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two timer stator. In turn, the pressure forces A SWITCH-PITCH TORQUE CONVERTER the piston to move, which changes the angle or pitch of the stator FOR 6-SPEED AUTOMATICS By Steven M. Green blades. The flatter the pitch, the higher the stall speed and torque orque converter design has on the mammoth GM models in 1964. multiplication will be. Since the always been a compromise (Remember "Switch the Pitch"?) converter is electrically activated, the T between stall speed and Kenne-Bell Performance Products driver can switch it manually for each efficiency. High stall speed converters of Pomona, California, has unearthed gear-in essence, creating a are necessary with modified engines a supply of new parts necessary to six-speed automatic transmission. to launch the car properly, but convert a Turbo 400 transmission to The stator change can also be anything over a 2500 rpm stall speed a two-speed torque converter signalled automatically with a is too ''loose" for street use. package. Essentially, the parts full-throttle kickdown switch. Excessive slippage and heat build-up consist of a different pump assembly, The K-B setup performs as well on are unsatisfactory on the boulevards. input shaft, torque converter and the street as on the strip. During An ideal torque converter would solenoid. normal driving there is minimal have a high stall speed in first gear The heart of the system is the slippage and fuss. Reliability is no to multiply engine torque, and then a stator, which is the middle element in problem, since the parts have low stall speed once the car is the torque converter. In the standard endured GM's testing and moving for economical operation. position, the converter will produce a development. All components are One possibility, which was discussed 2000 rpm stall speed; in the high stock, except for some machining on in the March '77 issue of CAR position, a 3000 rpm stall speed the stator piston. CRAFT, is a lock-up converter. results. Sometimes the best new idea is an Chrysler has adopted a similar The system is controlled by an adaptation of an old idea. What was design in its '78 cars. Another electric solenoid which routes the once designed for a Buick possibility is the old GM two-speed pressurized flow of transmission oil Roadmaster might well make you the converter device originally installed to a piston in the center of the local master of the road. An inexpensive adapter is available to mate a Chevy small-block to a complete Buick switch pitch Turbo 400 transmisson. The complete conversion kit (left) from Kenn e-Bell includes the torque converter, pump, input shaft and sole noid. Heart of the system (below) is the variable p tch stator (on left), compared with a fixed pitch stator (on right). These components are welded inside the torque converter.' CAR CRAFT NOVEMBER 1977 The GM Turbo Hydra-matic is an evolution of the series 300 two-speed, is exceptionally strong, can be beefed further for very tough labors. If the Turbo has a fixed pitch stator, part of the conversion required is pump assembly and switch units, avail- able through K-B. Pump assembly has drilled turbine shaft. Key to identification of variable pitch stator-equipped Turbos is small electrical connection at left rear of housing. VP units were made from 1964-'67, used in heavier cars. Jim Bell, part of the Kennedy-Bell Buick combine, displays one of the special K-B variable pitch converters used to get cars off the line quicker, keep Turbo Hydra-matics more efficient. Shown are a few of the converters tested during development of "switch-pi tch " six-speed. 20 Pump for variable pitch stator is at left, unit for fixed stator is at right. Note apparent difference in shafts. Pump shaft is also drilled to pass oil Difference in stators is readily apparent. Unit at left has along to operate stator blades All movable blades, fixed unit on right is cast as one piece. these parts must be'in excellent condi- Units shown are for different cars, thus difference in size. tion. WITH A FEW SIMPLE MODIFICATIONS, THE TURBO HYDRA-MATIC CAN BE- TUNED INTO A REAL TRICK-SHIFTING TROPHY GRABBER By Tex Smith All the time you hear about this or rest of us when it comes to getting cations and the variable pitch stator that hot dog's super-secret trick stuff that extra speed or cutting a quicker (VP) for the heavier cars. The variable that he uses to make the big quarter- ET. pitch stator is a hydraulically-adjusted mile runs. Sometimes there are tricks, Back in 1964, General Motors mechanism to make the torque con- but usually it's all a batch of supersti- introduced a new three-speed automa- verter more or less efficient. It has tious smoke deployed to