Port size vs. Flow Potential???
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Port size vs. Flow Potential??? Not trying to get my wittle brain overworked here, but which is more important in the consideration of engine output, the smaller port for a higher velocity or a larger port that outflows by a 15+cfm? Lets use a nitrous engine for track use as the example 
Reason I ask, I have ETP 11* 225cc Heads that flow I=332 E=234 @ .650" Lift on their bench...and looking at a runner volume of say 202cc that flow I=318 E=210 @ .650" Lift on that makers bench...would the smaller runner with its higher velocity make more power or is not close enough for the higher velocity to make up for sheer flow?
I do know there is a ton more to heads and making power, but wanting to which what the ratio if any there is.
Kind of like when you see a cam that has more duration but less lift on the exhaust side...the duration at less lift flows more than less duration more lift....
Charlie
Reason I ask, I have ETP 11* 225cc Heads that flow I=332 E=234 @ .650" Lift on their bench...and looking at a runner volume of say 202cc that flow I=318 E=210 @ .650" Lift on that makers bench...would the smaller runner with its higher velocity make more power or is not close enough for the higher velocity to make up for sheer flow? I do know there is a ton more to heads and making power, but wanting to which what the ratio if any there is.
Kind of like when you see a cam that has more duration but less lift on the exhaust side...the duration at less lift flows more than less duration more lift....
Charlie
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From: Tucson, Arizona
the simple answer is that assuming you have the compression to support it and the BIG cam with lots of duration to go with it then flow will make more peak power and torque than velocity especially at high rpm's. at lower rpm's velocity might make more torque though in a situation where you don't have as much compression as you should have and or a camshaft with a low amount of duration relative to the displacement of your engine. bottom line for a street/strip oriented motor i won't sacrifice velocity for nothin, but in a maximum effort all out race only engine its all about the flow
Your port size and velocity thru the port depend on the RPM range in which you run the motor, and the ability for the port to move the air/fuel and not have it seperate. The problem with this is that air will flow at a higher velocity and make tigher turns than fuel will so the mixture will seperate and your power will go down even though the velocity will improve. The velocity does count and it's very important but TOO much is going to hurt you more than it helps at WOT and higher RPM. I think people focus a little too much on this since most guys don't have a clue about what the head is actually doing in this reguard.
The bad thing is in your case the only real way to know whats going to work the best is to tune both heads on the motor and see which one works better for you in terms of power, TQ and what you want out of the car.
Bret
The bad thing is in your case the only real way to know whats going to work the best is to tune both heads on the motor and see which one works better for you in terms of power, TQ and what you want out of the car.
Bret
You could make a head run that but it would be a little bit of work. The problem is I don't think the injectors are big enough to work. The turbo Ecotec stuff is only big enough to fee 520-550hp or so more if you can feed them more pressure but I'm guessing the electronics and tuning would be the big PITA.
Bret
Bret
don't you have to worry more about the cross section of the port than the volume?the GMPP/Lingenfelter heads are around 250cc,and they seem to do good on the low end from the few dyno graphs i've seen.
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CAT3,
The REAL answer is to how each head does with the manifold attached. It is possible with the manifold attached for the smaller head to beat the larger one.
If the larger one carries the gains to with the manifolld attached, then it will depend on what the engine actually needs.
The REAL answer is to how each head does with the manifold attached. It is possible with the manifold attached for the smaller head to beat the larger one.
If the larger one carries the gains to with the manifolld attached, then it will depend on what the engine actually needs.
I guess I would look at it like this. You are spraying the car, so the down low torque is already to much. I would usually say go with the smaller port hands down, but, being there is giggle gas involed, the more air to mix in the motion, the more power.
The other thing to consider is the lower lift numbers of the head. If the small port beats the large port all the way up to your peak cam lift, it would be hands down go with the smaller port. To many guys compare heads with peak numbers that are beyond their camshafts lift range.
So, look over the full flow range and make a decision based on that.
The other thing to consider is the lower lift numbers of the head. If the small port beats the large port all the way up to your peak cam lift, it would be hands down go with the smaller port. To many guys compare heads with peak numbers that are beyond their camshafts lift range.
So, look over the full flow range and make a decision based on that.
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Thanks everyone. I'm not necessarily trying to compare sheer flow #'s. More less curious as to which has a greater impact, the flow or volume...like if you increased one or the other of any given head out there now, which would you want to increase? Much like cam's, where altering the duration will have a greater impact than lift.
Originally Posted by CAT3
Thanks everyone. I'm not necessarily trying to compare sheer flow #'s. More less curious as to which has a greater impact, the flow or volume...like if you increased one or the other of any given head out there now, which would you want to increase? Much like cam's, where altering the duration will have a greater impact than lift.
Originally Posted by CAT3
Thanks everyone. I'm not necessarily trying to compare sheer flow #'s. More less curious as to which has a greater impact, the flow or volume...like if you increased one or the other of any given head out there now, which would you want to increase? Much like cam's, where altering the duration will have a greater impact than lift.
Bret