BMW unveiled yesterday the X4 M40i, the M Performance Automobile also powered by a revised N55 unit. Looking at the specs, the engine of the BMW X4 M40i is a close relative of the engine for the BMW M2 F87, with the M2 Coupe getting an even sharper power stage with a power rating of 370 hp and improved response.
The basic N55 engine is used in both vehicles with a 3.0 liters of displacement and a twin scroll turbocharger, however, some components from the S55 are included for more stability and to allow an increase of boost pressure and injection quantity. An optimized air intake and an optimized exhaust system are also included.
The torque and power diagram shows the 360-hp N55 variant for the BMW X4 M40i with a rated output at 5,800 and 6,000 rpm/min. We currently estimate that the 370 hp version of the N55 will not provide its rated output in such a wide area, as well as can be expected with a little more torque.
The increase in performance compared to the normally offered 306hp, 320hp or 326 hp base engine is possible because BMW uses some parts from the 431 hp S55 engine. The forged steel crankshaft, the crankshaft bearings and the special pistons and high-power spark plugs will allow an increase in the peak power combined with optimum durability in most sports usage.
Thanks to further improved cooling with a separate oil cooler, the engine of the BMW M2 should also easily handles even the most demanding race tracks, like the Nürburgring Nordschleife. The official presentation of the BMW M2 with all technical details and numerous photographs is scheduled for October 14.[Source: Bimmertoday]