Propickup Digital Magazine
Issue link: http://read.dmtmag.com/i/150744
TURBOS & INTERCOOLERS Pump up diesel pickup performance with aftermarket turbos, intercoolers and exhaust brakes by Tim Walton W e task our diesel pickups with the biggest towing and hauling jobs from moving equipment between jobsites to carrying a bed loaded down with tools and equipment. Oft times we are pushing the truck's GVWR and GCWR limits day in and day out. Turbochargers breathe life into the modern diesel pickups. The newest turbos bring engine efficiency for increasingly impressive amounts of power and torque, while taking advantage of new technology to help the trucks brake more effectively and save on replacement/repair costs on pads and rotors. However, compromises in original equipment still leaves room for improvement in the turbocharger and related parts. Aftermarket turbo specialists have improved variable-vane or variable-geometry control, increased cooling capabilities and made the turbos themselves more efficient. COOL EFFICIENCY If you use your truck for towing heavy trailers or hauling heavy loads, replacing the factory charge-air-cooler (CAC), or intercooler, with a more efficient one is a good move. One of the side effects of compressing air is heat and heat means less dense air which means less oxygen, which will reduce the efficiency of your engine. An aftermarket CAC can help keep your intake temperatures closer to ambient. An aftermarket CAC can also significantly reduce turboboost pressure loss across the intercooler; some freer-flowing aftermarket units can reduce this drop to less than .5 pounds at 40psi versus a 4- to 5-pound drop with the OE unit. The efficiency in cooling of the CAC combined with the pressure drop allows the turbocharger to operate in a better efficiency plateau in the compressor map – the turbo doesn't have to work as hard so it produces a cooler charge. A word of caution here: an aftermarket CAC/intercooler can restrict air flow to the pickup's radiator, so watch for designs that address this issue when planning your overall setup. When you're upgrading, your CAC kits may replace the intercooler only or come more complete with aftermarket tubing as well. Tubing upgrades can bring a larger diameter, smoother mandrel bends and smoother transitions that can reduce turbulence and help make more torque and more horsepower while lowering EGTs. VANE GAINS Many newer vehicles come stock with variable vane turbochargers (VVT) or variable geometry turbochargers (VGT). Both use different technology to achieve variable area/radius (A/R). The function of both types is to change the A/R, which is the inlet cross-sectional area divided by the radius from the turbo centerline to the center of that area. A smaller A/R will give the turbo better turbine power at lower speeds, creating faster boost rise, because it provides increased exhaust gas velocity. The down side is the smaller A/R restricts the flow, creating more backpressure and limiting the effective flow capacity of the turbine wheel. VGT allows the turbocharger to be more effective at creating boost at low speeds, while allowing the turbocharger to flow more effectively at higher RPM range by making the change. Another use for this technology is to create additional back pressure to help slow the vehicle without using the physical brakes, which is especially effective when towing a heavy trailer. In fact, the Big Three's newest HD models come factory equipped with exhaust braking systems to ease the burden of slowing down a 120 PROPICKUP Big Book 2013 PPBB13PG000_Turbos Intercoolers.indd 120 8/6/13 10:51 AM