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The Quest For Turbo Boost

Super Street Magazine
Text and photos by Brent Romans
turboboost1.jpg (27806 bytes)
On any given turbo, generating additional boost is simply a matter of having the turbine wheel spin faster. This is controlled primarily by the waste gate. The four turbos pictured in the lead shot are for a second-gen Mitsubishi Eclipse. Starting clockwise from the top left, they are a stock Garrett T-25, a Garrett T4/T3, a Garrett TS-04, and a GReddy TDO5-18G. The stock turbo is limited to about 250 hp; the TS-04 can theoretically generate enough pressure to support 600 hp!
More Power & A Squeaky voice; 
Hey, it's Just Like Steroids!


A wonderful little thing, this turbo. Hands down, it's the most efficient way to increase the horsepower output of your car. Think of the world's most renowned sports cars. At least half (examples being the Porsche 911 Turbo, the Lotus Esprit Turbo, and the Nissan Skyline) use a turbo system. If you want power, and lots of it, you need one, too. 

Getting more power out of a turbo is a deceptively simple matter of generating additional boost pressure. For enthusiasts looking for more power out of a turbo car, the choices are increasing the output of their vehicle's stock turbo, or, when that's not enough, replacing the stock turbo with a larger or better turbo. The problem with a bigger turbo is the resulting turbo lag. A large turbo doesn't spool up as quickly and will be less responsive at low engine rpms. On a racetrack this isn't much of a problem, but on the street it can really hamper performance. 

Whether you're installing a larger turbo on a factory turbo car or adding a turbocharger to a normally aspirated car, critical attention must be paid to a number of factors. These include additional fuel, ignition timing, compatibility with the factory computer, and compression ratio.
turboboost2.jpg (11900 bytes)
Porting the turbo and the turbo outlet is an inexpensive way 
to get more power from the parts that you already have.
This is a manual boost controller. While the design is simple, it is a good choice for someone wanting more power on a budget. turboboost4.jpg (10732 bytes)
turboboost3.jpg (10662 bytes) The GReddy PRofec-B is an electronic boost controller. It offers more features than a manual boost controller. Below the PRofec-B are an  AFC and ITC. When boost is increased over factory limits, these units help adjust fuel and timing for optimum performance.
Boost Controllers

On factory turbo cars, extra power often comes in the form of extra boost. Turbo cars from the factory are set at a predetermined and generally conservative level (usually around 5-12 psi). But from experience, performance tuners have learned that additional boost and fuel can be used without harming the engine.

On a stock turbo, the job of gaining additional boost falls in the hands of a boost controller. They range from simple manual controllers (inexpensive) to sophisticated electronic controllers (expensive). Both take control of the turbo's waste gate in order to generate the desired boost. While inexpensive, manual controllers are usually mounted in the engine bay, requiring the driver to get out of the vehicle whenever a change in boost is desired. Electronic controllers generally offer more precise control over boost and have additional safety and performance features.

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Last updated 4/04mw