27-07-2010, 05:50 PM
Variable Valve Timing
The concept behind this is simple :alter the timing and/or size of the intake and exhaust ports at different engine RPMs to ensure that the engine is as efficient as possible throughout it's range of operating speeds. In the normal cases , the the internal combustion engine works at the maximum efficiency at one particular range of speeds. Speeds higher or lower will reduce the fuel efficiency and power. variable valve timing solves this issue by adjusting the timing of valve to adjust the intake so that the engine has maximum efficiency over a wider range of speeds. Some engines that have this technology are:
Honda VTEC
VTEC is the acrronym for Variable Valve Timing and Electronic Lift Control.The VTEC allows the valves to remain open for two different durations:
1)for low-speed operation, it works at short opening time for give good torque and acceleration, and
2)a larger opening time for higher speeds
BMW Valvetronic
This technology by BMW alters the pivot point of the cam follower thereby providing different deflections of the tip of the follower. valve opening is increased by the arger movement .
Audi Valvelift
In this engine, choice is made between two differently-shaped cam lobes . a pair of sliding cam lobes is used on a splined part of the camshaft.
For more details, visit these links:
http://www.freepatentsonline7308877.html
http://www.carbiblesfuel_engine_bible_vvt.html
http://www.faqspatents/app/20090255495
There is also a ppt:
Variable-Valve-Timing-Intelligent-system.ppt (Size: 2.43 MB / Downloads: 641)
The concept behind this is simple :alter the timing and/or size of the intake and exhaust ports at different engine RPMs to ensure that the engine is as efficient as possible throughout it's range of operating speeds. In the normal cases , the the internal combustion engine works at the maximum efficiency at one particular range of speeds. Speeds higher or lower will reduce the fuel efficiency and power. variable valve timing solves this issue by adjusting the timing of valve to adjust the intake so that the engine has maximum efficiency over a wider range of speeds. Some engines that have this technology are:
Honda VTEC
VTEC is the acrronym for Variable Valve Timing and Electronic Lift Control.The VTEC allows the valves to remain open for two different durations:
1)for low-speed operation, it works at short opening time for give good torque and acceleration, and
2)a larger opening time for higher speeds
BMW Valvetronic
This technology by BMW alters the pivot point of the cam follower thereby providing different deflections of the tip of the follower. valve opening is increased by the arger movement .
Audi Valvelift
In this engine, choice is made between two differently-shaped cam lobes . a pair of sliding cam lobes is used on a splined part of the camshaft.
For more details, visit these links:
http://www.freepatentsonline7308877.html
http://www.carbiblesfuel_engine_bible_vvt.html
http://www.faqspatents/app/20090255495
There is also a ppt:
Variable-Valve-Timing-Intelligent-system.ppt (Size: 2.43 MB / Downloads: 641)