan looks like from the front:



and if you haven't held a loose pan in your hands (actually, I haven't), this is what the rear half of the pan looks like before that sump drops down:



And here's what the e34 oil pan looks like, which is the magic 5 series pan that lets us install all M5x's up through the S54 into an e30:



This pan only exists because the e34 5 series was released as a front-sump car in 1987 with an M20 just like the e30, and later got upgraded to the M50 when that engine was developed. From a "what do we do with the oil" approach, this is a pretty simple geometric matter of making a shallow tray that drains to the front on level ground (despite the engine declination to the rear), and incorporating any other features that we might want into the new pan. An e34 pan doesn't have the e30 oil level sensor (I think it has a different one? dunno. don't care) and an N52 pan doesn't have a dipstick. I want both. Another concern I had early on is why on earth the e34 m50 pan looks like this on the bottom:



What the frik is all that gusseting to the flywheel cover for. Typically this is a separate piece of pressed steel and does nothing but barely keep the dust out. I'm pretty sure that on the M50, which was (other than the e34) expecting a rear sump, the transmission to pan bolts are very much part of the engine/transmission package structure. Very early on this was a big worry of mine when trying to hack together an oil pan for a late model bmw engine. Luckily there was a miraculous design change between the M54 and N52 which completely addresses this.



Rather than using individual bearing caps on the crank and hoping to stiffen the block with a cast pan, the N52 uses a 2-piece block. The upper casting holds the cylinders, and the lower casting holds the bearing caps, and the crank is sandwiched between. Adhesive is injected between the two to seal them. This is one bullet point on the long list of amazing features of this engine, but it means that manual transmission, RWD N52 cars (like my donor) were delivered with cheap, flimsy, pressed steel oil pans that look like an afterthought compared to this bananas engine block. This really simplifies what we have to do with the pan design, as it only has to be strong enough to hold oil.

[hubcapboy]

So we know we're going to kinda build something that looks like the above pans, but out of flat pieces of steel bent or welded. The most complicated and precise piece of this is the flange that needs to mate up to the bottom of the engine block. This came in two types on the factory engines: a beefy aluminum casting with aluminum bolts, and a flimsy steel pressing which came with the same bolts, but with a spacer the same thickness as the aluminum flange pan (so that the torque-to-yield aluminum bolt can be the same design). We're building a steel pan, but I'm going to use the same thickness steel for my flange as the aluminum pan. This way I can use the bolts intended for the factory aluminum pan (without the spacers) and they'll perform correctly. Here are the bolts for a thin flange:



And here are the bolts for a thick flange:



Note that I need *more* of the short bolts than are provided in the aluminum pan kit - mine are all the same. I bought two kits worth of the bolts without the spacers and thew the longer bolts in a drawer (they're actually the same size as some other bolts on the engine, so don't throw them away).

To make a flange, I flipped my engine block upside down and stared at it for a while. Then I ordered a flat bed scanner and a new oil pan gasket. I scanned each segment of the gasket with the flatbed:



Then I re-aligned them all in autocad:



and then checked a few key dimensions against the block to make sure I hadn't warped or stretched anything. After laser cutting the drawing to the right thickness, I had a flange for my oil pan:



With this bolted to the bottom of the block and the block supported by the new engine arms and motor mounts, I can warm up the glue gun and start mocking up an oil pan.

[hubcapboy]

The goal for mocking up the pan in plywood is to give me something that I can tear apart, trace, and refine, and eventually draw in CAD to be able to cut. I'd like my pan to have around the same ground clearance as the factory m20 pan, because after seeing a few e34 pan engine swaps it's very concerning that going that route reduces groud clearance even further. A good guide for this is my M20 skidplate, which has plenty of battlescars from driving around the city, and which an e34 pan doesn't fit inside of:



my markups here are showing that I have a little way to go back, but you can see in the background that the gear on the steering rack prevents me from going back much further. In order to get the skidplate to lift up into place, I need to either bevel or severely cut back the front of the sump.



This is just the sump "wing" sticking out to the side. I made it as long as I could, and it actually goes past the edge of the M20 skidplate in the prior photo, so I do have to cut or grind down the vertical return on this side, but it seemed like a reasonable compromise. The top of the wing can't come up much further and hold oil, because the oil level would be above the pan gasket on the starboard side (don't forget the gasket is at a 30 degree angle along with the block).



