Exhaust
Burning Brakes
Joined: Nov 2004
Posts: 993
Likes: 0
From: PA
Take a view of the LS1 (or any internal combustion engine) as basically an air pump. Air intake fills the combustion chamber, add fuel and an ignition source, the explosion is converted to mechanical energy, the exhaust then needs to be evacuated... out the headers, through the plumbing into the atmosphere.
That is an over simplification, but in a nutshell, thats what the air intake, MAF, intake manifold and cylinder head intake valves do. The head exhaust valves provide a path to evacuate the remnants of the combustion chemical process. The rest of the exhaust path is akin to the plumbing in your house. The waste water needs a place to go, and the less restrictions in that pipe path, the easier (less energy required) the waste is 'evacuated' from your house. Plug up the drain, its not good, get a larger waste pipe, and the flow is easier.
Now for the confusing part: Within a pipe, as fluid flows due do a pressure differential (cylinder exhaust pressure minus exhaust tip pressure [atmosphere]) the fluid's internal energy decreases (it cools off, pressure is reduced and converted to flow energy [enthalpy]). This is why some towns have a booster pumping station for potable water. Now if you increase the size of the pipe and maintain the same inlet pressure(cylinder exhaust pressure), there is a point where the gases will not flow due to greater pipewall area, increased friction, etc. resulting in a lack of 'evacuation of combustion remnants' resulting in poor engine performance (don't want to go into that now).
Standard aftermarket cat-back systems will NOT reduce the 'back-pressure' felt at the cylinder head exhaust significantly to reduce engine power (Hp and Torque). It will souind louder (or better) and some cat-back manufacturer's claim a small Hp gain from their system (jury's still out on that reviewing the DNA evidence
) there is virtually no net change in performance of the LS1. Now, bolt on a set of long tube headers, hi-flow cats (or no cats) and there is a measureable increase in Hp and Torque.
Sorry for rambling, but
with what zeevette said.
That is an over simplification, but in a nutshell, thats what the air intake, MAF, intake manifold and cylinder head intake valves do. The head exhaust valves provide a path to evacuate the remnants of the combustion chemical process. The rest of the exhaust path is akin to the plumbing in your house. The waste water needs a place to go, and the less restrictions in that pipe path, the easier (less energy required) the waste is 'evacuated' from your house. Plug up the drain, its not good, get a larger waste pipe, and the flow is easier.
Now for the confusing part: Within a pipe, as fluid flows due do a pressure differential (cylinder exhaust pressure minus exhaust tip pressure [atmosphere]) the fluid's internal energy decreases (it cools off, pressure is reduced and converted to flow energy [enthalpy]). This is why some towns have a booster pumping station for potable water. Now if you increase the size of the pipe and maintain the same inlet pressure(cylinder exhaust pressure), there is a point where the gases will not flow due to greater pipewall area, increased friction, etc. resulting in a lack of 'evacuation of combustion remnants' resulting in poor engine performance (don't want to go into that now).
Standard aftermarket cat-back systems will NOT reduce the 'back-pressure' felt at the cylinder head exhaust significantly to reduce engine power (Hp and Torque). It will souind louder (or better) and some cat-back manufacturer's claim a small Hp gain from their system (jury's still out on that reviewing the DNA evidence
) there is virtually no net change in performance of the LS1. Now, bolt on a set of long tube headers, hi-flow cats (or no cats) and there is a measureable increase in Hp and Torque.Sorry for rambling, but
with what zeevette said.
Last edited by Silver98; Sep 14, 2006 at 07:30 PM.
