Several months elapsed between the completion of the swap in August 2013 and the end of the 2013 season. The car was subjected to autocrosses, open track days, thousands of miles of street driving, and the kind of treatment that I’d normally reserve for Nazis and members of ISIS. Nothing catastrophic happened, however plenty of potential for improvement was found.
The car proved itself to be quick, so working to wring out every last ounce of performance was not the priority–at least not yet. Rather, I focused on tackling the things that made me uneasy as a driver. The cooling system, the brakes, and the clutch topped the list.
The cooling system worked well when the car was in motion however a defective radiator led the temperature to climb at low speeds. Typical radiators consist of two end takes that are connected to one another by rows of flat tubes. Fins are connected to, and located between, the tubes. The tubes on my radiator expanded, ceasing to be flat, and crushed many of the fins. Air needs to flow through those fins. Airflow through the radiator was decreased due to a greater pressure differential being required to overcome the resistance introduced by the crushed fins. Replacing the radiator would have fixed this. I replaced the radiator along with most of what was nearby.
The objectives for the new cooling system were less weight and ample cooling performance for all foreseeable conditions. The weight was reduced by using a smaller radiator and an electric water pump that happened to weigh less than the original mechanical pump. For functionality, low speed performance was improved, likely at the cost of some high speed performance. The flow of the electric water pump is not dependent on the speed of the engine as the mechanical pump is, so the system can operate at 100% at idle. Low speed performance was also improved by ducting that forces the fans to draw air through all of the available surface area of the radiator core. This change allows a greater volume of air to be drawn through the core per unit of time without actually changing the fans.
A standalone controller, a Tecomotive TinyCWA, controls the water pump and fans. The water pump is a Pierburg CWA-200. This pump is OEM on some BMW’s and the speed is controlled by a PWM input. The controller attempts to maintain a user-defined target temperature. Mine is set for 185 F. This system works wonderfully in moderate to warm weather. Heat retention in cold weather is a problem, but one that I can live with by partially covering the air inlet late in the season.
Supporting changes include a different air intake, accessory drive, and swaybar mounts. An air intake from a C6 Corvette is now being used with a newer blade style MAF sensor in place of the much clunkier old style MAF sensor. The alternator is the only belt driven accessory now. While not totally necessary, the sway bar was replaced and moved back some. The stock sway bar mounts have a number of documented failures. The mounts that I made have no failures, documented or otherwise. Yes, I just built them. No, I do not expect for that to change.
These blocks adapt from a 1.5″ hose to a pair of 12an hose ends. They allow the water pump and radiator to interface with the AN adapters that are bolted to the engine block.
The pedal effort for the brakes was higher than I would have liked and I experienced some fade on the track. Fixing this was simple. I switched to 1″ bore master cylinders, which are one size down from what I had been using. That reduced braking effort to an acceptable level. Fade was addressed by switching to different brake pads. Hawk DTC-70′s were used in place of Hawk HP+’s. This change helped considerably however brake cooling ducts are still on the agenda.
The stock clutch that was included with my powertrain pullout did not respond well to rapid shifting, even with an aftermarket master cylinder and hydraulic line. After one or two shifts in rapid succession, the next would grind. Apparently this is a common issue, and one that can be addressed with an aftermarket clutch. I chose a Monster stage 2 clutch with a light weight flywheel. My shifting woes went away. Yay!