This is the view from the front, and you can see that the left "wall" of the sump comes straight down parallel with the engine lean. There's a ton of room on the starboard side for extra oil volume, but extending the pan in this direction leads to challenges with installing the pan bolts. Some pans do use through-bolt or long bolts with reinforcement through the pan to do this, such as the VAC Motorsports pan for the M10/S14:



As an aside, I would have loved it if I had some practice tig welding aluminum, and when I get around to it I could easily adapt the pan design I ended up with to this type of construction... but the expense of farming this production out was too much compared to the ease of cutting and welding steel. After messing with plywood and hot glue, measuring, drawing, printing, gluing my templates to some plate I had lying around (too impatient to wait for laser cutting) bending, and tacking, I had this:

[hubcapboy]

One side of the pan was left open so that I could size up the best way to build an oil pickup. Here's a similar angle to the plywood mockup, but this is my tacked together pan bolted in place. You can see my paper template is still glued to the inside of the pan for some reason:



The skidplate is in place, and there's enough clearance for a rock to fall through. Here's where the rear tray section overlaps the sump to (hopefully, one day) let the oil drain forward:



And here's what that tray section looks like looking forward from the transmission:



At this point I decided this ugly piece of crap was good enough to finish instead of throwing away as a prototype, so I improvised a method to remove the paper templates:



I'd already drawn and cut a doubler plate for the oil level sensor, and I drilled and installed a bung for a dipstick:

[hubcapboy]

There are a few other components that need to go into the oil pan, such as the drain for the PCV system, which you'll have if your engine is a magnesium valve cover. I just cut this off the factory steel oil pan and moved it over to the same location on the new oil pan:



And the oil pickup, which is made from a very standard DIY chevrolet V8 pickup kit, with a steel adapter turned to fit the oil pump. The turned steel piece that fits into the oil pump matches the geometry of the plastic pickup, and even uses the same O-ring:



Setting that at the correct angle and at the correct height for the bottom of your sump lets you build a little bracket to hold it to the windage tray bolts:



Another issue that came up during construction here: I sized the tray around the factory windage tray that's bolted up to the bottom of the block bedplate... but didn't consider that the crank counterbalance at the rear actually comes VERY close to the inside face of the engine block - off the end of the windage tray. hoveringuy discovered this while rotating his engine, and mine cleared, but I checked it with putty anyway:



and I eased the edge of the gasket flange just to be safe:

[hubcapboy]

All the pieces I've drawn or templated so far just made sense and fell into place. I'm a little more proud of this one. Similar to the pressure to adapt headers, I was starting to hear rumbling about how all track-bound BMW's need an oil baffle, and that without one rear-sump cars get oil starvation under braking, and all cars get oil starvation around long right hand corners. I'd thought about designing the entire pan around an available drop-in baffle, but after thinking about what a baffle actually does, and staring at a few hundred examples... it seemed like pretty much everyone was just guessing based on a few common concepts. Oil should be able to go into the baffled area but not out unless it's deep enough, oil shouldn't be able to go from one side of the sump to the other without passing through and filling the baffled area, and oil draining from the engine should ideally drain to the baffled area and then overflow to the rest of the sump. Many aftermarket baffles use hinged plates, but the ones that interested me the most were based on Cosworth style flaps:



These were actually used in the original factory e30 M3 baffle, and are part number 11131309428. Don't look too closely at the price. I think this type of trap door is better sealing, quicker-acting, and less error prone than a metal flap with a hinge, which is going to constantly wear and shed metal, and could get stuck.



Taking all of this into account, this is what I came up with:





The oil pickup will drop into the baffled trap, and the flaps will allow oil to flow into the trap under left hand turns or acceleration, will keep oil in the trap under braking or right hand turns, and the trap will be constantly filled by the tray from the rear of the engine and the top-plate, which collects oil from the front of the engine and forces it into the trap until it overflows through the holes along the top of the trap walls:

[Trevbot]

Every time my brother comes over to sip a beer and look at the car he shrugs and says "you know you can buy this engine in a 1 series... right?"

I got sick of waiting for you to finish and tried this engine and transmission in a Z4 coupe. It wasn’t a big enough upgrade to replace my FRS, but what if it had a back seat and lost 500lbs… 🤔

[lukeADE335i]

Great work on documenting your swap! With so much work on the engine arms, sump and oil pickup etc. do you intend to sell a kit at some point?

[hoveringuy]

Great work on documenting your swap! With so much work on the engine arms, sump and oil pickup etc. do you intend to sell a kit at some point?

I hope so, and if he does I can tell you that I've been working really hard to find any engineering deficiencies. It's been rock solid after a full season of tracking, and my feeling is that the more people that get the N52 the more we can innovate and gain from shared knowledge!

[moatilliatta]

Does the oil pan subatute as a block girdle also? Looks like it'll be ready for war. :)

[nando]

Block girdle? the N52 has a bed plate, so the main caps are cast into the lower half of the block itself. it's waaaay stiffer than an M54 block with standard steel caps.