Story and Photos by Zach Mayne
Mission creep is a term the military uses to describe operations that gradually increase in scope until the end result has little in common with the original intent. Mission creep can also describe the evolution of many a project car, like the 2004 M3 pictured here, owned by Southern California resident Robert Henning. When he first decided to start tuning the car for more performance, only a few upgrades were envisioned. “I think the first real modification was a rear CSL-style carbon fiber diffuser,” he recalls. “I had been looking into full exhaust and pulley packages after that but the price was almost as much as a supercharger.” The thought of a turbocharger entered his mind next. While researching the various companies that developed turbo systems for BMWs, Henning came across Horsepower Freaks, formally known as HPF. “I decided to go with HPF after watching all the videos from them on Youtube and talking to them,” he says. “I wanted to have something different from everyone and at the time not too many HPF cars were on the road.”
Before long the M3 was delivered to HPF’s headquarters to be reconfigured for big power. In order to ensure that the S54 could reliably deal with the power output provided by the turbo, HPF pulled the engine from the car and completely disassembled it. The sturdy OEM crankshaft was left alone but the stock rods were replaced with HPF’s proprietary connecting rods specifically designed for high-power turbo applications. The rods are bolted to forged pistons with ceramic-coated skirts and radiused edges to eliminate hot spots and reduce the chances of the pistons becoming damaged from the intense heat they are subjected to. The rods and pistons are mated together with thicker, custom wrist pins. The S54 head is left stock but are fastened to the block with ARP L19 head studs. “The standard ARPs literally stretch under the extreme cylinder pressures,” says HPF’s Chris Bergemann. The L19 studs reduce this tendency thanks to their stronger tensile strength of 260,000-psi.
A 71-mm billet Precision turbo provided the desired boost. The turbo features dual ball-bearings and a CNC machined turbine wheel that it is lighter and has been designed with optimal vane geometry. HPF installed the turbo below the oil pan, so an oil-scavenging pump was installed to circulate the engine oil to the turbo housing. Additionally, the turbo is cooled with a supply of coolant piped in from the BMW’s cooling system. Incoming air is routed through HPF’s proprietary intake manifold and cooled by a massive intercooler mounted up front. The intake manifold uses methanol injection to cool incoming air for an instant power boost when the methanol is activated by a cockpit-mounted controller. HPF engineered a piggy back ECU that controls the factory DME. Fuel delivery consists of a stock fuel pump backed up by dual Walbro 255 pumps and an additional fuel line that runs from the tank to the fuel rail. The stock fuel injectors are replaced with 1200-cc fuel injectors that lower the fuel pressure from 73-psi to 40-psi. Under max boost, fuel pressure rises to around 65-psi. An AEM fuel injector driver box controls the fuel system.
When it was strapped to the dyno, the M3’s turbo engine pumped out 635-rwhp with 17-lbs of boost and running 91-octane pump gas. At 23-lbs of boost and adding the methanol injection the power climbed to 766-rwhp. With higher octane race fuel and methanol injection the engine produced 817-rwhp, which is just short of 1000 horsepower at the crank. To keep the M3 on the road, HPF engineered a traction control system that limits the amount of available power based on the speed of the vehicle. The faster the car is traveling, the more power the system feeds to the rear wheels. The result is a BMW that accelerates its fastest when its headed towards triple digits, since full boost is not available until over 80-mph. The system has four settings for Race, Sport, Street and Rain.
Henning modified the exterior of the M3 with a carbon fiber, vented hood from Asuka and a carbon fiber trunk, front bumper and rear diffuser from Vorsteiner. He also installed excellent looking BBS LM three-piece alloys that measure 19x8.5-inches up front and 19x9.5-inches at the back. The wheels wear 235/35ZR19 Nitto NT05s at the front and 275/30ZR19 Toyo R888s at the rear. Inside, the seats have been replaced with one-piece leather Recaro Pole Positions. The rest of the interior is stock, save for a smattering of gauges and knobs that monitor the health of the car and control the various functions. With the exception of the exhaust- which is embarrassingly loud- onlookers would likely assume this was simply a mildly modified M3. The suspension consists of KW coilovers that imbue the M3 with a more nimble chassis and suspension. On the stopping end of things is a Rotora big brake kit with 6-piston calipers at the starboard end and four piston calipers at the aft end.
While the suspension and brakes are nice upgrades, the real point hook here is the horsepower that this beast produces. “It steps sideway pretty quick when you get on it,” says Henning casually from the passenger’s seat as I steer the BMW onto an onramp of the 210 Freeway in Pasadena. Not exactly the most comforting words, though to be fair, at the moment it’s “only” putting out about 650-rwhp. Accelerating onto the on-ramp, I press the gas pedal to the floor and the M3 rockets forward. With 650-hp available with a twitch of my right foot, acceleration is extremely strong, the BMW lunging forward with a loud shriek from the exhaust and a whistle from the turbo as it spools up. Upshifts through the SMG transmission that Henning’s example is equipped with are accompanied by the spitting noise of the wastegate. Once I’ve become slightly familiar with the acceleration, Henning bumps the power up with a flick of a switch to the full 768 horsepower available with the pump gas we’re running on today.
As the gas pedal heads to the floor, the M3 takes on another demented level of acceleration that is sense scrambling in its immediacy. As though some survival instinct kicks in, my right hand subconsiously pulls back the right SMG paddle for an upshift before the engine has even revved past 6,000-rpm, temporarily slowing the car. It takes a few runs up through the gears to become accustomed to the absolutely ferocious acceleration that the car produces. It’s not an entirely comfortable feeling, but it is extremely invigorating. The unmuffled, metallic shriek of the S54 is joined by a blow-off valve that shpitts! rudely at every upshift. The rear tires easily break traction under full throttle at freeway speeds and blasts of acceleration become an exercise in compressing distance. I’m not sure I entirely see the point of an E46 M3 with this much power and frankly cars like the Porsche 996, 997 and later Turbos an are more suited to this level of power thanks to their superior traction. However, there is no denying it’s a fascinating exercise in excessiveness.