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N54 Twin Turbo Six
The BMW tuning platform for a new generation

There is a certain quiet reality in BMW tuning circles. Seems the current engines from Bavaria are so spot-on the U.S. tuners can't really get much more power out of them with simple bolt-ons or downloads.

The Bavarians are optimizing their engines out of the box. Sure, we can do things with throttle bodies, exhaust systems, and intakes, and maybe pick up 10 hp or so-but for well over $1,000. Bolt-on bang for the buck kind of went away after the wild '80s and '90s. To get big results we have to pony up for forced induction.

Finally, BMW has delivered a twin turbocharged six cylinder engine. Their first gasoline turbo since the 1979-1986 E23 745i turbo, and possible spiritual successor to the mighty 1974 2002 Turbo, the 2007 335i Coupe will be powered by a 3.0-liter double VANOS twin turbo engine, internally designated N54, yielding 306 bhp at 5800 rpm and 295 lb-ft torque at a mere 1300 rpm and remaining steady to 5000 rpm, with a red ine of 7000.

They probably didn't really want to do it, having made certain pronouncements against forced induction gasoline engines in the not-too-distant past. BMW was confronted with the harsh reality of its own price points, which places the new coupe squarely within the sights of competitors with 300-bhp V8 power. True, we are on the cusp of the V8 3 Series now-the E92 M3 will have a 415-bhp V8. Yet BMW probably didn't want to jump in with a non-M V8 3 Series for a number of reasons, including M3 exclusivity. With 300 bhp now the door charge for entry into the $50,000 luxury GT coupe world, BMW really had no choice but forced induction. If they stuck with normal aspiration, they would have had to increase the size of the engine to V8 proportions. By going with the twin turbo six, BMW saved 154 pounds of weight, considerable fuel economy, and gave tuners a gift-wrapped present.

This is not a case of bolting a couple of blowers onto an N52 engine, even though BMW wisely started with a proven performer-the straight six-cylinder engine. This plant is extremely efficient, weighing just 355 pounds, a figure attributed to an aluminum crankcase and a cylinder head and bedplate of extra-light aluminum alloy. The valve cover is magnesium, and the camshafts are hollow. Note the magnesium/aluminum insert block design of the N52 was eschewed for the turbo engine.

BMW calls its second generation of direct fuel injection "High Precision Fuel Injection." The system uses extremely high fuel pressure boosted by a crankshaft-driven mechanical fuel pump. Pressure comes out of the main fuel pump at 5 bar (72.52 psi), and out of the mechanical pump at a whopping 200 bar (2,900.76 psi). The pump supplies piezoelectric fuel injectors pressed into the top of the cylinder head, aimed squarely at a pocket in the tops of the pistons. Right next to it is a four-electrode high-energy spark plug. The benefit is complete combustion, which allows BMW to run a very high compression ratio for a turbocharged engine (10.2:1), lower emissions and improve fuel economy.

BMW's double VANOS system provides variable camshaft control over a huge range, allowing the intake and exhaust cam timing to be optimized for the driving conditions. Cam timing is retarded at low engine speeds for smooth running, and advanced at high engine speeds for more power.

A small turbocharger for each bank of three cylinders yields low inertia momentum, with the blowers responding instantly to the smallest throttle opening. This means no turbo lag. The turbines themselves are high-heat-resistant special steel able to handle temperatures up to 1,900 degrees F. According to BMW, there is no need for coolant or enhanced fuel supply. (We'll see about that!)

When I first saw the N54 engine at BMW Innovation Day in Munich in April 2006, I thought of the first time I saw Katie Holmes on television, the sole legitimate reason to tune in Dawson's Creek. The "what ifs" were obvious. Looking at the N54 for the first time that day in Munich, I just couldn't help but wonder what it would be like with... bigger turbos, of course. Or even just dialed-up boost. Once you've got an engine already wearing forced induction, it's a lot less difficult to extract more power. What you're looking at here is the probably the premier BMW tuning platform for the current, and perhaps next, generation of cars.

We can't wait to see what Dinan is going to do with this engine. Our guess is more airflow through the engine with a cold-air intake, revised VANOS, boost and engine management protocols, a free-flow exhaust system, and a pair of Jennifer Love Hewett-sized turbos. Our guess is... 400 bhp.