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| JE forged pistons are made of tough 2618 low silicon aluminum alloy. This alloy is tougher than typical high silicon alloys found in cast and some forged pistons. Low silicon aluminum expands more with heat so they must run wider clearances. Even with wider clearances the pistons run clatter free. The lustrous look is due to WPC treatment. WPC helps lubrication and reduces wear. We WPC treated the pistons, piston pins and rings. |
The pistons are designed with a full round skirt with JE’s turbo cam profile to just about eliminate the possibility of scuffing. The turbo cam shape is more pronounced as the crown of the piston is subjected to more heat under boost and will grow more. The dome volume is -12.6 cc which should give a turbo friendly compression ratio of 8.5:1 with a 0.63mm head gasket. The piston pin is a thick wall steel part to prevent flexing, a problem that can hurt the small end of the rod with a boosted motor. The piston comes drilled with double pin oilers. These are passages from the oil ring grooves to the pin bores. Oil scraped off of the cylinder walls by the oil rings is then pressure fed to the pin, a nice feature. The complete piston weighs in at a lightweight 380 grams.
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| The JE piston has a dish to give a compression ratio of 8.5:1. The grooves around the top of the piston above the first ring groove are anti detonation grooves. They help control expansion around the top of the piston to reduce the odds of scuffing and act like a shock wave buffer to reduce pressure spikes to the rings. |
JE gives the piston top generous radii so nothing will need deburring, speeding preparation time. This also helps improve flame travel for better combustion. The number one ring land also features anti detonation grooves. These serve two purposes. First, if the piston top gets really hot and expands, the grooves give the material an area to expand into so the overall piston diameter grows less. This helps reduce scuffing in this area. Second, the grooves act like a baffle, helping to dissipate the pressure waves that detonation can produce, buffering the rings from it. This can help reduce ring flutter. The pistons are machined for a thin low tension ring package, 1.2 mm for the two compression rings and 2.5 mm for the oil control ring. The thin lightweight rings will have less friction and will seal better at high rpm. The top ring has a chrome face while the second ring is nitrided for low friction and longer life.
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| These holes in the pin bore are dual pin oilers. The holes go to the oil rings where oil scraped from the cylinder walls is fed to the pin bore to help lubricate the pin. The slot between the holes is a reservoir for the oil. |
With no time for coatings and other tricks we normally use, we took the pistons to WPC to have them rush treated. WPC is the Japanese micro shotpeening treatment we use on many of our engine projects. WPC bombards metal parts with microscopic special media at hypersonic speeds which refines the metal’s grain on the surface and imparts compressive stress which improves surface hardness, fatigue strength and lubricity to a large degree. We WPC treated the pistons, rings and piston pins. The WPC process should greatly reduce scuffing, which we figured might be important for an engine that would literally have no break in time and reduce friction. For more on how WPC works click here.
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| The under crown details of the piston show that the forging is pretty close to net shape for minimal weight. Look at all the smooth radii and graduated contours of the interior. These are signs of a thoroughly stress analyzed design. |
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| The ring set uses lightweight and thin low tension rings for low friction and minimal ring flutter. The piston pin is a thick walled steel part. Thin pins flex with turbo engines and can spin or damage the small end rod bushing. We WPC treated the pin, rings and piston for long life and reduced friction. |
