We chose Eddie Rios's shop, Addiction Motorsports, as the location to shoot this month's cover. Rios has nearly a decade of experience building and tuning both carbureted and fuel-injected race cars. He built a turbocharged Mustang that made 866 hp at the wheels and was featured in the Dec. '06 issue of Modified Mustangs & Fords, so he knows turbochargers, too. He told us the biggest mistake his customers make is buying a turbocharger just because it was cheap, then asking him to make it work on their cars. "People come up to me and say, ‘I have this turbo…' and I have to break their hearts," he says. "The turbocharger needs to be sized right. If it's too big, it won't spool. If it's too small, [boost] will come on too fast, and there will be no top-end power." He knows from experience what turbochargers to recommend to his customers, but he suggests people research some of the online sizing guides and consult owners of cars with similar combinations. Rios echoed Ken Bjonnes warnings against inexpensive wastegates: "Some have two-piece seats that aren't installed correctly. They leak pressure and won't build boost."
Eddie Rios directed us to Josh Deeds' shop. He does custom fabrication work for street and race cars and has years of experience with turbochargers. A guy who doesn't mince words, Josh began our discussion by saying, "Almost everyone makes this mistake: They buy junkyard turbos like a Garrett P38 off a 7.3L diesel, which was designed to work within an operating range of 3,000 [engine] rpm, and they want to put two of them of their car. Will it work? Yes, but it won't come in until 5,000 rpm, and below that the engine won't make power. If the turbo is sized right, there should be as little lag as possible." So how do you know which size is right? Josh says the online sizing guides can be useful to getting you close to the right size for your application, but you're better off asking someone with experience building and racing turbo cars. Walk around the pits at the track and see who're using what and how well it's working. You'll likely find a person willing to share advice and information.
Another common problem Josh has seen is with the oil return from the turbocharger. The bearings are fed pressurized oil from the engine, which lubricates the bearings, then drains back to the oil pan through a low-pressure return hose. Some people encounter problems when the turbos are located below the oil level in the pan. Without gravity to drain the oil, it will pool up in the bearing housing and eventually leak past the seals, and you'll begin to see blue smoke in the exhaust. Some people will try to remedy this by installing a fluid pump to send oil back to the oil pan, but that doesn't always solve the problem. According to Josh, "Oil gets whipped up as it passes through the bearings because the shaft speed of turbochargers is very high. It turns to foam, and pumps don't do very well pumping air, so it may not be able to scavenge the oil well enough to prevent it from leaking past the seals. You still may have smoke in the exhaust, even with a pump." If you can't locate the turbos above the oil pan, Josh recommends adding a catch can between the oil outlet and the pump. The catch can will separate the air from the oil, which can then be more efficiently pumped back to the pan.