Understanding The Working Principle Of Short Travel Lifters

Short travel lifters are designed to address the limitations of standard hydraulic lifters in performance engines. When engines are equipped with a hydraulic lifter, high rpm is limited by the improper position of the lifter’s internal piston as the lifter inevitably 'pumps up'. This improper location results in open valves and therefore leads to lost power or sometimes even engine failure. Short travel lifters limit that internal movement to a minimum to cut down on these issues and allow more engine rpm.

Short travel lifters are designed to limit the lifter's internal piston as it is pumped up

Short-travel lifters are designed to limit the lifter's internal piston as it is pumped up. This is achieved by reducing the travel distance of the internal piston, which in turn prevents the lifter from "pumping up" and holding the valves open, a condition that can lead to power loss or engine failure.

In a standard hydraulic lifter, the piston has a range of travel that allows it to take up any lash in the valve train system. However, at high RPMs, the valves can start to float due to inadequate valve spring pressure or harmonics. When this happens, the lifter's piston adjusts on the base circle of the cam to take up the clearance, but when the valve spring catches up, it cannot close the valve completely because the lifter has extended. This results in a loss of power as the valves are held slightly open.

Short-travel lifters address this issue by reducing the piston's travel distance to a minimum, typically less than half of that of a standard production lifter. This limited travel distance ensures that even if valve float occurs, the lifter piston cannot extend far enough to hold the valves open. By preventing the lifter from pumping up, short-travel lifters maintain valve control and allow engines to reach higher RPMs without losing power.

Additionally, short-travel lifters are designed with tighter tolerances and faster refill rates, ensuring that the lifter piston returns to its neutral state quickly and minimizing the potential for lifter piston pump-down. The combination of limited travel and faster refill rates enables the use of higher valve spring pressures, which further contributes to improved valve control and higher RPM capabilities.

Overall, the design of short-travel lifters, with their reduced piston travel and optimized refill rates, enhances the performance and reliability of hydraulic roller lifters in high-performance and racing applications.

They cut down on the loss of power and limit valvetrain failure at higher rpm

Short travel lifters are designed to address the issue of ""pump-up" in hydraulic lifters, which can lead to power loss and engine failure at higher RPMs. When a hydraulic lifter "pumps up", the internal piston moves into an improper position due to the high RPM, resulting in open valves. This can cause a loss of power and, in some cases, engine failure.

Short travel lifters work by limiting the internal movement of the lifter's piston, reducing the "pump-up" effect. By restricting the piston's travel, the valves are prevented from opening fully, which helps to maintain power and reduce the risk of engine failure. This is especially beneficial for performance engines that operate at higher RPMs and use stronger valve spring pressures.

The use of short travel lifters can also improve valvetrain stability and reduce the need for frequent valve adjustments. They provide a smoother curve, allowing the valves to follow the camshaft's commands more accurately. Additionally, they can be beneficial for street engines, as they allow for higher RPM ranges while maintaining the quietness of a hydraulic cam.

It is important to note that short travel lifters require careful adjustment of preload and pushrod length to function optimally. Improper adjustment can lead to valve train damage or reduced performance.

Short travel lifters are harder on valve train components but allow greater valve train stability

Short-travel lifters are a type of lifter used in engines to improve performance. They are designed to limit the movement of the lifter's internal piston, which can cause issues at high engine speeds. At high rpm, inadequate valve spring pressure or harmonics can cause the valves to float, resulting in a loss of power. Short travel lifters help to minimise this issue and allow engines to reach higher rpm without losing power.

Short travel lifters function similarly to mechanical lifters and are considered much harder on valve train components. They are typically used with higher spring pressures in performance engines. When the valve is almost fully open, the short travel lifter collapses, sending a shockwave to the camshaft lobe's surface. This shock load can be detrimental to the mating surfaces, especially when using a roller lifter. Tests have shown that short travel lifters can reduce roller bearing life by up to 70%.

To compensate for the increased stress on valve train components, it is recommended to use stronger and more rigid pushrods. Larger diameter and thicker-walled pushrods can help to reduce pushrod deflection and improve valvetrain stability. Additionally, one-piece pushrods are preferred over three-piece pushrods as they offer greater reliability and reduce the risk of failure under extreme racing conditions.

While short travel lifters can be harder on valve train components, they offer greater valve train stability and allow engines to operate at higher rpm with improved power output.

Short travel lifters are more like solid lifters with a little cushion

Short-travel lifters are designed to address the limitations of standard hydraulic lifters in performance engines. They are an intermediate option between hydraulic and solid lifters, offering the benefits of both while minimising their drawbacks.

Hydraulic lifters are designed to maintain zero lash clearance, providing more precise valve control, silent operation, and reduced wear. However, they struggle with the higher spring pressures used in performance engines, which can lead to "lifter pump-up" and "lifter pump-down". Lifter pump-up occurs when the spring loses control of the valve, causing a float condition where the internal chamber fills with oil and pushes the valve off its seat, resulting in power loss. Lifter pump-down, on the other hand, is caused by high spring pressure and inertia loading depressing the piston, leading to a loss of valve lift and reduced performance.

Short-travel lifters are designed to address these issues by limiting the travel of the internal piston, hence the name. This restricted movement prevents the piston from being depressed too far, reducing the risk of lifter pump-down. Additionally, the shorter travel distance means that there is less opportunity for air to become trapped in the system, which can contribute to lifter pump-up.

By combining the features of hydraulic and solid lifters, short-travel lifters offer the best of both worlds. They provide the accuracy and long-term valve adjustment benefits of solid lifters while maintaining the quiet operation typically associated with hydraulic lifters.

When setting up short-travel lifters, it is crucial to follow the manufacturer's recommendations for preload. Unlike standard hydraulic lifters, which typically have a preload of 1 to 1-1/2 turns, short-travel lifters usually require a much smaller preload of around 1/4 turn. This reduced preload further helps to minimise the risk of lifter pump-up and ensures that the lifters operate optimally.

They are designed to handle heavier valve spring loads without losing valve lift or collapsing

Short travel lifters are designed to handle heavier valve spring loads without losing valve lift or collapsing. They are made with a spacer to reduce the piston's travel, which keeps the amount of valve lift loss to a minimum. This is in contrast to standard hydraulic lifters, which cannot handle the higher spring pressures used in performance engines.

The spacer in a short travel lifter reduces the piston's travel so that the valve does not stay open longer than necessary, which would result in a loss of power. This is especially important at high RPMs, where the valves can float because of inadequate valve spring pressure or harmonics.

In addition, short travel lifters can provide a smoother curve, as they allow valves to start more accurately following the cam's commands. They also allow for more RPM and are harder on valve train components.

Overall, short travel lifters are a good choice for performance engines that require more RPM and need to handle heavier valve spring loads without losing valve lift or collapsing.

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