Free power is cool. Concealing it from the outside world while never having to worry about turning it on is even cooler. Only a turbocharger can give you the best of all worlds, and we wanted to know what makes them tick and why they have suddenly "appeared" on the market as the best power-adder available. We know that turbos are nothing new and have been making power on automobile engines for decades. Unfortunately, turbocharging was often overlooked in the past as a viable power adder due to its inherently high costs and troublesome installation--until now.
While it's true that turbos will always be a costly bolt-on, huge advances in computers and EFI technology have given the average street guy access to usable turbo systems for his everyday car. And it's these advances that have allowed regular-guy racers, who are not typically fond of installing computers and EFI along with the expensive exhaust systems needed to drive a turbo, to overlook these difficulties and take advantage of all the power a turbo can make. Today, records are being broken in just about every form of motorsports thanks to turbos and there's relatively little chance of that trend slowing down now.
WHAT MAKES A TURBO BETTER?
A turbocharger is a very efficient way to supercharge the engine by pumping more air into it than it could normally breath. Turbos are also as close to free horsepower as we might ever get. That's because, unlike a blower that's driven off the crankshaft, a turbo uses the engine's exhaust gasses to drive it. And unlike nitrous, a turbo is on all the time and requires little maintenance. But, as with blowers and nitrous oxide, turbos also need extra fuel to burn with all that extra air so any turbo upgrade will probably require a fuel system revamp as well. While turbos have been tried on carbureted engines with moderate success in the past, it's been the giant leaps in racing EFI systems that have given turbos a new resurgence of success. And with the cost of EFI reaching very attainable levels, all of a sudden, bolting a turbo onto your ride doesn't seem so daunting.
OEM-installed turbo systems of the past also gave the whole concept a bad rap. While the automakers were trying everything in their bags of tricks to up the power and economy of their mid-'80s cars, the technology needed to back them up just wasn't there. So, many factory turbo systems failed to catch on and aftermarket turbocharging was pushed under the shelf, so to speak. Then, with the huge resurgence of "Street Car"-type drag racing came a whole new addiction to any type of power adder. While nitrous still plays a dominant role in that type of racing, turbos are quickly taking over. The reasons for turbos moving ahead of nitrous on the racetrack are the same as on the street--advancements in EFI technology. But with turbos come more reliability and more easily controlled power enhancement. Sure, the costs can be 5-10 times greater to build a competitive turbocharged race car, but when you're standing in the winner's circle, nobody ever seems to recall how much it cost to get there.
The guys at Innovative Turbo have seen more than their share of turbo-related carnage and gave us the low-down on what causes turbo failures and how to avoid them. Most turbocharger damage can be traced back to just a few basic causes: lubrication problems, foreign object damage, temperature extremes, or poor materials and workmanship. While you have little control over the last one, the first three are within your grasp. Since turbos are lubricated and cooled by engine oil and, in some cases, engine-cooling water as well, it's critical to maintain a strict oil/coolant maintenance schedule when running a turbo. If you're adding a turbo to your daily driver, it's not a bad idea to make the switch to 100 percent pure synthetic motor oil due to its high-heat handling capabilities. Installing dual remote oil filters connected to auxiliary oil coolers is also a great idea because after a hard run at full boost, the oil temp will rise, and it's important to quickly get it cooled down to normal operating temperature. The turbo's bearings are lubed with pressurized oil from the engine's oil pump, and since pressures are at their lowest at idle, a turbocharged car should not be idled after a hard run. Instead, slowly drive the car around in low gear, maintaining high oil pressure, but opening the throttle as little as possible so there won't be much exhaust gas flowing to load the turbo. Of course, the compressor side of the turbo is also subject to damage when its inlet is not properly maintained. The best defense against destroying a turbo on its inlet side is a tightly sealed air intake using a high-quality filter.
As OEMs and aftermarket companies continue to develop new and improved EFI systems and racers continue to push the envelope, better turbo systems will be the end result. We will all benefit from this new wave of turbo technology, so take advantage of it and after you've read this story and consider yourself a graduate of Turbogineering 101.
Presented for your education...
Presented for your education is a turbocharger dissected. From left-to-right is the aluminum compressor housing, where the boost is made, the Center Housing Rotating Assembly, or CHRA, where the shaft and bearings reside, and the cast-iron turbine housing, where exhaust gasses enter and drive the turbo.
The turbine wheel is what...
The turbine wheel is what the exhaust gas hits to spin the turbo. The turbine wheel is investment--cast in a vacuum-melt foundry from extremely high-grade materials, MAR-M in this case--which basically means not just anybody can make one and they are expensive.
The wastegate is mounted upstream...
The wastegate is mounted upstream between the exhaust gasses coming out of the cylinder head and the turbine housing inlet. It controls turbo speed by bypassing exhaust gasses around the turbo. The wastegate is controlled by boost pressure and the machine in the background tests its operation.
Plumbing can get crazy with...
Plumbing can get crazy with a turbo system. This is Innovative's land-speed record-breaking Corvette and its twin-turbocharged 302-cid EFI small-block. The engine makes close to 4 hp per ci and has propelled the stock-bodied Vette past 200 mph.
Many race-sanctioning bodies...
Many race-sanctioning bodies dictate how big a turbo can be used. The size refers to the compressor housing's inlet opening as shown here. This directly controls how much air will get into the turbo to make boost. A bigger turbo is kind of like swapping on a bigger carburetor to allow the engine to breathe well.
This Center Housing Rotating...
This Center Housing Rotating Assembly (CHRA) is cooled by engine coolant routed through the fitting indicated by the pencil. The coolant flows around the bearing mounts and back into the engine. The exhaust turbine wheel is on the right and the compressor impeller is on the left.
Compressor shaft speeds inside...
Compressor shaft speeds inside a turbo can exceed 100000 rpm, so it must be precision-balanced to the extreme. This machine is made strictly for that purpose.
This photo shows the complicated...
This photo shows the complicated exhaust routing involved with a typical turbo. The wastegate bypasses extra exhaust gasses from the header collector, allowing only the correct amount of exhaust into the turbo housing, which is wrapped in the heat blanket. The compressor housing outlet, welded to the intercooler tubing, can be seen to the right of the wastegate with the pressurized steel hard line for oil coming from the engine just in front of the number four header tube. Try changing spark plugs in there!
Anatomy Of A Turbo
The guys at Innovative Turbo explained turbos to us in full detail. We learned how a turbo is driven, where it gets it's air, where it sends it to, and some of the various control devices used with turbos. This photo shows the drive side of the turbo, called the Turbine Housing, which is usually made of cast iron due to the extremely high temperatures it must endure. The aluminum compressor housing is on the right. The exhaust gases drive one impeller in the turbine housing that's connected through a common shaft to the boost impeller inside the compressor housing. Exhaust gases are sealed off from the compressor housing so they cannot mix with fresh incoming air.
Hot exhaust gas enters the Turbine inlet here (1) and is routed directly into the housing's Volute. The Wastegate is typically mounted here, except in tight race-car chassis. The exhaust gas then strikes the turbine diameter blades in the center of the housing (2), which are then connected to a common shaft driving the compressor's impeller. The gas then exits the housing (3) and goes straight out the tailpipe.
This is where filtered, outside air is introduced into the compressor (4). The air is then accelerated through the impeller wheel and across the radiused contour (5). The Impeller discharges the air into the diffuser (6), which slows the air down and increases its pressure, creating boost. The boosted air is recovered in the volute (7) and is directed through the discharge nozzle (8) into the engine or intercooler. Turbos run "dry," boosting only inlet air. Fuel is mixed in downstream, usually just before the boosted air enters the cylinder head.