BMW Introduces \’TwinPower\’ Four Cylinder Engine Destined for US Market

Today BMW took the wraps off of the next generation of four cylinder engines today with the launch of the X1 28i. But don ‘t let the model launch fool you. Today is about this new N20 245 hp four cylinder turbo which will find it ‘s way into almost every BMW model range (up to the 5 Series) in the years ahead. But the best part? It ‘s coming to the US.

BMW TwinPower Turbo technology gives the new four-cylinder engine the sort of power which naturally aspirated engines can only achieve through more cylinders and substantially larger displacement. The four-cylinder engine with its all-aluminium crankcase (including a motor sport-derived bedplate) is lighter and more compact than a six-cylinder engine of equivalent power. It ‘s also much more fuel efficient. But more on that in a minute.

First lets talk about the weight. Reducing the weight of engines is paramount to BMW ‘s lighter weight strategy for future products. And the most important place for weight reduction dynamically speaking (except for the roof) is over the front axle. Reducing front axle load increases agility and turn-in. It ‘s one of those core characteristics that gives many BMW ‘s that feel we all love. (Full specifications after the break)

The new engine offers more torque than previous four cylinder engines. The engine ‘s 350 Newton metres of torque (258 ft lbs) comes on at just 1,250 rpm giving the engine exceptional low-end response. This power delivery (only slightly above idling) will likely be one of the defining characteristics of this engine. But like naturally aspirated engines of the past the new 2.0 four cylinder also revs quickly all the way to the upper load range. The result is a sprint from 0-62 mph in an official 6.1 second. Knowing how conservative BMW can be with acceleration numbers you can imagine 0-60 times in the mid 5s aren ‘t entirely out of the equation. Top speed on the X1 28i is 149 mph but in other lighter applications (read the F20 1er or F30 3er) you can expect even more.

The turbocharger is a twin-scroll system similar to the N55 and the Prince engine on the MINI Cooper S. The exhaust streams leaving the two pairs of cylinders are kept completely separate as they flow through the exhaust manifold and the turbocharger, taking a spiral path to the turbine wheel. This configuration results in very low exhaust back pressure at low engine rpm, and allows the energy of the exhaust gas pulses to be optimally managed and translated into powerful rotation of the turbine blades, without a response delay. The result is instant throttle reaction and typical BMW fast-revving performance. Compare this to a tradition turbo and the difference would be immediately obvious. Power as soon as you put your foot down with no lag.

In total it means more dynamic performance plus reduced emissions, thanks to VALVETRONIC, double-VANOS and direct injection. The fully cylinder head-integrated VALVETRONIC variable valve control system, and the double-VANOS variable intake and exhaust camshaft timing, have a further positive impact on power development.

The engine features assembled intake and exhaust camshafts and a latest-generation VALVETRONIC system which is even faster-acting thanks to an optimised stepper motor with integrated sensor.

The patented BMW VALVETRONIC system with seamlessly variable intake valve lift control dispenses with the throttle valve system typical of earlier engine generations. Instead, combustion air mass is controlled inside the engine, resulting in much faster response. Pumping losses are kept to a minimum, so making the engine more efficient.

The new engine’s unusually high efficiency, for a turbocharged unit, is also down to the High Precision Injection petrol direct-injection system. Centrally positioned between the valves, solenoid injectors with a maximum injection pressure of 200 bar precisely control the supply of fuel. The fuel is injected very close to the spark plug, resulting in clean and homogeneous combustion. The cooling effect of the injected fuel also results in a higher compression ratio than on turbocharged naturally aspirated engines. This results in further efficiency improvements.

It doesn ‘t take long for one to realize how closely related this new four cylinder is to the award winning N55 inline six already offered across the BMW line-up.

BMW isn ‘t the only manufacturer with a twinscroll four cylinder with loads of power. Hyundai (of all brands) leads the way with a 272 hp two liter twin scroll turbo. The engine produces 269 ft lbs of torque yet still gets 34 mpg on the highway. So while we are excited to see this new engine the pressure will be on to quickly iterate on this new 2.0L in the years ahead.

