Y.E.I.S and the like

YEIS or Yamaha Industion Energy System is an additional tool in the original intake system is designed to improve the efficiency of the machines 2 steps. This technology is not new and it is a trend in the 80s. Almost all manufacturers of motor 2 steps such as Honda, Yamaha, Suzuki, Kawasaki, Aprilia, KTM, Husqvarna, Polaris, and Husaberg make this system as their standard. His name is also varied depending on the manufacturers who use it. Technology abroad is better known by naa "Boost Bottle", the intake chamber, or "Hemholtz Chamber". In general, this technology among international tuners commonly called by the name of the intake chamber.
(IC). To my knowledge the first manufacturer to publish in detail about their research on this IC are YAMAHA, this can be seen in SAE Papers no. 810 923 - Modification of Two Stroke Intake System for Improvements of Fuel Consumption and Performance through the Yamaha Energy Induction System (YEIS), by Noriyuki Hata, Takeo Fujita, and Noritaka Matsuo - Yamaha Motor Co., Ltd.

One of the shortcomings of the engine 2 step is not separation of the combustion process and inclusion. Combustion exhaust gas driven out by the insistence of the new gas coming from the crankcase (crankcase). The more effective flushing system (scavenging) combustion is the quality of the next will be better because of the possibility of the exhaust gas is mixed with the new gas will be reduced. However, if the gas comes dibilaskan "as much" then they will all be wasted toward the exhaust without generating useful power. As most already know, the exhaust on the motor 2 step plays an important role in producing power once, sometimes> 30%. Modern engine exhaust 2 steps designed not only able to "suck" the exhaust gas and new gas flushing process is perfect, but is also able to "push back" the new gas that previously had been sucked out back towards the engine. This is what causes the engine 2 steps mempu achieve volumetric efficiency (VE)> 100%. In the non-turbo 4 stroke engine and supercharger VE ranged between 60-75% for vehicle production and close to 90% for a racing engine (static condition, the engine rotation region only). So with 60% VE engine with a volume of 60cc 100cc only able to burn gas and fuel mixture. According to data from Eric Gorr, GP125 engines typically achieve up to 144% VE, which means they burn with a cylinder capacity of 180cc 125cc only just! At the time of maximum VE, fuel consumption also decreased by the calculation engine
BSFC of course!
BSFC = Brake Specific Fuel Consumption, which means how much power an engine can be produced per unit of fuel consumed.
Therefore the motor maker 2 step increase exhaust design to get better power and efficiency. But unfortunately, this condition is not free. Exhaust is designed to work efficiently in a certain round tends to make the operation in the other rounds to be inefficient. Details of how the exhaust will not discuss here because it will make the topic focus blur, if the ADA is interested, then I will post in a separate thread.
In short order to get a machine that is able to operate efficiently in a certain round, the manufacturer has been forced to compromise on other engine rotation. In terms Yamaha condition called "through of torque" (TOT). In this condition decreased engine power, fuel consumption and decreased levels of motor rideability. The use of IC or YEIS was able to reduce the loss of good exhaust design. In this way the efficient operation of the machine extends. Suppose-powered motor starts before start of round 5000rpm - 8000rpm, can now be 3000rpm - 8000rpm. The easiest way to know how the engine on lap mesn experiencing TOT is to open the air filter and carburetor see when a light mist spewed outward. This will disrupt the thin mist burning because the engine will get fuel mixture is too rich (mostly gasoline). This thin mist of gasoline occurs because the exhaust pulse wave back to before the time machine, build an incoming fuel will vomit out again through the carburetor. At the time of this pulse passing through the carburetor venturi he always raised the gasoline from the carburetor bowl because of the nature of the carburetor venturi itself. If we reduce the supply of gasoline in the round then the solution remains unanswered arena under full load engine instead of gasoline shortage. Similar simalakama fruit. The motors are set good for light use does not have the same setting is comfortable with the machine accelerates.
Yamaha found that the condition "of torque through" occurs in the condition:
- Cost of light
- The opening of a small gas <1 div = "div" throttle = "throttle">
In finding the optimal dimensions of the tube YEIS, Yamaha conducts research that eventually led to the following results:
The working principle of pulse wave resonance intake (intake) - Intake resonant pulse. Of the many models and names on the market, its principles remain the same. The principle works utilizing the phenomenon found by Hemholtz host. Mr. Hemholtz has formulated a universal formula that underlies the theory of resonance gas in a tube. General formula is as follows:
F = Vs / 2pi * ((A / VC (L + 1/2 (A * pi) ^ 0.5)) ^ 0.5
where,
F = resonant frequency (Hz)
Vs = speed of sound in the gas (cm / min)
A = area of ​​tube (cm ^ 2)
L = length of tube (cm)
Vc = volume of the tube (cm ^ 3)
pi = 3.14.
For the case of the IC then the formula changed as follows:
F = a / 2pi * ((pi * (Dp / 2) ^ 2 / Vb * (Lp + 1.57 * (Dp / 2))) ^ 0.5
where,
F = frequency of resonance / spin machine (Hz)
pi = 3.14
Dp = diameter of the pipe stem IC (cm)
Lp = length of pipe IC (cm)
Vb = Volume of the tube (not pipe) IC (cm)
a = speed of sound in the gas, commonly used 204000 cm / sec
Machines that become research material at the time it has specs
as follows:
Bore / piston diameter = 56mm
Stroke / piston measures 50mm
Volume / capacity = 123cc
CR / compression = 1: 6.67
Port timings
Exhaust / exhaust port = 90deg
Transfer / rinse hole = 121deg
If you notice very similar to the model of Indonesia, known by the name RX-King is not it? It's just with a smaller compression ratio and cylinder capacity only 123cc.Dari YEIS research results proved that it is able to restore the lost torque due to engine design and reduces fuel consumption up to 14% on everyday operating conditions.
For example:
Vb = 400cc
Dp = 0,8cm
Lp = 20cm
then be obtained,
F for 41,667Hz or 2500rpm
Based on the experiments conducted by Yamaha finally obtained the following conclusions.
YEIS optimal functioning conditions:
- The maximum frequency of YEIS should be made equal to the frequency (rpm) when the engine is experiencing TOT
- The volume of the main tube YEIS must be made at least equal to the volume of the engine cylinder.
- Cross-sectional area of the stem YEIS located on the intake manifold must be at least equal to the size of the effective cross-sectional area at the opening of the desired carburetor. Eg 1/4 throttle on the carburetor at 28mm with 1/4 x pi x (14) ^ 2 = 2 ^ 153,938mm
From the experimental results well known that YEIS not show meaningful reduction in output WOT (wide open throttle) - WOT = full throttle condition, very little decrease of the maximum output of the engine.
In my opinion as long as the shape of the intake passage and hole position YEIS manifild not overly impede the flow of incoming gas, then use YEIS provide will always give you an advantage.
According to John Robinson in his book: 4 stroke tuning, use the intake chamber also provide benefits by reducing the blowback in the carburetor. The result would force fuel consumption better at low rpm. My personal experience also proves that the use of the IC on the motor 4 stroke (GL Pro and Supra) greatly improve engine response at low rpm (1000 - 2000rpm). The problem is only complicated because confused tubes sticking-sticking around the intake manifold.
Hopefully useful.