Radio Control Car Action - September 2009

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What is a smart diff?

The Smart Diff was developed by Losi and it’s basically a self-adjusting differential. It’s used in the front and/or center of the Losi 8IGHT series buggies and truggies. When you apply power, the diff tightens and distributes equal power to both sides of the diff. When you let off the power, the diff opens up and spins freely, which allows for

better rotation through turns. There have been similar diffs out there called Torsen (short for torque sensing) diffs. These diffs sort of do the same thing as a smart diff but they are non-adjustable and lock up instantly, which causes erratic performance depending on the track that you’re running on. The Smart Diffs are fully adjustable. You can change the spring rate inside, which will change the lock up rate of the diff. If you choose to do so, you can also tune it with silicon fluid. The Torsen diff can only accept light oil or grease.

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There are two things to check on your buggy to solve this problem. First, remove the linkage from the servo-saver and rotate the front tires back and forth.

Make sure that all the parts rotate smoothly. If there is any binding in the steering system, you’ll need to find the part that is binding and replace it. Next, check the servo-saver. A lot of people tighten it up to get better steering response, but that ends up putting too much stress on the servo. If you want to run a tighter servo-saver, find a stronger servo to put in your buggy. HPI now offers the SFL-30MG (item no. 102612) large-scale digital servo that has lots of torque and a heat sink to keep the operating temperature of the servo down. Your other option is to install a standard-size servo that has more torque and a stronger drivetrain. This can be done by installing a servo adapter made by Gabe Brown Engineering.