Sport Compact Project – Nissan Engine Build
by Mike Kojima
Time to get serious. In part nine of our series, we go inside the engine in a last grab for power.
As an added precaution, we sent our pistons to Swain Tech Coatings to be treated with their Poly-Moly dry film lubricant coating on the skirts and their GoldCoat thermal barrier coating on the crowns. Developed by Dan Swain, a noted ex-GM ceramic engineer, Swain Tech’s GoldCoat thermal barrier coating has some interesting properties. First, it is a three-layer coating instead of the typical one layer, consisting of a proprietary combination of different ceramics. Swain’s GoldCoat has a unique gold color and is especially designed to withstand the rigors of turbocharged and nitrous oxide injected motors. GoldCoat reduces heat transmission to the underlying metal by 20-40 percent. This helps protect the piston from detonation-induced heat as well as reducing thermal expansion, allowing a tighter piston to wall clearance. Since pistons do not have the benefit of water jackets like those in cylinder heads, keeping heat out of them is a good thing. By reflecting this heat back into the combustion chamber, the coating helps promote a better burn, harnessing this bit of otherwise wasted heat.
Swain Tech’s GoldCoat also does something no other thermal barrier coating currently claims: it transfers heat through the surface of the coating, but not past it to the underlying metal. This promotes even heating across the piston crown, thus helping to reduce the potential of detonation causing hot spots and promoting an even burn for good flame travel.
Unlike other early coatings which tended to flake off due to different coefficients of expansion or a brittle nature, the Swain coatings bond to metal at a molecular level and will not crack or flake off.
We also had Swain apply their Poly-Moly coating to the skirts of our pistons. This is very similar to the coating used by the Nissan factory on their new VQ30DE motors to reduce wear and friction. It uses molybdenum disulfide and tungsten disulfide in a heat-conducting polymer resin matrix to make a tough, lubricious surface. Piston skirt coatings used by other companies often exhibit “creep” under thrust loads. Creep is an engineering term for force induced distortion. This causes the coating to smear and stick under load and causes tolerances to change. Since the primary way a piston cools itself is through conduction to the cylinder walls, you do not want to insulate the skirts! We feel that the Poly-Moly coating will help improve piston skirt and cylinder wall wear and reduce thrust-load-induced friction.
Swain Tech coated the tops of the pistons with their GoldCoat ceramic coating that not only reduces heat transfer into the piston crown, but also distributes heat evenly across the surface of the piston. The skirts were coated with Swain’s Poly-Moly coating, a high-strength, low-friction coating that allows heat transfer so the pistons can shed heat into the cylinder walls.
Swain Tech coated the tops of the pistons with their GoldCoat ceramic coating that not only reduces heat transfer into the piston crown, but also distributes heat evenly across the surface of the piston. The skirts were coated with Swain’s Poly-Moly coating, a high-strength, low-friction coating that allows heat transfer so the pistons can shed heat into the cylinder walls. The Swain coatings are allowing us to run piston-to-wall clearance down to the minimum spec Nissan recommends, 0.0004-inch. This should help reduce oil consumption and improve ring sealing as well as reduce noise. The engine builders of Nissan motorsports use Swain coatings in the IRL Indy engine as well as other competition engines and report longer life and reduced wear…
This cutout in the piston skirt is designed to clear the oil squirters (notice Swain Tech’s Poly-Moly coating of the skirt).
We were pretty impressed with the thoroughness of Dan Swain’s development methodology. Instead of settling for just applying commercially available coatings like most other coating houses, Swain develops his own unique and superior specialized engine-specific coatings. For even more extreme applications Swain offers a plethora of engineering coatings, from wear resistant barriers to black body radiating coatings. Project SE-R’s big sister, Project Nissan 300ZX Twin Turbo will delve into more extensive coating usage to help its new 600 hp turbo engine live! That’s the new engine for now. Join us again in the future as we assemble, tune and test our new monster SR20.