As you may expect, as much, if not more, attention went into chassis development. The factory-spec M6 is a decent handling car, but never feels as though it really wants to attack corners. It pulls an impressive g and will change direction quickly enough, but understeer and a lack of that knife-edge precision expected from a real sports car seems to elude the bigger BMWs. Springs, a rear sway bar, and various other bits combine to give Dinan's S3 M6 a lowered ride and fight roll with more success. There are a few more interesting things going on here, however. First, geometry changes in front add the steering feel normally missing. Notable among the improvements is slightly more caster. Not only does it add a more precise on-center feel, it adds just enough resistance from trail and weight jacking to make turn-in feel racecar precise.
The second point of interest in the Dinan car is how the problem of severely limited stock suspension travel was dealt with. BMW had to keep its shock towers extremely low to maximize trunk space. The result is limited travel in back and a rather rough ride. Dinan re-engineered the rear spring perches to maximize travel and designed custom bump stops that work in conjunction with the extra stroke. The result is a car with an inch lower ride height, more suspension travel, and the factory's electronically adjustable shocks still fully functional.
The S3's dynamics are aggressive yet still at least as comfortable as stock, maybe more so. Driving it isn't a battle with the front wheels as with the stock car. It's very neutral and easy to rotate. It also puts power down surprisingly well, thanks in part to bigger contact patches at the rear, but also due to the chassis not immediately squatting down onto the bump stops. In the first three gears, there's plenty of torque to swing the back end around at will. In faster corners, the car remains thankfully well behaved and doesn't feel like it wants to swap ends, even hard on the throttle. Again, it's the smooth power delivery of a big displacement engine coupled with a well-sorted chassis. Dial in steering and throttle inputs smoothly and the car rewards with fast, clean cornering. Flick-and-stomp results in some seriously fun drifting. You could go through a pair of rear tires in one afternoon of hoonage, but it might just be worth it.
So what does something like a Dinan S3 cost? The final price on the entire conversion hasn't been announced yet. The engine package alone is roughly 40 grand, but this is for essentially a race engine with a full four-year/ 50,000-mile warranty. Simply chipping your stock BMW will have the dealership tearing up your warranty papers and showing you the door. Dinan's warranty has to justify at least a quarter of the asking price.
Options on the car we tested included a free-flow intake system that uses two high-capacity cone filters encased in two separate airboxes with beautiful and functional carbon-fiber lids. They also include larger air-mass sensors with relocated air temperature sensors for accurate metering. On the other end was a Dinan exhaust system composed of a middle section designed for higher flow rates and rear mufflers with Dinan-designed "cool-tips" that pull in a small amount of outside air just at the tips to keep temperatures down and avoid discoloration. Inside the car, the new exhaust note is hardly perceptible. At wide-open throttle, the exhaust sounds like the world's meanest sport bike. It wails with a deep undertone that lets you know you aren't dealing with some 3.0-liter screamer.
Exterior modifications are left to a minimum. Dinan lightweight 19-inch wheels look the part, but more importantly shave a total of 32 pounds off the rotating and unsprung weight. Combine that with a few more pounds off each corner from the Brembo-built brakes and you have a drop in mass that really makes a big difference in performance.