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


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Old 09-10-2004, 03:31 PM   #1
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Default Thoughts on intake flow rates etc......and filters.

Quote:
DrJay: how does a k&n drop=in filter make more hp?
wrens67: My theory?
wrens67: Only on a SC engine. I don't think the paper can pass demand at WOT.
wrens67: Maybe above 4k rpms?
wrens67: We could actually prove it if we wanted. Need to check flow rates through a Delco paper filter.
DrJay: oh there'* no doubt that the k&n will flow more
wrens67: But the box inlet is still pretty damn restrictive, too.
wrens67: I don't think the K&N drop-in gets enough flow unless you ventilate the box.
DrJay: but what effect does that have past the filter...is there just not enough air for the cylinder demand?
wrens67: I'm assuming that. Because I felt it when I dropped it in myself. And felt it again when I vented the box. Before the ADTR. I'm assuming 5hp each step, but only at a certain RPM level, which makes sense.
wrens67: I'd love to have a micro camera in a stock airbox, and watch the paper filter flex at WOT. Compare NA to SC that way.
wrens67: Good questions.
DrJay: why not just read maf readings? but anyway here'* my thought and tell me where its weak
wrens67: You experienced poor flow in a filter by reading MAF. Not a bad idea.
wrens67: At idle, 2k, and 4k maybe.
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
wrens67: We're freeing up parasitic loss, not increasing flow.
DrJay: exactly
wrens67: I dunno. That cone you had was flowing less. You saw it on the scantool.
wrens67: I still have my stock box and filters. But you have my scantool!
wrens67: We should do this.
DrJay: but that was a very short "test" if you can even call it that
DrJay: I checked it a few times later and at idle it would pull 800-1000
DrJay: it all depends on what the IAC is doing
DrJay: ^^^ "AHHH"
DrJay: its a thought, totally up for debate
DrJay: but I think its a good one
wrens67: You cool with me posting this conversation in performance?
DrJay: sure
wrens67: You still have your stock airbox too?
wrens67: We can do some comparisons.
wrens67: I may come back up that way soon to work with dj again.
wrens67: And he'* got the same setup we did stock.
wrens67: With a drop-in.
DrJay: oh here'* another thing to remember..a 460cfm engine will only ever pull 460cfm reguardless of how much more a K&N flows
wrens67: I might leave him my modified stock box.
DrJay: I kind of have my stock air-box
DrJay: its in pieces and spread around
wrens67: hahahaha
wrens67: You're so organized.
DrJay: lovely huh
DrJay: i think most of it is in the trunk
DrJay: but I moved
DrJay: and didn't keep great track of it
DrJay: oh but hey what got me thinking about this theory
DrJay: is that you said the k&n actually increased some peoples MPG a little
wrens67: Dig around and see if you can find it. We can compare your non-ventilated box to my modified box, with both paper and drop-in K&N'*, then compare to our custom intakes.
DrJay: Less parasitic loss = less fuel needed
wrens67: Yes it did. That makes sense, bud.
wrens67: That'* at least PART of the equation.
DrJay: much more to discuss but lunch is calling
DrJay: i'll be back in like 15-20min
wrens67: Work is calling me. I have contractors tearing up a lab. TTYL. I'll post this.
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Old 09-10-2004, 06:07 PM   #2
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Makes alot of sense... Get those readings eh?
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Old 09-10-2004, 08:42 PM   #3
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Which readings?

I've been thinking about this over lunch and the more I think about it the more sense it makes. Especially with all the talk about higher MPG. Keep in mind this is just some hair-brained thought I had less than 8 hours ago and I think I might have been drunk or something haha...but really, think it over and lemme know what you think.

Consider this, you install a K&N and get a 6hp increase. When speaking about HP gains using strictly increased airflow its not free, it takes an equal amount of fuel to produce that power. We all know this, right? More air needs more fuel to produce more power..

So lets play with the numbers... Assuming a BSFC of 0.55 it means this gain needs 3.3 pounds more fuel per hour from the system as a whole. Using a 205hp engine (heh) this would mean a 3.7% increase in fuel consumption at peak HP. Now there'* all this talk about how you can save fuel by being able to use a smaller percentage of the throttle to maintain speed. This would indicate (and I'm sure K&N brags about) that the HP gain is all across the RPM range. For instance if 50% throttle used to mean 150hp and 50mph maybe now 45% throttle means 150hp and 50mph. BUT this doesn't mean you're using any less fuel because it takes the same amount of air/fuel to make that amount of power, no matter how little you press on the throttle to achieve it. Heck even a small 2hp gain would require 1.2% more fuel from the system at peak HP. There is no way to get MORE mpg by simply putting more air into it.

