Tech: EcoBoost Mustang Torque Converter

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VMP Tuning beefs up its EgoBoost Mustang with a Circle D converter

By Steve Turner
Photos by Steve Turner and courtesy of VMP Tuning

The automatic transmissions in the latest Mustangs are quite capable. Back in the day choosing the slushbox meant your car was slower. These days, opting for the 6R80 six-speed automatic often means your Mustang is quicker and more consistent than the manual-trans ’Stang in the next lane.

VMP Tuning’s BJ McCarty was having a hard time building boost off the line with the footbrake and stock converter, so he turned to Circle D Specialties for a new torque converter.
VMP Tuning’s BJ McCarty was having a hard time building boost off the line with the footbrake and stock converter, so he turned to Circle D Specialties for a new torque converter.

That said, an automatic presents a challenge in a hopped up EcoBoost Mustang that lacks a factory line-lock. Standing on the brake pedal and revving the engine at the starting line to build boost is a challenge with the stock transmission, especially when you have modded the car for increased power with a Borg Warner EFR 7670.

“While the larger turbo exhibits outstanding driving characteristics for daily driving and blasting past Camaros, Challengers and stock Coyotes, the stock converter wouldn’t allow us to foot brake any higher than about 2,700 rpm,” VMP Tuning Business Manager BJ McCarty said. “That didn’t produce the boost we wanted at launch in a drag scenario. A higher stall would allow us not only to build more boost but to spend less time spooling it up.”

To that end, BJ turned to Circle D Specialties for one of its Pro Series Stage III Billet Multi Disk Torque Converters. See BJ’s car and its converter outrun VMP’s stock GT350 project here…

“Circle D’s reputation is well-known throughout the industry and our own work with them on Rebecca Starkey’s Coyote Modified car showed us that their converter and the 6R80 was a great match,” BJ added.

Circle D recommended a 245mm unit (right) for BJ’s small-cube, boosted setup, and it features 100 Square inches of clutch lining for lock-up at wide open throttle, which should help BJ’s cause. The rugged Circle D units are furnace brazed and hand welded and feature Torrington bearing, billet fronts, billet pistons, and a hand-assembled impeller hub.
Circle D recommended a 245mm unit (right) for BJ’s small-cube, boosted setup, and it features 100 Square inches of clutch lining for lock-up at wide open throttle, which should help BJ’s cause. The rugged Circle D units are furnace brazed and hand welded and feature Torrington bearing, billet fronts, billet pistons, and a hand-assembled impeller hub.

The company offers a wide variety of torque converter upgrades for the six-speed automatic in the latest Mustangs. The nature of the 2.3-liter EcoBoost engine is much different from a naturally aspirated 5.0-liter, so the experts at Circle D spec’d out just what BJ needed.

“When we build a converter for a 6R80 the two areas we are focused on are performance and durability. The durability side we handle with our exclusive Circle D Specialties billet parts, made in-house on our CNC equipment,” Chris Sehorn of Circle D Specialties said. “It is an extremely rigid setup to prevent any flexing and it is loaded with ball bearings and needle bearings, plus furnace-brazed and TIG-welded, flanged impeller hubs and heat-treated clutch packs. All of which add up to a killer converter.”

Before you remove the stock trans and converter, use a straight edge to verify the converter pad depth so you can reference that distance when you install the new converter. Once the stock trans and converter are out of the way, inspect the factory flywheel for damage. If everything looks good, you can proceed with the swap.
Before you remove the stock trans and converter, use a straight edge to verify the converter pad depth so you can reference that distance when you install the new converter. Once the stock trans and converter are out of the way, inspect the factory flywheel for damage. If everything looks good, you can proceed with the swap.

“On the performance side we have several choices depending on the powerplant. 245mm, 258mm or even a 265mm converter, all with multiple pump and stator choices to match the power curve and desired driving style,” Chris added. “For the EcoBoost Mustang we are using our 245mm units and a special stator that works well with the smaller-cube, boosted setups. Five E is the part number that is on BJ’s car, with his current setup is working very well. It is a continual evolution, we are always looking for ways to take it to the next level.”

You probably should check the converter on the flexplate first to ensure the bolts line up. Then you can pre-lube the new converter with a half quart of fluid. It may take a little time for the fluid to fill the new unit.
You probably should check the converter on the flexplate first to ensure the bolts line up. Then you can pre-lube the new converter with a half quart of fluid. It may take a little time for the fluid to fill the new unit.

BJ was kind enough to document the upgrade on his car in photos and share them with us, so we’ll hit the highlights here.

“The installation really isn’t tough. A lift and a trans jack (and perhaps a second set of hands) is about it,” BJ said. “Pull the driveshaft, then the trans and the converter is pretty much a straight up swap. Circle D provided an excellent instruction tip sheet for reference.”

The install was definitely worth the effort. At the drag strip, the converter flashes to well above 4,000 rpm and BJ is able to build 20 pounds of boost on the foot brake versus the 10 he could generate with the stock converter. Thus far he has run a best e.t. of 11.72 at 115 mph, which is enough to surprise a lot of NA Coyotes.

Slide the converter onto the transmission input shaft and reinstall the transmission. Be sure to keep checking the converter clearance as you tighten things up. If you don’t have clearance, stop.
Slide the converter onto the transmission input shaft and reinstall the transmission. Be sure to keep checking the converter clearance as you tighten things up. If you don’t have clearance, stop.
No you can bolt up the converter, which is supplied with hardened bolts, washers, and medium-strength thread locker.
No you can bolt up the converter, which is supplied with hardened bolts, washers, and medium-strength thread locker.
Apply thread locker and torque each fastener to the factory spec, keeping an eye on the clearance as you go. Once everything is bolted up and checked out, fill the transmission with fluid, reconnect the factory harnesses, and you are ready to go.
Apply thread locker and torque each fastener to the factory spec, keeping an eye on the clearance as you go. Once everything is bolted up and checked out, fill the transmission with fluid, reconnect the factory harnesses, and you are ready to go.

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