MINI Cooper Intercooler- Optimizing Air Temperature to Increase Performance of the MINI Engine

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Mini Cooper Intercooler performance The current generation MINI Cooper “S” is an impressive performance automobile.  It features the proven technology of a mechanical compressor (supercharger) to force more air and fuel into the combustion chamber.  The supercharger is a relatively simple means to boost the performance of a small displacement engine, resulting in improved power to weight ratio. But the MINI is a shining example of the art of ‘compromise’. The stock supercharger setup is ultimately a compromise of technology potential and manufacturing practicality to produce an end result that also compromises performance for general public appeal.  The engineers involved in the design of the Eaton Supercharged MINI Cooper ‘S’ did a marvelous job of packaging their unit in the tight confines of the engine bay.  The Eaton M 45 is a cut down version of the venerable M 62, first featured in the early Buick V6’s.  This is a roots design used on many new cars since it was introduced in the late 1980’s on the Ford S/C Coupe.  It is a fine unit for mass production on engines with five to six pounds of boost.  Above that it makes excessive heat, especially when you exceed seven pounds of boost. The MINI’s stock boost level is about ten pounds, and if a smaller diameter supercharger pulley is installed, the boost level – and therefore heat output – is increased even further.   Compressing gasses by nature creates heat, and it is no different with a supercharger. To compensate for the heat generated in the forced induction process, it is mandatory to cool the intake charge considerably.  Reducing the intake charge temperature with an intercooler has several benefits: Increases the density of the intake charge resulting in a more powerful combustion. More complete combustion with lower temperatures creating more power. Reduces the need for the ECU to retard timing and increase fuel delivery, minimizing this power-reducing ‘preservation mode’. Reduction of engine operating temperature increases longevity of the engine.   The MINI factory understood this and installed an intercooler.  But space and cost considerations resulted in the use of an air-to-air intercooler based on the BEHR design.  This kept the MINI accountants happy because it is inexpensive; but is very inefficient and limits the potential performance of the MINI with stock or upgraded boost. The intercooler design on the MINI has several drawbacks: Located directly over the engine - the biggest source of radiated heat in the car. Minimal airflow resulting from a small hood scoop. Minimal exit path for the airflow due to the engine and its components.   In the MINI, the superheated gasses from the supercharger pass through the intercooler; a considerable amount of heat remaining in the gasses is passed on into the combustion chamber.  Since air expands when heated, the oxygen content of the intake charge is reduced, resulting in a lean condition which elevates the combustion temperatures and greatly increases the potential for engine knock and detonation.  The car’s ECU detects the high exhaust gas temperatures and goes into a ‘preservation mode’ which increases the fuel delivery and retards the timing in an effort to reduce the temperatures.  The net effect is reduced power output. An ‘ideal’ air-to-air intercooler would have the following characteristics: High volume of airflow across the cooling elements. Availability of corresponding exit path for the airflow. Minimal pressure drop within the intercooler and associated plumbing. Located away from heat sources such as the engine or exhaust manifold. In performance-critical racing applications, a very efficient air-to-air intercooler is mounted in the front of car in maximum airflow to ensure maximum reduction of charge temperature. An intercooler at this location can work for extended periods of time at maximum efficiency.  This is not a cost efficient solution for the MINI because of the additional plumbing required (with associated pressure drop), and the modification necessary to fit an adequate sized intercooler in the tight confines behind the bumper. An alternative solution is a ‘water-to-air’ intercooler.  As the name suggests, this intercooler uses water as the cooling medium, instead of direct airflow.  The water-based intercooler takes advantage of a huge gain in efficiency over the air units in the far greater heat transfer coefficient between aluminum and water (fourteen fold).  By using water instead of air to cool the compressed charge we are able to bypass the limitations of the available location (affecting air inlet and outlet) to provide a far more effective system.   The ULTRIK water-to-air intercooler (NME5005) is the first intercooler produced for the MINI which addresses the shortcomings of the stock air-to-air design using an innovative and patented technology. It fits elegantly within the existing engine bay while delivering performance gains that could not be achieved with the conventional air-to-air intercooler.  Some water-to-air intercoolers simply add a water jacket over the plate-type air-to-air unit or other extruded tube type intercooler.  These units perform adequately, but the innovative Laminar design used by the ULTRIK intercooler is 20% more efficient than water jacket-style intercoolers. The finned exterior on the cooler core creates a larger surface area compared to that of traditional “radiator” style coolers, offering unparalleled heat transfer with minimal pressure drop.  Tests show up to 2.2 times the amount of heat removed at the same pressure drop as conventional tube and fin exchanger.  The net effect is better torque, response and performance compared to conventional coolers. Primary advantages of this system are: Maximum cooling of intake charge while keeping the temperature of the intake charge nearly constant. Ability to “bank” cooling capacity in the water loop.  The stored capacity allows for instantaneous and maximum cooling response in passing situations or other times when instant power is needed. Dramatic reduction in heat buildup at low speeds and idle, as often encountered in stop-and-go traffic.    For every 10° F reduction of the intake charge temperature, the MINI produces 1% more power.  Under adverse conditions, the intake charge with a factory intercooler can reach and exceed temperature of 300°F.  The ULTRIK Intercooler will keep the intake charge temperatures about 30°F to 40°F above ambient, or as much as 200°F lower than the stock intercooler, equating to 20% greater power output.   The ULTRIK intercooler also addresses the issue of ‘heat soaking’. Unlike race applications, a street driven car is frequently stopped at intersections or in traffic. Once the car is stopped, the stock intercooler acts as a big heat sink, absorbing heat rising from the engine and transferring it to the induction charge. The first hard pull creates discharge temperatures of 250° F to 300° F, resulting in the ECU pulling back on timing and adding fuel, resulting in poor off-the-line performance until fresh air entering the hood scoop can cool the entire unit back down. The ULTRIK intercooler has a continuously flowing coolant system, which continues to remove heat from the induction charge even when the vehicle is stopped. Heat from the intercooler is moved to the exchanger in front of the radiator, where it is dissipated to the atmosphere even when the cooling fan is off. In the traffic scenario above, the ULTRIK-equipped engine is ready to deliver its full potential when the light turns green. An ULTRIK charge cooler usually drops discharge temperatures within 15° F of ambient air. It consistently keeps a street driven car’s discharge temperaturess at levels where the engine management system can fuel and time the engine for maximum power. Depending on the outside temperatures, this can result in power gains of as much as 15%. The ULTRIK water-to-air intercooler is a bolt-in design which drops directly into the stock location. The system’s radiator sits at the front of the engine bay using existing mounting points. For those considering engine bay esthetics, the entire intercooler system is neat, compact and well-crafted; it was designed to look like a factory option.   If you are looking for increased performance from your MINI Cooper ‘S’, the ULTRIK water-to-air intercooler is more effective than the stock or even other water-to-air designs. Surprisingly affordable, and guaranteed by Mini Mania for the remainder of your OEM warranty or longer, the ULTRIK intercooler delivers a genuine boost in horsepower for minimal effort.

Article Date: Jan 25, 2005
Car Accociations: NEW_MINI
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