Building the FR-S FA20 with Stay Crushing: Installing the Engine and Making Big Power!

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After aligning the pressure plate and disc, Howard holds the flywheel with a special tool and torques down the pressure plate in a cross pattern.

The stock throwout bearing fork breaks easily around the pivot ball.  If it doesn’t break, it wears out quickly in this area, so we replaced the stock part with a heavy duty fork from Verus Engineering.

The Verus part is machined from a stronger material than the stock stamped sheet steel fork. 4140 Chromoly steel is the material of choice. In the annealed state, 4140 is 12% stronger in yield strength than typical sheet steel. Verus increased the wall thickness by 25% throughout the fork. Then they removed the major stress risers in the stock design.

 

The new throwout fork is 60% stronger than stock.  It is pretty obvious when looking at it versus the stock part. It is even stronger than that in the area of the pivot where it cracks.

The clutch fork pivot ball was redesigned as well by Verus. The stock mild steel pivot galls, wears quickly and corrodes. These factors make for a stiff and inconsistent clutch feel.  The new Verus part is made of hard, strong and wear resistant 17/4 precipitation hardening stainless steel.

17/4 stainless is the ideal material for the pivot, and it is CNC-machined with an ultra smooth finish for less friction. The new pivot and clutch fork assures that we will always have a smooth and consistent clutch action.

To keep our engine in place we used some motor mounts from Perrin Performance. The Perrin Engine Mount kit uses mounts made of polyurethane with a patented Interlock design to prevent catastrophic failure.

Unlike OEM and STI Group N mounts, the unique shape of the Perrin mounts steel internals keep the mount from physically tearing apart. Oil leaks and exposure to exhaust gasses combined with extreme temperature changes in the engine compartment will make OEM and Group N rubber mounts brittle, which leads to failure, so the Perrin mounts are made of polyurethane.

The Perrin Engine Mount kit is made from 75A durometer polyurethane that is impervious to oils and other chemicals, easily outlasting the OEM mounts. The material is soft enough to damp out vibrations but firm enough to control engine movement better than stock.  This resists wheel hop, improves shifting and is easier on the drivetrain.

 

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