Tell me what is up with these flow numbers?
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Registered User
Joined: May 2003
Posts: 503
From: Washington, PA
Tell me what is up with these flow numbers?
Here is the link to my post in LT1 tech. Look at the ported intake flow numbers without the attachment, then compare it to the numbers with the attachment. Why would there be such a drastic change?
http://web.camaross.com/forums/showt...postid=1544961
http://web.camaross.com/forums/showt...postid=1544961
Thread Starter
Registered User
Joined: May 2003
Posts: 503
From: Washington, PA
The attachments were some type of pipe (used for either the Intake or exhaust), then something formed of clay to use as a pipe for the opposite side. Guess they areused to attach to the flow machine?!?! Thats what I understood...I might have it wrong.
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Joined: Feb 2000
Posts: 35
From: Chickasha, OK
N2O,
The attachment your buddy is referring to is a piece of clay attached to the intake port. The clay is formed to radius the flow into the port. What this does is eliminates the 'vena-contracta' caused by flow coverging into a pipe (or port). As the velocity goes up, the flow will automatically restrict itself, and cause a choke point just inside the port. That is why you see the difference grow as flow increases. To eliminate this, and mimick the use of an intake manifold, the flow plate (or clay) is used.
On the exhaust side, they just used a short piece of pipe, usually the header primary diameter. This also usually increases exhaust port flow becuase it reduces the pressure drop associated with releasing the flow into the atmosphere. This loss coefficient is equal to 1 (k=1), and the pressure drop varies with the velocity squared, so if you can lower the velocity, even just a little, it can make a big difference in the pressure drop accross the port exit.
Hope this helps.
Shane
The attachment your buddy is referring to is a piece of clay attached to the intake port. The clay is formed to radius the flow into the port. What this does is eliminates the 'vena-contracta' caused by flow coverging into a pipe (or port). As the velocity goes up, the flow will automatically restrict itself, and cause a choke point just inside the port. That is why you see the difference grow as flow increases. To eliminate this, and mimick the use of an intake manifold, the flow plate (or clay) is used.
On the exhaust side, they just used a short piece of pipe, usually the header primary diameter. This also usually increases exhaust port flow becuase it reduces the pressure drop associated with releasing the flow into the atmosphere. This loss coefficient is equal to 1 (k=1), and the pressure drop varies with the velocity squared, so if you can lower the velocity, even just a little, it can make a big difference in the pressure drop accross the port exit.
Hope this helps.
Shane
Thread Starter
Registered User
Joined: May 2003
Posts: 503
From: Washington, PA
So, does that mean that the numbers with the attachment are realistic of what the heads will see when installed and running? What importance do the numbers without the attachments have? I would hate for someone to put heads on thinking they flow 261...only to find out the flow 229max and thats at wimpy(but important.400-.450lift).
Registered User
Joined: Feb 2000
Posts: 35
From: Chickasha, OK
N2O,
Almost noone flows heads without a flow plate (not a good shop anyway). The numbers without a flow plate are useless. As for what the heads will flow installed; yes, the flow plate is there to eliminate the vena-contracta, and there will be no vena-contracta with the intake manifold installed. However, you must realize that although the flow potential of the heads is higher, the overall system will flow less than the head itself due to the fact that you added the intake manifold onto the system, and thus added pressure drop. So, the flow POTENTIAL of the heads will be the higher numbers, but the actual flow of the port once installed with the manifold and throttle body will be less.
I guess the bottom line is when comparing your heads to others' heads, use the numbers with the flow plate attached. That is how all heads are flowed; it puts everyone on a level playing field. Ignore the flow numbers without the flow plate.
Hopefully all this makes sense.
Shane
Almost noone flows heads without a flow plate (not a good shop anyway). The numbers without a flow plate are useless. As for what the heads will flow installed; yes, the flow plate is there to eliminate the vena-contracta, and there will be no vena-contracta with the intake manifold installed. However, you must realize that although the flow potential of the heads is higher, the overall system will flow less than the head itself due to the fact that you added the intake manifold onto the system, and thus added pressure drop. So, the flow POTENTIAL of the heads will be the higher numbers, but the actual flow of the port once installed with the manifold and throttle body will be less.
I guess the bottom line is when comparing your heads to others' heads, use the numbers with the flow plate attached. That is how all heads are flowed; it puts everyone on a level playing field. Ignore the flow numbers without the flow plate.
Hopefully all this makes sense.
Shane
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