4-stroke power valve system
Encyclopedia
A Four-stroke power valve is a device fitted to four-stroke engines that constantly adjusts the internal diameter of the exhaust system to better suit engine speed. At low engine speeds the wave pressure within the pipe network is low. A full oscillation of the Helmholtz resonance
occurs before the exhaust valve is closed, and to increase low-speed torque, large-amplitude exhaust pressure waves are artificially induced. This is achieved by partial closing of an internal butterfly valve
within the exhaust at the point where the four primary pipes from the cylinders join. This junction point essentially behaves as an artificial atmosphere. The alteration of the pressure at this point controls the behavior of reflected waves at this sudden increase in area discontinuity. Closing the valve increases the local pressure, inducing the formation of larger-amplitude negative reflected expansion waves. A servo motor
controlled by the ECU
opens and shuts the valve. The valve goes from being almost fully closed at idle speed, through to fully open at higher engine speeds. This ensures superior low to mid-range performance, more linear power output and reduced exhaust noise levels while the valve is in its reduced opening position.
Yamaha
was the first to develop such a system, called the Exhaust Ultimate Power Valve (EXUP). It is found on such models as the R6
, R1
, XV1900, MT-01
and Apex snowmobiles.
Later versions from Honda
went by the names Honda Titanium Exhaust Valve (HTEV) and Honda Variable Intake/Exhaust (H-VIX), appearing on the CBR600RR
and Honda CBR929RR. Suzuki
's version is called Suzuki Exhaust Tuning (SET). The system is also used on the Triumph Daytona 675
triple.
Helmholtz resonance
Helmholtz resonance is the phenomenon of air resonance in a cavity, such as when one blows across the top of an empty bottle. The name comes from a device created in the 1850s by Hermann von Helmholtz, the "Helmholtz resonator", which he, the author of the classic study of acoustic science, used to...
occurs before the exhaust valve is closed, and to increase low-speed torque, large-amplitude exhaust pressure waves are artificially induced. This is achieved by partial closing of an internal butterfly valve
Butterfly valve
A butterfly valve is a valve which can be used for isolating or regulating flow. The closing mechanism takes the form of a disk. Operation is similar to that of a ball valve, which allows for quick shut off. Butterfly valves are generally favored because they are lower in cost to other valve...
within the exhaust at the point where the four primary pipes from the cylinders join. This junction point essentially behaves as an artificial atmosphere. The alteration of the pressure at this point controls the behavior of reflected waves at this sudden increase in area discontinuity. Closing the valve increases the local pressure, inducing the formation of larger-amplitude negative reflected expansion waves. A servo motor
Servomechanism
thumb|right|200px|Industrial servomotorThe grey/green cylinder is the [[Brush |brush-type]] [[DC motor]]. The black section at the bottom contains the [[Epicyclic gearing|planetary]] [[Reduction drive|reduction gear]], and the black object on top of the motor is the optical [[rotary encoder]] for...
controlled by the ECU
Engine control unit
An engine control unit is a type of electronic control unit that determines the amount of fuel, ignition timing and other parameters an internal combustion engine needs to keep running...
opens and shuts the valve. The valve goes from being almost fully closed at idle speed, through to fully open at higher engine speeds. This ensures superior low to mid-range performance, more linear power output and reduced exhaust noise levels while the valve is in its reduced opening position.
Yamaha
Yamaha Motor Company
, is a Japanese motorized vehicle-producing company. Yamaha Motor is part of Yamaha Corporation and its headquarter is located in Iwata, Shizuoka. Along with expanding Yamaha Corporation into the world's biggest piano maker, then Yamaha CEO Genichi Kawakami took Yamaha into the field of motorized...
was the first to develop such a system, called the Exhaust Ultimate Power Valve (EXUP). It is found on such models as the R6
Yamaha YZF-R6
Yamaha's YZF-R6 is a 600 class sport bike motorcycle, first introduced in 1998, updated in 2001, 2003, 2006, 2008 and revised in the years in between.-History:...
, R1
Yamaha YZF-R1
The Yamaha YZF-R1 is an open class sport bike, or superbike, motorcycle manufactured by Yamaha Motor Company since 1998.-1998–1999:Yamaha launched the YZF-R1 after redesigning the Genesis engine to offset the crankshaft, gearbox input, and output shafts. This "compacting" of the engine made the...
, XV1900, MT-01
Yamaha MT-01
The MT-01 is a motorcycle made by Yamaha since 2005, available in Australia, Europe, India, Japan and North America. It has unusual features with a cruiser-style air-cooled, overhead valve V-twin engine but sportbike or naked bike style frame and suspension...
and Apex snowmobiles.
Later versions from Honda
Honda
is a Japanese public multinational corporation primarily known as a manufacturer of automobiles and motorcycles.Honda has been the world's largest motorcycle manufacturer since 1959, as well as the world's largest manufacturer of internal combustion engines measured by volume, producing more than...
went by the names Honda Titanium Exhaust Valve (HTEV) and Honda Variable Intake/Exhaust (H-VIX), appearing on the CBR600RR
Honda CBR600RR
The Honda CBR600RR is a sport motorcycle that was introduced by Honda in 2003 as a race replica version of Honda's CBRFx series motorcycles. It won every Supersport World Championship title from 2002 to 2008.- Racing roots :...
and Honda CBR929RR. Suzuki
Suzuki
is a Japanese multinational corporation headquartered in Hamamatsu, Japan that specializes in manufacturing compact automobiles and 4x4 vehicles, a full range of motorcycles, all-terrain vehicles , outboard marine engines, wheelchairs and a variety of other small internal combustion engines...
's version is called Suzuki Exhaust Tuning (SET). The system is also used on the Triumph Daytona 675
Triumph Daytona 675
Introduced in 2006, the Triumph Daytona 675 is a 600 class sport bike motorcycle built by Triumph Motorcycles to replace the Daytona 650.The 2008 model has a tested dry weight of and wet weight of...
triple.