BMW 850 CSI manual (Japanese Auction)

[Michael. 2313]

Quite hard to pin point which manufacture started it. Seems various makers were doing it by the late 80s

The difference is however, which ones were a passive and active system as that makes all the difference to the resulting performance.

Mine works with the TRC system so if slip is detected, and the yaw sensor picks up motion it articulates the rear wheels to keep the car straighter, particularly for when taking off on wet roads.

[M3AN 4016]

My 1989 VR-4 (4G63 ftw) had it, it was available since 1988 on that platform.

Mitsubishi eventually replaced it with a tricky centre diff (AYC - Active Yaw Control) and that was way, way, way, way better.

[Michael. 2313]

The silly thing with dynamic control systems & tricky diffs is they can't do in phase or out of phase rear steering, tight cornering and lane changes are always going to be practically possible with 4ws.

It's interesting to find some new cars for 201X have returned to having an electric 4ws for such reasons.

[bmwwgn 14]

The AHK rear wheel steering system on the 850CSi only worked above approx. 60 km/h, turning the rear wheels in the same direction as the fronts, up to a maximum 2.5 degrees depending on the amount of steering input.

I could certainly feel it working in my CSi on a few occasions but, as previously mentioned, it really came into good effect when manoeuvering at speed on the European motorways and fast winding roads, which the car was designed for.

[KwS 2425]

most nissan muppets ripped it out of their cars because they didnt understand it, and it caused them to overcook it when dirfting. I actually really likes how it felt to drive my R33s with the hicas (R33 onwards is all electronic, anything older is a hydraulic rack).

[Jacko 2154]

Damnit, someone give me $100k to play with.

Wasnt that engine the basis of the mclaren f1s powerplant?

[M3AN 4016]

Damnit, someone give me $100k to play with.

Wasnt that engine the basis of the mclaren f1s powerplant?

The S50 was the basis of the McLaren F1, they soldered two together I think (may have also used duct tape).

[jeffbebe 1559]

Pretty sure Jacko is right otherwise why call the F1 powerplant an S70/2?

[BreakMyWindow 1874]

Tough call to say it's based on either. The s70/2 is v12 but also Dohc with itb's. I'd say based on both.

[Michael. 2313]

Those F1 V12s must also have a different crank / firing arrangement as they sound pretty hot compared to the standard V12

[bmwwgn 14]

The S70 V12 was a BMW M-fettled version of the M70 - which I've always likened to 2x M30's bolted together (some sources say M20, but the V12's cams were chain driven, like the M30).

Anyway, here's a good summary of the S70B56 engine, which was only used in the 850CSi (courtesy BMW M-Registry):

"How is the S70 engine different from the M70 V12 upon which it is based?

When creating the 850CSi's S70 V12 motor, BMW Motorsport began with the standard 24-valve SOHC M70 engine and instituted the following changes:

-Increased bore (from 84mm to 86mm) and stroke (from 75mm to 80mm) for a new total displacement of 5,576cc (from 4,988cc)
-Lighter pistons

-Increased compression (from 8.8:1 to 9.8:1)

-More aggressive valve timing for increased high-rpm power
-Larger diameter exhaust pipes
-Variable rpm limit (6,400 in 1st+2nd, 6,200 in 3rd, 6,100 in 4th. 6,000 in 5th+6th)
-Adjustable throttle sensitivity via dual mode (Sport or Komfort) console-mounted switch
-Engine oil cooler (European-spec models only)

These modifications resulted in an increase in maximum power from 300 hp (DIN) or 296 hp (SAE) at 5,200 rpm to 380 hp (DIN) or 372 hp (SAE) at 5,300 rpm. In addition, maximum torque was increased from 332 lb/ft at 4,100 rpm to 402 lb/ft at 4,000 rpm.

This engine can be identified by the "Powered by M" inscription on the central cam cover between the two banks of cylinders."

The 627 hp S70/2 used in the McLaren F1 was a 48-valve derivative of the same engine, but heavily modified, with alloy block and 4-valve heads.

It had an 11:1 compression ratio, ran a dry sump oil system, and also had VANOS.

[Michael. 2313]

Oh wow 8.8:1 from a 90s performance engine... no wonder they were a bit low on the performance figures!

If it was an American V12 I could forgive them but thats quite surprising for a German product.

Most engines of a sporting nature by the early 90s were pushing high 9s or early 10s, if not higher.

[bmwwgn 14]

Oh wow 8.8:1 from a 90s performance engine... no wonder they were a bit low on the performance figures!

If it was an American V12 I could forgive them but thats quite surprising for a German product.

Most engines of a sporting nature by the early 90s were pushing high 9s or early 10s, if not higher.

Yep, the CSi definitely benefitted from the 9.8:1 compression of the S70.

The lower compression M70 was more of a lazy twelve.

[bmwwgn 14]

Rare (I think?) Color too. Nice.

According to 8coupe.com, there were only 43 850CSi's produced in Barbadosgrun Metallic (247).

Of the 160 RHD CSi's built, only two were ordered in this colour (it was a 'BMW Individual' order option).

[Michael. 2313]

I loved the 90s BMW individual options, they were quite cool, although some colours were a bit questionable!

[M3AN 4016]

Interesting, good to be corrected on that because I've believed it for a long time! Seems like an internet myth but repeated less frequently now than back in the day.

[nath 134]

Completely hideous interior