The only way you're going to get more horsepower and still use less fuel is by reducing parasitic loss. One example is by replacing your crank driven fan with an electrical one. I believe the other is by putting a free flowing filter in.

Also, since the increase in flow would mean a decrease in fuel effeciency and really you're getting better mileage, it would mean that the gains by reducing parasitic loss are GREATER than the gains from increased airflow.

Any thoughts?
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Old 09-10-2004, 09:14 PM   #4
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When the piston drops in draws in air, if the air intake is restrictive (paper filter) it takes more force (power) to fill the space inside the cylinder. The less restrictive (k&n) the less force is required to fill the same cylinder.
Another way of looking at it is through boost and vacum (or negative boost).
If boost means power, what'* negative boost then? A power loss, that'* what. And hunting down and eliminating those negative boosts is a very cheap and effective way of gaining power.
This can be a strong case for parasitic loss and therefore a reason why the fuel economy goes up when the air intake is made less restrictive?
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Old 09-10-2004, 09:17 PM   #5
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I can see why free flow filter would improve MPG because like you say it reduces parasitic losses, that being the resistance of sucking air through less restriction.

Running an electric fan kind of shifts the burden from the crank to the alternator. The more amps being pulled, the more mechanical resistance being created in the alternator. The real savings in electric fan is that it doesn't have to run constantly, but a crank driven fan is always running, even when not needed.

I think what would be the ultimate is a clutch driven supercharger, so when you don't need the boost, it doesn't spin.
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Old 09-10-2004, 09:19 PM   #6
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Quote:
Originally Posted by PontiacDad
When the piston drops in draws in air, if the air intake is restrictive (paper filter) it takes more force (power) to fill the space inside the cylinder. The less restrictive (k&n) the less force is required to fill the same cylinder.
Another way of looking at it is through boost and vacum (or negative boost).
If boost means power, what'* negative boost then? A power loss, that'* what. And hunting down and eliminating those negative boosts is a very cheap and effective way of gaining power.
This can be a strong case for parasitic loss and therefore a reason why the fuel economy goes up when the air intake is made less restrictive?
Yes, that was my basis for the thought so I completely agree. This would also explain some of why you get worse gas mileage with a clogged filter, yea?
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Old 09-10-2004, 09:21 PM   #7
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Quote:
Originally Posted by GreenMachine
I can see why free flow filter would improve MPG because like you say it reduces parasitic losses, that being the resistance of sucking air through less restriction.

Running an electric fan kind of shifts the burden from the crank to the alternator. The more amps being pulled, the more mechanical resistance being created in the alternator. The real savings in electric fan is that it doesn't have to run constantly, but a crank driven fan is always running, even when not needed.

I think what would be the ultimate is a clutch driven supercharger, so when you don't need the boost, it doesn't spin.
Depending on a lot of factors, the crank driven fan can take up to 20hp to turn...I dunno how much the alternator pulls but your're right I'm sure a gooood portion of it is because it doesn't always run..

Clutch driven superchargers are used by mercedes on their version of the m62..cuts off above 3000rpm depending on model
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Old 09-10-2004, 10:04 PM   #8
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Mercedes has one, its called the Kompressor (yes, I spelled it right). I will see if I can find some info on it. I think it is a good idea, the SC shuts off when you are on the highway or only turns enough to not be a restriction.

The electric fans only make a difference at high RPMs, when that belt is spinning alot and turning it. No matter if its on or off, FRICTION is what you are losing power to. You have to have an alternator, so it makes more sense to run the pump electrically. Am I making sense?
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Old 09-10-2004, 10:07 PM   #9
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Quote:
Originally Posted by macho_mike21
The electric fans only make a difference at high RPMs, when that belt is spinning alot and turning it. No matter if its on or off, FRICTION is what you are losing power to. You have to have an alternator, so it makes more sense to run the pump electrically. Am I making sense?
Kinda sorta and I've never understood how this works entirely but when the alternator is energized it uses more power to spin. I've tried this in my crap-tastic ford focus. I can make the engine bog by holding the window-down button after its already down. I just assume thats whats causing it. Can anyone explain this to me?
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Old 09-10-2004, 10:08 PM   #10
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The Boost Control Solenoid is kind of a clutch as removes much of the boost and frees up engine power when its not needed (while in reverse, idle)?
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