tumble in the intake port? ¿Por Que?
Thread Starter
Banned
Joined: Aug 2001
Posts: 3,505
From: looking for a flow bench so Brook and I can race
tumble in the intake port? ¿Por Que?
talking to my friend, he advised a bit of a rough finish on the intake ports of my heads to promote tumble. can somoene explain this to me and why its better than a "jet stream" of air
Why is not as "needed" in the exhuast ports?
how rough is optimal?
Registered User
Joined: Sep 2002
Posts: 655
Leaving the runners and the base of the intake rough will promote
atomization of the air/fuel mixture.
It is not necessary at the exhaust because the combustion has
already taken place.
Atomization of the mixture will help with a more even and full
combustion.
atomization of the air/fuel mixture.
It is not necessary at the exhaust because the combustion has
already taken place.
Atomization of the mixture will help with a more even and full
combustion.
Registered User
Joined: Jul 2002
Posts: 3,768
From: Friendswood, TX, USA
It's almost impossible to do a proper explanation on a board like this. In short, in a wet system the fuel will stick to the walls of a highly polished surface. At some point these droplets will become large enough to break off and go into the compustion camber. This effects the A/F ratio and combustion process. On a some what rough surface this "sticking " is reduced. Most people consider the normal cast surface or that created by a medium die grinder to be about right.
Registered User
Joined: Nov 2001
Posts: 2,985
From: In a house by the bay
I think your friend is confused on what "tumble" actually is. The port direction and how it relates to the combustion chamber is gonna dictate tumble. The surface finish of the actual port has next to nothing to do with it.
If you follow Mondello's advice, he recommends 50-60 grit for the intake port finishing and 300-400 grit for the exhaust followed by a cross buff polishing. Nuttin to do with "tumble" though.
-Mindgame
If you follow Mondello's advice, he recommends 50-60 grit for the intake port finishing and 300-400 grit for the exhaust followed by a cross buff polishing. Nuttin to do with "tumble" though.
-Mindgame
Thread Starter
Banned
Joined: Aug 2001
Posts: 3,505
From: looking for a flow bench so Brook and I can race
Originally posted by Mindgame
I think your friend is confused on what "tumble" actually is. The port direction and how it relates to the combustion chamber is gonna dictate tumble. The surface finish of the actual port has next to nothing to do with it.
If you follow Mondello's advice, he recommends 50-60 grit for the intake port finishing and 300-400 grit for the exhaust followed by a cross buff polishing. Nuttin to do with "tumble" though.
-Mindgame
I think your friend is confused on what "tumble" actually is. The port direction and how it relates to the combustion chamber is gonna dictate tumble. The surface finish of the actual port has next to nothing to do with it.
If you follow Mondello's advice, he recommends 50-60 grit for the intake port finishing and 300-400 grit for the exhaust followed by a cross buff polishing. Nuttin to do with "tumble" though.
-Mindgame
he explained head porting in a 25 min phone convo and i had a migrane
Registered User
Joined: Jul 2002
Posts: 3,768
From: Friendswood, TX, USA
Mindgame, is correct "tumble " is a combustion camber term. But I think we all know that Trey is asking about surface finish and not tumble.
Ellis, and yes most of the LT1/LS1 intake is dry, but the injectors are upstream of the intake port. So the surface finish of the ports are still valid for this discussion.
Ok, what we are really talking about is the viscous flow of a real fluid along a flat plate. And the difference between a laminar flow boundary layer and a turbulent flow boundary layer.
In a real fluid a very thin film of fluid adheres to the surface. This is called the no slip condition. It states that at the surface of a body the flow is zero, as one moves away from the body the velocity of the fluid gradually increases until at some point the velocity becomes a constant value. The layer of fluid where the velocity is changing form zero to a constant value is called the bountry layer.
For laminar flow the boundary layer is steady and layered, hence laminar. For turbulent flow there is random motion in the boundary layer as well as a down stream directed motion. This layer is very thin, less than a centimeter and must go from zero at the surface to hundereds of m/sec. at the outer edge of the boundary layer. An important difference between the laminar and turbulent boundry layer is the fact that the velocity of the turbular boundary layer builds up more quickly as one moves away from the wall. Another is the tendency of the fluid in a turbulent boundary layer to reenergize the slower moving fluid near the wall.
So, whats this all mean to my intake runners. Well a highly polished intake runner helps create a laminar flow on the walls of the runner, this allows fuel vapor to collect on the surface, that is not stripped off until they become relatively large. A "rough" surface helps to create a turbulent flow which discourages the fuel from collecting.
Any question?
Ellis, and yes most of the LT1/LS1 intake is dry, but the injectors are upstream of the intake port. So the surface finish of the ports are still valid for this discussion.
Ok, what we are really talking about is the viscous flow of a real fluid along a flat plate. And the difference between a laminar flow boundary layer and a turbulent flow boundary layer.
In a real fluid a very thin film of fluid adheres to the surface. This is called the no slip condition. It states that at the surface of a body the flow is zero, as one moves away from the body the velocity of the fluid gradually increases until at some point the velocity becomes a constant value. The layer of fluid where the velocity is changing form zero to a constant value is called the bountry layer.
For laminar flow the boundary layer is steady and layered, hence laminar. For turbulent flow there is random motion in the boundary layer as well as a down stream directed motion. This layer is very thin, less than a centimeter and must go from zero at the surface to hundereds of m/sec. at the outer edge of the boundary layer. An important difference between the laminar and turbulent boundry layer is the fact that the velocity of the turbular boundary layer builds up more quickly as one moves away from the wall. Another is the tendency of the fluid in a turbulent boundary layer to reenergize the slower moving fluid near the wall.
So, whats this all mean to my intake runners. Well a highly polished intake runner helps create a laminar flow on the walls of the runner, this allows fuel vapor to collect on the surface, that is not stripped off until they become relatively large. A "rough" surface helps to create a turbulent flow which discourages the fuel from collecting.
Any question?
Registered User
Joined: Sep 2002
Posts: 655
Yes, one question.
Understanding all the posts, and Physics stated above I'd like
to ask more about the Atomization of the charge.
Edelbrock made an intake manifold (they still may produce it?) that
incorporates a raised grid pattern on the base of the manifold.
I recall the summary of the manifold spec stating that the grid
would help break up the air/fuel for better combustion.
I was also told that 'glass beading' an intake, or polishing would
hinder performance and it would be better to leave a rough finish
to promote atomization.
Is that because of the concepts you all are stating, or because
the charge is getting 'roughed up' from traveling along an abbrasive intake runner/manifold base?
Understanding all the posts, and Physics stated above I'd like
to ask more about the Atomization of the charge.
Edelbrock made an intake manifold (they still may produce it?) that
incorporates a raised grid pattern on the base of the manifold.
I recall the summary of the manifold spec stating that the grid
would help break up the air/fuel for better combustion.
I was also told that 'glass beading' an intake, or polishing would
hinder performance and it would be better to leave a rough finish
to promote atomization.
Is that because of the concepts you all are stating, or because
the charge is getting 'roughed up' from traveling along an abbrasive intake runner/manifold base?
Thread
Thread Starter
Forum
Replies
Last Post
carguyshu
Parts For Sale
20
Jan 22, 2017 11:19 AM