BMW really wanted a six-cylinder engine for the E39 M5. This, on its face, was not unusual; the E28 and E34 M5s both had straight-six power, but as we all know, the E39 M5 ended up with a 5.0-liter V-8. It took a while for BMW to get there, though, and the company even considered something unthinkable—a V-6.
BMW Blog brought our attention to this story from BMW North America about the development of the E39 M5. In it, Alex Hildebrandt, the E39 M5’s chief engineer, revealed that before settling on a V-8, BMW M mooted a V-6, a straight-six, and even turbocharging for the third-generation M5.
“We were at the end of the energy crisis in Europe, and there was some doubt about whether this kind of car would find further demand on the market,” Hildebrandt said of the M5. “[Karlheinz Kalbfell, then leader of BMW M] was eager to play this card of fuel efficiency, which didn’t mean we wouldn’t have powerful engines, but that the efficiency of the engines should be outstanding in comparison to the power. There was no way to come to that with a V-8, because in the end, eight cylinders have to be fed. We had a lot of discussions about turbocharging, but at the time, turbocharging mainly added fuel consumption and power at the upper end of the rev range, rather than torque in the middle.”
Photo by: BMW
BMW started working on the E39 M5 back in 1993, and Hildebrandt said the company spent two years considering a bespoke engine for the car. BMW didn’t reveal any details on either the turbocharged straight-six or V-6, so we don’t know how far along the idea got. Other automakers were abandoning their straight-sixes for V-6s in the 1990s, but BMW steadfastly remained in favor of keeping its six cylinders in a row.
Kalbfell apparently didn’t like the idea of a V-8, though. He believed that the straight-six was BMW’s heart and soul, and he also felt that M cars should have high-revving engines. An M5 shouldn’t be a muscle car with a lazy V-8.
But, the six-cylinder idea just wasn’t working. BMW wasn’t satisfied with turbocharging, and management didn’t want to spend big developing a complicated, bespoke engine for a low-volume car. BMW’s first M cars were hugely expensive sales disasters, in large part because of their race-derived engines that pushed MSRPs far beyond their non-M counterparts. Meanwhile, the US-spec E36 M3 with its more pedestrian, production-based straight-six and reasonable base price was selling in huge numbers, setting a template of success for M cars to come.
Photo by: BMW
After years of dilly-dallying, BMW M finally bit the bullet. It took the 4.4-liter M62 V-8 in the 540i, enlarged it to 5.0 liters, fit a dry-sump oiling system, and individual throttle bodies. The S62 V-8 for the M5 revved to “just” 6,600 rpm, but it reached the target of 400 horsepower. No one really cared about the low redline, and in practice, the S62 was anything but lazy. With that kind of power allied to an upgraded version of the already excellent 5 Series chassis, and a six-speed manual gearbox, the BMW M executed a fine recipe to perfection with the E39 M5.
BMW ended up selling 20,482 examples of the E39 M5. Not a ton of cars in the big scheme of things, but way more than either of its predecessors. And with a price of just under $70,000 in the US, the E39 M5 was a huge hit in America, with about half of total production reaching the states. BMW sold around three times as many E39 M5s here as it did E28s and E34s combined.
“Without the V-8, we wouldn’t have had a chance to get the US on board,” Hildebrandt said, “and without US volumes the project wouldn’t have been profitable at all.”
The BMW M brand is well-established now, thanks in huge part to the E39 M5. BMW M got to return to its high-revving ways in the 2000s with the V-10-powered E60 M5 and E63/E64 M6 and the V-8-powered E90/E92/E93 M3, but those days are over. The competing needs of more power with better economy and emissions forced M to embrace turbocharging, and now, electrification.
All perhaps unthinkable just a few years ago. But not as unthinkable as a BMW V-6.
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