To make the S2000 more responsive, we ditched the stock flywheel and installed an XACT Prolite flywheel. ACT flywheels are one piece CNC machined from chromoly forgings. Chromoly is a steel alloy with a high chromium and molybdenum content. This makes a steel alloy with nearly twice the tensile strength per weight as regular high carbon steel.
Forging is also cool as it orients the metal's grain for best strength. It also works the metal and refines the grain which gives additional strength. The ACT Prolite flywheel is made of lightweight forged heat treated chromoly steel. It has a lot of milling to reduce weight. It is also resurfaceable.
The back side of the ACT XACT Prolite flywheel is all hollowed out for less weight. The flywheel is one piece and lightening holes are milled out around the flywheel's perimeter to reduce its moment of inertia. This one piece construction is pretty cool! The starter ring gear teeth are induction hardened for longer life.
The XACT flywheel for the AP1 S2000 weighs in at 8.1 lbs. The stock AP1 flywheel is 15 lbs and the AP2 flywheel is a whopping 21 lbs. Vince happens to have an AP1 so he is saving 7 lbs of rotating weight. As lightweight flywheels go, this is not a huge difference but it will be still enough to make a discernible difference in acceleration.
Lightweight flywheels are easier on the transmission syncros which allows faster up and down shifting and helps the syncros live longer. Happy syncros means grinding and miss shifting are less likely.
ACT flywheels are engineered using FEA stress analysis for best utilization of materials for strength and light weight. The flywheels are then burst tested and SFI certified, a very important item for your safety as well.
The first step to accessing the clutch on an S2K is to drop the engine down on its crossmember. This makes getting to all of the bellhousing bolts easy and give you room to separate the transmission from the engine. You must first undo the steering shaft from the rack and to get to it you need to take off the air intake to reach it from the top.
With the intake off and the alternator swung out of the way, Howard reaches down to undo the steering shaft from the rack. This is the easiest way to get to it.
Here is the view from underneath. The S2K is pretty cool, the oil pan is ribbed for cooling as is the transmission case.
Howard undoes the exhaust manifold from the exhaust system so the entire engine/trans can be dropped.