N52>e30 Build Thread for the Sophisticated Gentleman

[Mike36]

[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.

[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