Torque Converter Lockup: the point at which the converter in an automatic transmission is the most efficiently providing the most Horsepower (HP) and Torque. It's the sweet spot tuners know will get that car down the track with consistent HP, and the best ET’s. However, knowing just where that point is can be a challenge. So, we're going to give everyone a road map to finding that right point. Before you get started, always ensure torque converter and clutches are rated to handle the Horsepower and Torque of the combination. You can get this information directly from the converter manufacturer. For example, typically you need a quality triple disc converter to hold the power while locked up behind a powerful forced induction application.
To get started, we recommend having the following materials:
- Dynamometer (preferably Eddie Current Loaded)
- Your favorite tuning software
- Your favorite scanning software
- Fans to ensure engine and transmission temperatures stay constant to get consistent run information
Using the dyno, make two pulls in the 1:1 gear ratio of the transmission, with the torque converter unlocked. For example, the 1:1 gear ratio of a Ford 6R80 automatic transmission is 5th gear. Then after a short cooling period, make two pulls in the 1:1 gear ratio of the transmission with the converter locked. When looking at the dyno chart, there is an area where the Horsepower and Torque from each run cross each other. When looking at this, make sure the Horsepower and Torque axis values match. On our chart, both the Horsepower and Torque values start at 100 and end at 415. This is important for the next steps to be accurate. There is a diamond shape created within the charted pulls, as seen in green on our chart. This space is the best area to start the lockup of the torque converter to reduce slippage loss without reducing the acceleration rate.
Based on this information, and using your software of choice, set the mph or RPM goal, as well as the gear for the converter to lock in. Locking the converter can be done in 1st through all forward gears, depending on what your transmission supports. Make sure that any timers for the lockup and the lockup rate are set correctly to ensure proper timing of the lockup in the window we want to see (the green diamond area). If you need more information on how to lock or tune, check out our transmission tuning courses.
After uploading your new changes, determine if locking the torque converter has improved the ET/MPH, continuing the changes until you find the best lockup point and gear.
Each vehicle has certain challenges related to determining the optimal lockup point, but here are a few things to keep in mind:
- A properly timed lockup can overcome a loose converter or a high ratio rear gear which will help achieve a faster mph.
- Finite tuning for the converter can make a bracket car very consistent.
- Most (but not all), forced induction applications will benefit from locking the converter, but not many naturally aspirated applications will unless they have a very “loose” converter. This is due to a lack of torque without the power adder.
For more details about converter locking points, watch our related Tech Tuesday with Tony Gonyon, our resident Ford Instructor; and don’t forget to check out our transmission tuning guides at https://thetuningschool.com/