But numbers aside we know that this engine will be free-revving and ‘BMW like ‘ in it ‘s operations. And perhaps the best part is that many of the entry level models we love will lose two cylinders yet gains at least 15 horsepower. What about efficiency? In UK the all wheel drive X1 28i gets 35.7 mpg. In the US that would be roughly equivalent to 31 mpg – a full 16% improvement over the previous X1 28i with the N52. You can imagine how that would improve even further with a two wheel drive application.

Based on rumors don ‘t be surprised to see the Z4 28i get this new four cylinder for the 2012 model year. Following that it would make sense for the 5 Series and ultimately the X1 to also receive this engine for the US market (and others). What about the current 3er? With the E90 on it ‘s way out after 2012 we doubt BMW will go through the trouble of fitting this engine to the E90 so expect the next generation 3 Series (the F30) to be the first to get the new four cylinder. The same holds true for the current 1 Series which will go out of production late this year (or perhaps early next). Look for the F20 1 Series to feature this engine throughout the range. The X3 will likely make the transition in a year or two given that the 28i model was just launched months ago with the old-school inline six.

As we wrote a months back the naturally aspirated engine is dead at BMW. Yes it will continue on for a few more years in a few cars but the writing is on the wall. The future is here and it ‘s more powerful and more efficient.

Full Specifications

Official Specifications: BMW X1 xDrive28i

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  • Bimmer1

    Well it may not have much turbo lag, but I can almost guarantee it will still have the typical BMW electronic throttle delay that’s crippling the driving experience these days in all the other non ///M cars.

  • Stefan

    So wait.. the new 2L 4cyl turbo is getting the same moniker as the outgoing 2.8L 4cyl NA N52 engine? OK…

    Does anyone else feel that a high peak hp number is attainable? Granted we may need to give up some of that flat torque curve but it seems like it’s not competitive where it is now.

    • The outgoing 28i motor was naturally aspirated, 6 cylinder and 3.0 liters. The BMW number in the moniker has not meant displacement for almost a decade.

      So yes the 6 is being replaced by a turbo 4 as we have reported for sometime. The EU market will see a turbo 3 cylinder replace the current 4 cylinders as well in the near future.

      -M

  • This is exciting. Do you guys know the code name for this unit?

  • JonPD

    While the lighter weight and higher efficiency is a bonus one thing is for sure. I will take a naturally aspirated engine over any forced induction motor to better long term viability. I am sure this is the first step towards moving the MINI brand to 3 cylinders. Guess no surprise since even Porsche is saying that sometime in the future the 911 is going to go with a four cylinder motor.

    One thing that makes me wonder about long term efficiency is if slightly greater efficiency is offset by shorter car lifespans and repair costs. I think small gains made in efficiency could be offset by making replacement cars on a shorter duration.

  • Stefan

    @Michael sorry that’s what I meant 3.0L. I’m having trouble keeping track these days. I vote for a return to the E36 era of nomenclature.

  • Evan

    I figured we’d be hearing about this engine soon.

    Its about 50lbft up on the current 328i and comes on 1500rpm earlier, so performance should be brisk. A higher tune is certainly possible. Maybe they should make this the 325i and have a higher tune in the 330i then have the tubo-6 in the 335i since we’re losing the NA I6 all together, which is a very sad thing. I think the NA I6 is what defined BMW. I understand progress, but will greatly miss that sound.

    Size-wise, do we know how this engine compares to the current 1.6L I4 Prince engine? I only wonder if this new 2L turbo 4 could fit in the MINI, or the JCW MINI, or the R60 Countryman.

    I get 30+mpg in my RWD 325i on the highway, so I’d expect this new engine to return in the mid-30s on straight highway runs. Add in stop-start and it doesn’t sound too bad.

