454 rebuild with blower... Pistons and clearances.
01-23-2015 | 03:40 PM
#92
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From: Grand Rapids, MI
Also, this gets into better flowing heads = less restriction = less boost conundrum, which is great for me!
01-23-2015 | 04:53 PM
#95
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From: chicago
Something thats been going thru my mind lately. Maybe one of you guys can help straighten me out.
We all by now, know the importance of velocity, and how without it, we get poor cylinder filling, esp at low speeds, esp on an engine relying on atmospheric pressure. Now, in my boat, at cruise, lets say 3000RPM. My intake manifold, is right around 0" of vacuum. If my boat was N/A, obviously I wouldn't have 0'' manifold vacuum, unless of course I was WOT.
Roots style blowers do not compress air, they simple move air. Kind of like a fan. It takes air from one place, and moves it to another, but at a greater speed. Forcing this air into the manifold, produces a positive pressure, or "boost". So, even though technically my engine at 3000RPM, is not seeing "boost", its still seeing a higher pressure, than if it were naturally aspirated. This is not a car running down the highway at 2000RPM in high vacuum. So in reality, even though your roots/screw blown marine engine is not technically registering boost on the gauge, its also not just running "on motor" so to speak. The blower is still helping. Whether or not its making more power at the flywheel at that point, I guess depends on the parasitic drag from the blower being more or less than its actually helping.
I guess my question is, while we can flow a port at 28" of mercury, and see numbers, what do we see when we are in real world? I suppose if the small high velocity port, never becomes a point of restriction, then there would be no power loss anywhere in the rpm band, and probably nothing to be gained. But, if it does become a restriction, say maybe at 5500RPM, where a larger head may start making more power, than obviously, its a loss above and beyond that point.
On the dyno, at 3000RPM with a roots blower doing a pull with the throttle blades wide open, and say 6psi of positive pressure, that is not what things are shaped like at 3000RPM, with 0" of pressure, nor 6'' of vacuum when cruising down the lake at 3000RPM. Just thoughts that run thru my head, and may not make any sense whatsover lol
We all by now, know the importance of velocity, and how without it, we get poor cylinder filling, esp at low speeds, esp on an engine relying on atmospheric pressure. Now, in my boat, at cruise, lets say 3000RPM. My intake manifold, is right around 0" of vacuum. If my boat was N/A, obviously I wouldn't have 0'' manifold vacuum, unless of course I was WOT.
Roots style blowers do not compress air, they simple move air. Kind of like a fan. It takes air from one place, and moves it to another, but at a greater speed. Forcing this air into the manifold, produces a positive pressure, or "boost". So, even though technically my engine at 3000RPM, is not seeing "boost", its still seeing a higher pressure, than if it were naturally aspirated. This is not a car running down the highway at 2000RPM in high vacuum. So in reality, even though your roots/screw blown marine engine is not technically registering boost on the gauge, its also not just running "on motor" so to speak. The blower is still helping. Whether or not its making more power at the flywheel at that point, I guess depends on the parasitic drag from the blower being more or less than its actually helping.
I guess my question is, while we can flow a port at 28" of mercury, and see numbers, what do we see when we are in real world? I suppose if the small high velocity port, never becomes a point of restriction, then there would be no power loss anywhere in the rpm band, and probably nothing to be gained. But, if it does become a restriction, say maybe at 5500RPM, where a larger head may start making more power, than obviously, its a loss above and beyond that point.
On the dyno, at 3000RPM with a roots blower doing a pull with the throttle blades wide open, and say 6psi of positive pressure, that is not what things are shaped like at 3000RPM, with 0" of pressure, nor 6'' of vacuum when cruising down the lake at 3000RPM. Just thoughts that run thru my head, and may not make any sense whatsover lol
01-23-2015 | 05:19 PM
#96
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From: wisconsin
Yes the blower does compress air... maybe not very efficient, but it does. And I get what you are thinking in your last paragraph. Different loads, throttle positions, barometric pressure, etc...will change what you see on the boost gauge. Thats why if you take a blown carb'd engine it will have different numbers from dyno, to boat, or say a single engine 19' to a single 30' boat; or put that same motor in a car.
01-23-2015 | 05:20 PM
#97
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From: yorkville,il
Something thats been going thru my mind lately. Maybe one of you guys can help straighten me out.
We all by now, know the importance of velocity, and how without it, we get poor cylinder filling, esp at low speeds, esp on an engine relying on atmospheric pressure. Now, in my boat, at cruise, lets say 3000RPM. My intake manifold, is right around 0" of vacuum. If my boat was N/A, obviously I wouldn't have 0'' manifold vacuum, unless of course I was WOT.
