Brideport 6-port Ideas
10-08-2003, 11:13 AM
#51
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The premise behind runner tuning is to tune th elengths where the intake pulse travels the length of the runner as a negative pulse, the inverts when the runner ends(preferably in a bell-radios mouth). The inverted pulse is a positive pulse, or high pressure wave. You want to time it so this pulse arrives back at the port just before it closes. You want the high pressure wave to make it into the port, and then the port to close before rversion occurs, which would force the high pressure out of the port.
The bridged aux port opens a full 60 degreese before the stock aux port. Most of the time, the top of the port is raised, which would also delay the closing of th eport, extending the duration even more, but for now, we will just concentrate on the bridged vs non-bridged opening. When the port opens sooner, and lasts longer, there will be more time between the opening and closing of the port. The pulse will not slow down, so for it to arrive back at the right time, it will have to travel more distance, hence a longer runner.
But not all manifolds are tuned this way. Not all manifolds are tuned period. Many, such as the TWM wnd weber manifolds make power from sheer flow alone. Big short runners that pose very little restriction to airflow. But big flow does not mean they are tuned.
The bridged aux port opens a full 60 degreese before the stock aux port. Most of the time, the top of the port is raised, which would also delay the closing of th eport, extending the duration even more, but for now, we will just concentrate on the bridged vs non-bridged opening. When the port opens sooner, and lasts longer, there will be more time between the opening and closing of the port. The pulse will not slow down, so for it to arrive back at the right time, it will have to travel more distance, hence a longer runner.
But not all manifolds are tuned this way. Not all manifolds are tuned period. Many, such as the TWM wnd weber manifolds make power from sheer flow alone. Big short runners that pose very little restriction to airflow. But big flow does not mean they are tuned.
10-08-2003, 11:59 AM
#53
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Join Date: May 2002
Location: California
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Originally Posted by mazdaspeed7' date='Oct 8 2003, 08:13 AM
The premise behind runner tuning is to tune th elengths where the intake pulse travels the length of the runner as a negative pulse, the inverts when the runner ends(preferably in a bell-radios mouth). The inverted pulse is a positive pulse, or high pressure wave. You want to time it so this pulse arrives back at the port just before it closes. You want the high pressure wave to make it into the port, and then the port to close before rversion occurs, which would force the high pressure out of the port.
The bridged aux port opens a full 60 degreese before the stock aux port. Most of the time, the top of the port is raised, which would also delay the closing of th eport, extending the duration even more, but for now, we will just concentrate on the bridged vs non-bridged opening. When the port opens sooner, and lasts longer, there will be more time between the opening and closing of the port. The pulse will not slow down, so for it to arrive back at the right time, it will have to travel more distance, hence a longer runner.
But not all manifolds are tuned this way. Not all manifolds are tuned period. Many, such as the TWM wnd weber manifolds make power from sheer flow alone. Big short runners that pose very little restriction to airflow. But big flow does not mean they are tuned.
The bridged aux port opens a full 60 degreese before the stock aux port. Most of the time, the top of the port is raised, which would also delay the closing of th eport, extending the duration even more, but for now, we will just concentrate on the bridged vs non-bridged opening. When the port opens sooner, and lasts longer, there will be more time between the opening and closing of the port. The pulse will not slow down, so for it to arrive back at the right time, it will have to travel more distance, hence a longer runner.
But not all manifolds are tuned this way. Not all manifolds are tuned period. Many, such as the TWM wnd weber manifolds make power from sheer flow alone. Big short runners that pose very little restriction to airflow. But big flow does not mean they are tuned.
mike
10-08-2003, 06:23 PM
#55
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Thread Starter
Join Date: Oct 2003
Posts: 177
Originally Posted by mazdaspeed7' date='Oct 8 2003, 08:13 AM
The premise behind runner tuning is to tune th elengths where the intake pulse travels the length of the runner as a negative pulse, the inverts when the runner ends(preferably in a bell-radios mouth). The inverted pulse is a positive pulse, or high pressure wave. You want to time it so this pulse arrives back at the port just before it closes. You want the high pressure wave to make it into the port, and then the port to close before rversion occurs, which would force the high pressure out of the port.
The bridged aux port opens a full 60 degreese before the stock aux port. Most of the time, the top of the port is raised, which would also delay the closing of th eport, extending the duration even more, but for now, we will just concentrate on the bridged vs non-bridged opening. When the port opens sooner, and lasts longer, there will be more time between the opening and closing of the port. The pulse will not slow down, so for it to arrive back at the right time, it will have to travel more distance, hence a longer runner.
But not all manifolds are tuned this way. Not all manifolds are tuned period. Many, such as the TWM wnd weber manifolds make power from sheer flow alone. Big short runners that pose very little restriction to airflow. But big flow does not mean they are tuned.
The bridged aux port opens a full 60 degreese before the stock aux port. Most of the time, the top of the port is raised, which would also delay the closing of th eport, extending the duration even more, but for now, we will just concentrate on the bridged vs non-bridged opening. When the port opens sooner, and lasts longer, there will be more time between the opening and closing of the port. The pulse will not slow down, so for it to arrive back at the right time, it will have to travel more distance, hence a longer runner.
But not all manifolds are tuned this way. Not all manifolds are tuned period. Many, such as the TWM wnd weber manifolds make power from sheer flow alone. Big short runners that pose very little restriction to airflow. But big flow does not mean they are tuned.
Their peripheral ports had a much earlier opening and later closing IIRC than any BP you'll find...
They have a very interesting tech paper on their site with a nice little graph which shows Veerry cleary the relationship between intake runner length and torque.
So unless a BP motor has fundementally different intake wave charateristics, then this graph would still apply.
