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Old 02-27-2012, 09:36 AM   #533
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But too much space and you can lose power correct? Sounds like a fine line and we don't know where the line is yet...but its worth looking into for sure!

Jay...just realized you have CF mirrors...or is that a vinyl overlay? Looks awesome.
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Old 02-27-2012, 09:42 AM   #534
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Originally Posted by bmorecam View Post
not that I know of yet lol.

only planned dyno is with vince on this new tune. just waiting.
lol....so many story lines rambling around in my head.
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Old 02-27-2012, 09:45 AM   #535
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Quote:
Originally Posted by KMPrenger View Post
But too much space and you can lose power correct? Sounds like a fine line and we don't know where the line is yet...but its worth looking into for sure!

Jay...just realized you have CF mirrors...or is that a vinyl overlay? Looks awesome.
its the whole real cf mirror cover picking up the cf hood and cf trunk sometime today. a local shop is clearing out I believe so I got a really sweet deal.

not sure if there's a limit to plenum volume but that hump on top of the plenum cover is there for that particular reason. I don't think 12mm or anything under should be an issue.
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Old 02-27-2012, 11:08 AM   #536
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Originally Posted by KMPrenger View Post
But too much space and you can lose power correct? Sounds like a fine line and we don't know where the line is yet...but its worth looking into for sure!

Jay...just realized you have CF mirrors...or is that a vinyl overlay? Looks awesome.

KM,

there is a lot of discussion on plenum size in comparison to engine displacement. anywhere from 70% to 10x's the size. a smaller plenum theoretically improves throttle response but at the expense of high end HP and a larger plenum hurts throttle response with gains in high end HP.

from the research i've been doing, i think its possible to increase our plenum size (not sure of the numbers, it'll take some real world testing) and still maintain good throttle response by creating a more efficient and even distribution of air flow to the cylinders. plenum size and throttle response can be varied by Throttle Body size as well. gonne take some real world testing. unless somebody with the software takes the time to dive into it...
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Old 02-27-2012, 11:14 AM   #537
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You been coming up with some very interesting stuff lately aaron
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Old 02-27-2012, 11:17 AM   #538
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i've been busy...
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Old 02-27-2012, 04:02 PM   #539
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Quote:
Originally Posted by KMPrenger View Post
But too much space and you can lose power correct? Sounds like a fine line and we don't know where the line is yet...but its worth looking into for sure!

Jay...just realized you have CF mirrors...or is that a vinyl overlay? Looks awesome.
Quote:
Originally Posted by hapisok View Post
KM,

there is a lot of discussion on plenum size in comparison to engine displacement. anywhere from 70% to 10x's the size. a smaller plenum theoretically improves throttle response but at the expense of high end HP and a larger plenum hurts throttle response with gains in high end HP.

from the research i've been doing, i think its possible to increase our plenum size (not sure of the numbers, it'll take some real world testing) and still maintain good throttle response by creating a more efficient and even distribution of air flow to the cylinders. plenum size and throttle response can be varied by Throttle Body size as well. gonne take some real world testing. unless somebody with the software takes the time to dive into it...
So I thought the whole idea behind porting the throttle body was to increase the speed and therefore the mass of the air entering the combustion chamber. Wouldn't "slowing it down" by using the plenum spacer negate this effect and cause less air per combustion cycle to enter the chamber?
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Old 02-27-2012, 04:37 PM   #540
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So I thought the whole idea behind porting the throttle body was to increase the speed and therefore the mass of the air entering the combustion chamber. Wouldn't "slowing it down" by using the plenum spacer negate this effect and cause less air per combustion cycle to enter the chamber?
not necessarily. porting the runners does help improve air flow by cleaning up the factory surfaces which creates turbulence. air working against itself causes friction and slows down the airflow and velocity. once air is moving in the same direction, airflow improves therefore your velocity improves. but too much volume in the runner means slower moving air. there is a balance between volume and velocity which directly affects the RPM band (HP/TQ).

having a larger plenum isn't always a good thing as it can have a negative affect on performance. but too small can hurt you also. air pressure, velocity, fluid dynamics and flow are complicated. as air rushes through the throttle body, it is moving at a high velocity just before it dumps into the plenum where it slows down. the purpose of the plenum is to provide ALL the cylinders with the same amount of air at the highest pressure possible (being N/A means 14.7psi). remember the motor is an air pump so its sucking air in creating a vacuum. in a poorly designed IM, the first 2 cylinders run rich because due to velocity as air rushes past them to the back of the manifold. and the last 2 run lean because they get all the air once it hits the back wall and slows down...so even distribution of air is essential. slowing the air down is what allows for this "redistribution". also, air doesn't like to change direction quickly, say in the form of 90* bends. so slowing it down aids in the redirection of flow and distribution of pressure.

the slowing of air doesn't take away from the amount of air each cylinder has to draw from, it actually increases it, higher velocity = lower pressure, which is why the first 2 cylinders can run rich...not enough air. the problem that a larger plenum, or should i say...to large of a plenum creates, is that the amount of air that is readily available is gone when you mash the peddle. throttle response suffers because refilling the plenum takes longer due to the time it takes to fill the vacuum that is created in the larger area.

not sure if any of that made sense or answered your question. but hope it helps. and if i missed anything or am way off on something, feel free to correct me...im still learning.

