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