||The torque converter article was published in the December 1995 issue of HPP. We would like to update the events since that time, and review the additional experiences with torque converters. I also would like to thank Tom DeMauro for allowing Twisting Force to be republished on this Pontiac website.
At the time the article was prepared, we were running a full size 13" Continental converter that had been designed to provide very good performance with the relatively heavy wagon while minimally degrading the all around driveability. It literally felt and acted like a stock converter in all normal driving, but upon application of full throttle, it would flash to about 2600-2700. This provided some improvement in the quarter or eight mile ET and speed over the previous unit. However, it seemed to ET best if the stall rpm was raised to only about 1200-1400 at staging, and then full throttle to leave. The wagon ran a best of 12.15 at 113+ with this converter.
Friend and fellow racer Dave Kawallek runs at the same track (KCIR, Kansas City, Mo) and has steadily improved the performance of his 71 TA. (See Torque Power on this site for details of Daves car.) We do a lot of racing each other to gage the progress each has made. In late 1996, Dave made some changes that not only made him competitive with the old wagon, but he began whipping on us! The most significant change seemed to be his new "tight 10" converter from Continental. As Dave drove to and from the track (about 50 miles round trip), we knew how it felt and drove on the road, I could see/hear it run down the track, and also had a chance to feel the effects at idle and in Drive. Although Daves car is a bit lighter, it is still a relatively heavy machine, and the converter seemed to be a blend of improved performance while still retaining relatively good driveability.
With all this in mind, I called Kris at Continental and discussed the expected results of Daves unit, or a similar converter, in the wagon. After extensive discussions, an identical converter was purchased and installed. The first and most noticeable feature was that the wagon would still creep at idle (true 750 rpm in Drive) on a level surface. And it would accelerate and move out quite well at light throttle. It did not require the engine to approach stall rpm to get the car to move. We did notice more slippage at low rpm when the throttle was kicked harder, or we were moving up a steep incline. All in all, the wagon drove very well on the street at light throttle.
When it came time for a real test of full throttle, we found a fairly quiet stretch of road with good traction, stopped, raised the rpm to the regular range of about 1400, and let her rip! Shock! The tires spun and left very visible trails for about as long as we held the throttle down through first gear. The wagon had excellent traction, and up to that time, a hard leave would cause a sound somewhat similar to running over a pregnant mouse - a little squeak and that was it. We tried several more times, and although the car left hard, it spun both 11" tires admirably.
Thus mentally prepared, a trip to the track was in order. Leaving at the normal 1400, the ET was about the same but the MPH dropped several MPH. This definitely was not in the plans, and after several runs, we become somewhat disappointed. Son Tom decided to try his luck, and he drove more by feel and immediately picked up both ET and MPH. He raised the staging rpm and the converter responded. We eventually found that the best performance was obtained when staging at about 1800-1900, although we could get it up to 2400 on the line. Traction became a significant problem, so steps were made to improve it. Adjustable shocks were installed along with special springs to allow a bit more body movement. The rear shocks were set to allow the body to separate from the chassis easily, but to not allow the body to drop without applying full weight on the rear axle. The front shocks were set to allow the front to lift easily. These changes got the traction problem under control, and the wagon responded with a total gain from the converter of about .3 seconds and about 2 MPH in the quarter on average.
As with most automotive products, the after market manufacturers, and individual specialists, have made great progress in developing converters with more torque multiplication, while minimizing slippage. While the cheaper generic converters havent changed much, custom or semi custom units have improved and can now provide surprisingly good drivability while allowing very hard launches when necessary.
In summary, the converter we now run still provides acceptable road performance while working excellently at the strip. It obviously is looser, and that would affect gas mileage on the street, but with a moderate throttle input, it is very driveable. At full throttle in any gear, the engine almost immediately will flash to the approximate 3200 flash/stall rpm. At that point, it is coupled very tightly, and will cause the tires to object vocally at both the 1-2 and 2-3 shift points (5500).
As a result of stepping up to a quality (and expensive) converter, we saw improved performance, but with a minor loss in overall driveability. In other words, the closer we get to a race converter, the more the car acts like a race car. The converter we are using is probably not acceptable in a true "daily driven to work" street car due to the slippage and resulting poorer mileage, and added slippage below 3000, in comparison to a stock style converter. In a hobby car that is driven on weekends, to the races, and general fun events, it is still totally acceptable. It proves what was discussed in the original article and that is that careful consideration must be given to all aspects of the total car setup - usage, weight, engine torque output at lower rpm, gears, traction, shift rpm, staging techniques, and all the other things previously mentioned. A generic converter off the shelf is usually intended for use in a light car with a low torque, higher revving engine, and will be disastrous for most Pontiac applications. -- Jim Hand, November, 1999.