The development of the E39 M5, a car revered for its performance and iconic V-8, involved a period of intense internal debate at BMW. Contrary to its eventual configuration, there was significant consideration within the company to power this formidable machine with an engine other than the celebrated 5.0-liter V-8. For a time, even a V-6, a radical departure from BMW's traditional straight-six philosophy, was on the table, alongside proposals for a turbocharged inline-six. This historical insight reveals the intricate decision-making process behind one of BMW M's most successful models, balancing performance aspirations with market realities and the brand's core engineering principles.
The journey to the E39 M5's final design began in 1993, with BMW exploring various powertrain options for two years. Alex Hildebrandt, the chief engineer for the E39 M5 project, highlighted the prevailing market sentiment at the time, particularly the lingering effects of the European energy crisis. There was a genuine concern about the demand for high-performance vehicles, which prompted BMW M to prioritize fuel efficiency alongside raw power. Karlheinz Kalbfell, then head of BMW M, championed the idea of highly efficient engines that would still deliver exceptional performance, leading to a complex evaluation of engine types.
During this critical period, the option of forced induction was also thoroughly examined. While turbocharging was considered, Hildebrandt noted that, at the time, this technology tended to boost power primarily at higher RPMs and increased fuel consumption, rather than providing the desired mid-range torque. This limitation steered BMW away from a turbocharged straight-six, despite the company's historical allegiance to this engine configuration. The brand's management was also hesitant to invest heavily in developing a specialized, high-cost engine for what was perceived as a niche, low-volume model, mindful of the financial struggles faced by earlier M cars that featured bespoke, race-derived powerplants.
Kalbfell, a staunch advocate for BMW's signature inline-six engines, initially resisted the idea of a V-8. He believed that the straight-six embodied the very essence of BMW and that M cars should be characterized by their high-revving nature, distinctly separating them from American muscle cars with their lower-revving V-8s. However, the constraints and the unsuitability of the six-cylinder options for the desired performance and market appeal eventually swayed the decision. The success of the US-spec E36 M3, which utilized a more production-friendly, less bespoke straight-six and retailed at a more accessible price point, demonstrated a viable path forward for the M division.
Ultimately, BMW M made a pragmatic decision, opting to modify the existing 4.4-liter M62 V-8 from the 540i. This engine was enlarged to 5.0 liters, incorporating a dry-sump lubrication system and individual throttle bodies, culminating in the S62 V-8. Although its redline was a comparatively modest 6,600 rpm, the S62 successfully met the 400 horsepower target and delivered a dynamic driving experience. Paired with an enhanced 5 Series chassis and a six-speed manual transmission, the E39 M5 became an automotive masterpiece. Its design, performance, and strategic pricing, particularly in the US market, led to unprecedented sales success, significantly more than its predecessors, firmly establishing the M brand's global presence. This pivotal choice not only ensured the E39 M5's profitability but also cemented its legacy as a benchmark in performance sedans, paving the way for BMW M's future endeavors, even as engine technologies evolve towards turbocharging and electrification, concepts once deemed almost unimaginable for the brand's core identity.