Just looking around and thought about asking this question. Is there any benefit of cutting the tube between the end pipes on the header and welding up the holes? Just curious of this. Sorry if it is a newb question.
Dont do it. The reason that those connecters are there is because when the #1 cylynder has spent its exhaust gas, and is closing the #2 is opening, pushing more of the spent gas through the #1 tube. Its called scavenging, and is imperitive to pulling the last bit of spent gases out of the closing combustion chamber. That's one reason that after market headers are far superior to stock.
Think of exhaust gases as a piston moving down through the tubular system. As each pulse travels down the system, it creates a vacuum behind itself. The negative pressure behind each, is the scavenging effect. As the velocity of the pulses increase, the negative pressures also increase. As you have an increase in velocity, the length of time that you have a negative pressure in the system is increased. The net result of higher velocity to assist in scavenging is increased performance of the intake and exhaust system. Maintaining higher exhaust temperatures throughout the system increases performance in many ways.
Think of exhaust gases as a heavy liquid such as an oil additive. If the liquid were traveling down a tubular system in a cold state, it would move very slowly. If you were to heat the liquid, the density of the fluid changes. The liquid responds to the heat increasing Its velocity. Exhaust gases respond In the same manner. Higher temperatures in a system increases the flow of the system. If the liquid is allowed to cool in the system, It slows down the flow of the liquid. By this Illustration, you can now see the importance of maintaining higher temperatures in a exhaust system.
The Incoming air charge increases due to many different factors. First, the lowering of air induction temperatures and cooler fuel coming into the engine will increase horse power by over 1% per Degree drop In temperature. Other areas of performance are Improved by the increased scavenging effect. Increasing the scavenging effect of the exhaust allows the engine to breathe more efficiently. A engine in many ways is like an air compressor, the pushing of exhaust gases from the combustion chamber creates a condition called pumping losses. This is the loss of power due to the piston pushing these exhaust gases Into the system and out of the system. Increased scavenging not only lowers pumping losses but also allows more efficient clearing of exhaust gases from the combustion chamber. This means cleaner air fuel mixture, this means power. The increased scavenging effect of the exhaust also benefits the intake of air & fuel during the overlap phase of the intake stroke. During the overlap phase, both the intake & exhaust valve are open. The exhaust gases create a vacuum effect which pulls the air fuel mixture at a higher velocity through the intake.
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