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I ran the BMW in GT2, in which it's massively outclassed. Qualified 7th or 8th out of a dozen, got passed by a 600 hp Corvette at the start, then spent the rest of the race trying (and failing) to get around him. The new track is fun, but I think it'll be better for track days and TT than it is for racing. Was a super fun event though!
Well, it's been a year. The Miata is running and registered, sans turbo. We reinstalled the AC, but I haven't gotten it charged yet. I've been driving it around, it's leaking a fair bit of oil from the front right corner of the block. I thought it was the oil cooler/fittings, but I ripped all of that out and it's still doing it, so now I think it might be a failed oil pump O-ring. Sigh. Fixing that means pulling the motor out.
Speaking of pulled out motors, though, I started tearing down the original motor from the M3. This one did 230 hours on track before getting pulled for low compression and swapping in a junkyard block. That junkyard motor now has like 160 hours, and will be due for VANOS/rod bearing service sometime late spring/early summer. My goal is to rebuild the old one and swap it back in rather than doing that.
So, here are some engine photos with a couple extra cylinders:
The guys at TC pulled the old motor a couple years ago, it's been sitting in my garage wrapped up in plastic since then. I pulled most of the remaining accessories off before I start taking photos.
More throttle bodies than all of the rest of my cars put together.
The infamous VANOS unit.
And the infamous exhaust cam oil pump drive gear. The VANOS runs off super high oil pressure and has its own pump on the exhaust cam, with an accumulator to maintain that pressure for when it needs to use it. The two teeth on the gear stick into the pump disc and turn it, but there's a fair bit of slop in the factor config and the rattling around tends to break the teeth off. There are various aftermarket improvements for this.
Cam gears with the drive gears removed. There's a helical splined gear that goes between the drive gears and the cams, the VANOS slides that forwards and backwards to adjust the cam timing.
Unlike the Miata, pulling an S54 head requires taking the cams out. I pulled them out, put them on the bench, then put them back in once I had the head off so that it all stays in one piece for the trip to the machine shop.
Head without cams:
Oil pump.
Oil pump drive chain. On earlier cars the drive gear was prone to falling off, but AFAIK that's fixed on the E46.
One of the infamous S54 rod bearings. This one has 100 track hours on it. Not terrible yet, but definitely would want to be replaced even if I weren't doing a rebuild.
All the rotating bits.
Not all that different form a Miata block, except for being 50% longer.
As for the rebuild itself, I'm not planning anything too fancy. The motor was just down on compression, so theoretically I might be able to get away with rings and a re-hone. Need to see what the machine shop has to say about that, but I expect it'll be an overbore, so probably some 11.6:1 Mahle forged pistons. Higher compression pistons are available (stock is 11.5), but I'd like to keep it running on 91 octane and I don't see any need to spend a bunch of extra money on 5-6 hp when I'm detuning it for ST4 rules anyway. I'm undecided on reusing the rods vs replacing them -- this motor saw 9000+ RPM a couple times when I mis-shifted it. It survived (rev limiter is 8250), but I'm a little concerned and might replace them just to be safe. The stock ports look like this so I don't see much reason to do anything beyond a basic valve job on it.
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