Dragbike Yunani Style

Yoshimura Manifold

Yoshimura carburateur

engine jupiter

d2speed

Supri Indra Paul Afif Dani

Dani Paul Supri Indra Kicli

Paul Dani Indra

Jupiter Ungu

Paul

Honda Supra With Big Valve

hehehehehe.....watch it........on my honda 1997 bike.....

Intake Porting Suzuki Smash
take from http://ratmotorsport.wordpress.com

Exhaust Tuning

1. What is Exhaust Tuning?
When I was fooling around with racing 4-stroke motorcycles a long time back, we used exhaust tuning to increase horsepower by cutting each pipe to a specific length. In order to gain the maximum effect the pipes have to be totally separate from each other, with no common manifold between any of the cylinders. That is not always practical, but it's the ideal. You will notice that on drag racing engines there are always individual pipes sticking out the sides, and those pipes are set to a specific length, which is critical.
We used a formula to determine the length of the exhaust pipe. Because the pressure waves in an exhaust system travel at the speed of sound, we had to know the approximate temperature of the exhaust gases because sound waves move faster in hot air than in cold air. Meaning, it travels further in the same amount of time in a hot gas environment versus a cold gas environment.
Then we calculated how long it would take a sound wave to move from the exhaust valve seat to the end of the pipe and back again. A round trip. Next we needed to know the approximate RPM at which we wanted to run at top end, and then determine how long the exhaust valve would be open from beginning of travel to end of travel.

2. Exhaust Tuning in 4-Stroke Engines; Valve Overlap
When we got it right we would have an exhaust pipe that would carry a positive pressure wave of exhaust pulse down the pipe to the open end. There it would collapse and create a negative pressure wave that would return back up the pipe. If the negative wave arrives back at the exhaust valve just before it closes, it will suck more of the exhaust gases out of the cylinder. This lowers the pressure inside the cylinder and makes the next intake stroke more efficient.
On a 4-stroke, the intake valve begins to open while the exhaust valve is still off it's seat. This is valve overlap. This allows the negative exhaust pulse (the reflection of the positive pulse) to actually pull more fresh mixture past the intake valve and into the cylinder. Here's how it works, and it has nothing to do with exhaust tuning as such.
When the combustion cycle begins, the piston is forced downward; this is the power stroke. Near the bottom of the power stroke the energy is mostly spent and the exhaust valve starts to open. It will actually start to open slightly before bottom dead center. The exhaust charge then begins to rush out the exhaust pipe.
The exhaust gases rushing out are further assisted by the piston pushing up on the exhaust stroke. This forms a stream of hot gas in very rapid motion away from the cylinder. This stream of hot gas has inertia and it will tend to continue moving in the same direction out the exhaust pipe even after the piston stops pushing it. This creates a region of reduced pressure in the vicinity of the exhaust valve.
By opening the intake valve just prior to top dead center, while the exhaust valve is still open (overlap), the gases going out the exhaust pipe will begin pulling the new intake mixture in behind them. Or, the intake stream will try to flow into the region of reduced pressure behind the exhaust stream, if you want to look at it that way. So overlap merely takes advantage of the inertia of the exhaust gases and the low-pressure region that it produces near the exhaust valve at the end of the exhaust stroke.
That part of the overlap design is common to all 4-stroke engines in order to gain additional charging of the cylinder with fuel mix at high RPM. The higher the RPM we design for, the greater the intake and exhaust overlap we build into the cam lobes. Most engines are fitted with exhaust manifolds that collect all the gases from a bank of cylinders. They also usually have a long pipe and muffler. So, while the physics of gases in motion will apply there, tuning for the exhaust pulse will not.

3. Intake Tuning on a 4-Stroke Engine
On the 4-stroke, intake tuning is also a consideration. When the intake valve opens, it creates a negative pressure wave which will travel to the end of the intake pipe. It is reflected as a positive wave which then travels back down the pipe. It will create a sharp, supercharging effect if it can be timed to arrive just before the intake valve closes. That requires individual carb throats to each cylinder though, and no common intake manifold.
The old Dodge Ramchargers used that method in the days when carbs were the standard way to get fuel mixture into an engine, and you could see the eight intake stacks sticking up from the hood. Those intake stacks were cut to a specific length for tuning. The intake tuning was used to "ram" a little more charge into the cylinder just before the intake valve closed; hence the name of that racing team, the Ramchargers.
So you can see the principle involved here and why both intake and exhaust systems are engineered for specific lengths if we want to make use of the pulses within the pipes. Two-strokes use the same principles, but the intake side is not tuned. We can see one undesirable side effect of the intake system on our 2-strokes, however, which is spitting back of some of the fuel mixture at lower rpms.