Torque converter stall torque ratio

This device's torque corresponds to the maximum amount of torque it can produce without breaking or damaging. Measuring torque while the unit is stalled is the best way to gather accurate information. Various types of torque converters have measurable stall torques as well. For these devices, the stall torque is greater than or equal to the maximum output torque for a given input speed.

The industry standard by which all other converters are judged is the Borg Warner torque converter, designed by a fluid dynamicist from General Motors.

The Borg Warner converter is considered the standard because of its unique qualities while stalled, including its resistance to moving around in stall mode. A torque converter multiplies the stall torque ratio of a normal torque device.

For instance, the low rpm torque readings will be high due to the torque multiplication of the torque converter being run in partial stall. Likewise, the high rpm torque readings will be low due to the long period of time the dynamometer takes to allow the torque converter to transition from partial torque multiplication to a hydraulic locked condition. The only cure for this phenomenon is to rewrite the dynamometer software to prevent this from happening.

Torque converters with a low STR or low stall are not as adversely affected by this phenomenon. Conversely, a lighter vehicle takes less resistance to move. This brings us to the resistance against the pressure that tries to move the vehicle. The more resistance weight against the torque converter, the higher the stall speed to move that weight. The less resistance against moving the vehicle, the lower the stall will be in the torque converter.

Therefore, a 4. It is also a usable gear ratio to compensate for tall tires, commonly used for drag racing. Along with gear ratio, the height of the tire makes a big difference on actual output and the performance of the vehicle. For our calculations and easier math, we round it up and use 1. As you can see in the picture below, the taller tire will travel further than the smaller tire with only one revolution. To understand the effect of vehicle, gear ratio, and tire height, Gill offers up a case study based on a vehicle with a curb weight of 3, pounds:.

When considering gears and tire combinations, there is another factor that comes into play: rolling resistance. This increased rotating mass robs horsepower. With the gear ratio and the rollout of the tire, you can better see how much resistance there is against moving the vehicle.

As we mentioned in the first post of the series , that resistance and the diameter of the torque converter dictate how the torque converter stalls. The combined information of these All About Stall posts should help you understand that actual stall range is variable and depends on your engine and vehicle setup.