New to the market is the Racer Elite - the first ever 450 asymmetrical pistion design that netted a 2.9hp gain while reducing blow-by. Also new is Wiseco's economically priced 450cc enhanced pin tower piston that's designed for endurance.
Dirt-bike enthusiasts and racers have two new piston options from Wiseco Performance Products with the release of the 450 Enhanced and Racer Elite series.
“The 450 Enhanced is our service level piston and designed to be more durable under high RPM and loads over a standard piston,” says Wiseco engineer Dave Sulecki. “The Racer Elite is an asymmetrical piston, which is unique for the powersports market.
Designed to withstand the demands single-cylinder, 4-stroke engines that rev over 14,000 rpm under often brutal off-road conditions, both piston series are constructed from 2618 aluminum alloy.
“2618 has greater tensile strength [over 4032 alloy], which in a 4-stroke engine application is desirable,” explains Sulecki. “If a piston is going to fail, it will be under tensile load on the exhaust stroke when it's being stretched. 2618 material has a much stronger threshold in tension than a 4000 series alloy. Also, 4-stroke engines run at very high temperatures that a 2000 series alloy deals with better than the 4000 series alloys. It doesn't lose its hardness as quickly as the engine runs through the heat cycling process.”
The 450 Enhanced series features an enlarged wrist-pin tower design to improve durability for off-road use and some racing.
“It’s basically stronger than a stock piston,” adds Sulecki. “That’s due to the box structure we put into the parts. Because we can optimize the design using our state-of-the-art forging process, the piston has the same weight as the OEM part. Because of this, there are no added stress loads to the connecting rod and crankshaft.”
Crown geometry is specific to each engine application, and all dome designs are engineered for improved flame travel to maximize combustion. In many applications a piston can also be ordered with an increased dome volume to boost the compression ratio.
“ We tailor-fit the crown for each model, and we maintain an even crown thickness, which helps with heat dissipation and strength,” says Sulecki. “Several compression ratios are available for each model, so you can buy anything from a standard compression for the guy who really just wants that stock feel and performance. We also offer an increased compression for the guys who want to have a little more performance.”
Putting a Ring on it
The ring packages for each series includes a gas-nitrided top ring designed with positive-twist geometry. That is, the ring features a bevel cut on the top inside edge that promotes a positive or upwards direction of the ring face when viewed from the profile side of the piston. Basically, this design is used to help take up clearance in the ring groove by using cylinder pressure to push down on the inside bottom edge of the ring—which then makes contact with the floor of the ring groove. This action also forces the outside top edge to twist upwards and make contact with the roof of the ring groove—thus, creating a better seal that reduces blow-by around the top compression ring.
“None of these applications have a traditional 3-ring package. The top ring actually has to do the work of a top and second ring, so the positive twist and the asymmetrical face geometry on the ring allow the ring to seal compression, but also scrape oil as it goes through the downstroke,” says Sulecki. “These rings are very thin, less than a milometer in most cases. They're very conformable to the bore, but they're also very hard material. A conformable ring is desired for the ultimate ring seal, as the ring can better manage changes and undulations in the bore surface as the ring moves along the length of the cylinder wall.”
With only two rings to handle cylinder seal and oil control, the grooves in the pistons are inspected for flatness as well as proper angle relative to the axial height, which is also precise to complement the ring width and thickness. Wiseco also positions the ring grooves closer to the piston crown.”
“That actually helps improve compression and efficiency,” says Sulecki. “That's a horsepower gain that you can feel at the throttle.”
For the Racer Elite series, Wiseco matches the compression ring to the piston groove.
"This technology is common in NASCAR and Pro Stock drag racing...commonly use a lapped ring to a precise ring-groove fit, and we're introducing this technology to powersports.”
“The compression ring is actually lapped using a proprietary process to fit into a precise ring groove width. That solution by itself will increase ring seal and horsepower over a standard design,” continues Sulecki. “This technology is common in NASCAR and Pro Stock drag racing. Those levels of competition commonly use a lapped ring to a precise ring-groove fit, and we're introducing this technology to powersports.”
With this procedure, Wiseco says the clearance between axial height of the groove and the ring itself is less than .001-inch. The ring, therefore, lies flat against the floor of the groove to reduce the chance of blow-by around the ring. Blow-by is a negative situation where combustion gasses can pass by the piston, reducing efficiency and costing you performance.
Racer Elite - First Asymetrical Powersports Piston
As mentioned earlier, the Racer Elite piston features a billet asymmetrical design, meaning the width of thrust-side skirt is larger than the opposing skirt where there is less piston contact with the cylinder wall. This design reduces friction considerably over a traditional piston with a full-round design.
“It's a design that the powersports market really hasn't seen,” says Sulecki. “This has become more common in automotive applications. I know a lot of the sport-compact market and now some of the domestic applications are starting to see asymmetrical piston designs, but this is something that's very unique to powerports.”
In addition to a beefy wrist-pin support structure, the new Racer Elite series will come with DLC (diamond-like coating) 9000 series steel pin that is secured with circlips.
“It's a longer wrist pin so that you get greater strength in the pin tower, yet we're able to maintain a lightweight assembly,” explains Sulecki. “What we've done with the pin tower is increased the footprint, so the size of the pin tower where it meets the piston crown underneath is much larger than traditional designs. That's where the strength comes.”
Racer Elite pistons also feature Armor Glide skirt coatings that helps reduce friction and scuffs along with providing a quieter operation.
“It's for friction reduction, and any time you reduce friction you increase power. Our proprietary coating also takes up some distance between the piston and the cylinder wall, which helps reduce sound from piston rock,” says Sulecki, adding that Armor Glide is not a break-in coating. “In the aftermarket, you see a lot of spray-on coatings that are just there to break the piston in for 30 minutes, and then it's worn off and gone. Our skirt coating is permanently bonded to the piston skirt, and is there for the life of the part.”
The 450 Enhanced and Racer Elite series are available for all popular motocross models, including those with 250cc, 350cc and 450cc engines. These high performance pistons will be available to the market starting in April 2017.