The APR Valve Spring System is a high performance, lightweight upgrade designed to increase valve control and eradicate valve float common on many applications. APR's design specifications called for a valve spring, retainer and spring seat combination that doesn't overpower and snap the OEM valves or erode the aluminum spring seat, while still maintaining exceptional valve control. The result is an advanced design that's 28% lighter yet 20% stiffer than the high performance OEM Golf R setup and is proven to eliminate the OEM valve train's weakest link. We call it Performance Without Compromise!
Valve Springs: Weight reduction, and not necessary stiffness, is absolutely necessary to increasing valve control. The APR Valve Spring utilizes a beehive design that allows for a reduction in mass in not only the spring itself, but also through use of a smaller titanium retainer. The springs feature an ovate wire design that allows for even stress distribution resulting in better control at high RPMs through a resistance of harmful valve float inducing harmonics. The lightweight design also accomplishes accurate valve control without requiring an overly stiff spring which has been proven to snap OEM valves in half. Each valve spring weights 29 grams and represents a 19% weight reduction over the OEM Golf R spring. The result is a highly engineered design that's simply plug and play!
Valve Spring Retainers: Through the use of a beehive design, APR's Engineers were able to design and supply a valve spring retainer that's smaller than stock to reduce weight as much as possible. In an effort to offer extreme weight savings, at an additional 71% over the OEM Golf R retainers, American 6AL4V titanium was used for its high specific strength weighing in at only 2 grams each. By offering outstanding weight savings, exceptional valve control characteristic are achieved while only requiring a modest 20% increase in stiffness over the OEM Golf R spring.
Valve Spring Seats: Often an overlooked piece of an upgraded valve train is the valve spring seat. The factory heads are aluminum, and unfortunately increased spring pressure can distort or erode the mating surface overtime as they mate directly to the bare head. To prevent this from happening, APR's Engineers designed valve spring seats out of 4140 heat-treated chrome molly steel with a black oxide coating. The spring seats are strong enough to withstand pressure from the springs and provide a mating surface that evenly distributes spring load across a larger area than the spring it self, allowing an increased spring rate without negative side effects to the aluminum head.
Eliminating Valve Float: It's not uncommon to experience valve float with the OEM valve springs, even below the OEM rev limit. On some applications like the 2.0 TSI, back pressure from the K04 turbocharger has been known to force the exhaust valves open. This has been noticed on vehicles with overly weak OEM valve springs and some with higher miles that have simply lost their stiffness over time. This issue accompanies misfires commonly above 5000 RPM. In some extreme cases, valves are forced open and the vehicle ceases accelerating any further. A quick datalog of intake mass airflow and boost pressure at wide open throttle will show a sudden rise in boost pressure with an immediate loss of airflow as pressure from the open valves is pushed back into the intake manifold. On other applications, valve float can begin to occur just beyond the OEM rev limit. While other components, such as higher strength valves are often required for extremely high revving applications, the APR Valve Spring System will eliminate float well beyond the revving constraints set forth by the other components.