Blower trivia
10-14-2003 | 08:02 PM
#21
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From: Monroe, LA
Originally posted by Iggy
You have to remember that those Rolls Merlin engines were over 1700 ci in displacement.
It's not like you're trying to stuff 32 lbs of boost into a 454.
1700 ci divided by 12 cylinders = 141.67 ci/cyl.
You have to remember that those Rolls Merlin engines were over 1700 ci in displacement.
It's not like you're trying to stuff 32 lbs of boost into a 454.
1700 ci divided by 12 cylinders = 141.67 ci/cyl.
But 32 psi is 32 psi whether it is in a 56 ci cylinder, a 141.67 ci cylinder, or a scuba tank of compressed air.
10-14-2003 | 09:36 PM
#22
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From: tn
Yeah, boost is boost.
2 atmospheres (29psi, 60inches, etc) is going to be the same PERCENTAGE increase on any size engine.
Volume-Pressure relationship is affected also by temperature. The math for figuring this relationship is shown in the "ideal gas equation": PV=nRT (where Pressure x Volume = molecular quantity x gas constant x Temperature). Ignore the R since they wash out when comparing the same gas (in this case it is essentially regular air with some fuel suspended in it). This illustrates that PV~nT.
If we reverse the equation to solve for n, then it becomes: n~PV/T
It becomes evident here that the discharge temp of the blower or aftercooler will dramatically affect the "n" (the actual number of molecules of air) that are crammed into the cylinders. This, in turn, is what will create more power, assuming that it can be lit off without detonating. Looking at the equation, a "doubling" of the discharge temp (in degrees on the K scale) will HALVE the molecular count of the charge, if introduced at the same pressure. We know, though, that a blower will introduce a higher pressure at a higher temperature. As long as the temperature (adiabatic efficiency) curve of the blower is in its design zone this temp increase is expected and is simply part of running a higher boost. As the blower reaches the upper limit of its design range, it will begin to raise the TEMPERATURE far more for each unit increase in boost pressure. This is where the equation will show that you are no longer actually feeding the motor any more effective intake charge - only more heat and pressure which invites detonation...
The comparison chart for a 454 vs a Merlin would be incomplete without comprehensive temperature/pressure curves for each supercharger and aftercooler...
m
2 atmospheres (29psi, 60inches, etc) is going to be the same PERCENTAGE increase on any size engine.
Volume-Pressure relationship is affected also by temperature. The math for figuring this relationship is shown in the "ideal gas equation": PV=nRT (where Pressure x Volume = molecular quantity x gas constant x Temperature). Ignore the R since they wash out when comparing the same gas (in this case it is essentially regular air with some fuel suspended in it). This illustrates that PV~nT.
If we reverse the equation to solve for n, then it becomes: n~PV/T
It becomes evident here that the discharge temp of the blower or aftercooler will dramatically affect the "n" (the actual number of molecules of air) that are crammed into the cylinders. This, in turn, is what will create more power, assuming that it can be lit off without detonating. Looking at the equation, a "doubling" of the discharge temp (in degrees on the K scale) will HALVE the molecular count of the charge, if introduced at the same pressure. We know, though, that a blower will introduce a higher pressure at a higher temperature. As long as the temperature (adiabatic efficiency) curve of the blower is in its design zone this temp increase is expected and is simply part of running a higher boost. As the blower reaches the upper limit of its design range, it will begin to raise the TEMPERATURE far more for each unit increase in boost pressure. This is where the equation will show that you are no longer actually feeding the motor any more effective intake charge - only more heat and pressure which invites detonation...
The comparison chart for a 454 vs a Merlin would be incomplete without comprehensive temperature/pressure curves for each supercharger and aftercooler...
m
10-15-2003 | 05:17 AM
#26
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From: Kissimmee, Florida
The Studebaker Hawk came in a supercharged version as well as the Ford Thunderbird.
The Studebaker Avanti of the early 60's had a Paxton supercharged version too.
Shelby built a couple of turbocharged examples of the 427 Cobra (Bill Cosby had one) and paxton supercharged versions of the GT-350 Mustang. And Chevrolet built the Corvair Spyder which was turbocharged.
There were a couple of cars built in the 30's that had blowers mounted in front of the engine and connected directly to the crankshaft. Just don't remember which ones.
The Studebaker Avanti of the early 60's had a Paxton supercharged version too.
