Twin Charging.........
Heres the text:
Originally Posted by Wiki
Compound turbocharging
Compound turbocharging is a technique used to achieve extremely high pressure ratios. It is common in racing with diesel engines (For example Tractor pulling) due to their combustion properties that take well to high boost pressures and are not limited by fuel stability like spark ignition engines. Boost pressures of around 7 bar gauge pressure (101 psi) are common and as high as 10 bar (145psi) in some cases. A normal turbocharger has a maximum pressure ratio of around 3 but there are turbochargers in existence specially designed for high boost which have maximum pressure ratios of typically 4-5. In this configuration one turbocharger is used to pressurize the air coming into the inlet of the other, resulting in a multiplication of the pressure ratios. Same goes for exhaust plumbing. For example if both turbochargers are running at pressure ratios of 3.0 and the atmospheric pressure is 1 bar the resulting pressures will be 3 bar absolute pressure at the inlet of the second turbocharger and 9 bar absolute pressure (8 bar gauge) at the inlet manifold of the engine. The pressure ratio in this example becomes 9.
Compound turbocharging is a technique used to achieve extremely high pressure ratios. It is common in racing with diesel engines (For example Tractor pulling) due to their combustion properties that take well to high boost pressures and are not limited by fuel stability like spark ignition engines. Boost pressures of around 7 bar gauge pressure (101 psi) are common and as high as 10 bar (145psi) in some cases. A normal turbocharger has a maximum pressure ratio of around 3 but there are turbochargers in existence specially designed for high boost which have maximum pressure ratios of typically 4-5. In this configuration one turbocharger is used to pressurize the air coming into the inlet of the other, resulting in a multiplication of the pressure ratios. Same goes for exhaust plumbing. For example if both turbochargers are running at pressure ratios of 3.0 and the atmospheric pressure is 1 bar the resulting pressures will be 3 bar absolute pressure at the inlet of the second turbocharger and 9 bar absolute pressure (8 bar gauge) at the inlet manifold of the engine. The pressure ratio in this example becomes 9.
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Joined: Nov 2004
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From: tennessee
OK... It's getting better, now.
Is it true that turbos must be operating near their maximum boost pressure potential before the full multiplication effect occurs?
I see the maximum pressure ratio of a normal turbocharger is about 3:1. Does that mean its maximum boost potential is 3 x 14.7 = 44.1 PSI?
Then such a turbo would be operating at a fraction of its potential maximum boost pressure when it is putting out 14.7 + 5 = 19.7 PSI, right? In fact, that is only about 45% of its maximum pressure potential.
So, I conclude the multiplier of boost made by the sc is (.45 x 5) = 2.25.
The resulting boost pressure in the manifold would be 5 x 2.25 = 11.25 PSI.
Does this example unify our thinking?
Is it true that turbos must be operating near their maximum boost pressure potential before the full multiplication effect occurs?
I see the maximum pressure ratio of a normal turbocharger is about 3:1. Does that mean its maximum boost potential is 3 x 14.7 = 44.1 PSI?
Then such a turbo would be operating at a fraction of its potential maximum boost pressure when it is putting out 14.7 + 5 = 19.7 PSI, right? In fact, that is only about 45% of its maximum pressure potential.
So, I conclude the multiplier of boost made by the sc is (.45 x 5) = 2.25.
The resulting boost pressure in the manifold would be 5 x 2.25 = 11.25 PSI.
Does this example unify our thinking?
Originally Posted by bullseye
OK... It's getting better, now.
Is it true that turbos must be operating near their maximum boost pressure potential before the full multiplication effect occurs?
I see the maximum pressure ratio of a normal turbocharger is about 3:1. Does that mean its maximum boost potential is 3 x 14.7 = 44.1 PSI?
Then such a turbo would be operating at a fraction of its potential maximum boost pressure when it is putting out 14.7 + 5 = 19.7 PSI, right? In fact, that is only about 45% of its maximum pressure potential.
So, I conclude the multiplier of boost made by the sc is (.45 x 5) = 2.25.
The resulting boost pressure in the manifold would be 5 x 2.25 = 11.25 PSI.
Does this example unify our thinking?
Is it true that turbos must be operating near their maximum boost pressure potential before the full multiplication effect occurs?
I see the maximum pressure ratio of a normal turbocharger is about 3:1. Does that mean its maximum boost potential is 3 x 14.7 = 44.1 PSI?
Then such a turbo would be operating at a fraction of its potential maximum boost pressure when it is putting out 14.7 + 5 = 19.7 PSI, right? In fact, that is only about 45% of its maximum pressure potential.
So, I conclude the multiplier of boost made by the sc is (.45 x 5) = 2.25.
The resulting boost pressure in the manifold would be 5 x 2.25 = 11.25 PSI.
Does this example unify our thinking?
Not necessary. Ambient pressure is typically 1 bar. So if your supercharger is pressurizing air to 2:1 but is being fed by a turbo that is also pressurizing 2:1 the net pressure is 4:1 at the manifold. But thats just the pressure ratio. 2:1 with ambient pressure actually means 14.7 PSI above ambient. This however may be drastically different depending on the pressure above ambient you are running on the supercharger and turbocharger. So lets say your turbo is making 8 PSI... That is roughly a 1.544 pressure ratio. Now your supercharger is running at lets say 7 PSI. The supercharger is techincally running a pressure ratio of 1.476. So you need to mutiply the pressure ratio of the first compressor by the pressure ratio o the second compressor to get the total pressure ratio at the manifold. 2.278 is the final pressure ratio at the manifold.
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Joined: Oct 2006
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From: Atlanta, GA
Originally Posted by MIAPLAYA
Not necessary. Ambient pressure is typically 1 bar. So if your supercharger is pressurizing air to 2:1 but is being fed by a turbo that is also pressurizing 2:1 the net pressure is 4:1 at the manifold. But thats just the pressure ratio. 2:1 with ambient pressure actually means 14.7 PSI above ambient. This however may be drastically different depending on the pressure above ambient you are running on the supercharger and turbocharger. So lets say your turbo is making 8 PSI... That is roughly a 1.544 pressure ratio. Now your supercharger is running at lets say 7 PSI. The supercharger is techincally running a pressure ratio of 1.476. So you need to mutiply the pressure ratio of the first compressor by the pressure ratio o the second compressor to get the total pressure ratio at the manifold. 2.278 is the final pressure ratio at the manifold.
