N52>e30 Build Thread for the Sophisticated Gentleman

[hubcapboy]

We've been scratching our heads about this engine and this swap for 2 years now over here:

https://www.r3vlimited.com/board/forum/e30-technical-forums/24v-engine-swaps/385417-n52-swap-discussion

There were at least 2 swaps complete when we started, but they both used a modified subframe which allowed the rear sump pan to be retained or modified, they weren't terribly well documented (sorry guys, we love you... I think they were enjoying driving them too much), and there were some functions that I really wanted to maintain that they hadn't included, such as AC and the 3-stage intake from the 330i or Z4 3.0si.

This thread isn't going to include the dead ends or speculation that the other thread is clogged with, although I hope to still participate over there when we need to figure something out. This is (hopefully) going to be everything I ended up including while I built the car.

My car is a 1987 325e that I'd been commuting and polishing up for about 3 years. The suspension is pretty well sorted out, but there's no way it was putting more than 100 hp to the rear wheels. I was getting wasted by Wranglers on onramps.



I knew the head gasket was leaky, but and I was happy to keep up with maintenance (this car never let me down once) but in summer of 2020 it took one last trip to the (4700rpm) redline and pulled into the driveway puking its guts.



There's been a ton of poking around at the N52 that I already had sitting in the yard, but until the last week I actually hadn't touched my car except to take the skidplate off to peek at the shape of the oil pan. That changed after another forum member pushing this engine project along got his installed and moving.



This was a pretty clean and unmolested car when I bought it, and the engine bay cleaned up nicely:



The first job is to get the engine bay ready to drop the N52 package into. This is going to involve at least:

-Building radiator brackets. This is an early e30 and had the "square" radiator supported from below on the rubber pads at the bottom. Late e30's reversed the flow direction of the radiator (from inlet on the top right to inlet on the top left) and that direction carried through until the current models. These late e30 radiators were supported on pegs that sit on brackets at the frame rail either side, a dimension that was carried over through e36 and z3's. Since we need the radiator flow to match the engine and the later style radiators are much easier to find aftermarket replacements for, I need to add the brackets.

-A slight modification to the starboard frame. This isn't mandatory for anyone considering this swap, but I made a decision with the exhaust headers that requires a little more clearance. Since it's in front of the shock tower, this is really only in the part of the frame rail that's designed for crash protection anyway (you can see dimples along the top of the frame rails at the inside top corner where the frame is supposed to buckle during impact)

-Modification of the motor mount pads to accept e46-style hydraulic motor mounts. The motor mounts from the N52 are too large, and since there aren't OEM engine arms I decided to design around e46 motor mounts. There are still high-performance and solid mounts available in that shape, but I'm expecting that the modern(ish) design is going to be a huge vibration and noise improvement over the rubber mounts I'd been using.

-Re-soundproofing and re-insulation of the firewall. The M20 came with a big fiber reinforced rubber blanket on the firewall. Mine was soft enough that it was falling off in chunks and was mostly just sitting on the transmission. I don't love how it's possible for water to get trapped between the firewall and this big rubber blanket, but I do like that it's effective in keeping the cabin quiet. The mat is at least a half inch thick, and they're still available, but I don't like the idea of putting one back in. I'm going to be using spray-rubber undercoating to provide some sound deadening, and adhesive fiberglass panels on top of that for insulation.

-A few rivnuts for mounting radiator plumbing that wasn't originally in this car.

-Probably something that I'll forget until the engine is in

[hubcapboy]

Why N52?