Shelby built a couple of turbocharged examples of the 427 Cobra (Bill Cosby had one) and paxton supercharged versions of the GT-350 Mustang. And Chevrolet built the Corvair Spyder which was turbocharged.
There were a couple of cars built in the 30's that had blowers mounted in front of the engine and connected directly to the crankshaft. Just don't remember which ones.
Last edited by Iggy; 10-15-2003 at 05:20 AM.
10-15-2003 | 12:40 PM
#28
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From: tn
Don't have much time for TV - 'cept for reruns of Dark Angel and any show with Britney Spears on it...
1950's cars with centrifugal blowers? Stude Hawk and TBird both had Paxtons. The Studebaker version was actually marketed as a "Paxton by McCulloch" supercharger and had a variable-speed drive based off of a ball-ramp type system that was controlled by a boost-sensing diaphragm that worked against spring pressure to reduce the overdrive ratio once the blower showed good boost pressure. This setup never supported BIG boost pressure, as the ball drive would slip - this is why we don't see that style of variable speed drive anymore.
1950's cars with centrifugal blowers? Stude Hawk and TBird both had Paxtons. The Studebaker version was actually marketed as a "Paxton by McCulloch" supercharger and had a variable-speed drive based off of a ball-ramp type system that was controlled by a boost-sensing diaphragm that worked against spring pressure to reduce the overdrive ratio once the blower showed good boost pressure. This setup never supported BIG boost pressure, as the ball drive would slip - this is why we don't see that style of variable speed drive anymore.
10-15-2003 | 01:18 PM
#29
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From: Monroe, LA
Originally posted by mcollinstn
Volume-Pressure relationship is affected also by temperature. The math for figuring this relationship is shown in the "ideal gas equation": PV=nRT (where Pressure x Volume = molecular quantity x gas constant x Temperature). Ignore the R since they wash out when comparing the same gas (in this case it is essentially regular air with some fuel suspended in it). This illustrates that PV~nT.
If we reverse the equation to solve for n, then it becomes: n~PV/T
It becomes evident here that the discharge temp of the blower or aftercooler will dramatically affect the "n" (the actual number of molecules of air) that are crammed into the cylinders. This, in turn, is what will create more power, assuming that it can be lit off without detonating. Looking at the equation, a "doubling" of the discharge temp (in degrees on the K scale) will HALVE the molecular count of the charge, if introduced at the same pressure. We know, though, that a blower will introduce a higher pressure at a higher temperature. As long as the temperature (adiabatic efficiency) curve of the blower is in its design zone this temp increase is expected and is simply part of running a higher boost. As the blower reaches the upper limit of its design range, it will begin to raise the TEMPERATURE far more for each unit increase in boost pressure. This is where the equation will show that you are no longer actually feeding the motor any more effective intake charge - only more heat and pressure which invites detonation...
The comparison chart for a 454 vs a Merlin would be incomplete without comprehensive temperature/pressure curves for each supercharger and aftercooler...
m
Volume-Pressure relationship is affected also by temperature. The math for figuring this relationship is shown in the "ideal gas equation": PV=nRT (where Pressure x Volume = molecular quantity x gas constant x Temperature). Ignore the R since they wash out when comparing the same gas (in this case it is essentially regular air with some fuel suspended in it). This illustrates that PV~nT.
If we reverse the equation to solve for n, then it becomes: n~PV/T
It becomes evident here that the discharge temp of the blower or aftercooler will dramatically affect the "n" (the actual number of molecules of air) that are crammed into the cylinders. This, in turn, is what will create more power, assuming that it can be lit off without detonating. Looking at the equation, a "doubling" of the discharge temp (in degrees on the K scale) will HALVE the molecular count of the charge, if introduced at the same pressure. We know, though, that a blower will introduce a higher pressure at a higher temperature. As long as the temperature (adiabatic efficiency) curve of the blower is in its design zone this temp increase is expected and is simply part of running a higher boost. As the blower reaches the upper limit of its design range, it will begin to raise the TEMPERATURE far more for each unit increase in boost pressure. This is where the equation will show that you are no longer actually feeding the motor any more effective intake charge - only more heat and pressure which invites detonation...
The comparison chart for a 454 vs a Merlin would be incomplete without comprehensive temperature/pressure curves for each supercharger and aftercooler...
m