  • lava

    Will it fit in a JCW R56?

  • goat

    JonPD – you have very valid points about overall environmental impacts… a Life Cycle Assessment would be needed to sort out all the eco-accounting.

    Some good and bad with this. The good is that it will have more torque for day-to-day driving than the N52, which is a disappointing motor in that regard, especially in the larger e9x sedans (can’t even imagine it in the F10). Fuel economy gains also should be significant (as can be seen from the figures posted for the X3). Power gains via tuning like Procede/BurgerTuning offer for the N54/N55 motors should be a big plus for the enthusiast owner community. The bad is that no matter how smooth it is an I4 just cannot match the harmonic balance of an I6. Also that the I6 was a lovely smooth snarly thing over 5000rpm and a turbo-4, just like the turbo-6, is unlikely to have the same high-end rush of power (at least not without ECU tuning). Some tradition is being lost here… BMW has always been associated with the smooth “woofly” straight-six for me, and for many enthusiasts.

    As for “soft” throttle response, I agree wholeheartedly with Bimmer1… BMW needs to sharpen it in their non-M cars. Particularly as it is as easy as a software setting that can be made available via iDrive, for example (as Audi currently offers). Throttle response isn’t HORRIBLE (in that other cars are even worse) but it is not right especially coupled with additional non-linearity from the Clutch Delay Valve BMW insists on splicing into the clutch line on the manual gearbox cars.

  • Don’t underestimate the power of technological progress in regards to vibration difference between 6 and 4 cyl engines. As the bushing and flywheel technologies advance the amount of nagative vibration sent from the engine into the chassis should decrease and fade the difference btween the 4 and 6 cyl motors.

  • goat

    re: NVH. I4’s can certainly be made smooth in idling and revving – however – there is no debating that I6’s are harmonically balanced whereas I4’s are not (neither are V6’s) and hence those latter (and more common) cylinder configurations require greater engineering workarounds (e.g., counter-rotating balance shafts) to smooth the harmonic imbalances that result from the cylinder pulses.

    As one relevant example, no one could fairly accuse Audi’s 2.0T of being a rough four-cylinder engine, yet driving it back to back with the N52 makes it very clear which engine is “smooth – for a four” and which is inherently balanced. In fact, driving the 2.0T back-to-back with Audi’s own V6 in the same A4 platform vehicle also shows a significant reduction in engine NVH… and the harmonically balanced inline cylinder layout that BMW famously uses is smoother still. There is a pretty good summary on Wikipedia: http://en.wikipedia.org/wiki/Straight-six_engine

    But, technical advantages aside, it’s just cool – peculiar even – to have a straight-6 engine in a car these days… something that has set BMW apart engineering and marketing-wise. Their I4’s are very good as well… the e30’s motor (318ti) was free revving and sounded good (weak on torque, mind) and the famous M turbo-4… well, I have yet to drive an e30 M3 so I have no idea if that is a smooth motor or not. I have a feeling I wouldn’t care… I’d be too busy grinning from ear to ear and tossing it into corners. 🙂

  • As an owner of an E30 M3 I can tell you that “smooth” is the very last word I would use to describe this engine 🙂 But then again, it might be my body shaking from an adrenaline rush.

  • chas58

    The current throttle delay is that bad if you have an automatic transmission and/or AWD. Its not that bad with RWD and a stick. It is there partially for fuel economy – its pretty inexpensive and easy to by an aftermarket kit to sharpen up the throttle of the I6 engine.

    The problem with little turbo engines is that if you drive them like an enthusiast, the thermal and torque loads do a lot to greatly reduce engine/turbo life. They are great if you only use the turbo occasionally.

    The 328i wagon (6MT/sports-package) looks like it will be the last of its kind in more ways than one.

  • Hans

    They need to get this into the MINI Coupe, that car needs a better motor!

    If they can get us a 1 series with this by early 2012, I’d probably get one.