GT Motorsports® VQ35DE Head Packages
Why are these flow charts so different than the ones from Cosworth? Even the numbers Cosworth posts for the stock heads are vastly higher. Is there a difference in the flow benching methods?
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Joined: Aug 2002
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From: Australia
Originally Posted by 350Zteve
Why are these flow charts so different than the ones from Cosworth? Even the numbers Cosworth posts for the stock heads are vastly higher. Is there a difference in the flow benching methods?
As with dyno's, you are looking for an increase in figures after modifications.
Having said that, a cubic foot is a cubic foot & a minute is a minute & it is my belief that the Cosworth flow bench chart is greatly overstated.
In my tests the stock inlet port flows a little over 250 CFM @ 11mm lift
The Nismo Spec 1 head flows about 255 CFM @ the same lift
The Nismo Spec 2 head flows about 275 CFM @ the same lift
The full house GT300 Nismo race heads with 1mm larger valves flow about 285 CFM @ 13mm lift.
These figures are much closer to Sam's GTM testing results for the stock & modified heads than Cosworth's very high figures
New Member
Joined: Aug 2002
Posts: 467
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From: Australia
I have just checked the published flow figures for both the GTM & Cosworth Cylinder Heads & while the figures are vastly different, the increase in flow in the inlet port for both heads is apox 19% @ max lift
the vaccum on the flow bench makes a difference.
I forget what the industry standard for flowbench vaccum is. i think it is something like 26" or 28" of H2O. whatever it is, you need to make sure that the flowbench work was done at the same vaccum level.
I forget what the industry standard for flowbench vaccum is. i think it is something like 26" or 28" of H2O. whatever it is, you need to make sure that the flowbench work was done at the same vaccum level.
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Joined: Sep 2005
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From: So.Cali 626-951
Originally Posted by Nathan
Different flow bench machines will give different readings as do different dyno's for the same motor.
As with dyno's, you are looking for an increase in figures after modifications.
Having said that, a cubic foot is a cubic foot & a minute is a minute & it is my belief that the Cosworth flow bench chart is greatly overstated.
In my tests the stock inlet port flows a little over 250 CFM @ 11mm lift
The Nismo Spec 1 head flows about 255 CFM @ the same lift
The Nismo Spec 2 head flows about 275 CFM @ the same lift
The full house GT300 Nismo race heads with 1mm larger valves flow about 285 CFM @ 13mm lift.
These figures are much closer to Sam's GTM testing results for the stock & modified heads than Cosworth's very high figures
As with dyno's, you are looking for an increase in figures after modifications.
Having said that, a cubic foot is a cubic foot & a minute is a minute & it is my belief that the Cosworth flow bench chart is greatly overstated.
In my tests the stock inlet port flows a little over 250 CFM @ 11mm lift
The Nismo Spec 1 head flows about 255 CFM @ the same lift
The Nismo Spec 2 head flows about 275 CFM @ the same lift
The full house GT300 Nismo race heads with 1mm larger valves flow about 285 CFM @ 13mm lift.
These figures are much closer to Sam's GTM testing results for the stock & modified heads than Cosworth's very high figures
So are you saying that the GTM heads flow as goof or better than the Nismo s2's and gt300 race heads? IF they do then sign me up. Sam...you are amazing. Keep it up.
Any chance we can see a CFM chart of the GTM stage 3 or 4 heads? Or at least give us the specs lol.
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