Torque Converter Selection - CHP How It Works

Driveline Pros At TCI And Pro Torque Offer Hard-Hitting Insight On Torque Converter Selection & Design.

Stephen Kim Nov 12, 2010 0 Comment(s)
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"The benefits of data acquisition technology in the development of race converters gets trickled down throughout our entire product line. From the fastest automatic-equipped race cars to the tree-trunk pulling torque of modified diesels, and right down to your street car. For instance, the converters we developed for the fifth-gen Camaro is really a byproduct of all the work we are doing with high-horsepower Outlaw turbo cars. Our billet stators feature a proprietary blade design that offers more stall speed and unbelievable part-throttle characteristics. The process used to create these new billet stators is really revolutionary. We CAD/CAM design the individual blades, and then create a stator based off the physical space requirements. Next, we four-axis machine the parts out of one solid chunk of steel or aluminum. During testing, we rely heavily on our Racepak data acquisition system to find out exactly how to apply the power to the tires.

"When you're making converter changes, you need to understand that every time you change something in the converter, you're making a dynamic change. Kind of like playing a game of Jenga, if you move one piece of the puzzle everything moves along with it. In turbo cars, we worked very hard to find a converter design that both spools the turbos quickly and efficiently transfers power to the wheels. In the past that was very difficult, but with data acquisition and CAD/CAM technology we have been able to create completely different stator designs very quickly to get the best of both worlds. With the Racepak data logging system, we can measure wheel speed, driveshaft speed, g's at launch, and the average g's throughout the run to see how changes to the converter improves performance at the track. Truthfully, we'd be in the dark without data acquisition systems that chart our progress at the track."

Stall Speed
Stanley Poff: "The stall speed of a torque converter plays an important role in overall vehicle performance. Stall speed is determined by the amount of flash rpm the converter is allowed to reach before the vehicle starts to move. Different torque converter cores, stator combinations, and pump fin angles can allow for different stall ranges in a torque converter. It is possible to reach the same stall-speed in a torque converter with different stators and pump/fin combinations, and one of the combinations may yield a better torque multiplication ratio than the others. The optimum stall speed and torque multiplication of a converter is achieved with R&D time on a dynamometer. TCI has an in-house dynamometer that uses a 900hp engine. This dyno was built specifically to test torque converter stall speeds without using a transmission. TCI can map different torque converters with different stall speeds and achieve a unit that will deliver the best stall speed and torque multiplication ratio.

"There are dozens of variables involved in selecting the correct stall speed for an application. First, we ask the customer a series of questions to determine what the vehicle will be used for. Is the car a grocery getter, a street machine, or a weekend warrior? Will it be a heavy cruiser or a lightweight all-out race application? Next, we examine the engine combo by asking for things like the duration of the camshaft and the type of induction system they're running to determine what type of horsepower we are dealing with. We're actually trying to dyno the engine in our heads with the specs we gather, so the customer being truthful when relaying those specs ensures a closer fit in stall speed and an optimum torque converter. Obviously, a converter will flash stall more in a heavy car than it will in a light car. Likewise, a converter will normally stall higher in a big-block application than it will in a small-block application, unless a power-adder is used on the small-block. A higher-rpm engine normally has to use a much higher stall speed than a low-rpm torque engine."

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