"So, what's your favorite car?"
The question invariably rears its ambiguous head every time someone learns what I do for a living. You'd think after 15 years in the business I'd have an answer, or at least narrowed it down to a few vehicles. The truth is, I don't have one favorite-I have a bunch of them. Yeah, that's a weak response, but it's the truth.
Last week it was Ford's RS200 (it tied with the Lancia Delta Integrale). The week before, it was Audi's A4 Avant. Yesterday it was Editor Brown's Porsche C4S.
Today, however, my favorite car is the Dinan S2 M5. Although more than 2 months have passed since I drove it, its memory has been indelibly etched on my mind. You cannot forget a car so fundamentally good.
The S2 is the product of Steve Dinan's meticulous approach to automotive tuning. Every gear, length of tube, screw or bit of software has been tried, tested and tortured to the point of disintegration. Time-consuming? You bet. Expensive? Sort of. But considering Dinan is the only North American tuner recognized by BMW with fully warranted products, a Dinan BMW is a bargain.
Although a stock M5 is by no means an underachiever, the S2 manages to leave it wanting. Shod with what are perhaps the broadest shoulders of all sport sedans, Dinan coaxed significantly more performance from the M5 with a program largely based upon bolt-on components. The engine has been massaged to improve breathing, or more accurately, give the M5 a pair of god-like lungs. The airbox was augmented with Dinan's cold air intake system, featuring dual intake tubes wrought from carbon fiber. The filters are relocated outside the engine compartment to ensure the motor gets plenty of cold, dense air as well as providing insulation from engine compartment heat. The stock plastic air mass meters have been replaced with larger diameter machined units, increasing flow by some 25%. The eight throttle bodies' internal diameters have been increased for a substantial boost in airflow. The stock velocity stacks have also been replaced by shorter, larger diameter aluminum units that have been tuned to optimize their performance at higher rpm. Lastly, a CNC-machined plenum spacer increases plenum volume by 20%, and the camshaft timing was reprogrammed to take advantage of the intakes' increased capacities.
On the exhaust side lies perhaps the most gorgeous set of headers to ever grace a BMW. The intricate curves and bends leave these stainless-steel, ceramic-coated 4-2-1 anti-reversion headers with an organic appearance, like the guts of some metal beast. Matt Taylor, a 20-year employee with Dinan, artfully designed these units, which replace the restrictive stock exhaust manifolds. The headers alone netted a gain of some 28 hp. The S2 M5 exhales through Dinan's stainless-steel free-flow exhaust, providing a roarty tone and a significant weight savings over the stock parts.