In the scheme of performance improvements, engine modifications get all the glory. When it comes to getting from point A to point B quickly the most obvious solution is adding more power. But there is an often-overlooked improvement with automatic transmission-equipped vehicles, which enhances performance with no loss of drivability. Best of all, it’s a true bolt-on part that can be installed in an afternoon. That simple change is a torque converter swap.
The subject of our swap, a 2006 Mustang GT, was completely stock right down to the P235 tires. This untouched Mustang would be perfect for our torque converter test as the recipient of the latest in torque converter science as applied by the engineers at
TCI Automotive.
After a quick stop by the Memphis Motorsports Park for some baseline performance figures we headed over the dyno at
COMP Cams headquarters. Testing for rear wheel horsepower and torque the bone-stock ‘Stang netted 248 horsepower and 241 pound-feet of torque. With the number locked down, we were ready to see just what was possible.
Zack Tibbet’s 2006 Ford Mustang exhibited excellent performance right off the showroom floor. In street trim using the all factory parts, the black GT turned at best time of 14.35 seconds at 97.05 MPH. Why does it Improve Performance?
Torque converters are truly a mysterious component to most performance enthusiasts. Understanding just what they do can be challenging. Inside that simple shell, a lot is going on. In a nutshell, the torque converter does exactly what they name implies and converts engine power into torque that drives the transmission and ultimately your rear tires. Furthermore, it multiplies this engine torque, providing required performance benefits to your transmission’s operation.
With the TCI performance torque converter, the stall speed is changed through modification of the stator. In addition to the TCI
Streetfighter torque converter we’re installing in this stock Mustang, TCI also offers the top-of-the-line
Super StreetFighter torque converter for S197 Mustangs. In the Super StreetFighter, the multiplication is further enhanced through the usage of a completely custom hand-built steel stator, creating as much as a 2.5-to-1 torque increase. In either case, this moves the “flash” stall speed (the point at which the vehicle begins to first move under wide open throttle) to a higher RPM. With our stock Mustang, the flash stall speed of the factory converter was approximately 2500 RPM. With the new
StreetFighter, the new stall speed was nearly 3000 RPM.
Using the COMP Cams chassis dyno, the power numbers for the Mustang were checked. The results were very consistent at close to 250hp and 240 pound-feet of torque.
So how does this help performance? With the higher stall speed, three good things happen. First, the increased torque multiplication of the converter results in quicker 60-foot acceleration times. Second, the engine RPM is higher at the start of the run, placing it at a higher horsepower point within the engine’s power curve. Third, the engine RPM drop during gear changes is reduced, increasing the efficiency of the acceleration run.
Horsepower isn’t the Whole Story
With our new StreetFighter torque converter safely back in place, we again headed for the chassis dyno to see the fruits of our labor. The result – exactly the same power figures for both torque and power. That didn’t surprise TCI Engineer Kevin Winstead. “With a torque converter change such as this where the stall speed is raised, the rear wheel dyno power can actually be slightly reduced,” he explained. “The performance benefit is in the performance feel and shift point selection.” That fact was clearly realized by the owner of the vehicle Zach Tibbett who noted a “personality change" to the vehicle the instant he first stepped on the accelerator. Despite the higher stall speed, he felt the vehicle reacted more quickly to throttle input and faster even in cruise mode.
“There was an immediate difference in seat-of-the-pants performance,” said Tibbett. “The car is much quicker than previously. In comparison to the original converter, the car’s acceleration seemed greatly improved and the shifting felt crisper. The performance figures from the track further backed that up.”
In a power braking stall speed check (holding down the brake and pressing on the throttle until the car moves) the stock converter let the engine rev to 2100 RPM.
How much faster was the Mustang after the torque converter change? How about 0.41 seconds in the quarter mile with no other adjustments. With the new converter installed, the best time for the black ‘Stang was now 13.94 seconds at 96.45 MPH. Noting that true engine horsepower to the rear wheels is denoted by the mph numbers, the fact that this was slightly down was in keeping with Winstead’s expectations.
