Both Hybrid Racing and Skunk2 also address the tensioner's piston and safety mechanism. Both use stiffer internal springs that prevent the exhaust camshaft from slamming shut at low engine speeds by eliminating chain slack, even under low oil pressure conditions where the factory spring is typically compromised. Both companies' tensioners are based off of Honda's design but are machined from scratch. Worst of all, you'll never know any of this is happening until it's too late since you can't readily monitor the tensioner and, even if you could, all of this happens way to quickly.īoth Hybrid Racing and Skunk2 offer more comprehensive solutions. All of this can lead to a loose chain, a failed safety mechanism, and engine damage, even on unmodified engines. Of course, none of this is good since the ratchet and piston teeth are the only things that prevent the piston from being pushed in too far. Steeper exhaust closing ramps and stiffer valve springs that close the valves even quicker are to blame. It should be noted that although dealership technicians have reported worn tensioner pistons on otherwise stock engines, it's more likely once camshafts and springs have been swapped. Aftermarket cams with aggressive profiles and stiffer valve springs only pronounce this. And each time they slam shut, the tensioner's piston bashes against its ratcheting mechanism. Each time they slam shut, the chain builds slack. You see, by design, K-series exhaust valves close rapidly. The results can cause the piston teeth to slam against the tensioner's ratchet, ultimately grinding their tips off, rendering them ineffective. Unfortunately, Honda's internal tensioner spring doesn't always work as you'd expect, and excess tensioner piston travel (more than 0.25-inch) and timing chain slack when oil pressure is low is common-especially while cranking and at low engine speeds when the spring is doing all the work. Sounds like Honda has it all figured out. Additionally, a ratcheting mechanism and teeth built into the piston ensure that it doesn't retract too far back into its housing and loosen up the chain. A check valve ensures the oil doesn't escape prematurely and a release valve lets it out when the tensioner's done, well, tensioning things. As engine speed and oil pressure rise, the spring relaxes and oil pressurizes the tensioner's chamber, hydraulically pushing its piston toward the chain's guide. At low engine speeds, when oil pressure is low, the tensioner's internal spring mechanically moves its piston toward the timing chain guide, reducing chain slack on the chain's exhaust side. They do so hydraulically-not unlike older H22A tensioners-which means K-series tensioners operate by way of oil pressure, but they also incorporate a small, internal spring for mechanical purposes. K-series tensioners aren't terribly complex and, simply put, do little more than push a small piston back and forth against the engine's timing chain guide, keeping the chain tight. The situation isn't much different from the power window regulator that dies first on the window you use least. Engines that are regularly cycled condition their belts evenly, which arguably adds life to them. Imagine for a moment the stress that's placed on an unused engine's belt as it's continually stretched in one specific region while the rest of the engine takes a breather. But timing belts are prone to wear-just as much so on engines that rarely see the light of day as they are on daily driven ones, which is why Honda's timing belt replacement intervals are based on both time and mileage. Perhaps that's because timing belts simply work, and when replaced periodically, are as reliable as any chain. It's only recently that the company's switched to chains in order to link its engines' camshafts to their crankshafts and control valve timing. Accords, Civics, Integras, Preludes, NSXs, you name it they've all been belt-driven. Honda's engineers have long been fans of belt-driven valvetrain assemblies.
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