put a mental tic transmission to the performance been virtually discarded by automatic hole shot on the opposition. Not so market, just in time to keep up with transmission experts, who are nor- with a scoop we've just unearthed out the spiraling demands of super engines. mally working with lightweight vehi- at Kennedy-Bell, Glendora, Calif. These new automatics were originally cles and can therefore rely on the For a number of years now, the introduced in the big cars, such as fixed pitch stator. Kennedy-Bell has K-B duo has been laying it on compe- Cadillac and Buick, but became stand- used the variable pitch stator with tition, and doing it with a most incon- ard options the following year for all great success, however, because they gruous machine - a Buick. While it is smaller GM lines. The success of this are working with heavier cars and true the pair are considered inside- transmission, the series 400 Turbo usually with engines having excellent outsiders (they help the factory in Hydra-matic is now history, but one low-end torque. It is necessary to performance evaluations), they don't peculiar design attribute has gone understand the function of a torque work with the bundles of lettuce so largely unnoticed. And this is the K-B converter to appreciate the variable many performance consultants do. secret. pitch stator. They're just ordinary hot rodders with When the Turbo Hydra-matic trans- The idea behind any automatic a special pass to the engineering mission was introduced, it included transmission is to put the maximum department. Which means, in short, two different kinds of stator assem- engine power on the road with a that they are in the same boat with the blies, the fixed stator for general appli- minimum loss of power enroute. As Blades in open and closed position, showing how much affect they have on oil flow and unit efficiency. adjusted by the mechanic, the automa- tic will shift at exactly the right time relative to engine rpm and torque. Getting this power into the automatic is a load absorption device - the converter, or fluid coupling. Early automatics used a fluid coupler, which is simply a slipping clutch. The torque converter actually multiplies available torque. The Turbo Hydra-matic converter is si milar to most units, including a driving member (pump impeller), driven member (turbine) and reaction discharges the fluid at the pump rim stator is fitted between the pump and member (stator). The stator is what between the blades. turbine, mounted on a one-way roller we're concerned with here. The pump shells and blades are clutch. This clutch is a sort of sophis- I n the variable pitch (VP) design, shaped to make the flowing oil spin in ticated roller bearing, constructed so t he individual stator blades are hydrau- a clockwise direction toward the tur- t hat it will turn in a clockwise direc- lically-operated to assume either high bine blades, causing the turbine to tion, but when it tries to turn counter- or low angle, with the low angle turn. At low engine speeds, the oil clockwise, the rollers are jammed be- ( about 1 3 degrees to the plane of force is not sufficient to turn the t ween outer and inner races. They rotation) being the position for maxi- turbine efficiently, but the efficiency then lock up. The oil from the turbine mum efficiency. At wide throttle increases rapidly as rpm increases. The spinning counter-clockwise is then settings, where good acceleration and oil flow in the turbine blades and shell again reversed across the stator blades overall performance are both is reversed, so it leaves the turbine and hits the pump inlet spinning in the demanded, the blades switch to a high center spinning counter-clockwise. correct direction. angle (about 26 degrees). This high When this has happened, the tur- The energy of this oil pressure is angle is also used when the engine is bine has absorbed the force required added to the engine torque already idling in gear, to effectively reduce the to reverse the oil flow direction, there- turning the pump, and the overall tendency of the car to creep (the unit by creating greater torque at the tur- torque is again multiplied. With the is less efficient at the high angle, thus bine than is being directly delivered by engine running at full throttle, trans- giving less torque multiplication). In the engine. The process of multiplying mission in gear, and the car motion- converter is thus capable of t he fixed stator design, the blades are engine torque through the converter less, a stationary at the maximum compro- has begun. multiplying engine torque by about mise efficiency angle, at about 23 Were the counter-clockwise spin- 2-to-1.

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