Many car enthusiasts believe the path to better performance is through engine modifications. The problem is that many engine modifications don't work out exactly as you might expect. Modifying the car and engine you drive everyday can be tricky business. Most engine modifications are compromises -- low-end torque for top-end horsepower, fuel economy for acceleration, or even worse, reliability for that newfound performance.
What many car enthusiasts don't know, or simply overlook, is that you can get more performance out of the power you already have. Power (more accurately, torque) is never delivered directly from the flywheel to the pavement without first being multiplied by gear ratios in the transmission and the differential. The math is pretty simple: A car with a 4.0:1:1 gear ratio puts 33 percent more torque to the wheels than a car with a 3.0:1 gear ratio with no increase in engine torque. However, changing gear ratios is another one of those compromises. Drive-ability is adversely affected because the engine revs higher at all speeds, uses more fuel and wears itself out faster. Bottom line: Gears will help your car accelerate quicker, you'll just hate the added rpm if you drive your vehicle any distance.
Meet the Torque Multiplier
If your car has an automatic transmission, it has an additional torque multiplier above and beyond the trans and the differential gears. It's called the torque converter because it is a fluid coupling that disengages the engine from the transmission at idle so you can pull to a stop or shift gears without stalling the engine. The torque converter is actually a misnomer -- it should be called the torque multiplier because it doesn't simply provide a one-to-one connection to the transmission like a clutch does with a manual transmission.
A torque converter will multiply engine torque on takeoff. This torque multiplication factor remains in effect until the vehicle speed catches up with engine speed. A purpose-built high-performance torque converter can multiply torque even more, as much as 2-1/2 times. OEM torque converters can vary greatly in the amount of torque multiplication and stall speed. Replacing your stock torque converter with a high-performance torque converter can decrease quarter-mile times by 0.4 to 0.6 seconds with no other changes. Installing a high-performance torque converter should be the first step in any performance upgrade program.
Torque multiplication is just one important parameter for selecting a torque converter. Stall speed, the speed at which the converter slips under full-throttle, full-load operation is important as well. Early race/street-type converters built a few years ago focused solely on stall speed. As long as the converter slipped enough to get the engine into the torque peak, it was considered a success -- not very efficient, but it worked. Today's new trucks have efficient torque converters, but lack the necessary stall speeds for optimum performance.
Custom Performance Torque Converters
That's where custom torque converter manufacturers such as Pro Torque come in. They analyze your vehicle -- items such as horsepower, torque, weight, transmission type, gear ratio, and tire size and then design a custom torque converter specifically for your vehicle. Pro Torque custom-machines the internal components to provide the correct stall speed (slip) and torque multiplication to match your vehicle combination. They also modify the unit for increased durability through the process of furnace brazing the impeller and turbine vanes in place, installing Torrington bearings, and installing a larger ceramic-impregnated lockup clutch.
With today's lockup overdrive transmissions, there is not much of a down side to installing a high-performance converter. Typically Pro Torque builds torque converters with stall speeds of 2,400-2,800 rpm versus OE factory stall speeds of 1,300-1,700 rpm. In normal driving conditions, you won't notice much difference. Under heavier throttle applications you may notice the engine revs a little quicker. But as soon as the vehicle hits the higher gears, the torque converter locks up and the engine and transmission become solidly coupled.
We found a perfect vehicle to do a Pro Torque custom torque converter installation. Tommy Pierson, president of K&P Engineering in Irwindale, California (one of the nation's oldest Go-Kart manufacturers), was tweaking and testing a 2000 supercharged Ford Lightning F-150 pickup truck. He had installed the usual bolt-ons including an 80mm throttle body, a Swanson Performance engine management chip, and a set of 26x11.5x16 Mickey Thompson slicks. The sum of these changes had reduced his quarter-mile times from the low 14s to 13.33 at 102.5 mph. However, the Lightening still felt lazy off the starting line. Pro Torque had just the solution -- a 10-1/2-inch-diameter 2,400-rpm stall speed, lockup torque converter.
Tommy took his truck to a local transmission shop where the stock torque converter was removed and the Pro Torque installed in approximately 7 hours (see step-by-step installation tips). The results were pretty impressive. His quarter-mile times dropped to 12.86 at 104.6 mph with no other changes. That's a 0.47-second reduction in quarter-mile performance. Tommy reports virtually no loss in driveability and the ability to smoke the rear tires at will.
A torque converter is something a well-equipped do-it-yourselfer can do if he or she has a transmission jack and the means to raise the vehicle up high enough to use it. Follow along as we show the step-by-step installation segment.
Pro TorqueDept. TR
1440 Church St.
Bohemia, NY 11716
Tommy Pierson smokes the tires prior to a 12.86-second, 104.6-mph run at Pomona Raceway. T
1. George Hiatt of San Dimas Auto began the converter swap by removing the center crossmem
2. Next, the battery was disconnected and the starter was removed for better access to the
3. The driveshaft was removed after loosening the bolts that fastened the U-joints to the
4. A transmission jack was used to support the transmission while the bellhousing bolts we
5. Hiatt wasn't sure that the exhaust system would have to be removed, but it did. Note th
6. Now the transmission was eased back away from the engine. Make certain that all linkage
7. The stock torque converter came out with the transmission. Carefully remove it by simpl
8. A & B This photographically shows the difference in overall diameter between the 10-1/2
9. Hiatt slid the new Pro Torque converter in place after filling it with transmission fl
10. Here the trans/converter assembly was ready to be bolted back in place just reversing