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Old 02-27-2012, 06:12 PM   #541
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hapisok is correct. On a traditional carb or port injected application increasing plenum volumne/area can result in increased power in the upper RPM ranges, but this is an unknown until it is tested on the DI 3.6 as these engines are so dependant on velocity for the power. CFM flow #'s that we used to follow so close have to be balanced with velocity and volumetric efficiency on these motrs so much of what we have used as far as the science & technology of the past cannot be followed on these. I am anxious to see how they will work and it may be a hit. We'll see what Mace finds.
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Old 02-27-2012, 06:22 PM   #542
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In summary to what hapisok has mentioned (very well written BTW )

Basically slowing down a fluid (in this case air) increases pressure. This is based off Bernoulli's equation http://en.wikipedia.org/wiki/Bernoulli%27s_principle

It's the same reason that the space shuttle has rocket nozzles that increase in size (to increase thrust/pressure) and the same reason that planes fly (faster air speed on top of the wing, slower air speed on the bottom = net vertical lift)

Of course there is a right way and a wrong way to this with manifold designs. For arguments sake, we offer two different sized plenum spacers for our L36 range of engines for running boost and for ones not running boost.

Hope this helps
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Old 02-27-2012, 06:22 PM   #543
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Quote:
Originally Posted by hapisok View Post
not necessarily. porting the runners does help improve air flow by cleaning up the factory surfaces which creates turbulence. air working against itself causes friction and slows down the airflow and velocity. once air is moving in the same direction, airflow improves therefore your velocity improves. but too much volume in the runner means slower moving air. there is a balance between volume and velocity which directly affects the RPM band (HP/TQ).

having a larger plenum isn't always a good thing as it can have a negative affect on performance. but too small can hurt you also. air pressure, velocity, fluid dynamics and flow are complicated. as air rushes through the throttle body, it is moving at a high velocity just before it dumps into the plenum where it slows down. the purpose of the plenum is to provide ALL the cylinders with the same amount of air at the highest pressure possible (being N/A means 14.7psi). remember the motor is an air pump so its sucking air in creating a vacuum. in a poorly designed IM, the first 2 cylinders run rich because due to velocity as air rushes past them to the back of the manifold. and the last 2 run lean because they get all the air once it hits the back wall and slows down...so even distribution of air is essential. slowing the air down is what allows for this "redistribution". also, air doesn't like to change direction quickly, say in the form of 90* bends. so slowing it down aids in the redirection of flow and distribution of pressure.

the slowing of air doesn't take away from the amount of air each cylinder has to draw from, it actually increases it, higher velocity = lower pressure, which is why the first 2 cylinders can run rich...not enough air. the problem that a larger plenum, or should i say...to large of a plenum creates, is that the amount of air that is readily available is gone when you mash the peddle. throttle response suffers because refilling the plenum takes longer due to the time it takes to fill the vacuum that is created in the larger area.

not sure if any of that made sense or answered your question. but hope it helps. and if i missed anything or am way off on something, feel free to correct me...im still learning.

Quote:
Originally Posted by SC2150 View Post
hapisok is correct. On a traditional carb or port injected application increasing plenum volumne/area can result in increased power in the upper RPM ranges, but this is an unknown until it is tested on the DI 3.6 as these engines are so dependant on velocity for the power. CFM flow #'s that we used to follow so close have to be balanced with velocity and volumetric efficiency on these motrs so much of what we have used as far as the science & technology of the past cannot be followed on these. I am anxious to see how they will work and it may be a hit. We'll see what Mace finds.


because DI mix air/fuel directly in the chamber some things that can have great affect on normal port injected engines won't be the same for DI. For our DI it's all air until the chamber remember that. Also have to agree with VE. It play a bigger role with DI engines.

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Old 02-27-2012, 07:19 PM   #544
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I have an airraid v2 intake. Do you think the 25mm will work with it?
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Old 02-27-2012, 07:19 PM   #545
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I have an airraid v2 intake. Do you think the 25mm will work with it?
I have this setup and it works perfectly fine.
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Old 02-27-2012, 07:30 PM   #546
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Quote:
Originally Posted by hapisok View Post
not necessarily. porting the runners does help improve air flow by cleaning up the factory surfaces which creates turbulence. air working against itself causes friction and slows down the airflow and velocity. once air is moving in the same direction, airflow improves therefore your velocity improves. but too much volume in the runner means slower moving air. there is a balance between volume and velocity which directly affects the RPM band (HP/TQ).

having a larger plenum isn't always a good thing as it can have a negative affect on performance. but too small can hurt you also. air pressure, velocity, fluid dynamics and flow are complicated. as air rushes through the throttle body, it is moving at a high velocity just before it dumps into the plenum where it slows down. the purpose of the plenum is to provide ALL the cylinders with the same amount of air at the highest pressure possible (being N/A means 14.7psi). remember the motor is an air pump so its sucking air in creating a vacuum. in a poorly designed IM, the first 2 cylinders run rich because due to velocity as air rushes past them to the back of the manifold. and the last 2 run lean because they get all the air once it hits the back wall and slows down...so even distribution of air is essential. slowing the air down is what allows for this "redistribution". also, air doesn't like to change direction quickly, say in the form of 90* bends. so slowing it down aids in the redirection of flow and distribution of pressure.

the slowing of air doesn't take away from the amount of air each cylinder has to draw from, it actually increases it, higher velocity = lower pressure, which is why the first 2 cylinders can run rich...not enough air. the problem that a larger plenum, or should i say...to large of a plenum creates, is that the amount of air that is readily available is gone when you mash the peddle. throttle response suffers because refilling the plenum takes longer due to the time it takes to fill the vacuum that is created in the larger area.

not sure if any of that made sense or answered your question. but hope it helps. and if i missed anything or am way off on something, feel free to correct me...im still learning.

Good explanation!
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