WITH TURBO FOUR-CYLINDERS replacing free-breathing V8s in Germanís premier touring car series this year, BMW, like most car makers with a deep regard for its past, has been keen to link the new engine to that of the old. In this case, thatís the first of its turbocharged race engines, the M121 which powered Dieter Quester to the 1969 European Touring Car Championship while slung between the chassis rails of a 2002 Ti. Thing is, while the brand is keen to suggest lots and lots of heritage - and the two engines do have a fair bit in common - thereís also half a century of tech development poking its nose in, too.
So what remains of the M121 when it comes to the new P48 that will be seen in this yearís M4 DTM car? Fundamentally, the connection between the two engines amounts to the inlinefour cylinder arrangement, the use of turbocharging, alloy construction and the two-litre capacity. Beyond that, the game has really changed.
While the M121 was limited to about one bar of boost to avoid blowing the head into orbit, the new P48 has no such problem and can reportedly handle sustained boost of about 2.5 bar.
Which means that, compared with the 210kW at 6500rpm of the old girl, the new 2.0-litre manages something like 450kW at a thought-provoking 9500rpm. It should sound amazing.
Thereís also word of a 5.0-second, 22kW push-to-pass function that should help cure boring races. Besides the extra boost, the power gains are all down to efficiency. The new engine has throttle-by-wire, a dry-sump, intercooler and direct injection using a mechanical pump to create fuel-rail pressures of something like 350 bar which, surprisingly, is no higher than a contemporary BMW road car, yet is still about on par with the pressure created by the best industrial pressure-cleaners.
Lightness is another key point and at 85kg, the new engine is super-light. Mind you, that has involved moving stuff like the starter-motor and alternator to the rear-mounted transaxle (which has improved weight distribution).
Itís been said a million times but finishing first involves finishing, so reliability is a key factor in the P48ís design. Apparently, the unit is good for 6000km of racing, meaning each car should only need one engine change per DTM season. Weíll see about that.