Flow balancing

Fahlin Racing

Fahlin Racing

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Being that we need to get as much in and just as much out of the cylinder, I am thinking we need to achieve the proper flow ratio between the intake and exhaust.

David Vizard states a minimum 0.90:1 ratio can be used with success :pop:

Any thoughts?
 
I know the guy that used to port our fuel bike heads had some sort of formula to determine what he was trying to achieve with port flow, but I dont know what it was.
 
there is no magic number. Everything changes with RPM and so forth and if you were to achieve a certain ratio at X rpm it will change above and below that.
 
Would you say, the power output goal a person had in mind will be dictating this ratio no matter what in the same general sense of port sizing to rpm then?

Mr Vizard didn't mention rpms involving the flow ratio, he just stated that if you ran a forced induction or nitrous equipped rig, from his experiences he said the 0.90:1 would be best, I believe would be taken as a baseline point. Like you said though plenty of variables out there to consider and may be a smaller or larger ratio exhaust to intake flow for optimum performance within the application. The faster we spin the engine the more we move the quantity of the working fluid.

Would we be more concerned with working with the balancing the system pressures or would be include the CFM numbers too?
 
Fahlin Racing said:
Would you say, the power output goal a person had in mind will be dictating this ratio no matter what in the same general sense of port sizing to rpm then?

Mr Vizard didn't mention rpms involving the flow ratio, he just stated that if you ran a forced induction or nitrous equipped rig, from his experiences he said the 0.90:1 would be best, I believe would be taken as a baseline point. Like you said though plenty of variables out there to consider and may be a smaller or larger ratio exhaust to intake flow for optimum performance within the application. The faster we spin the engine the more we move the quantity of the working fluid.

Would we be more concerned with working with the balancing the system pressures or would be include the CFM numbers too?
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Huh?
 
He mentioned that flow ratio would be best or above that in terms of the force-fed mills breathing. However, its only his view on things from engines he has worked with.

What would you say is more important Lenahan, balancing our flow numbers, balancing pressures of a combo of the two?
 
Fahlin Racing said:
He mentioned that flow ratio would be best or above that in terms of the force-fed mills breathing. However, its only his view on things from engines he has worked with.

What would you say is more important Lenahan, balancing our flow numbers, balancing pressures of a combo of the two?
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i think you look way to hard into things and think to hard about a lot of things. all you need to do is get air in and out of the motor and begin to work on ways to lower timing to get effiency up. that is the easiest way to build big horsepower (effiency). a motor being blown or not really doesnt have a lot of effect on flow ratio if im understanding what your talkin about.
 
lenahan05 said:
i think you look way to hard into things and think to hard about a lot of things. all you need to do is get air in and out of the motor and begin to work on ways to lower timing to get effiency up. that is the easiest way to build big horsepower (effiency). a motor being blown or not really doesnt have a lot of effect on flow ratio if im understanding what your talkin about.
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Lower timing? You mean shorten the injection window?


That flow ratio between intake and exhaust is gonna be hard to nail down without trying a bunch of compressors and turbines....velocity and density are going to be so hard to predict and select the proper charger(s).
 
straight 6 roar said:
Lower timing? You mean shorten the injection window?


That flow ratio between intake and exhaust is gonna be hard to nail down without trying a bunch of compressors and turbines....velocity and density are going to be so hard to predict and select the proper charger(s).
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no. i mean lower timing just like it sounds. most dont grasp how much timing matters in an engine....its the thing books dont talk about and you cant learn reading. the main goal in efficiency is to get the timing as low as possible. if your not trying to do that then your going in the wrong direction IMO.
 
The heads i had done they shoot for a .8:1 exhaust to intake. To keep velocity up in the exhaust stream...
Other than what i was told that one time.... Subscribed!
 
24vriviera said:
The heads i had done they shoot for a .8:1 exhaust to intake. To keep velocity up in the exhaust stream...
Other than what i was told that one time.... Subscribed!
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does that make any sense to you?
 
I ask looking for ah article i read a long time ago in car craft. About big block Ford heads,
They worked the intake side over like crazy to gain flow but did nothing but Polish the exhaust side and clean it up to try to maintain a .75:1 exhaust to intake, to maintain velocity..
Most heads flow less On exhaust, from what i have read..
So in a way it does make sense to me..
But again that its what I have read and told once, and applied to gasser heads.
i am awaiting more explanation myself!

Edit. Just skimmed a couple pages of interesting info on this topic.
http://www.yellowbullet.com/forum/showthread.php?t=451038
 
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lenahan05 said:
no. i mean lower timing just like it sounds. most dont grasp how much timing matters in an engine....its the thing books dont talk about and you cant learn reading. the main goal in efficiency is to get the timing as low as possible. if your not trying to do that then your going in the wrong direction IMO.
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I've heard this before from Dan Clarke. Dang sure didn't argue and the truck just keeps getting better.
 
Remember there is more mass flow out of the exhaust than the intake. I am not sure if that matters though.

Tobin
 
smoke machine said:
I've heard this before from Dan Clarke. Dang sure didn't argue and the truck just keeps getting better.
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yeah you can really take advantage of the lower timing on a CR since its so controllable with efi. i think if your running a stock motor with high compression 20deg max timing and a big nozzle (ex 5x12) with low mPa (duration) and a lot of rail pressure (25-30,00psi) with a good head and a stock duration big lobe lift cam with a wide LSA would be something to surprise a lot of people....
 
lenahan05 said:
yeah you can really take advantage of the lower timing on a CR since its so controllable with efi. i think if your running a stock motor with high compression 20deg max timing and a big nozzle (ex 5x12) with low mPa (duration) and a lot of rail pressure (25-30,00psi) with a good head and a stock duration big lobe lift cam with a wide LSA would be something to surprise a lot of people....
Click to expand...

30KSI on a CR injector??


Tobin
 
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