Roots style blowers do not compress air, they simple move air. Kind of like a fan. It takes air from one place, and moves it to another, but at a greater speed. Forcing this air into the manifold, produces a positive pressure, or "boost". So, even though technically my engine at 3000RPM, is not seeing "boost", its still seeing a higher pressure, than if it were naturally aspirated. This is not a car running down the highway at 2000RPM in high vacuum. So in reality, even though your roots/screw blown marine engine is not technically registering boost on the gauge, its also not just running "on motor" so to speak. The blower is still helping. Whether or not its making more power at the flywheel at that point, I guess depends on the parasitic drag from the blower being more or less than its actually helping.
I guess my question is, while we can flow a port at 28" of mercury, and see numbers, what do we see when we are in real world? I suppose if the small high velocity port, never becomes a point of restriction, then there would be no power loss anywhere in the rpm band, and probably nothing to be gained. But, if it does become a restriction, say maybe at 5500RPM, where a larger head may start making more power, than obviously, its a loss above and beyond that point.
On the dyno, at 3000RPM with a roots blower doing a pull with the throttle blades wide open, and say 6psi of positive pressure, that is not what things are shaped like at 3000RPM, with 0" of pressure, nor 6'' of vacuum when cruising down the lake at 3000RPM. Just thoughts that run thru my head, and may not make any sense whatsover lol
We all by now, know the importance of velocity, and how without it, we get poor cylinder filling, esp at low speeds, esp on an engine relying on atmospheric pressure. Now, in my boat, at cruise, lets say 3000RPM. My intake manifold, is right around 0" of vacuum. If my boat was N/A, obviously I wouldn't have 0'' manifold vacuum, unless of course I was WOT.
Roots style blowers do not compress air, they simple move air. Kind of like a fan. It takes air from one place, and moves it to another, but at a greater speed. Forcing this air into the manifold, produces a positive pressure, or "boost". So, even though technically my engine at 3000RPM, is not seeing "boost", its still seeing a higher pressure, than if it were naturally aspirated. This is not a car running down the highway at 2000RPM in high vacuum. So in reality, even though your roots/screw blown marine engine is not technically registering boost on the gauge, its also not just running "on motor" so to speak. The blower is still helping. Whether or not its making more power at the flywheel at that point, I guess depends on the parasitic drag from the blower being more or less than its actually helping.
I guess my question is, while we can flow a port at 28" of mercury, and see numbers, what do we see when we are in real world? I suppose if the small high velocity port, never becomes a point of restriction, then there would be no power loss anywhere in the rpm band, and probably nothing to be gained. But, if it does become a restriction, say maybe at 5500RPM, where a larger head may start making more power, than obviously, its a loss above and beyond that point.
On the dyno, at 3000RPM with a roots blower doing a pull with the throttle blades wide open, and say 6psi of positive pressure, that is not what things are shaped like at 3000RPM, with 0" of pressure, nor 6'' of vacuum when cruising down the lake at 3000RPM. Just thoughts that run thru my head, and may not make any sense whatsover lol
01-23-2015 | 05:28 PM
#98
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From: yorkville,il
a standard roots blower does not compress air in the supercharger unless it has a delta opening,most high helix roots blowers have a delta opening,most standard helix roots blowers do not.a psi or whipple screw blower does compress air in the blower.a standard roots blower simply moves air from one place to another.
01-23-2015 | 05:39 PM
#99
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Posts: 688
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From: wisconsin
a standard roots blower does not compress air in the supercharger unless it has a delta opening,most high helix roots blowers have a delta opening,most standard helix roots blowers do not.a psi or whipple screw blower does compress air in the blower.a standard roots blower simply moves air from one place to another.
01-23-2015 | 05:56 PM
#100
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Joined: Oct 2007
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From: yorkville,il
No I don't think that the bore and compression will make any real difference, I am using the stock Holley 1050 dominator that has been set up, flowed, and boost referenced through AED. Dyno sheets from 2 separate builders, seperate dyno's even if the same brand, seperate dyno operators, and in 2 different parts of the country are not comparable to say that the 305 made/didnt make/or is the same power as the 265. What correction factor was the dyno set up at? Is the Dyno calibrated? How often is it calibrated? Looks like your dyno doesn't use a water break for load? If my guy ran mine and it made 650 and I said pull it again and make it show 690 it would be no problem. We could pull it and make X, let everything cool down while keeping the oil temp hot, and do a quick blast and I promise you it will make more power then the pull before where we let everything get up to temp. The only real data in this thread is Haxby's post where he has literally tested back to back all the same and just changed the 1 component. Your dyno sheet isn't real data, its a reference, but its not data. If you ran that exact motor with no changes its HIGHLY unlikely that you would get the same numbers dyno to dyno with all these different variables.
