91BLOWNBIRD
Registered User
I thought this was interesting I found this guy's thoughts on a wrangler forum
"bubba_zenetti11-17-2010, 11:47 PM
All exhaust systems (and intakes) have a drone to them. That drone is the resonant frequency of the pipe length. It is called Helmholtz resonance. Even the stock system does, You just need to be outside the vehicle to hear it.
You can demonstrate Helmholtz resonance by blowing your lips across the top of a bottle. vary the height of the bottle or the width and you will vary the frequency of the resonance.
This resonance plays a very important factor in power tuning. Since gas flow is never a one way thing out of an exhaust because of resonance, it is important that the resonant frequency be timed just right to help suck the air fuel mixture into the combustion chamber as the valve are in their overlap period.
Generally speaking, a well tuned exhaust system will produce some sort of resonating note at some point in the RPM range.
This same principle applies to intake runners as well. Longer ones tend to make more low end torque while shorter ones make more torque at peak rpms. There is still a point where the intake resonates and if it is timed right with the valves, it will push the air fuel mixture into the combustion chamber before the valve closes."
thoughts?
"bubba_zenetti11-17-2010, 11:47 PM
All exhaust systems (and intakes) have a drone to them. That drone is the resonant frequency of the pipe length. It is called Helmholtz resonance. Even the stock system does, You just need to be outside the vehicle to hear it.
You can demonstrate Helmholtz resonance by blowing your lips across the top of a bottle. vary the height of the bottle or the width and you will vary the frequency of the resonance.
This resonance plays a very important factor in power tuning. Since gas flow is never a one way thing out of an exhaust because of resonance, it is important that the resonant frequency be timed just right to help suck the air fuel mixture into the combustion chamber as the valve are in their overlap period.
Generally speaking, a well tuned exhaust system will produce some sort of resonating note at some point in the RPM range.
This same principle applies to intake runners as well. Longer ones tend to make more low end torque while shorter ones make more torque at peak rpms. There is still a point where the intake resonates and if it is timed right with the valves, it will push the air fuel mixture into the combustion chamber before the valve closes."
thoughts?