Tomei Powered VALVE SPRINGS - Manual (Page 7)

■TOMEI NEW-CONCEPT Valve Spring Features
（Except L4/6）
● Advanced Oil Tempered Chrome-Silicone Alloy Core
The adopted wire design shows the best design method that suits race applications, ① jump and ② bounce is
reduced so higher rpm limits can be raised. ③ the fatigue limit is raised to increase durability.
● Variable Stage Unequal Pitch Springs
In each spring the design and the set spring rate is set to have a higher natural frequency so to reduce
the chances of resonance. ④ chances of surging is greatly reduced.
● Nitrided
The spring material is surface treated with Nitrogen for improved strength to cope with stress fatigue.
Compatible with high lift camshafts to maximize the life expectancy of these springs.
● Shot Penning
A process that strikes many small steel balls onto the surface of the spring at high speeds is made to enhance
the surface of the spring to raise its fatigue limit. Although it has been carried out earlier during
the manufacturing process.
● Hot Setting
High stress loads that are placed on the springs when hot can cause permanent deformation.
So the added measures were taken to guarantee the problems from “⑤Fading” is prevented.
① JUMP At high RPM the high lift cams can cause the phenomenon of the valve to leave contact
of the cam lobe "jump" which will cause it to slam back onto the camshafts surface on
return.
② Bounce When the valve returns at such high speeds and landing with a shock on the valve seat
the bounce phenomenon can occur repeatedly.
③ Fatigue The harsh conditions that the valve springs are subjected to when used with high cam
(Stress) lifts and high RPM can cause fatigue in the spring and breakages are a common problem
④ Surging The wire of the valve spring can vibrate which will cause the vibration (resonance) over
(Surge) the entire spring, this phenomenon will have the waves of vibrations going back and forth
in the spring.
⑤ Fading This phenomenon happens when the spring is subjected to maximum stress loads during
operating conditions.
● Oval Core Wire *4G63, VQ35, VR38DETT
The use of the oval shaped spring wire are designed to compress more than the standard design which allows
these engines to run high lift camshafts without comprimise.
Standard Valve Spring Oval Core Valve Spring
7
Standrd Compressed Standrd Compressed