THE SHOP

Performance & Hotrod Business - April '15

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April 2015 n PRECISION ENGINE n 9 This greater density (oxygen) will pro- vide a more efficient combustion process that will create more power, better fuel economy, and be less prone to detonation. On a modern forced-induction vehicle, an intercooler is a must. In the early days of stock turbo- charging, some vehicle models were not equipped with an intercooler system. Over time, manufacturers were exposed to the necessity of this system, and it is now commonplace. So, which components should we be aware of in an intercooler system? We will be highlighting and referencing the five major components in this article. 1. Turbocharger Compressor Housing This is the component that starts every- thing. The compressor side (often referred to as the cold side) of the turbocharger sucks in ambient air and uses an impeller to compress the air and force it around the housing and into the piping. The shaft of the impeller runs the entire length of the turbocharger. The opposite end features another impeller that is spun by exhaust gases. A typical turbocharger has a bead- rolled, pipe-style outlet connected to the piping via a boot of some sort. A few stock turbochargers feature a flange that mates to a specific pipe. The turbocharger heats and compresses the air; the other components (below) must then cool down that air. 2. CAC Boots The boots create all the connection points in your system. These components are the most failure-prone parts, and as we know, a system is only as good as its weakest link. Boots link the piping to the turbo- charger, to the intercooler and to the throttle-body/intake manifold. These units are in place to allow for engine movement, and they work to absorb this shock. If the system were solid and with- out flex, the turbocharger would move, which would result in bending or crack- ing of the piping or the intercooler itself. Additionally, the boots provide connection points to separate the components, allow- ing for individual servicing. 3. CAC Piping The piping on this system routes the airflow from the turbocharger through to the rest of the system. It is normally com- posed of bent steel tubing or plastic piping. Most aftermarket offerings select alu- minum piping for its lower weight com- pared to steel, as well as its heat dissipation properties. Pipe diameter can be enlarged to increase flow, which is common with the kits offered by Mishimoto. We also uti- lize mandrel-bent aluminum to provide the smoothest possible flow. 4. Intercooler The intercooler is the component in the system that does all the work. An inter- cooler, or charge-air cooler, is an air-to-air heat exchanger that cools the internal air- flow by using air moving through external fins. Intercooler core design can vary sig- nificantly, but two main core types exist. A tube-and-fin design is more commonly equipped on vehicles from the factory due to its light weight and lower expense. These coolers are composed of internal tubes separated by external fins. Aftermarket coolers generally feature a bar-and-plate core that is heavier, yet more efficient, for heat transfer. These coolers are constructed with a series of bars and plates to create an internal area for air- flow. These components are then attached directly to external fins that work to trans- fer heat from the internal air. A typical performance upgrade would move to a larger-volume bar-and-plate core, which will improve the transfer of heat, thereby lowering intake tempera- tures. The intercooler is installed between the turbocharger and engine. 5. Bypass Valve Lastly we have our bypass valve. This component is nearly always found on modern CAC systems—its primary function being to reduce compressor surge when the throttle is closed (during shifts). This allows pressure to vent into the atmosphere instead of building up in the system. Compressor surge occurs when air pres- sure after the housing is higher than what the unit itself can maintain. At times, this can result in a compressor stall and even turbocharger bearing failure. The bypass valve is important, as it opens up during these high-pressure instances to decrease pressure and keep the turbocharger properly in boost. This component can be found mounted to the intake piping, with a vacuum line running to the engine. What a Leak Can Do To Your Vehicle So, why should you be concerned with a leaking CAC system? A leak in the CAC system will result in a loss of pressure, which will affect power output and reduce fuel mileage. A small, Turbocharger from a Subaru engine. A Mishimoto Duracore intercooler boot. A Mishimoto Evolution X intercooler pipe kit. Mishimoto's 6.7-liter Cummins intercooler.

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