N52 vs other 24v swaps for lightweight E30?

[Maxhouse97]

From the general forum to get engine swap specific feedback:

Hi,

New to the e30 community, coming from a couple of different automotive experiences (Miata, GTI, 911, Cayman, E46 M3 - last two I still own). Looking to get into a e30 for these reasons:

• I like small, lightweight cars. Drive a slow-ish car fast kind of thing. Go-kart, short gears, a “you make a control input and the car moves immediately” dynamic.
• I’m a NA engine geek, high-reving but decent torque lover (S54 perfect combo). Prioritize engine responsiveness (fast reving, sound, lack of vibration) over outright power.
• I have a European preference, had good experience with BMW (E46, Z3). Also like the 80s nostalgia. Was thinking of going back to aircooled 911s but prices are ridiculous. And so are e30 M3s.
• Looking for a street car, canyon carver, OEM + build/look, no track planned but would want “track in a pinch” options (E46 is my track car). I’m approaching 50 so want a car with full A/C, amenities, etc.
• I can do some of my own mechanical work (have pulled engines/trans and swapped suspensions) but don’t have a ton of time and don’t do well with electronics/computers so in general prefer OEM like kits/simplicity. Willing to spend some money to get there.
• I don’t want another Miata

As I started to research e30s, I quickly gravitated to the 318is for its ultimate lightweight package. Balanced handling due to low weight over the front end, etc. However as I’m also an engine guy, I don’t think the M42 will cut it. I read the 2019 Grassroots Motorsports article where they spent 8k rebuilding the motor and still seemed to get a meh result. Therefore I quickly resolved to look into good engine swaps that would add some power (and torque for the street) yet keep the lightweight feel.

Here are the options as have I gathered them (it’s funny how detailed some of the swap forum threads get when you’re looking for high level thoughts/details):

• K24/20: this is where I started, I have been intrigued by this motor for some time as it’s a model of NA, high/reving power. I spoke to K-tune and they can do a complete swap with labor. Upsides: lightweight with power torque, amazing aftermarket, reliable, everywhere. Downsides: does not keep it BMW, might be a money pit that would not have residual value in the eyes of e30 enthusiasts, second order vibrations from the long stroke 2.4 motor (K-tune kit gets rid of the balance shafts).
• Stroked M42 + ITBs - then went this way, why not stick with what it came with? Upsides: no swap needed, keeps the lightweight part but adds the motorsports feel. Downsides: $$, don’t think the motor was designed with this in mind (S42 notwithstanding), Grassroots article really turned me off. Very little support. Must be a reason very few have done this.
• S50/52/54 motor - came here next. I love ITBs and M engines. Upsides: pedigree, motorsports feel, great power/torque, good support. Downsides: super heavy, violates requirement number 1 and compromises handling. Expensive. Only thing I’ve thought about is putting a S54 in if I have to sell my E46, but that’s not in the cards now. Feel the S54 would make it into a very different car than the 318is, more AC cobra/muscle car.
• M54 - progressed to this motor. Stout, forged crank, tried and true. They are being raced all the time in Spec E46. E46 330 ZHP is a car I like. Upsides: AL block cuts down on weight (according to a post with pictures of scales, 70lbs lighter than an M20), has been done many times, relatively modern motor. Seem to sound good. Downsides: don’t rev very high or fast, not motorsports like? More torque focused than a balanced torque/upper end power motor. Still heavy compared to the M42. Seems to be the 2000/2010s option, but most now going S54 or something else.
• N52 - where I am now. From everything I can ascertain, this gets me the closest to where I want to be. Upsides: lowest weight BMW Six (hard to tell how close to a M42 weight), inline 6 naturally balanced. Great power/torque for NA, pinnacle of BMW NA engines before turbo took over. 7k or higher redline. Seems to be the “in” swap now, which means many of the smart people who know this platform better than me have landed on this. Very cheap motors. Valvetronic provides quasi-ITB like performance (RPD trumpet kit looks very intriguing with even more weight savings). Right amount of power (I don’t need more than 250 hp). Downsides: too new/clinical, lack of character & sound? Lack (or nascent but developing) support. Too hard to integrate electronics into a 1980s car. No plug and play kit. I have to admit some of these are unconfirmed, mostly concerns that could be proven wrong as I do more research.

