Turbocharger - Boost Basics

Back in the first muscle car era, Ford offered all manner of performance hardware. Powered by high-winding small-blocks, canted-valve Clevelands, and Boss 429s, Ford products were right in the thick of muscle car mania. Though things looked bleak during the dreaded smog era of the '70s, the '80s brought back factory Ford performance machinery. The introduction of electronic fuel injection brought with it a renewed interest in factory forced induction. In a quest to balance power and mileage, Ford employed both turbocharging and supercharging, offering the four-cylinder Turbo T-birds and six-cylinder Super Coupes. Sharing an even more powerful version of the turbocharged four-cylinder was the SVO Mustang. These force-fed Fords offered the power of a V-8 with the weight and economy of a V-6 or inline four-cylinder. These early factory efforts eventually paved the way for such great products as the supercharged, F-150-based Lightning, the legendary '03-'04 Cobra and most recently, the 5.4/5.8-liter Shelby GT500. This proliferation of factory forced induction powerplants, coupled with a strong aftermarket offering similar means of pressurizing the intake charge, makes it easy for current Ford owners (both modern and vintage) to utilize these technologies for both performance and for show.

Ford performance certainly predated the 5.0L Mustang, but owners of early carbureted small-blocks still owe a debt of gratitude to the late-model 5.0L, as Ford's injected wonder engine unleashed a tidal wave of performance products. Though some were exclusive to fuel injection, a great many carried over to the carbureted contingent. Thanks to an industry that now revolved around the 5.0L, early Ford fanatics could now enjoy all manner of aluminum cylinder heads, custom roller cam profiles and even forced induction. Though originally designed for the fuelie Fords, the current crop of aftermarket blower and turbo kits work equally well on carbureted engines. Just imagine popping the hood on your Blue Oval beast to reveal a turbo or supercharged small-block. Toss in the recent introduction of low-buck turbos from companies like CXRacing, and it's a good time to consider adding boost. For the ultimate in low buck, you can also source the majority of a usable system from the wrecking yard.

The Turbocharger

The main component in any turbo system is the turbo itself. A turbocharger, as it's widely known, is somewhat complex in design, but quite simple in operation. The turbocharger is made up of two distinct, but related sections. They are often referred to as the "Hot" and "Cold" sides, but are more technically the turbine and compressor sections. The turbine section is responsible for receiving all of the hot exhaust gases. In the case of a single-turbo V-8 application, the exhaust from each bank of the V-8 is channeled together into a common Y-pipe, then fed into the turbine section of the turbo. The heated exhaust gas energy is used to spin the impeller blades in the turbine section. The turbine is connected to a matching compressor wheel on the other side of the turbo via a common shaft. When the exhaust gas spins the turbine wheel, this causes the compressor wheel to spin at an identical speed. The spinning compressor wheel draws air into the compressor housing and force feeds the engine more air than it would be able to ingest on its own accord. The extra airflow forced into the engine builds in pressure, and is registered at boost or boost pressure.

There is a significant amount of knowledge and science that goes into selecting the proper turbo for a specific application, but in general, the turbo (or turbos) must be sized properly for the intended boost and power output. Small turbos offer improved boost response, while larger turbos maximize flow and power. The key is to select the turbo that offers the best compromise of both. Lucky for enthusiasts, the manufacturers have done most of the testing for you and will have a recommendation on turbo sizing for your application. The key is to be realistic about your power goals and usage. If you are looking to improve the power output of your 225hp 289 Ford by 50 percent, there is no need to order a turbo capable of supporting 1,000 hp. Both spool up and eventual power will be much less than if you had selected a turbo capable of supporting 500 hp (still 160 hp more than your motor will make). Another consideration is the fact that the 1,000hp turbo might cost $1,500-$2,000 (or more), while the 500hp unit can be purchased online for less than $500. Turbo sizing is one of the times when bigger is certainly not better.

Whenever talk turns to turbos, the subject of turbo lag always comes up. Turbo lag is a phrase that attempts to describe the time between when you step on the throttle and when the turbo is able to supply boost. Boost supplied by the turbo is a function of the relationship between the exhaust flow out of the engine and the turbo (primarily turbine) sizing. Properly sized, modern turbos can provide maximum (or full) boost as low as 1,500 rpm. The downside to having this rapid response can be excessive back pressure (pressure in the exhaust system) at higher engine speeds and/or boost levels. The best cure for turbo lag is a powerful normally aspirated engine and proper turbo sizing. Installation of a turbo on a 300hp, normally aspirated engine will result in greater turbo lag than on a 400hp engine. Smaller turbos will offer quicker response than larger turbos. The key is to optimize the combination to suit your particular needs. Of course, packaging might also determine turbo sizing, as it might be physically impossible to mount a given turbo size in the desired location.

Pricing for the actual turbocharger can vary from company to company, and also depends on the turbocharger size and options. Company's like Borg Warner, Garrett, Precision Turbo, and Turbonetics have been providing enthusiasts with quality turbochargers (or hairdryers as they are sometimes referred to in slang), however companies like CX Racing and Master Power now offer powerful, yet very affordable turbos in a variety of different sizes. We have combined a pair of CX's 76mm turbos to exceed 1,300 hp. CX Racing, as well as many of the other turbocharger companies, also offers numerous turbo components for the do-it-yourselfer, including intercoolers, polished aluminum tubing, oil lines and fittings, silicone couplers and clamps, and even complete kits.