BMW Chassis Codes & Engine Codes

Epilogue

A few bits of BMW trivia, facts, and figures (to keep you on the page).

1. Everyone believes the BMW roundel emblem is a "whirling propeller". That idea came from BMW advertising in the late 1920s. The emblem predates that advertising campaign and actually represents the official colors of Munich.

2. You might think that the last two numerals in a BMW model represent its engine size. And in the past you might be correct. But since the late 1990s the badge represents the power class. BMW has had a long tradition of bumping up the displacement for turbocharged models. And now that every BMW engine is a turbo the naming logic continues. Examples:
- E23 745i uses a turbocharged 3.2-liter engine (M102/M106). The logic dictates that the new turbocharged engine output equals a larger, 4.5-liter engine.
- E46 323i uses a naturally-aspirated 2.5-liter 6-cylinder engine (M52TU). But it's 169hp keeps it to a "23i" classification. Note the later E46 325i also uses a 2.5-liter but with 184hp.
- E90 325i/328i/330i models all use a naturally-aspirated 3.0-liter 6-cylinder engine (N52) but because they all had different power outputs they received different model names. 25i = 215hp, 28i = 231hp, 30i = 255hp.
- E90 335i uses a twin-turbocharged 3.0-liter engine (N54/N55) that, theoretically, puts out the same horsepower as a 3.5-liter engine.
- F44 M235i uses a turbocharged 2.0-liter 4-cylinder engine, yet carries a "35i" badge. There are two things at play here: one is that it's part of the M Sport line of cars, so it's a high-performance model. Two, is that its B48 engine puts out 300+ hp, which puts it into the "35i" power class.
- G20 M340i is not a 4.0-liter but it's 3.0-liter single-turbo engine has the same theoretical output that a 4.0-liter would (382hp).

3. The S70 engine used in the McLaren F1 is not the same engine as used in the E31 850CSi or M8 prototype. This is confusion and misunderstanding of BMW's engine codes (and a fuzzy timeline of model history). As explained at the top of this page, S is the prefix for a BMW M Gmbh engine, developed by M engineers (Paul Rosche). “7” is the code for a V12. “0” identifies the development phase of the engine (0-9). By code alone all engines in the F1, F1 GTR, 850CSi, and M8 are "S70" engines but they are not the same engine. BMW could have done a better job at naming the engines, S70, S71, S73, S74, etc. They did try to distinguish them with S70/2 and S70/3 designations but the suffix is easily dropped, leading to confusion.

The F1 and E31 M8 engines are very close - step-brothers perhaps. The timelines align very closely and they have much in common. We haven't been able to confirm all of the specs but we believe the M8 has: 6.0-liter displacement, 24-valve heads per side, coil-on-plug ignition, individual throttle bodies, and a dry-sump oil system. But Gordon Murray and McLaren determined that the M8 engine was too large and heavy. Ever the innovator, Rosche said, “We'll do a new engine.” At the time, Rosche already had the E36's Euro S50 engine under development. The S50B30 engine shared many impressive technical features, and added VANOS variable valve timing. The visual similarities between the S50 and S70/2 are obvious. The S70/2 looks very much like two S50s siamesed together. The M8 S70/1 is very different, especially when you study the available engine details in the limited photos available. Most notably, the valve cover and front of the engine are very different. The M8 engine does not appear to have any VANOs system at all. The original genesis of the M8 V12 was to take the existing M70 “as far as it could go” so we would expect it to retain some basic M70 architecture.

Much of this exotic technology is absent on the 850CSi engine. It also lacks VANOS and does not have individual throttle bodies or a dry-sump oil system (probably for good reasons). This doesn't make the CSi engine any less of an ///M product. It was built by M engineers and produced by BMW M and in company literature it carries the the distinction as the first “S70” engine code (although the timeline of the M8 is unknown). The 850CSi remains a powerful halo model for the E31 line.

The M8 engine is not the same as used in the F1 but came very close. Some of its technology and ideas migrated to the McLaren customer program and then found their way into the Euro S50 (which then became the S54). The M8 has become an important, but misunderstood, stepping stone in the development of the F1 and other Motorsport engines. While the F1 has became the most-famous member of the S70 family and it's DNA came from the very best of BMW's engineering talent. Tips of the hat to Hagerty Insurance, BMWBlog, Peloton25, Jay Leno, and the McLaren F1 Driving Ambition book for the extensive background and inside knowledge.