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BMW’s New Four Cylinder: a Detailed Look

What? BMW? MotoringFile is a MINI based site right? Yes and yes but today (thanks to our sister site BimmerFile) we bring you a look into the future of the MINI brand by looking at it’s corporate cousin. Earlier this year BMW released details on an entirely new family of four cylinder engines. The first up is the 2.0 N20 that will be most of the line-up within 18 months. It also signals a new where MINI is headed as well. For some time we’ve know that MINI will be moving to a three cylinder engine. What you see above will form the basis of that 1.5L 3 banger. And there may even be a chance that we’ll see a variation of the N20 in future MINI products. So to give you a head start at understanding where MINI will be heading in the years ahead, we’re going to take a deep dive in to the N20 and some of the technology at its heart.

We all know times are a changing; the age of horsepower wars and increasing performance through displacement is a closed chapter in the book of automotive history. Cheap and seemingly endless petroleum based fuels are really not so cheap these days and definitely will be approaching Mad Max like conditions sooner than many had originally thought. Greenhouse gas emissions threaten air quality and whether or not the climate is changing is a debate for another day but as a global society we are trying to get more from less in order to conserve what we do have. All of this has opened the eyes of auto manufactures and consumers, especially BMW through its Efficient Dynamics program and more recently introduced sub brand BMW i. Times have changed so drastically that the BMW brand will now be selling four cylinders in the US again, something that has not occurred since the 1990’s.

The aluminum N20 four cylinder is so advanced and such a marvel it is not even worth comparing it to the previous stateside BMW offering. The N20 will feature a single dual scroll turbo taking gasses from opposing cylinders to force feed the engine air at 10-11 PSI. It produces 240hp and 260 ft/lbs. Staggering, but possible due to a number of key components- direct injection, variable valve timing and lift (VANOS and Valvetronic). It produces a whopping 120 hp per liter! Some of the intricacies that would go unmentioned by most is what we found the most interesting.

In our discussions with Dr. Harald Unger at NYIAS, head of inline engine development in Munich, we developed an excellent feel for these new breakthroughs that make this engine look so good; at least on paper. This engine is the first from BMW that we know of that features LDS (Lichtbogendrahtspritzen) coated cylinder walls. LDS has already been used for a handful of years by other manufacturers (namely Mercedes Benz’s AMG division) with great success. LDS is also known as a twin wire arc spray process. A twin wire arc spray gun is composed of two consumable electrodes (two iron wires in BMWs case) brought toward a converging point wherein an electric arc is generated. This arc then melts the continuously advancing iron wires. An atomizing gas (inert) flowing through the arc produces a molten droplet spray jet that is directed toward the surface of the part to be coated, in this case the aluminum cylinder wall. It is basically a plasma cutter/welder that has the molten metal blown with the droplets creating a coating. What LDS permits is a thinner/lighter cylinder wall, for the N20 that is initially .4 mm which is honed down to .2mm; minuscule when compared to the typical iron sleeve. The decreased thickness allows for greater thermal transfer and consistency all while allowing extra cooling channels (part of the water jacket) between cylinder bores so the engine can been tuned “hotter” since the cooling properties are greater.

Aside from the space age coating, the engineers have tweaked the angles and balance in this engine to make it nearly as smooth at 5k rpms as the inline six it replaces. Unger explained, that NVH is as close to a six as is possible with current technologies but “it’s not possible to achieve it completely”. This is accomplished by first offsetting the crank and pistons by 14mm. The next step is to use two height staggered (but inline) balancer shafts which are located in the bottom end/oil pan to harmonically balance the engine as much as possible. The lower shaft also powers a MAP controlled oil pump- this essentially means the engine management software activates a solenoid which allows oil to be pumped through galleys. This pumping is based on engine demand (load/RPM and temperature) and is near instantaneous. To further improve smoothness the engineers used a dual mass fly wheel and centrifugal fly weights. These effectively act like those little weights on your car’s wheels, balancing rotation but unlike the wheel weights these are independently adjustable (really great stuff in our opinion).

With a flat torque curve and quicker 0-60 times, customers will feel the car as faster all while consuming 20% less dead dinosaur. Which in these days of $4.50+ premium is not a bad thing for the wallet or the planet. According to Dr. Unger, the 6 speed manual will see almost identical fuel economy numbers as the automatic. This is thanks to changes in gearing which were permitted because of the flat torque curve and quick revving nature of this engine.

So you have read this far and are concerned that we have not mentioned weight; How much does lopping off a few magnesium cylinders save you as compared the six cylinder the N20 is replacing? A 22 pound loss is netted and that is nothing to sneeze at considering a dual scroll turbo, Valvetronic and some plumbing was added.

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We look forward to testing the N20 engine as soon as we get the opportunity to as it sounds like a sweetheart of an engine and will form the basis of the majority of BMWs future offerings. It will even spawn an ///M version if sources are to be believed.

