Before we went further, we...
Before we went further, we disconnected the battery, as is customary with most work JDM does. It's even more important in our case since we had to undo the starter bolts and move the starter out of the way to remove the trans. We removed the starter after disconnecting the trans lines.
This high stall may be a concern for everyday street driving, but we didn't find this to be the case with the TCI unit. A converter's stall speed is the rpm that a given converter has to spin in order for it to overcome a given amount of load and drive the turbine.
Low stall speeds are great when you have gobs of low-rpm torque, as in a Lightning or with a positive-displacement blower. Obviously, the flip side is that the more stall speed, the higher the rpm needs to be before the turbine (and the car for that matter) starts to make headway.
This is the difference between a "tight" (low stall) converter and a "loose" (high stall) one. While you might think that a lower stall converter would get a car to move quicker, that's not necessarily the case. Ideally, for drag racing, you want a converter that stalls a few hundred rpm below maximum torque. If your 4.6 Three-Valve is making peak torque at 3,000 rpm, you want to be able to stall the car on the starting line near or somewhere below that, ideally in the neighborhood of 2,500-2,800 rpm. If you have a converter that stalls to 1,600 rpm, it will take time for the engine to reach its optimum powerband. Therefore, 60-foot times will be slow, and elapsed time as well as trap speed will be hurt as well. This is where torque-converter choice is both crucial and complex.
Here are the converters side...
Here are the converters side by side. The TCI converter (left) measures 10 inches, while the stock converter is a 12-inch piece. The difference lies in the internals, and the TCI converter features some stout pieces that increase durability as well as performance.
"The name of the game is to get the stall speed as high as possible," Akins says. "The stock converter will obviously offer better driveability, but it lacks in the performance department. When it comes to converter selection, first and foremost, the application in which the car is going to be used is key. If the car is a race-only vehicle, then an 8-inch converter would be perfect. For someone who wants to race their car on weekends and get good numbers, yet routinely drive it on the street, a compromise has to be made as something, be it ultimate performance or driveability, will suffer.
"In the performance arena, the perfect compromise is to get away with the most stall you can in street trim. Basically, we think 3,800 rpm is about the maximum amount of stall speed you would want on the street. The goal is to provide maximum power transfer with the least amount of slippage. Slippage creates heat, and heat is what kills a converter and a transmission."
The starter was bolted back...
The starter was bolted back into place. We checked the starter in relation to the flywheel and found that no shims were needed other than what were already utilized.
Once the purpose and application of the car are established, Akins and the rest of TCI's tech advisors look at a bunch of other factors before steering a customer in the right direction. "Once we know what the car is going to be used for, we then look at the rear gear ratio, the cam duration specs, the weight of the car, and whether or not the car is equipped with a power adder," Akins says. "Once we have all of that information, we give the customer an honest evaluation of what would best fit their needs based on our tech advisor's experience and knowledge."
TCI To The Test
We decided to test a TCI Super Streetfighter on a stroked naturally aspirated S197. The Mustang GT in question is owned by JDM Engineering's Jim D'Amore III and is equipped with a 298ci stroker engine sporting ported heads, stock camshafts, a custom tune, 4.56 gears, and no power adder. In this trim, the car has made 357 hp at the rear wheels. More importantly, though, with the stock converter, the Mustang has run a best of 11.879 at 115.30 mph while recording a 1.710 60-foot time. Oh, and one final note on our waiting patient: The car is driven on the street every day.
Knowing this little mod motor could benefit from a looser converter, we spent a day at JDM installing the TCI converter. We say a day because a bit of work had to be done to the factory converter plate to make things fit perfectly.
With the trans out of the...
With the trans out of the car, we removed the torque converter plate and then the stock converter. Once we pulled off the converter, we drained the trans fluid and measured how much came out. The fluid amounted to just under 3 quarts.
Before installing the TCI...
Before installing the TCI converter, we hit the snout of it with a handheld dremel to take off the paint for an easier installation. We also filled it with 3 quarts of Motorcraft Mercron transmission fluid.
We installed the converter,...
We installed the converter, spinning it around as we pressed on it to make sure it seated correctly.
We were reusing the stock...
We were reusing the stock converter plate, and on our first try found that the plate would not sit flush against the flywheel. The stock six-bolt flywheel on our Mustang was replaced with an aftermarket eight-bolt piece. Modification of the plate ensued, and eventually the plate was machined down and around so that it would sit flush against the flywheel. Once that problem was solved, we bolted the plate to the converter and torqued the bolts to 40 ft-lbs.
We then reinstalled the transmission....
We then reinstalled the transmission. Once the trans was in place, we tightened the bellhousing bolts first and the torque converter bolts second.
Here you can see the obvious...
Here you can see the obvious difference with the aftermarket flywheel, as it sports two extra bolts mating it to the crank.