Over the past few months we have been experimenting with various clutches in our Turbocharged Lotus Elise. Throughout last year, including 3 track days at over 300whp, we used the stock clutch without any issues. In preparation for the 2011 season, we were planning on pulling the motor for maintenance and decided to upgrade the clutch since the install would be simplified with the engine/transmission out of the vehicle. With plans to push the engine harder, the stock clutch might reach its max holding capability and a upgrade was necessary.
This picture shows ACT (top) and South Bend (bottom) clutches.
Having success with South Bend clutches on other applications, we chose their TZ Series KTY14 clutch. This clutch is rated for 25% more ft-lb of torque compared to the stock clutch. The pedal effort was very streetable similar to the Toyota clutch.
After installing the South Bend Clutch, we put around 50 miles on the clutch and then began dyno tuning. Toward the end of our dyno session we noticed some clutch slippage. At this point, the car was making about 220 ft-lb max torque. We thought the clutch was overheated and did not address the issue. The following track day at Portland International Raceway, after several successful sessions, the slipping issue returned.
After contacting South Bend, they requested that we return the clutch so they could examine and determine the problem. We are waiting for their diagnosis.
In the meantime, we installed an ACT TC2-XTG6 clutch. This is a 6-puck sprung disc with an "Xtreme" pressure plate. This clutch is rated at 400 ft-lb max torque (at the flywheel). We plan to test the GTX3076R (600+hp) turbo early next year using this clutch.
The ACT clutch comes with alignment tool. This is the first 2-piece tool we have seen for the 2ZZ-GE.
The alignment tool bushing gets pressed into the center of the flywheel as shown. This bushing remains in place even after the clutch is fully installed.
Advanced Clutch Technology (ACT) clutch completely installed.
After driving this clutch on the street we have noticed some differences. The increased pedal effort is prevalent but not unbearable. Also, there is no excessive chatter during clutch engagement. We will be putting this clutch to the test this coming weekend at the Lotus Cup USA HPDE event being held at Portland International Raceway. We will report back on its performance.
Hopefully, these experiences will allow us to make educated recommendations when discussing clutch upgrades with customers.