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While most enthusiasts have cried out in anger with the recent news that the ///M division has gone the forced induction road; the news may not be all that bad. The BMW ///M motors of the past have always been fairly low in displacement, peaky in horsepower and torque, but loving to rev to sky high red lines. The newest rendition from the ///M camp is a bit different from those engines; it was intentionally designed to be different and change the playing field. It is capable of producing more torque and more horsepower with less displacement and greater efficiency than the motors of the past.
The recently announced X5 & X6 ///M models have been chosen to usher in this new era of high performance BMW engines. With virtually the same block as the revolutionary N63 4.4l reverse flow V8 as in the 750i and X6 xDrive50i, this ///M motor features significant revisions in nearly every other aspect. The internal components have been upgraded along with the newly engineered cylinder heads (diesel standards for strength) to deal with the high compression ratio and increased forced induction. The dual twin scroll turbos put out an astonishing 21 lbs of max boost. Two high-capacity water-to-air intercoolers help cool the incoming combustion air before it is shot with precise amounts of fuel by another ///M first: Direct Injection. BMW has not offered Direct Injection on any naturally aspirated (non-turbo) motor in the US due to the sulfur content of US fuel and they do not plan on offering it on them in the future (as we have been told). So all of you on the fence about buying an ///M3 and fearing direct injection will be offered, can rest a little easier.
Turbo charging has come a long way in the past few years as many a BMW 335 (N54 I6 twin turbo) owner will tell you, but another significant improvement will debut on this motor. The Cylinder-bank Comprehensive Manifold (CCM) is a BMW patented exhaust manifold that separates this motor (and future variants) from the competition. The CCM solves the problem of an irregular schedule of exhaust gas pulses on the turbines. An irregular schedule of pulses causes lag and back pressure in typical turbo charging applications.
The CCM creates an exhaust gas pulse at every 90 degrees of crank rotation on one of the turbo scrolls, keeping the supply of exhaust gas regular and consistent. How this achieved is visible in our exclusive diagrams of the inner working of the CCM and twin scroll turbos from BMW ///M.
Complimentary cylinders are paired through the manifold’s pipes, which have been tuned for diameter and length, 1 + 6, 2 + 8, 3 + 5, and 4 + 7.
These pipes (each highlighted by a certain color in the diagrams) combine to feed one of 4 exhaust gas intakes on the 2 twin scroll turbos.
With the twin scroll setup there are two separate paths to each turbo, with each targeting its own set of vanes. The use of twin scroll chargers allows for the maximum capture of exhaust gas flow currently possible, thus increasing the turbos overall efficiency while keeping it spooled up. The concept of the CCM would be extremely cumbersome and inefficient without the development of the reverse flow V8, the development of one allowed for the other.
This complex network of pipes and turbos is entirely contained within the “V” of the engine, allowing for an engine with relatively small dimensions. Some of you are probably thinking that all of that exhaust piping and turbos within such a close proximity to engine block can not be good on a thermal level; BMW has designed the engine with that in mind and there are auxiliary cooling systems in place if the need should arise for them. It is not a general concern.
What all of this plumbing and forced induction produces is 555 hp at 6,000 rpm and 500 lb-ft of torque from 1500 to 5,650 rpm with reportedly no perceivable lag. The onboard engine control unit software has been programmed/tuned for this application in the SAVs and the specific driving needs of them, as is evidenced by the huge flat spot in the torque curve. It can be adjusted/tuned as is necessary in future applications and variations. What that means to us enthusiasts is that this engine is highly flexible and we may not yet be seeing its true capabilities. The true redline (not software induced) of this motor setup has yet to be disclosed by ///M at this time. With this motor as the basis of other future high performance ///M offerings we are fairly sure that there is some excess capacity to increase the performance on other models…
We have been told that many of the features of this motor will trickle down across the model line. We can expect to see the use of twin scroll turbos and future applications of a form of CCM in other models sooner than one would think. The current 1.6l John Cooper Works MINI (and MCS) engine is the only other BMW Group gasoline product currently using twin scroll turbos; a shift from variable vane is coming. With all of this turbo jargon we will be creating a guide to the terms and compare and contrast them as soon as we can!
While this engine is not a typical high-rev ///M offering, the shift to turbo charging was needed to increase efficiency and performance. On paper, it looks like a success and we will give you our final verdict once we can log some miles with it!
As always we would love to hear your opinion; feel free to comment on this motor and BMW heading down the road of high performance forced induction as a whole!