B58 swapping my F22, building the M240i BMW should have..

[Hydra Performance]

First some background, I bought me a nice Valencia Orange 6MT 228i slicktop back in the fall of 2022 as a sedate daily. Car was mostly stock save for a catless DP, Active Autowerks dual-exit axleback, and 17x9 ET30 Apex ARC8s. But the modding bug soon bit, so I started throwing parts at it left, right, & center. Highlights include the following:

complete M rear subframe with custom 188mm 3.91 Torsen LSD rear diff, with custom axles
M235iR front subframe with M aluminum undertray/bellypan & M235iR-specific front/side panels
M235i "2VL/Sport" steering rack
4x M front arms
28mm adjustable front sway bar (since an M bar wouldn't fit the non-M subframe)
M front knuckles/spindles with my custom 350mm brake setup (exact same setup I run on my 1er)
M2 Competition shocks with H&R Sport lowering springs
M2C front brace (with M shock mounts)
Custom Carbonfiber driveshaft
M engine mounts & transmission mounts
Recaro Pole Positions with custom 1pc mounts
17x8.5 +40F & 17x9 +52R Apex ARC8s, because the M rear subframe is +18.5mm wider per side, it was very difficult to find a wheel that would fit a narrowbody

Drivetrain was kept stock, save for a custom MHD tune which got it up to ~295-300 bhp & 420-430Nm of torque. 100-200 went from 17.7 pre-tune to 13.8 post-tune, so it was now *almost* as quick as a stock M235i, and slightly faster than a stock E46 M3. No intake no charge-pipe no FMIC, just DP & tune. I briefly tried running a LWFW (SPEC aluminum 6-bolt N54 that was on my 1er) but NVH was completely unacceptable so that came back off after a week.

Car eventually morphed into a pretty competent overall package, a 1400kg 4cyl M2C facsimile if you will. Tried my hand at a few race events, and won my class in the first (and so far only) event I did with fresh semi-slicks . Was the 2nd fastest 2WD street car overall that day, just behind that pesky 991.2 GT3 again.

So now the car got to the point where it was over-chassis'd & underpowered, so when I was at my friend's shop one day, and I happened to stumble upon a 2020 AMG A45S M139 turbocharger, I immediately knew what must be done. This thing has B58-sized wheels, but with ball-bearing construction, and a compressor wheel designed for higher PR operation shown to be good for >500whp. So I got to work adapting it to fit a dummy N20 block I had laying around , and several iterations later this is what I came up with.

Was close to finalizing everything, even fabbed new oil/water lines for it and started work on the EWG adapter, and just before everything was ready to finally bolt-on, I pay the same buddy another visit and see a shiny Gen1.5 2019 M240i BMW AG Test motor, used to calibrate NAVI software with just 39,276km, in a metal crate, silently urging me to take it home ...

So there I had it, the opportunity to get myself into B58 ownership for relatively little financial outlay, on an already highly-developed car, in a rare/unique color, and most importantly NO SUNROOF, since I refuse to own anything with a sunroof. Plus I already had a G8x S58 6MT transmission + flywheel & clutch lying around the shop, so it took me all of about 3 seconds of deliberation before telling my buddy to load it up & #sendit! Any of you fellas out there want the absolute BEST N20 turbo kit on the market? @WhyAnN20

To be continued...

 

[wheela]

Cool project, excited to watch this unfold!

 

[wheela]

@WhyAnN20 You should get his turbo kit

 

[ShocknAwe]

Very cool.

Once you've been into the B58 id love to hear your impressions vs the N54.

 

[Hydra Performance]

Having already modelled it in-depth with my engine simulation software I can tell you some thoughts right away before even driving it.

Intake flow is inferior to that of a stock N54, while exhaust flow is comparable to that of the N53, so the engine ends up with a pretty lop-sided I/E flow %

Stock B58 intake manifold has near-zero runner length, which actually works really well in conjunction with the stock intake cam specs & intake port flow. In fact, when I modelled aftermarket Stage 1 cams, I could not produce any worthwhile gains with my intended turbo sizing & boost levels. Interestingly enough, the S58 comes with longer intake cam duration, longer intake runners, and some 20% greater peak intake port flow vs the B58. Unfortunately, the S58 intake manifold isn't even close to bolting up to the B58 (already tried), and the S58 intake cam runs different trigger wheel phasing so that won't swap over either.

So as a base engine, I would say the B58 is actually quite similar to a vanilla N54 in terms of power production for a given turbo capacity when running pump gas & sub-20psi boost levels. If you were to remove the intercooler brick & chop off the turbine housing & run it on an engine dyno through an open exhaust it would make ~232bhp SAE @ 7000rpm naturally aspirated, vs 228bhp for the N54

The difference between them however, is amplified as you start cranking up boost levels & E-mix %, since the B58's higher compression increases its octane appetite obviously and responsiveness to E-mix.

What also greatly helps the B58's cause here, is that being a factory closed-deck design with 82mm bores (with more meat between the liners vs our siamesed 84mm bores given the same 91mm bore spacing) it can structurally handle much higher cylinder pressures. So what it ultimately lacks as an air pump, it makes up for in brute strength provided you have enough fueling capacity & octane available.

Speaking of fueling, the N54 is actually blessed in that regard. Our Piezo injectors, provided they're working right, are bigger than even the biggest aftermarket solenoid DI injectors. This opens up a lot of tuning flexibility if you have enough HPFP capacity, which we can easily attain with a simple pulley/sprocket change vs having to buy $2k injectors and $1.7k fuel pumps to keep it DI only.

Another advantage the N54 platform has is the cheap & plentiful availability of decent intercoolers compared to the B58. $400-500 will net you an 800bhp+ capable cooler whereas with the B58 you need to fork out 2k+ for something with inferior cooling capacity. Yes folks you read that right, w2a generally offers poorer thermal effectiveness vs a2a, it trades steady-state performance for transient-performance which is why the OEMs do it. Easy tradeoff to make when you're only designing for 8-13psi

Since my car already has an air/air intercooler (and matching radiator, AC condenser, and fan) I intend to sidestep this issue entirely by deleting the w2a brick (custom blockoff plate pictured below) & fabbing a couple of charge pipes to hook up to the Wagner F-series Evo2 Competition tube & fin FMIC I ordered. At 9kg, it was the lightest intercooler of (hopefully) sufficient capacity I could find...

Long story short, if you're willing to apply a bit of ingenuity & mix n' match parts like I am, you end up with something far superior to either of the above. A "K54" (N54 crossbred with a K24 ) like mine makes ~319bhp naturally aspirated, far in excess of any fully-developed B58 out there. Of course the latter can handle more boost & ultimately make more power.. But when you build your cars to be lightweight, with shorter gearing & minimum rotating inertia in the driveline like I do, it doesn't take all that much boost (torque really) to break traction and overwhelm the chassis. And besides, for a given power level, my K54 will ALWAYS be more responsive, and have a wider powerband than an equivalent B58, and you can take that to the bank... With that said, I'm not expecting any miracles from my intended B58 combination. 530bhp on 93oct , 600bhp on E30, and 650 in kill mode, with boost response no later than 250rpm vs stock, making power all the way to redline. Not too much to ask for I hope...


To sum up, both engines have their pros and cons. The chief advantage of the B58 is that its newer and fresher, and has a far-superior automatic transmission, but to paraphrase Mark Twain, reports of the N54's demise have been greatly exaggerated!

Very cool.

Once you've been into the B58 id love to hear your impressions vs the N54.

 

[evotme]

As always a super interesting reading. To sum up your summary: long live N54 (I have one)