The FSR is a strut type piston meaning that it has a reduced slipper skirt profile. In the past slipper skirts meant light weight and low friction, but lots of noise and sometimes rapid wear. Not so with FSR pistons. JE has the piston design and barrel profile down and we have found FSR pistons to run quietly when we have used them, great for street engines!
The JE FSR pistons’ asymmetrical skirt has a larger area on the more heavily loaded thrust side and a reduced profile on the non-thrust side for less friction and weight. The strut-type design also means minimal weight as there is no excess material, unlike fully skirted pistons.
As we said previously, the JE FSR pistons are made from low silicon 2618 alloy. 2618 is very ductile and tough, properties which are appropriate with detonation prone high boost turbo motors. 2618 expands more with heat and requires a wider piston to wall clearance than higher silicon alloys, typically about 0.002-0.003″ more.
In the past, this greater clearance meant a more noisy engine and many builders would spec a higher silicon but more brittle alloy like 4032. JE’s advanced skirt profiles have reduced the piston slap and the engines now run quietly even with wider clearances.
The compression rings are thin at 1.1mm and 1.2mm and low tension in design for less friction. Rings are the largest source of mechanical friction in an engine. The top ring is 1.1mm and is plasma chrome coated for low friction, long life, and heat resistance. The 1.2mm thick ductile iron second ring has a hooked face Napier profile. Napier rings break in quickly and give better oil control at high rpm and are really low friction.
Narrow profile and low tension describe JE’s oil rings. The scrapers and waffled separators are shown here. There are two scrapers on either side of the separator. The separator gives space for the oil to drain to the interior of the piston via holes in the oil ring groove. This helps keep the piston pin lubricated.
JE Pro Seal head gaskets are constructed from multiple layers of 301-stainless steel, which have each been precision laser cut and fastened together to ensure optimal alignment and sealing.
The Pro Seal head gasket also has a folded stopper layer which provides extra clamping force around the combustion chamber to greatly improve the seal even under tough conditions like endurance road racing with boost.
Since the rod bolts are perhaps the highest stressed and most critical part of the rod K1 does not skimp here one bit! These premium bolts have asymmetrical threads for more thrust engagement for better torque consistency.