M5 to revert back to V8 power?
2008-07-08 10:46
M5 engine
Next M5 kitted out with twin-turbo X6 sourced V8 power? Emission regulations may leave no choice.
BMW M-car fans hardly know which configuration to swear performance allegiance to these days. The hallowed M3 straight six has been replaced by a V8, and this happened just after the M5 went completely untraditional with its V10.
With power output one-upmanship continuing unabated amongst Audi, Mercedes-Benz and BMW, rumours are abounding as to the configuration of the next generation M5 powerplant.
Upping the game
When Audi released their 5.2-litre V10 RS6 with twin-turbo power last year they usurped AMG and BMW’s M-division with an otherworldly 426kW.
Issue is though: what is the power ceiling commensurate with emission regulations from these high performance saloon engines? AMG and the M-division have steered clear of forced induction as a solution, attempting to blend a characteristic, naturally aspirated dynamic purity into their high performance saloon cars.
With emission regulations becoming ever more stringent, smaller capacity forced induction engines are the only viable alternative. BMW have shown their hand here already by returning from a nearly three decade petrol turbocharging hiatus with the cracking 3-litre twin-turbo engine.
The future is forced induction
Audi have all but scrapped the possibility of a naturally aspirated V8 for the next RS4 in favour of a 3-litre, direct injection supercharged V6. Forced induction and direct-injection petrol engines get along famously and provide a marketable blend of performance and economy.
BMW has essentially two options for the next M5. The can either bore out the existing 5-litre V10 and add two low-pressure turbo's a la 335i, or seriously open up the latent tuning potential present in the X6 sourced 4.4-litre V8 currently producing 300 kW and 600 Nm.
The latter would seem the more likely option, though many believe a 5.5-litre 410kW turbocharged V10 – with stop-start technology – could be a viable solution.
Engineering emission friendly supercar saloons
Increasing capacity of the already tremendously trick 5-litre V10 and augmenting it with forced induction would hardly be a cheap or uncomplicated engineering exercise. Any capacity increases – even only 500cc - run commensurate with consumption and emission increases too, to be avoided at all costs currently.
Therefore a high-performance version of the 4.4-litre twin-turbo is the more likely candidate for position under any next generation M5 bonnet.
Rumoured to power to about 400kW, a twin-turbo V8 unit in the 335i mould would be very driveable. It should also provide performance in surfeit to its dynamometer powerfigures – as has been the case with BMWs kitted out with the awardwinning 3-litre twin-turbo engine currently.
Brand loyalists would quickly point out the proportional power increase is much less than between the E39 5-litre V8 and E60 5-litre V10 (295kW to 373kW versus 373kW to 400kW), yet emissions regulations are also much stricter now, curbing power.
Although purists will be aghast at the idea of a forced induction M car it surely is the apt compromise between performance aspirations and emissions realities, and an infinitely preferable state of affairs than no M cars at all.