So what have we learned? There is hidden performance locked within the torque converter of late-model Mustangs. The new StreetFighter line of torque converters can help you unleash that performance with a simple converter swap. Best of all, it serves as a great launch pad for other performance-adder options knowing that the torque converter is up to the task with improved internal quality way beyond the factory component. Better performance and durability – what more could you ask for? Well, how about a supercharged Mustang, made even quicker with just a converter swap?
Round Two - Super StreetFighter Installation
There’s always one guy in the crowd who decides to show everyone he’s truly serious. Kevin Estes purchased a 2005 Ford Mustang and promptly announced that his new white GT was to be his wife’s car while he drove the company work truck. And five days a week that’s true, but on weekends Kevin can often be found hammering on the Mustang at the local track. Kevin’s most recent performance: 12.15 seconds in the quarter mile from a very stock-appearing Mustang.
To take it to the next level, Estes offered up his Mustang for a torque converter swap. While the outside of the Mustang appears quite stock, under the skin is a highly modified Ford including a Saleen twin screw supercharger, headers, Steeda suspension parts, Strange shocks and host of subtle but potent changes. The test would be to see if a torque converter swap with this kind of vehicle can improve its quarter mile performance.
To handle the high horsepower Ford, TCI Engineer Kevin Winstead prepared a
TCI Automotive Super StreetFighter torque converter. Expecting a flash stall speed of 3500 RPM from the supercharged application, TCI engineers installed the converter in the same manner as the stock Mustang. The results? 11.746 at 116.02 MPH.
The Super StreetFighter constructed for Estes included a custom hand-built steel stator with performance-oriented blade angles and number of internal blades and a more aggressive pump fin angle. While the impeller blades were left at the stock angle, the turbine has been hand and furnace brazed to ensure that the converter achieved the highest performance and durability possible. Many of the lessons learned in the production of the PRO-X™ line of racing converters (capable of handling 2500-plus horsepower) have been used in the creation of the Super StreetFighter converter lineup.
Said Estes after his test runs, “As far as the torque converter goes, I am thrilled with the performance and streetability. The car is actually easier to manage on wet streets and limited traction situations. It really shines when the throttle is wicked open at low RPM, such as at the starting line. The revs immediately jump to about 3500 as the torque converter flashes, and you'd better have the car pointed in the right direction because the converter locks and she's gone right now! Shifts are still crisp and firm and the power band of the twin-screw blower is fully utilized with no wasted low-end torque. I couldn't be happier with the COMP cams/TCI Super StreetFighter torque converter.”
Follow along as we take a step-by-step look at how TCI upgraded Zach's GT with a new StreetFighter Torque Converter, and got Kevin deep into the 11’s with a Super StreetFighter tailored especially for his blown Mustang…
Step one was to unhook the battery cables. With computer-controlled systems, this is an important safety precaution. 
The driveshaft is a complex component in S197 Mustangs. Unbolt it from the rear of the transmission and then unbolt the rear-mounted hoop and move the driveshaft out of the way to provide clearance, allow lowering of the transmission. 
Note that a centering pin protrudes from the rear of the transmission and can hang up the driveshaft movement. 
On ‘05 and newer Mustangs equipped with the 5R55 transmission, it isn’t mandatory to drain the transmission oil. However you will need to refill the transmission once the new converter is installed because of the fluid lost during removal of the converter and the cooler lines. This transmission does not have a transmission fill tube so fluid must be pumped up into the transmission through this fitting to refill fill the pan.
Next, unplug the oxygen sensors from the underside of the transmission body. These sensors simply plug into the main wiring harness.
After removing the inspection cover, remove the nuts that attach the flex plate to the torque converter mounting plate. Four nuts must be removed. To keep them from backing off once they have been torqued in place, the factory uses special “pinch” nuts. The engine can be turned over with a remote starter switch but will require reconnecting the battery for this step. Remember to unhook it again once you’re finished, or use a crank socket and breaker bar to carefully rotate the engine instead of the starter.
Using a 22mm wrench, carefully remove the oxygen sensors from the exhaust pipes. If you don’t, there is a possibility of damaging them or the attached wiring.
Unhook the transmission cooler lines, making certain not to bend them or strip the line fittings. The cooler lines will leak fluid once you unhook them, so be ready with a catch pan.