I'll start this off by saying "because nando made it possible." As near as I can tell, one of the long-time forum members here was responsible for deleting enough code from the MSV70 DME to get it to run standalone. I picked up on this from reading about this project:

http://www.318ti.org/forum/showthread.php?t=43252

It absolutely wouldn't have been worth thinking about if not for the proven flashing that allows the DME to run by itself. One of the benefits of this engine is also something that pretty much ties it to it's original engine control software. The N52 doesn't run with a conventional throttle valve (although it does have one, it stays open in normal operation). I've explained this system over beer about 100 times by turning my knuckles into rockers and pushing on pretend valves, but the easiest way to think about it is that the engine has three cams. One conventional intake cam (with variable timing) one conventional exhaust cam (with variable timing) and one extra cam acting in between the intake cam and the rocker. All of the lobes on this extra cam are aligned, and rather than turning at half engine speed and opening and closing the valves along with the combustion cycle, it's job is to turn as you open the throttle and vary the valve lift.



This is a completely bananas system. Your throttle is no longer a variable valve a foot or two from the cylinder, your throttle is now the valve itself. At idle, they just barely move. Throttle-by-wire when you're adjusting the angle of an electronic butterfly is one thing, but managing a DC motor that turns a shaft and monitoring it's position fast enough to respond to pedal input is beyond what you'd want to do with megasquirt.

This engine design never got an M variant. From the M20 through the M50's, BMW did their best to add power without adding weight, switching from iron blocks and heads to aluminum to offset the increased weight from the DOHC M5x. The M variants of these engines (with a few exceptions) had to retain the iron block for strength, and ended up paying for the extra power with the additional weight. The N52 kept the traditional BMW 6 layout, with the same bore spacing, but completely revised the block. Rather than a classic design with an engine block and bearing caps, the engine block is split through the crank, with a beefy cast bedplate sandwiching the main bearings.



Taking advantage of this stronger design, the block is cast with an aluminum cylinder core and a magnesium structural block surrounding it. The lighter color here is aluminum, the darker color on the outside in magnesium:



This results in a block that weighs around 72 lbs, and a total engine/trans package for the N52B30 and it's heavier GS6-37BZ 6 speed manual transmission of 462 lbs (that is, heavier than 6 speeds mounted to the N52B28 and N52B25). The total weight of the M20 and Getrag 260 when I pulled it? 502 lbs. A 40 lb reduction isn't nothing, and it isn't magical, but consider that an S54B32 with a GS6-37BZ weighs roughly 620 lbs (similar to the lightest LS combos).

Why is it worth adapting this engine over any of the M5x blocks? M52's were made through 2000. That's 20 years ago. Best case, you're swapping a 20 year old engine based on a 30 year old engine. The car is only 33 years old... M54 came after that, and that's a good engine, but they were made through 2006... not much better. The S54 is the king of BMW swaps, but they're *expensive* and *heavy*. On top of that, all of these M5x swaps rely on you finding an front-sump oil pan from a 30 year old 5 series... and then you have less ground clearance than you started with under your m20.

The N52 was BMW's last attempt at making the most power out of the lightest 6 cylinder before losing the horsepower wars to V8's and turbos. That's the right engine for an e30.

The N52 is 150 lbs lighter than the S54. When I was engine shopping, S54 swaps were going for roughly $8k at 100k miles, easily 4x the price, and increasingly rare. N52's were produced through 2013, and used parts are cheap and plentiful.

[Mike36]

[moatilliatta]

Stoked.

[nando]

Just an aside - an "S" variant of the N52was planned, but ultimately cancelled due to the push towards turbos. If you study the N52 head you'll realize the design is based heavily on the S54 (even CNC machines intake ports).

The rumor is the M-team engineers really wanted to stick to N/A designs, but were overruled by upper management. Consequently, many of those engineers quit and went to work elsewhere - notably, Hyundai. It's not exactly a world class secret that modern M cars have lost the plot.. whether they're faster on paper or not.

Also, N54 swaps are just as doable. I'm not aware of any successful ones that didn't involve swapping all of the body electronics as well, except one in an E36, that I helped with. Personally, I don't really care about the N54 and turbo dick measuring contests - an N52 should easily be capable of 300hp, which is plenty in an E30 (especially considering the weight). But if turbo is your thing, I won't judge.. ;)

[Bored]

N52B30 is definitely what I'd consider a perfect engine for the E30. 6 pots, all in a nice straight line, tidy horsepower, dandy weight, and a very compelling design.

