So which is the better engine? On paper, at least, it looks like the BMW wins this round. But we'll have to wait until we drive the E92 M3 to know for sure.
One thing we know already is that it's going to be fast. Blisteringly fast. The twin-turbo 335i we tested last year gets to sixty in 5.1 seconds, which is only three tenths of a second behind the previous-generation E46 M3.
The 335i is rated at 300 hp and 300 lb-ft of torque, and while the new M3's normally aspirated V-8 makes 5 lb-ft less, it makes an additional 120 horsepower.
One hundred and twenty. More. That's fifteen more than a BMW 2002 made. And that was the original BMW sports sedan, don'tcha know.
The M3 V-8's design was inspired by the V-8 in the BMW Sauber Formula 1 car - and indeed its block is manufactured in the same plant, sharing both production methods and materials. Above all, the engine is designed to be light. It weighs 33 lb less than the previous inline-six, and, at 445 lb, is an astonishing 84 pounds lighter than the 5.0-liter V-8 in the E39 M5 (which made twenty horsepower less.)
The M3's V-8 shares its architecture (including bore, stroke, and compression ratio) with the V-10 in the M5 and M6. Instead of the V-10's single-row timing chain, though, the V-8 uses a twin-row setup along with an updated version of VANOS variable valve-timing system that longer requires separate high-pressure oil plumbing. Not that oil pressure should be an issue with two separate sumps and multiple pumps that guarantee sufficient oil pressure at cornering forces up to 1.4g.
In M tradition, each cylinder has its own individual throttle butterfly - actuated by two electronic servos, one for each bank of cylinders. Throttle response should be near instantaneous - the servos can fully open the throttles within 120 milliseconds, which, according to BMW, is about as quickly as a driver can press the pedal to the floor. (Obviously BMW's engineers haven't watched the fancy footwork of road-raging New York taxi drivers - but that's another story.)
BMW wanted to ensure that nothing gets in the way of air being sucked into the cylinders so it ditched the trouble-prone, expensive mass airflow sensor. Instead, three 32-bit processors help the computer to determine fueling by calculating engine load based on parameters like engine rpm, intake air temperature and pressure, throttle position, and VANOS position. The computer also monitors the resistance across the spark plug gap to identify detonation and misfiring.
We won't be getting it in the U.S., but elsewhere, the M3 will have BMW's new brake energy regeneration system, which sounds more complex and hybrid-y than it actually is. It's a brilliant, but simple, system that decouples the alternator when it's not needed. And by favoring running the alternator in overrun and under braking, the system helps fuel economy while simultaneously making more power available under acceleration.
The system does require a new type of battery - an AGM, or absorbent glass mat battery, which can better cope with the increased charging and discharging it will experience working with the regeneration system. There's been no word yet on whether there are any drawbacks to this type of battery, but we suspect that might be one reason we're not getting the system.
If there are any drawbacks to having an eight-pot M3, we haven't seen any evidence yet. We'll miss the previous engine's screaming, inline-six wail, for sure. But on paper, at least, the new V-8 looks like a win-win proposition.
We expect more information on the M3 to be released at the 2007 New York Auto Show, even though the car won't be there in the flesh.