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Discussion Starter #1
Looking at the magazines from way back, it seems like the plain spec, lighter Euro M535i cars (e12 & e28) sans impact bumpers, seem to have very similar performance figures to the North American S38 e28 M5.

For the Euro models 7 seconds flat, and 140-145 mph. US magazines seem to have drivers that get better 0-60 mph times for the same cars, so it seems to work out pretty even.

Similarly I think Motor Trend got 0-60 mph in 7 seconds for their M6 and I believe 7 seconds and 140 mph was what a Euro 635CSi with 218 bhp was good for.

Seems like the extra luxury equipment, impact bumpers and smog controls makes it even. I have heard the old formula that it takes an extra 15 hp for every extra 100lbs of weight.:nerd
 

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Looking at the magazines from way back, it seems like the plain spec, lighter Euro M535i cars (e12 & e28) sans impact bumpers, seem to have very similar performance figures to the North American S38 e28 M5.

For the Euro models 7 seconds flat, and 140-145 mph. US magazines seem to have drivers that get better 0-60 mph times for the same cars, so it seems to work out pretty even.

Similarly I think Motor Trend got 0-60 mph in 7 seconds for their M6 and I believe 7 seconds and 140 mph was what a Euro 635CSi with 218 bhp was good for.

Seems like the extra luxury equipment, impact bumpers and smog controls makes it even. I have heard the old formula that it takes an extra 15 hp for every extra 100lbs of weight.:nerd
Yeah, the NA E28 M5 is handicapped on low end acceleration, but of course has the hp to pass the E12 M535i once the speeds get higher. An easy way to drop some weight is to remove the SLS, the accumulators are heavy. Likewise, get rid of the stock bumper "shock absorbers" and replace with some aluminum tubing . . . not too difficult to fab up the flanges etc. Those two mods take an afternoon and if you are anal about originality, you can remove the items without destroying anything so they can sit and take up space on your shelves.

While the S38B35 is down 30 hp from the M88/3, it has a duplex timing chain which is a bonus. But then it is a good idea to get the Frank Fahey crank hub, which I dont recall the weight difference between that and the stock hub. Likewise installing M88/3 headers and a Dinan chip will provide a small bump in hp, while its small, it helps. I know people get more power with the Miller WAR system, I prefer standalone which not only helps with a small bump in power, it also increases fuel efficiency.

A lightweight flywheel such as the JB Racing unit is another area where weight can be dropped. I have one installed, drivability remains good, I dont have issues in grid lock. I know the billy boat exhaust is lighter than the stock unit and dropping the cats is helpful, but I still have cats on as I have to pass annual Colorado emissions :mad:

The extended leather is heavy, but it does look really good. Ive done nothing aside from installing an aftermarket head unit that is only FM/AM USB and Bluetooth, tape deck is deleted. Maybe a 1lb savings? Lol.

Its a fun car to drive, but an extra 30 hp would be huge. Something like a S38B36 could fit that bill. The altitude here is a killer, driving through the mountains on I-70 (doing the speed limit of course) is night and day when comparing the E34 and E28 M5.
 

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I just went and had a look at the Motor Trend M6 test, 6.96 secs 0-60 mph and 1/4 mile 15.45. Pretty similar to a Euro 635CSi, but that Euro didn't have dual a/c, full leather and what not. It's nice to have all the power gadgets and trim, but you start to think about the weight of all the electric motors and those impact bumpers. Mind you, as Rob Siegel (Hack Mechanic) has said, even imported Euro gray market cars had to get some smog tuning, so aren't as spry as they are in full Euro form, without any pollution controls.

S38B36 would be a killer drop in swap, and emissions legal. As you said there are things that can be done to drop some weight, and performance mods, depending on local smog test laws. I honestly don't think a Euro bumper conversion would lower the value of a s38 car. Unlike muscle cars I think you can make some changes and even raise the value.

I think back in 1996 BMW Car magazine covered the story of a s38 M6 owner that had BMW connections. He told BMW he found the M6's performance a little less than he expected, so they rebuilt his motor to 325 bhp. Car still had impact bumpers, and dual a/c. A triple black New York registered car if memory serves. I don't know how he got around smog legality. Even a 260 hp Alpina B10 M30 won't pass.
 

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I just went and had a look at the Motor Trend M6 test, 6.96 secs 0-60 mph and 1/4 mile 15.45. Pretty similar to a Euro 635CSi, but that Euro didn't have dual a/c, full leather and what not. It's nice to have all the power gadgets and trim, but you start to think about the weight of all the electric motors and those impact bumpers. Mind you, as Rob Siegel (Hack Mechanic) has said, even imported Euro gray market cars had to get some smog tuning, so aren't as spry as they are in full Euro form, without any pollution controls.

S38B36 would be a killer drop in swap, and emissions legal. As you said there are things that can be done to drop some weight, and performance mods, depending on local smog test laws. I honestly don't think a Euro bumper conversion would lower the value of a s38 car. Unlike muscle cars I think you can make some changes and even raise the value.

I think back in 1996 BMW Car magazine covered the story of a s38 M6 owner that had BMW connections. He told BMW he found the M6's performance a little less than he expected, so they rebuilt his motor to 325 bhp. Car still had impact bumpers, and dual a/c. A triple black New York registered car if memory serves. I don't know how he got around smog legality. Even a 260 hp Alpina B10 M30 won't pass.
I think the market is reaching a point where having a completely stock NA example with the diving board bumpers will fetch a higher value than one with the euro bumpers. That whole "numbers matching" stuff.

I know Nelson Piquet's M635CSi was hot rodded by M, but that was a M88/3. S38B36 is the most clear route for a huge bump in power, even more if you go with B38 cam gears and DME tuning. Of course you can take the B35 to Dinan, Fahey, or Rowe and have them punch it out to 3.9l and achieve some good numbers, but Im a bit more on the conservative side and would go with the 3.7l displacement. Plenty of power, drivability, and longevity. Though I do see a few B36 cores that come up for sale which would be such a quick swap with some fabrication for mounts.
 

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Yes, I am weary of those 3.9L engines. I remember reading that in IMSA with the Batmobile the bore was 94mm and BMW X rayed specially selected blocks to see if there was enough material left. The production M90, S38B35 and M88 are on 93.4mm with siamesed bores so that's enough. If you go for more stroke, I know the 3.8 M5 motor had 90mm the e3 3.3L 88.4mm, apart from durability it probably won't rev that well. Recently in a magazine there was an e34 M5 3.8 at the dealer Munich Legends and its engine rocked at idle. The technicisns said the 3.8L was really on the limit. BMW went beyond 3.5L because the e34 was a bigger car and they needed the torque. As it was, the e34 M5 3.6 was no faster than the e28 M5.
 
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