Thoughts on intake flow rates etc......and filters. - Page 5 - GM Forum - Buick, Cadillac, Chev, Olds, GMC & Pontiac chat


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Old 09-15-2004, 09:16 AM   #41
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you know J, i got thinking about this last night, and there was something bugging me:

Quote:
Originally Posted by drjay
DrJay: The piston creates a instant vacuum which forces air into it. reguardless of the restriction it will pull the same amount of air but it will take more force to do it. The power of almost any engine is more than capable of overcomming the restriction, at a cost of effeciency. It will still fill the cylinder properly, it must. but it will work harder to get it there
DrJay: in other words
DrJay: there isn't "more of a vacuum" left in the cylinder by paper than k&n
problem with that line of thinking is that it only applies to n/a cars. the entire point of a f/i car is that you're forcing more air into the cylinder than what was possible. the less restriction that your supercharger will face trying to pull air in, the more air you'll be able to put into your cylinders.

thoughts?
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Old 09-15-2004, 01:53 PM   #42
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Ahhh but the supercharger is driven by the crank and must still overcome restriction...but it looks by what PontiacDad found restriction isn't much of an issue..hmm...
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Old 09-15-2004, 03:36 PM   #43
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Ok, kind of related here......we're talking resistance here. Can someone explain why my idle changes drastically when I remove my oil cap breather and re-install the cap? And vice-versa? It does this both ways, and takes a day to settle back down. And yes, the PCV is operating just fine. (slightly off topic, but the CAUSE may be similar.....less resistance?)

The engine is a bit more 'free-revving' with the breather installed. Anyone else observe this?

On the topic of the filters and breathing, let'* look more at the differences in the NA and SC applications. What'* the CVM flow rate differences between these two engines at idle and WOT?
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Old 09-15-2004, 03:49 PM   #44
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Quote:
Originally Posted by willwren
Ok, kind of related here......we're talking resistance here. Can someone explain why my idle changes drastically when I remove my oil cap breather and re-install the cap? And vice-versa? It does this both ways, and takes a day to settle back down. And yes, the PCV is operating just fine. (slightly off topic, but the CAUSE may be similar.....less resistance?)

The engine is a bit more 'free-revving' with the breather installed. Anyone else observe this?

On the topic of the filters and breathing, let'* look more at the differences in the NA and SC applications. What'* the CVM flow rate differences between these two engines at idle and WOT?
i could be way off, but it really sounds like your vacuum is finding it'* way to your rocker covers. when you open it up, it has all the air it wants/needs to take in, and will rev up accordingly. at least, that'* what happens on cars i've tried opening up the vacuum on - they always jump up a few hundred RPM'* when they get the extra air. or less restricted air.

guess that was the question to begin with, huh?
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Old 09-15-2004, 09:16 PM   #45
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I guess the first thing would be, is it suction or pressure?
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Old 09-15-2004, 09:55 PM   #46
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Quote:
Originally Posted by macho_mike21
eventually you will be nit picking. IMO anything under like 4-5hp isnt worth it.
I just wanna hop in for a second... sure 3 hp peak doesn't sound like a whole lot for a mod... and really it isn't... but.. what did it do in the rest of the curve?.. maybe it straightened out a torque or hp "stutter" that you had lower in the rpm band... maybe below 4K rpm it added 10hp

peak hp numbers are great to spout off ...but theres a WHOLE lot more going on then just your peaks.... I know Will and I have gone round and round a couple times about stuff like the MSD DIS4 box... does it add peak hp... maybe 1 or 2 at peak... maybe it only adds 4 or 5 through out other areas... but lets say it added 4mpg to my city mileage, upped my throttle response off idle by 30% .. and took out some peaks and valleys in my torque and hp curves ... does this mean much to a race car... not at all... but to a multipurpose daily driver... it'* all the difference in the world.(note: those were just guesses and estimations for example... )

now I love drag racing as much as the next guy... but I've moved on a little bit, I still wanna go drag racing, but I also wanna go play on the roadcourse, go for a cruise around town with the boys on Friday night ... and still drive back and forth to school/work during the week. Alot of other ppl are looking for more then just drag racing stuff... which doesn't mean much, but it does mean we have to compromise here and there...

didn't mean to highjack the thread... but it'* something ppl from both sides of the fence should think about ... some ppl sit and think "why the heck do I need to worry about 3inch here and 3.5 inch there and 3000CFM filters for??? " ... where as someone like Willren or Dr.Jay are itching to know so they can squeeze that extra few hp out of already potent cars

it'* an excelent thread though guys... keep it up ... great stuff to think about and i hope you guys come up with some solid answers
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Old 09-15-2004, 10:31 PM   #47
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Quote:
Originally Posted by DrJay
I guess the first thing would be, is it suction or pressure?
A vacum gauge would tell us. Can you rig something up Bill?
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Old 09-15-2004, 10:38 PM   #48
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Quote:
Originally Posted by DrJay
I guess the first thing would be, is it suction or pressure?
i'm going to get geeky and say that suction is nothing more than a lower pressure area. when you 'suck' water or pop thru a straw, you're just reducing the pressure inside of the straw, and the pressure being applied to the fluid outside of the straw forces the liquid up it. so really, suction is nothing more than varying pressures in a system.

answer that question?
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Old 09-15-2004, 11:27 PM   #49
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Quote:
Originally Posted by PontiacDad
Quote:
Originally Posted by DrJay
I guess the first thing would be, is it suction or pressure?
A vacum gauge would tell us. Can you rig something up Bill?
Can do. I'll use a gauge for vac and pressure. I'll just drill/tap the gauge into a plastic plate, and hold it over the oil port.
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Old 09-15-2004, 11:45 PM   #50
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Would there be vacuum coming from the crankcase through the lifters/oil system/pushrods?
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