And I find it very hard to believe your bridged aux port motor has 60deg earlier opening than stock? thats a fair bit.. I can't see how you stayed in the aux port runner with that much earlier opening than stock? im assuming you mean 60deg before the primary/secondary ports open? not when the aux port opens?
I'll get back to my comment here about the guys that race their BP here in australia, all the EFI ones i've seen (a fair few) have had very short inlet runners with dual/quad throttles... these motors have all had considerable money spent on them.. I can't see them overlooking something like inlet runner tunning.
10-08-2003, 10:30 PM
#56
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A bridged 6 port will have more timing duration than a PP. They open about the same time, but the 6 port closes later. PP's and BP's open when the apex seal passes them. Side ports(street and stock) have to wait for the side seal to pass them to open. Thats where the extra timing is.
The Mazda Le Mans motor used relatively small PP's, and those runners were tuned EXACTLY in the manner I described. And on top of that, the runners were continuously variable, so the runners were optomized over a RPM band. That motor stayed below 9K rpm. You can get a street port 6 port to make power to 9K with a non-stock manifold/EMS. The PP will make more power, as the air has a straight shot into the chamber, instead of turning a corner.
White FC, no offense, but you need to study up some on the port timing of a rotary. I think www.howstuffworks.com has an illustration with the port timing lines marked every 10 degrees. You need to understand the timing to understand my arguments.
J9, I would really like to read up more on how exactly the VDI works. The initial pulse is always negative, and then a higher pressure wave follows it, but it is nowhere near the amplitude of the initial low pressure wave. The runner tuning I was referring to uses a bell curve mouth to invert the initial low pressure pulse. But the only way I can see the VDI working is utilizing the high pressure wave that follows the initial low pressure wave, and times it so the port closes just after the high pressure wave enters the chamber. But that still seems to be not as effective as inverting the initial wave. And it also seems that the losses out of the tuned range would be greater with the VDI setup.
The Mazda Le Mans motor used relatively small PP's, and those runners were tuned EXACTLY in the manner I described. And on top of that, the runners were continuously variable, so the runners were optomized over a RPM band. That motor stayed below 9K rpm. You can get a street port 6 port to make power to 9K with a non-stock manifold/EMS. The PP will make more power, as the air has a straight shot into the chamber, instead of turning a corner.
White FC, no offense, but you need to study up some on the port timing of a rotary. I think www.howstuffworks.com has an illustration with the port timing lines marked every 10 degrees. You need to understand the timing to understand my arguments.
J9, I would really like to read up more on how exactly the VDI works. The initial pulse is always negative, and then a higher pressure wave follows it, but it is nowhere near the amplitude of the initial low pressure wave. The runner tuning I was referring to uses a bell curve mouth to invert the initial low pressure pulse. But the only way I can see the VDI working is utilizing the high pressure wave that follows the initial low pressure wave, and times it so the port closes just after the high pressure wave enters the chamber. But that still seems to be not as effective as inverting the initial wave. And it also seems that the losses out of the tuned range would be greater with the VDI setup.
10-08-2003, 10:43 PM
#57
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Originally Posted by mazdaspeed7' date='Oct 8 2003, 07:30 PM
J9, I would really like to read up more on how exactly the VDI works. The initial pulse is always negative, and then a higher pressure wave follows it, but it is nowhere near the amplitude of the initial low pressure wave. The runner tuning I was referring to uses a bell curve mouth to invert the initial low pressure pulse. But the only way I can see the VDI working is utilizing the high pressure wave that follows the initial low pressure wave, and times it so the port closes just after the high pressure wave enters the chamber. But that still seems to be not as effective as inverting the initial wave. And it also seems that the losses out of the tuned range would be greater with the VDI setup.
oh and the 787b's trumpets are long at idle and get shorter when uncle koby revs it. it can actually move the trumpets as fast as the engine revs in neutral, its neat to see
mike
10-08-2003, 11:02 PM
#58
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Join Date: Oct 2003
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mazdaspeed7, no offense, but you need to study up some on inlet runner tunning as you obviously havn't been listening to me at all....
As I, and now j9fd3s, have both pointed out, the 26B has varibalbe inlets.. that are extended at idle and get shoter the higher the RPM is..
As I've said a few times theres an excellent little graph and a short explanation about this system in the mazda tech paper on the 787b.. Perhaps you should have a look at that.
I know a fair bit about the timing on a rotor, I understand how BP's and to a greater extent PP's open up earlier. That was not my point at all though, I don't understand how you could get 60deg earlier opening from just doing a bridge on the aux port.
Maybe if you did it on the primary/secondary port it would give you that much, but i can't see how doing on the aux runner would give you that number, please correct me, just doesn't look right, i'm here right now moving a rotor around its orbital rotation in a housing with a side plate on the back, and I can't see anyone getting THAT much extra timing from just a bridge on the aux runner.. doesn't add up.
As I, and now j9fd3s, have both pointed out, the 26B has varibalbe inlets.. that are extended at idle and get shoter the higher the RPM is..
As I've said a few times theres an excellent little graph and a short explanation about this system in the mazda tech paper on the 787b.. Perhaps you should have a look at that.
I know a fair bit about the timing on a rotor, I understand how BP's and to a greater extent PP's open up earlier. That was not my point at all though, I don't understand how you could get 60deg earlier opening from just doing a bridge on the aux port.
Maybe if you did it on the primary/secondary port it would give you that much, but i can't see how doing on the aux runner would give you that number, please correct me, just doesn't look right, i'm here right now moving a rotor around its orbital rotation in a housing with a side plate on the back, and I can't see anyone getting THAT much extra timing from just a bridge on the aux runner.. doesn't add up.