If you have been following along with our Turbocharging 101 series, you may remember that last month we broke down the theory and application of building a turbocharger's hot side system, which consisted of installing manifolds on the engine, fabricating 2.5-inch stainless steel piping to connect the manifolds to the turbocharger and mounting our Turbonetics turbocharger and wastegate. This month, we are turning our attention to the "cold side" of the turbocharger system, which consists of any piping or component related to the movement of compressed air from the turbocharger to the intake manifold. Basically, the cold side deals with fresh air as opposed to the hot side that deals exclusively in hot exhaust gas.
Choosing your components:
The cold side of a turbocharger can be, like everything else in life, as complicated or as simple as you would prefer to make it. That said, it is important to take the time to match each component to the next and build a system that will work efficiently within your desired operating range. For our build, which needs to make roughly 1,000 horsepower and do so for a mile at a time, cooling the incoming charge air (post-turbocharger) was the main concern, which meant the majority of our cold side component decisions centered around the needs of our air-to-liquid intercooler.
Cold Side Components
Turbonetics Y2K 88mm Turbocharger
Technically the only component of the entire build to be included in both the hot and cold side of the system, the turbocharger, is obviously the most important component of all. As hot exhaust gas expands across the turbine wheel, it converts that energy into rotational force, turning the mainshaft of the turbocharger assembly and spinning the compressor wheel. The compressor wheel, whose job is to collect fresh air and compress it (duh!), does so from the inlet of the compressor housing and then passes the compressed charge out of the housing via a discharge tube.
Turbonetics Air-to-Liquid Intercooler
Compressing air creates heat. Heat is bad, mmmkay? Thus, a critical cold side component is an intercooler, which, much like a radiator, acts as a way to draw heat out of the compressed air charge, lowering the incoming air temps to an acceptable and manageable level. With an air-to-liquid intercooler from Turbonetics, we will be able to maintain extremely low charge temperatures for the entire mile and, as a secondary function, be able to block most of the front bumper off from airflow, allowing the Trans Am to be less turbulent at speed. Along with the actual air-to-liquid intercooler, you will also need to install a water reservoir, pump and line system to feed the intercooler core with water, but this is something we will tackle in a future issue of GMHTP.
Turbonetics Godzilla Blow-Off Valve
Besides making awesome noises during throttle lift situations, a blow off valve's primary function is to divert trapped air away from the cold side piping system and into the atmosphere to prevent compressor surge or stall during lift-throttle conditions. Put another way, its job, quite literally, is to blow off excess boost pressure trapped in the system when the throttle blade closes. As you will see below, the blow-off valve can be welded almost anywhere on the cold side piping, although some fabricators have a certain preference, based on available space, distance from the turbo and other factors. Turbonetics' Godzilla blow off valve features a 1.8-inch-diameter stainless steel valve that, when open, can quickly divert airflow, keeping our turbocharger in mint condition even after years of abuse, which makes it a cheap insurance policy, if nothing else.
Edelbrock Pro-Flo XT Intake Manifold and 90mm Throttle Body
Ok, the intake manifold and throttle body are probably more a part of the engine than of the cold side of a turbocharger system, but we're including them here because choosing a proper intake for your build is just as important as choosing a turbo and you can't fabricate the cold side without first installing your manifold of choice. For our build and our goals of supporting big power for a long time across a broad RPM range, we chose to run the Edelbrock Pro-Flo XT intake manifold paired with a 90mm throttle body. With a large plenum volume and long, tapered runners, the Pro-Flo XT looks like it will be able to significantly out-power a traditional LS1/LS6 manifold and do so over and above 6,500-rpm, which is what we're looking for. That said, your turbocharged build may not need an intake of this size and, if that is the case, a traditional intake manifold can still make excellent power, as evidenced by several fast (8- and 9-second) LSX cars around the country.
Vibrant Performance Aluminum Tubing and VanJen Clamps
We've got the intercooler, turbocharger and an intake manifold, which means the only thing left to do is connect everything together. Once again, we turned to Vibrant Performance for our aluminum tubing needs and they had everything in stock to make it a painless and simple process assuming you don't include the hours and hours of cutting and welding needed to make everything work! The key here is to select piping that won't restrict flow (remember, the turbocharger is capable of moving 100 lb/hr of mass flow) but won't be too large, which will reduce velocity and hinder performance. That said, Jay Healy and the team at Vengeance Racing decided to use a mix of 3 and 3.5-inch aluminum tubing, along with the correct VanJen clamps. These ingenious clamps work by using two weld-on O-ringed fittings clamped between a union sleeve, which allows up to 15 degrees of "misalignment" and can handle up to 110 psi without leaking or blowing apart. Sure, we could have used regular silicone couplers and they probably would have worked, but the risk of blowing a coupler at a critical time (like, say at the 3⁄4-mile mark) or leaking boost and potentially over-speeding the turbocharger was too great and the sub-hundred-dollar-a-piece VanJen clamps were a no-brainer.