Now I have one admission to make - I HAVE NEVER DRIVEN AN E30. Up to now I have exclusively spent time with Porsche/E46 people. I have based all of the above on research/discussions with folks at C&C (I had an in depth one with a guy who swapped in a Pontiac Solstice motor). So I could be completely off base. But honestly I think the world is done making small, lightweight cars that are not Miata’s, so I think the e30 will hit the mark. I love my E46 and I know it was derived from the e30 (strut front, independent rear). And yes I plan to drive them once I can find a way to.

What are your thoughts? Is the N52 the right option for me?

And is the 318is the right starting point for a lightweight car? Feel I get can a real nice one for 10-15k, and then collect parts/build it over the next couple of years (I don’t want to start with a project car). Latest built model would help mitigate old car issues (although I really like pop out rear windows). Or would you suggest another e30 model?

Will be posting in different forums to get both platform/swap feedback. Thanks for reading this far.

[adam.nonis]

Hoveringuy will be your go-to for track experience w/different combos and might've even have corner weight of his car. Here's some info he sent me.

M20 with a G260 is about 497lbs.





M54 with G260 is 475





N52 with GS6-17 and everything but exhaust.





My E30 experience is limited to my car. The only E30 I've ever driven. I really enjoyed revving out my M20B25 and I thought it was fun to drive, but the N52 has completely transformed it. It pulls so good and revs like crazy. I love it. I also like the ability to get off the shelf maintenance parts for longer/easier since it's newer architecture.


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[hoveringuy]

My car is relatively light and I'm at 2440 lbs with full tank and spare, so my track weight is 2400+/- plus driver. The N52 is a great track motor, I would take it over any of the S50/S52 swaps and probably even the S54, given that I'm more or less stuck with 225 tires unless I go to some kind of body kit, which I don't want to do. I feel like I could add a lot of power with my current setup and not be much faster unless I went to bigger tires.

The Achilles heal of the E30 (or one of them...) is aero so if you're interested in going fast at a "big" track you will absolutely need a lot of power, like S54 power.

The K swaps are also super-cool and with a turbo you will slay!

My secret weapon is definitely my weight, my brakes and my ABS (MK60E5, FTW!) Notice I did not say "my driving", lol. I can reel-in a lot of newer cars just because they're so porky. I even gapped an SRT Challenger coming onto the straight.

The plusses for the N52 are that it's very light, it's readily available, the magnesium block is superior at damping vibrations and the general design makes it stiff and suitable for revving. With my S54 exhaust header it even sounds sweet. Even with the pedestrian dual-DISA intake which is NOTORIOUS for running out of breath I put down 245whp. With a freer intake 260whp is easy.

Here's my most recent video. https://youtu.be/2mdUblZVTh0 That white car ahead of me is a track-prepped E36.

Same E36 M3, different day... https://youtu.be/1VzKvtR4pfw

Same M3, this time at the Ridge and some other cars, same result... https://youtu.be/WGVeor9n8lY

Just to mix it up, a Shelby GT350. He gaps me on the straights but I always catch him... https://youtu.be/Sv7TC-FOQOo

[Maxhouse97]

Thanks guys, this is great data (especially the pics with the scales, very objective).

Hoveringuy - that’s exactly what I was thinking, too much power can be counterproductive here and not in line with what I’m looking for. Seems like the N52 at 240-260 is the perfect amount.

Looking for other opinions but you guys have reaffirmed my research and have me pumped for this (although I realize this is the N52 sub forum :) ).

[DesertBMW]

you never drove any E30 can ever in your life but you are asking all these engine swap questions. What if you test drive E30 and don't like it for what it is?

[Maxhouse97]

I acknowledge this, that’s why I mentioned it. Am in the process of finding a way to drive one. That being said I enjoy researching/thinking through what a cool build could be. That and the fact that I have owned/driven E36s/E46s/Z3s makes me confident I will enjoy the E30.