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Here are some concepts I found while searching information on turbo headers for the 60v6 engine. Mostly deals with pulse tuning the headers for a turbo. A topic I am deeply invested in myself. I need to build my own custom set and well, lets face it.....who doesn't love a pristine set of headers built by your own hands, research, math, etc.
Pulse Tuning:
A divided housing will benefit most from 240 crank degree separation of impulses per side. Noting the crank must rotate twice to complete one combustion event for every cylinder. In our 60v6, the next firing cylinder is 120 crank degrees later. Merging every other cylinder will allow the 240 optimal degree of separation. This is convenient for the 60v6 motor as it fires across each bank evenly. Equal length headers will definitely speed up spool if they are plumbed right.
A set of cut hoses the same length as the primaries, secured in place to simulate the header flange, bend them where they will go and the hose will give a rough path to start with. The primaries can then be designed around the hose paths. If a set of primaries were welded to flow as smooth a transition as the bent hoses, they will flow very well.
The collector should not have a larger cross section then the cross section of the turbine housing entrance.
Enhancing the Pulse Energy: (some stuff I found intriguing)
When the exhaust energy begins to escape the cylinder there is a strong pressure difference across the valve. The gases escape so fast they reach sonic speeds and will not flow any faster until the pressure gradient falls enough to slow the escaping gases.
When a pressure wave in a pipe enters a larger cross sectional area, a return wave of negative pressure is created and travels back up the pipe. If the pressure wave travels into a smaller cross sectional area a positive return wave is created.
This is why the stepped diameter from the exhaust port to the exhaust manifold provides greater flow. The escaping gas creates a return pulse of negative value and increase the pressure gradient across the exhaust valve. Which extends the time when the pressure gradient is great enough to support sonic flow of gases creating a stronger exhaust pulse with greater velocity downstream.
Reading from this article, the writer describes a part to a Formula 1 exhaust header seen in Illustration 1. There is a 10mm step placed to provide a negative return pulse arriving at the back of the exhaust valve while fully open, increasing the pressure difference across the cylinder and the exhaust port.
Ill. 1
Placement of the step to return the negative pressure wave just before the escaping exhaust begins to slow. Unless you can monitor exhaust port pressures, time it to land at the exhaust valve at the RPM of peak power. For a street performance engine, use peak torque RPM. For a track engine, use peak HP RPM.
More steps can be included broaden the range of power. But each included step sacrifices small amount of velocity, returning the energy where it can be useful. A delicate balance towards greater efficiency.
It MIGHT be beneficial to make a primary the same cross section as the exhaust port. Then create an equally proportioned step at the right spot downstream, timed to benefit cylinder scavenging at the peak power rpm. In a way, tuning the port step to benefit where we want it to. For a turbo, this will allow higher velocity upstream the primary and reduce primary volume for faster spooling.
The tapered flow in the Illustration above intrigues me. I believe the focusing of the pulse enhances the steps effect. But at the rpm's this header piece was intended for, our motors will need a far more gradual taper, to the point not worth including.
Pulse Tuning:
A divided housing will benefit most from 240 crank degree separation of impulses per side. Noting the crank must rotate twice to complete one combustion event for every cylinder. In our 60v6, the next firing cylinder is 120 crank degrees later. Merging every other cylinder will allow the 240 optimal degree of separation. This is convenient for the 60v6 motor as it fires across each bank evenly. Equal length headers will definitely speed up spool if they are plumbed right.
A set of cut hoses the same length as the primaries, secured in place to simulate the header flange, bend them where they will go and the hose will give a rough path to start with. The primaries can then be designed around the hose paths. If a set of primaries were welded to flow as smooth a transition as the bent hoses, they will flow very well.
The collector should not have a larger cross section then the cross section of the turbine housing entrance.
Enhancing the Pulse Energy: (some stuff I found intriguing)
When the exhaust energy begins to escape the cylinder there is a strong pressure difference across the valve. The gases escape so fast they reach sonic speeds and will not flow any faster until the pressure gradient falls enough to slow the escaping gases.
When a pressure wave in a pipe enters a larger cross sectional area, a return wave of negative pressure is created and travels back up the pipe. If the pressure wave travels into a smaller cross sectional area a positive return wave is created.
This is why the stepped diameter from the exhaust port to the exhaust manifold provides greater flow. The escaping gas creates a return pulse of negative value and increase the pressure gradient across the exhaust valve. Which extends the time when the pressure gradient is great enough to support sonic flow of gases creating a stronger exhaust pulse with greater velocity downstream.
Reading from this article, the writer describes a part to a Formula 1 exhaust header seen in Illustration 1. There is a 10mm step placed to provide a negative return pulse arriving at the back of the exhaust valve while fully open, increasing the pressure difference across the cylinder and the exhaust port.
Ill. 1
Placement of the step to return the negative pressure wave just before the escaping exhaust begins to slow. Unless you can monitor exhaust port pressures, time it to land at the exhaust valve at the RPM of peak power. For a street performance engine, use peak torque RPM. For a track engine, use peak HP RPM.
More steps can be included broaden the range of power. But each included step sacrifices small amount of velocity, returning the energy where it can be useful. A delicate balance towards greater efficiency.
It MIGHT be beneficial to make a primary the same cross section as the exhaust port. Then create an equally proportioned step at the right spot downstream, timed to benefit cylinder scavenging at the peak power rpm. In a way, tuning the port step to benefit where we want it to. For a turbo, this will allow higher velocity upstream the primary and reduce primary volume for faster spooling.
The tapered flow in the Illustration above intrigues me. I believe the focusing of the pulse enhances the steps effect. But at the rpm's this header piece was intended for, our motors will need a far more gradual taper, to the point not worth including.
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