[hubcapboy]

I told you I was going to forget something: fuel pressure regulator. I have to get a bracket built for that before the big day.

[TobyB]

Sophisticated Gentleman

Obviously, you've completely missed your market, and I'm completely ignoring you as I have an M54B30 ready to go into mine

he says, following this thread rather closely.

t
in for lots of deets.

[Victell]

Enthusiastic sub

[2mAn]

I know you wanted the other thread cleaned up, but thats neither sophisticated nor the gentlemans way. This thread is the Sophisticated Gentleman way.

+1 Subscriber

[hubcapboy]

First step of underhood prep was to figure out what I was going to do about the huge rubber blanket that mounts to the firewall on the e30. Mine was falling apart into chunks and was mostly just sitting on the bell housing, and although they're still available, it didn't seem like a great solution. I didn't find it straightforward to find a product that was really supposed to work here, so I went with a combination of 3M rubberized undercoating and a sticky heat shield:



Here's what 3 x 16 oz cans of rubber looks like on the firewall. I was feeling pretty good about it at this point. I've used this before and it set up to a durable finish in less than an hour.



Here's what it looked like after I stripped the masking off and started to panic because the top 1/8" had set up.... and looked like a pretty good vapor barrier... and it was plenty gooey underneath...



Fortunately... after a week with a heater sitting under the hood it was ready for the next step. This is HP Sticky Shield, which is an aluminum foil with a thin fiberglass batt and an adhesive on the back. The seams are another product from HP, which is a thinner aluminum and adhesive with woven glass fiber tape in between instead of the batt. The normal batt shield is pretty tricky... it's about as "strong" as regular pink fiberglass wall insulation, so it's super, super easy to pull the adhesive away from the aluminum. If you don't reinforce it and capture the edges with the tape... I don't see this lasting very long:



This treatment went most of the way back to the shifter boot, with all the little HVAC drains poking through and all of the original studs and washers from the rubber heat shield re-used as a backup to the adhesive:



I don't know if this will be as effective for heat OR noise as the original rubber to be honest...

[hubcapboy]

My original goal for this swap was to do it without ruining the car... as far as the chassis knew, there hadn't been a swap. I bent that rule for a few things, the first being the clearances for the headers. The n52 manifolds that come on the North American cars bring the front and rear banks together very quickly to be picked up by the first O2 sensor, and the catalyst is pushed up against the side of the engine so it gets heat as quickly as possible. There are N52 shorty headers from the factory on some European models, but I wasn't able to source them. There are a few aftermarket header designs for the e90, but they're all designed around tight tolerances in the e90 chassis... and my (also tight) tolerances are different. Most (all) of these BMW 6's have common bore spacings, so a $50 set of factory manifolds from an s54 adapted to new manifold flanges is what we settled on. After mocking them up, one of the primaries was too close to the frame rail for comfort. This part of the frame rail is in front of the shock tower and is already dimpled to act as a crumple zone, so cutting into it wasn't a huge concern.



The idea here is to trim out some of the inside rail and replace it with piece of a sweep from an exhaust 90. This is a heavy gauge stainless elbow:



No going back now... This location was determined measurements on my mock-up car, then hoveringuy making an impulsive decision, then my re-measuring his work:



It seemed easier to trim the rail to the profile of the elbow, then mark and trim the elbow back to what I needed. Oh look! there's the heater frantically trying to cure the soundproofing!



Here it is looking its worst... This got some high heat paint that's a poor match for the engine bay and some seam sealer that you'll see in later photos:

[hubcapboy]

There's a few things to note here. The first is the ugly paint on the frame rail. Sorry. Next, This is an early car, so there were tabs along the bottom of the radiator core to support the radiator and they've all been trimmed off (the little rectangles) to make room for a coolant crossover designed by hoveringuy that I don't understand fully yet. The last is that I don't have any way of supporting a radiator any more.