Our future review will come from behind the wheel of a roadster, the Z4 sDrive28i and not the as planned X1. The X1 was to launch in NY but thanks to the world markets consuming more than BMW can currently produce a US launch has been pushed back indefinitely- the X1 is coming just there is no set timeline currently but the four cylinder engine will be here and will be the base engine in new models for years to come.

And what about MINI? Expect similar technology packed in that 1.5L 3 cylinder design that we spoke about earlier. Power will range from approximately 122 hp on in the Cooper and 180 hp in the Cooper S. Yes that means MINI will have lighter engines with less cylinder making the same if not more horsepower. And efficiency? Expect upper 40s on the highway for the US cycle. Not a bad change in our book.

Source: R. Bolot, H. Liao, C. Mateus, C. Coddet et al. (unknown). Optimization of a Rotating Twin Wire-Arc Spray Gun. Unpublished White Paper

Written By: Gabe

  • Anonymous

    This has gotta go in a MINI!

  • Anonymous

    This has gotta go in a MINI!

  • Cze33r

    Sounds great, I’m looking forward to the new 3 cylinder MINI engines

  • b-

    So can we guess that a variation of this will be in future JCW cars while the rest of the field gets the 3 cylinder? That would be cool!

  • http://about.me/bentyyc Ben Tsui

    While I have some mental hang-up with it being a 3-cylinder, the rest of the info here is in the “what’s not to like” section of my brain.

    Bring it on!!

    • http://zadl.org ZADL

      I feel pretty much the same way. Less cylinders = moar bettar?

      But on the other hand, if there’s the same power range and less fuel being used, then why the heck not?

      • cct1

        Well, one potential issue of three cylinders doing the work of four is long-term wear and tear and reliability. Time will tell if this is an issue or not.

        It’s not a new arguement, it’s been brought up as a concern over the years on cars that go from 8 to 6, and from 6 to 4 cylinders, and so far the drop in cylinders has held up well, and hopefully will on these.

        I just wonder how far off are we from 2-cycle engines…:)

  • http://about.me/bentyyc Ben Tsui

    While I have some mental hang-up with it being a 3-cylinder, the rest of the info here is in the “what’s not to like” section of my brain.

    Bring it on!!

  • http://www.jwardell.com/ jwardell

    I’m thrilled BMW is finally offering some smaller engine options to the US, but I still wish they were smaller-displacement inline-6’s.

  • phlip

    “It produces a whopping 120 hp per liter!” That is pretty much the same HP/L that we’re already running in our 1.6L engines. Love the 3 cylinders, but…

    • JP

      “It produces a whopping 120 hp per liter!” Honda S2000s were making 120hp per liter a decade ago. Of course the N20 has more torque/usuable power, but that’s what a turbo will give you. Just sayin’ that 120hp/l is not the miraculous feat the author makes it out to be.

  • Jon

    Let’s hope that the next generation MINI will have room in the engine bay for this engine. MINI engineers: get your shoe-horns and pry-bars out!

  • Slap

    I don’t care for the idea that the oil lubrication is controlled by the engine software – if the solenoid goes bad, etc, the engine is toast.

    Hopefully, the next gen Mini will be at least 200 lbs lighter than the current due to the lighter engine, use of high strength steels, etc. But to get in the upper 40s? I just don’t see this engine being that much more fuel efficient – the S is already using variable valve timing and direct injection. Going to 3 cylinders will help, but they must be planning a big drop in weight to get it to the upper 40s on the highway.

    • faster,Tobias!

      The current engine in the R56 already has an oil pump that is controlled by software.

    • faster,Tobias!

      The current engine in the R56 already has an oil pump that is controlled by software.

    • Ggcadc

      If it fails, it would fail to an open state, these arent chrystler engineers from the 80s… cmon.

  • RC

    Drop the N20 into a Mini and ship it to me. Schnell!

  • CraigE

    The expected fuel economy numbers for the next generation MINI are definitely fantastic. Should we really expect a 10+mpg increase in the EPA highway number?

    Also, am I the only one who thought of the scene in Star Trek IV, when Kirk explains Spock’s strange behavior by saying he used too much “LDS” in college?

    • Harry Dill

      … he used too much “LDS” in college? Unless he was a Mormon at BYU it is a safe bet to conclude that he had little use for “LSD.”

    • Harry Dill

      … he used too much “LDS” in college? Unless he was a Mormon at BYU it is a safe bet to conclude that he had little use for “LSD.”

  • Benzz

    N20 = powerplant for JCW Countryman? I’d be on board with that.

  • Harry Dill

    Fantastic engine just waiting to occupy the space beneath the bonnet of MINI 2012.

  • http://twitter.com/thejasonknight Jason Knight

    Will the LDS coating wear down over time, or does it last more or less indefinitely?

  • Gbluheron

    Maybe I missed it… but how soon is this engine expected to hit the MINI? 2013….2015….2020?


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