Unbolt the starter using a quarter-inch-drive ratchet or box end wrench. The starter can be simply tucked out of the way to provide enough clearance to lower the transmission.
Using a long extension on a socket wrench, remove the bellhousing bolts. With a transmission jack carefully positioned under the transmission, unbolt the exhaust system at the catalytic converters and the rear crossmember. Slowly lower the transmission to provide enough clearance to reach the upper bellhousing bolts.
Be especially careful with the transmission linkage system. Pay close attention while unclipping the system and note the original position of these parts.
Carefully pry the flex plate away from the back of the engine. The studs protruding from the torque converter mounting plate have a tendency to catch on the back of the engine.
The 5R55 transmission has a number of connections on the passenger side of the unit. Carefully unscrew the main connector from the housing and unclip the other sensor connections. Note the original sensor placement for easier reinstallation later.
You just can’t be gentle enough when working with these plastic connectors. Most of them feature a pinch and release design, but some are far more complex. Take your time, as replacement connectors can be very expensive.
This is the most critical part of the torque converter swap. When lowering the transmission make certain it is carefully balanced - attaching it to the jack with straps is a good idea.
Clearing the transmission cooler lines can be a problem. Make certain they don’t become smashed or bent during the removal process.
The transmission, finally free from the car, is now ready for removal of the torque converter. Keep your hands on the converter as you move the transmission so that it can’t slip off.
Be careful that the transmission is balanced properly on the jack and remember that when you remove the converter, you are removing a large amount of weight and the transmission can become unbalanced. 
The converter holds approximately 3.5 to 4 quarts of ATF. When you remove it from the transmission, it will release some fluid, so catch it with a drain pan. Once out of the vehicle, drain the converter in a catch pan. 
Unbolt the torque converter mounting plate from the old converter in this manner. 
The old torque converter mounting plate must be bolted to the new TCI StreetFighter torque converter. Use the same nuts used by the factory to reinstall the flex plate and torque them to factory specs. Use a torque wrench, not an impact gun – we’re professionals and have specially-calibrated air tools, so there. 
Pre-filling the new torque converter with at least two quarts of the appropriate transmission fluid is an important step. Filling it completely will only cause it to leak out when you lift it back onto the transmission snout. 
Lift the converter onto the snout and twist it until it seats on the input shaft (you’ll hear it go into position). There are three distinct engagements to be made by the torque converter. Note the final position of the converter. If your converter doesn’t seat firmly or is not in the right position, work the converter back and forth until it’s where it needs to be. This is critical to making the transmission operate properly. 
“Reassembly is the reverse of disassembly,” as they say. The oxygen sensors must be reinstalled properly to make certain the vehicle electronics work correctly. Make certain that the coverings are in the right place and that the wiring is situated so it cannot come in contact with other parts or catch on road hazards. 
Without question, this is the most frustrating pan fill system we’ve ever encountered. Without a dipstick tube, pumping oil up through the center of the oil drain plug is the only way to top off this transmission. The inner tube in the drain plug sets the fluid level. Once the oil in the pan has reached the correct level, the fluid will drain back out of the center tube. In order to properly fill the car, it must be idling in park and be level. Make certain that the main drain plug is snugged up, fill the system, and then reinsert the center Torx-headed plug. 
Unlike Tibbett’s GT, Estes’ Mustang is not stock piece. The twin-screw Saleen supercharger is a big performance adder and required the installation of the TCI Super StreetFighter torque converter. 
A number of other performance-enhancing modifications have been completed on the Estes Mustang. Note that these headers have different O2 sensor positions from the factory installation. 
Pulling down the transmission was not a huge challenge, just a matter of logically removing the parts that were in the way to ensure nothing was damaged, especially wiring loom components. 
The master technicians at TCI removed the original torque converter and installed the new Super StreetFighter converter. The original torque plate was used as shown here. 
The result of the converter swap was a best pass of 11.746 at 116.02 MPH – a full 0.41-second improvement in the quarter with no other additional modifications. Source:
TCI
Web:
www.tciauto.com
Phone: 888-776-9824
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