These are brackets that I *think* will reproduce the radiator mounts from a late-model e30, which are common geometry through the e36 and z3. I didn't document these very well because there's a ton of better ways of doing this... the easiest being ordering the original pieces to weld in, but I was poorly prepared for that. I also don't know if I'll ever be able to mount a different radiator because I located these off my ebay radiator... so I hope it's close.



The idea is that they sit here:



And here:



And using a late e30 radiator clamp for the top and some foam tape against the core, the rad is held in place.



I'm using a dual-core radiator with a built-in pressure tank on the drivers side... This is a "performance" upgrade from some 4 cyl z3's and I think some european 4 cyl e36's. Another early car issue is that I have my pressure tank on the wrong side for the new engine, and although I have a late tank and the brackets this seemed like just as good of an option (if it doesn't interfere with the engine... which I hope it wont...) The area is smaller than a 6 cyl radiator, but it's double core... and the core that is there is better aligned with where the fan will be (circles don't inscribe very well into a rectangle).

[hubcapboy]

If anyone reading is hoping to do this swap and they bought parts from me (if I ever sell them to anyone), this is where you need to pay very careful attention.

These are the two subframes I have at hand. The top photo came out of an '88, and the bottom photo is from my '87. There's a slot and a hole for the m20 motor mounts, but *YESTERDAY* I learned that the web between the slot and the hole is a different width on these two frames.

Originally, when I designed the adapters, I didn't account for two things: 1. I didn't know about this web difference, and my reference point was the inside edge of the slot and 2. I forgot that my '87 subframe had been reinforced with a doubler plate inside and was thicker than the one on my mockup car. If there's conflicting information on how this geometry works from any previous posts... this is why.

Here's the subframe from the '88 (maybe it's actually an '88, maybe not):



Here's the subframe from the '87 (Maybe it's an '87, maybe not):



That extra 1/8" of web on each side is unsettling, but fortunately the distance between the two round holes (which for the e30 are what locate the mounts) are the same. So our new method of locating these plates is using that hole. Good thing I put it there I guess? The second problem is the reinforced subframe. This adapter plate is to adapt an e46 hydraulic motor mount to our e30 chassis:



It's thick because we need to lift the motor mount up to clear the frame rail, and it fits on the motor mount like this:



The hole on the left is for the motor mount stud, the middle hole aligns with the round hole in the e30 subframe, and the hole on the right is only there for the nub on the motor mount to stop it from rotating. When I was using these plates in the mockup car, I had just enough thread engagement to feel ok about the nut... but it wasn't great. I was planning on tacking this plate in place to fix it for rotation (using a bolt through the common hole) and just using it as a spacer, but with any reinforcement in the subframe there wasn't enough to feel good about it. luckily, this plate already had to be thick to space the mount up, so it's plenty strong enough to *be* the reinforcement, and the nut can snug up to the bottom of it after making some clearance:



Here's what your poor subframe looks like after doing that. Make sure you leave enough of the round hole to locate a bolt, but the slot does need to be opened up to connect with it. It needs to be large enough to fit the flanged nut for the motor mount, which is 22mm OD. I did this using a step drill roughly in the slot and then a die grinder to open it up a little further. If you have the "lower" reinforcement piece on, you're going to end up drilling into that too, but it also needs to be opened up to allow the nut to be tightened, so just keep going with the step drill.

[hubcapboy]

Here's the old (now blind) round hole next to our new nut clearance, with the bottom subframe reinforcement trimmed back for socket clearance:



I secured the plate through the common hole:



and started thinking about tacking them in like this:




I lost a perfect rotation reference when I opened the slot for the nut clearance... so these now need to be located by aligning the three holes across both sides. It's pretty paranoid to worry about this, because the hole we're rotating around is so close to the center that it's really not moving much... but a straight edge between the mount plates aligning with the six holes will get them in the right spot.



Bzzzzzzzzzz then some paint: