Actually Alpina went the turbo charger route and did a bi-turbo set up on our E34 (albiet not on the S38 engine) to make their version of an M5. Is it more reliable than our S38? That I have no idea on but it does perform as well or better than the S38 engine 3.6 or 3.8 version.
M5 is not good for turbo , it is high CR bla bla bla
Here are 3 new turboed S38 - I know 3-4 more and this winter 4-5 will be ready - S38 is perfect engine
Yes, but they did exactly what was necessary to do it properly, they dropped the compression ratio! That is what you need to do, which on an engine like a highly stresed, highly tuned, high compression S38 engine is the opposite of what it's about!
This is why there are so few about. What's the point? Why not do it to a cheaper engine with more gains to be had? If you want bangs for your buck, nitrous an early 540i!!
Alpina did a stunning job on the E34 B10 BiTurbo
New forged Mahle pistons to get the ALL CONQUERING REDUCED COMPRESSION RATIO </rant> of 7.2:1, uprated con-rods, completely revised cams, new valves, all the engine management remapping that little lot involved. They also custom built a system drilling holes so oil could be sprayed on the underside of the pistons for more cooling. Did I mention the compression ratio came down?
Add in the cooling intakes and the stainless steel exhausts, intake and water coolers, new Motronic, to handle the lowered compression ratio, new intake manifold and you can see why a £30,000 535i suddenly became way over twice that! Even the throttle bodies are the opposite side to my humble 535i so there doesn't have to be a pipe going over the top of the engine. Oh, lets add diff-oil cooling systems, lowered compression ratio, revised bodykit, lowered compression ratio, bigger fuel tank, lowered compression ratio, new LSD diff, lowered compression ratio, uprated axle, lowered compression ratio, all the interior trim, lowered compression ratio, new suspension, lowered compression ratio, the wooden Alpina bits too... plus other stuff I can't recall!!
Also, if my memory recalls correctly, they may have made the pistons squash the air a little bit less than before, but I'm not sure of the technical term for it, although I understand it's quite important if you're gonna add a turbo...
You can go fast in a S38, but it's a law of diminishing returns. Kamikadze has already put a S38 into a 3 series, taking loads of weight off, so if he really wants to go much faster, he ought to buy Vidar Strand a Sunseeker and ask him what black magic he worked on that mad mad mad 1000bhp M5, although if you take one look at the engines layout... well... better make it two boats!
Anyhoo. Flame suit on, I'm going down the pub!
Ivan