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CFM Experts...V2 w/ 10lbs on a 4v -vs- 2v boost

Old 08-08-2008, 12:15 AM
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Sxynerd
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Default CFM Experts...V2 w/ 10lbs on a 4v -vs- 2v boost

Easy question!

All you CFM math men, how much boost will I make with a 4v if with the same pulley I'm making 10lbs on a 2v....

My question comes from the fact that 4v has less restriction and flows more air and will in essence create less boost.
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Old 08-08-2008, 01:00 AM
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mustangcat
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Default RE: CFM Experts...V2 w/ 10lbs on a 4v -vs- 2v boost

Correct me if I'm wrong; but wouldn't the boost be the same? Since it's measured in the intake manifold before being flowed into the crappy 2v heads?
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Old 08-08-2008, 06:32 AM
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Default RE: CFM Experts...V2 w/ 10lbs on a 4v -vs- 2v boost

I'm thinkinghe's talking volumetric efficiency, versus boost applied from the S/Cer..


I'd have to know what the flow rate of the 4v heads were, and the 2v heads..




JT
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Old 08-08-2008, 07:21 AM
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Default RE: CFM Experts...V2 w/ 10lbs on a 4v -vs- 2v boost

ORIGINAL: mustangcat

Correct me if I'm wrong; but wouldn't the boost be the same? Since it's measured in the intake manifold before being flowed into the crappy 2v heads?
YOu said it yourself, "crappy heads." The intakes are not the problem, and doesn't give the bulk of the restriction. It's like a huge tunnel of air getting blocked by a wall with only a pinhole for air to escape. That would be the example for great pressure and higher boost numbers. Think of the huge tunnel now with a hole the size of a car; that would let more air through, creating less restriction, and the measurement of pressure in PSI numberically would be less. 10lbs of boost for a 2v car vs 6-7lbs of boost for a 4v car.

The air pump wouldn't have to work so hard.


Yes, Volumetric efficiency. Since boost is just a measure of resistance and 4v heads flow better than 2v heads, then it should be like having ported 2v's and in that case boost levels go down.

Anyone know the numbers?
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Old 08-08-2008, 09:09 AM
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Default RE: CFM Experts...V2 w/ 10lbs on a 4v -vs- 2v boost

Do you know off hand what the flow rates are for the specific heads??




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Old 08-08-2008, 09:30 AM
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Default RE: CFM Experts...V2 w/ 10lbs on a 4v -vs- 2v boost

I don't know what heads you have now but by your numbers I'm guessing you have stage 2 or 3 heads and flowing around 220-230 cfm with them. If your using a 10lbs pulley, good flowing exhaust, intercooler and some nice cams you are probably seeing around 8psi on the boost gauge. If you are gonna use 03-04 cobra heads untouched you should see the same amount of boost since they flow similar to stage 3 2v heads. 96-98 4v heads you might drop some boost since they are much better flowing heads. Now if you have the 4v heads ported you might want to change the pulleys.
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Old 08-08-2008, 11:32 AM
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Default RE: CFM Experts...V2 w/ 10lbs on a 4v -vs- 2v boost

I always thought the 03-04 cobras had the best heads and the 96-98 4v's had the best cams...
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