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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Multiplication Ratio
Joe Rivera: "Most people are familiar with what a converter's stall speed is, but a converter's multiplication ratio is an important performance factor as well. Back in day, all you'd hear about is stall speed, but you can have a converter with a lower stall speed and a higher torque multiplication ratio that accelerates a car faster than a converter with a higher stall speed and lower multiplication ratio. Every torque converter has the ability to multiply torque. This is a product of the converter taking energy from the trans fluid and redirecting it, which multiplies torque. As the ratio of turbine speed to pump speed increases, torque multiplication decreases. The confusing part is that multiplication ratio is independent of stall speed, and it's based mostly upon the design of the stator and pump. The average converter has a multiplication ratio between 1.9- and 2.5:1. The goal is to match the stall speed with an engine's power curve, and maximize the multiplication ratio as much as possible."

Stanley Poff: "Furnace brazing is a term that's thrown around a lot by converter manufacturers, and is a very common method of strengthening the internals. During the furnace brazing process, the turbine and the pump impeller are loaded with a powder brazing and run through an oven that causes that powder to melt and conform along the entire length of the fins. These fins are not very stationary from the factory since they're mass-produced pieces, so they're tightened down at TCI before the process begins. The powdered brazing material melts in the oven, and conforms to the complex contours of the fins. After it cools, the brazing materials bonds to the fins, creating one solid and uniform component. The final product is substantially stronger than an OEM torque converter, which are rarely furnace brazed."

Stanley Poff: "Even though the pump impeller and turbine inside a torque converter don't physically touch each other, the extreme pressures inside a converter can distort its internals. Factory torque converters are mass-produced, and aren't designed to work or last under higher-horsepower applications. They usually incorporate thrust washers instead of needle bearings, inferior stamped steel mounting fronts, and non-brazed internals. To endure the demands of high-hp engines, a TCI performance torque converter has a fully furnace brazed pump impeller and turbine, a machined stator, and sometimes even handbuilt steel stators with bearings that ride on both the surface of the turbine and pump impeller. In some instances we install anti-ballooning plates to the pump impeller and the mounting front to reinforce them for strength. In extreme-hp applications, we use forged or billet front covers."

Joe Rivera: "When it comes to torque converters, everyone hears about features like billet covers and furnace brazing, but do they really understand what that means? There's a lot of time and energy that goes into building a durable product that performs properly. What really good shops do is pay attention to the finer details. One of the things we do differently is box weld the anti-ballooning plates to ensure there is no flex or movement in the pump. We also use anti-ballooning plates on the turbines to make sure they don't move around either. Other tricks include billet stators that are machined from a single hunk of billet steel, and top-of-the-line billet front covers to make sure that they are as light and as strong as they can be. No one talks much about bearings, but they're a critical component in building a durable converter. We use oversized bearings that can withstand the load of up to 4,000 horsepower.


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