xxxtreme22r

Time to make someone's head hurt

just to back this up as far as hole size and CFM. A 3" hole for air to go through can have the same CFM rating as a 5" hole. How?

CFM = (velocity in (FPM) Feet per Minute times the Squared footage of the duct area)

or

Volume (CFM) = Velocity (LFM) * area (ft²)

The area of each hole would be π multiplied by the radius squared.

or

Area = π * r²

Since we are dealing with ft² we have to convert the in² to ft² which is done by dividing the radius by 12.

Area (in square footage) = π * (r/12)²

so now we would look like this:

Volume (CFM) = Velocity (LFM) * area ( π * (r/12)² )

now say for math purposes only the CFM of the 5" hole is 250 CFM and the area is 0.136 ft²

250 CFM = Velocity (LFM) * 0.136 ft² (area)

the velocity of the 5" hole would be:

Velocity (LFM) = Volume (250 CFM) / area (0.136 ft²) = 1838.235 LFM



so how do we make the 3" hole have the same 250 CFM rating you ask ?

lets look at this again but use the area of the 3" hole which is 0.049 ft²

Velocity (LFM) = Volume (250 CFM) / area (0.049 ft²) = 5102.041 LFM

as you can see that will up the velocity value.

How do we do this?

By using the venturi effect.

If you want me to put up all those numbers then I can, but all you have to do is Wikipedia venturi effect to understand it.

EDIT: of coarse we will have to take into account for air resistance across the tube which is called derating the free air volume. we do this by multiplying the CFM rating by a certain determined percentage.

xxxtreme22r

GNarly I understand what you are saying, if properly designed and researched it is possible for a 3" tube to flow as much air into a box or throttle body as a 5" tube.

Is this properly designed does it flow more? not sure. I feel the same way you do.

Without the data to prove this bass tube flows as much if not more CFM as the factory box before the air filter, it's hard to say if bass tube mod is actually what gives you more power.

I highly doubt that little bit of tapered lip on the otherwise equal diameter bass tube is enough to cause a venturi effect.


BTW this same principle is what functional RamAir hoods are designed off of. But most manufactures have the airflow data to back that up

xxxtreme22r

I think the problem is, is people are thinking the base tube actually allows more air into the engine. Plain and simple. It doesn't.

What does is the fact you just removed the air box from the front of the filter. Why does this allow more air? Because when the motor sucks it's air in through the air box, it causes a pressure drop across the inlet to the air box and then again across the filter itself. Because you just removed that box this causes the pressure on the air side of the filter to effectively increase. Leading to a greater differential pressure across the filter. Hence the extra flow. And we all know more air flow means more power.

For this reason and only this reason I don't believe the bass tube is what actually increased the power to the motor. What I do believe is that the tube allows for a better way to direct cooler air to the filter than the original deckplate. But at the same time, makes me wonder whether or not the filter is actually pulling air through it sitting still on a dyno. Personally I think it's just pulling the air from around the tube when the truck is not in motion. Therefore it isn't really pulling cooler air when the truck is not moving. Which is why I mentioned above the lack of the filter box is the only reason why the engine picked up power.

xxxtreme22r

my first one of the venturi effect was a little off-topic for the bass tube, which led to confusion I think. It was just an argument when people dogged the size of the bass tube and how much CFM it flows. I thought I mentioned that, but I guess it wasn't clear enough.

DailyDrive

I put one of these on my intake. Now going down the freeway I'm boosting like a turbo, 20psi no less! Getting 400hp and 500 lb/ft torque more. Nobody believe me? Well go try it yourself before you knock it!! How can you say it doesn't work if you didn't try it? I've tried it, you didn't. I'm right, you are wrong!!

Deceptiwave

LOL! Stick - I love the way you write, brother. I dont care if you guys were arguing about which off-white toaster goes better in a yellow kitchen, the way you get your ideas out is so damn entertaining! Great articles by the way.
I wish I could get your radio show up here in the NW.

gdutch

Look, Stick, I support what you're trying to do here, but if you want to compare against the Deckplate Mod, you need to do a run against the Deckplate Mod, not against stock. Ideally, it'd be versus all three. You can't say Velocity Stack it's better than a Deckplate because of "SCIENCE." You make the claim, so the burden of proof is on you. I am very interested to see your results.

SharpStick

Thanks again for the compliments. If you want to hear my show, log on to KCBQ.com at 6: PM Saturdays for the simulcast.

Heat didn't kill the tube - no melty on-trail yesterday, and it was damn hot.

Appreciate the in-depth physics, gentlemen. Nice to see more people who are actually getting this stuff and don't just sqwuak like a cage full of parrots. As for comparisons, well, there is no dyno number for the deck-plate mod, so there's technically no comparison. Anyone? Deck plate dyno numbers? All we have is a guestimate of 7hp - has anyone tested it? If someone in San Diego has the deck-plate mod, I will dyno it at my next session.

I'm tired of justifying the stack - it's a better way to direct air to the filter than just cutting a hole in the airbox. The physics of a duct versus a hole aren't complicated, and it made 8hp. If y'all are not interested in 8hp, don't do it, and if you are, then you shouldn't care if the stack magically grinds up hamsters as an offering to the smog lords to make that power.

I don't have the time to sit here and diagnose the minutia over and over, and I'm pretty sure the doubters here would find other threads to worry when proof is laid out. Like I said, I'm not making Reese Tuning do a bunch more dyno time for me to prove things to people who will find something else to doubt next, unless they want to put their money up for the time...

Stay tuned for the K&N drop-in test, though. Most of you will enjoy that story.

STICK

xxxtreme22r

Prove it. That's all we are asking. If you just added the hole with the tube to the original deckplate mod with before and after Dyno's You would have. But you separated the box from the air filter and then added the tube. And took dyno's over factory.

Or how about this, you take the factory air box apart leave the air filter take a dyno with and without the tube there. That would also proove it.

Sorry if none of those are done, hardly any people that know anything about how an engine makes it's power is gonna believe you. Only the gullable Noobs will. These would be the same idiots who think tornadoes in their throttle body, electric supercharges etc etc work as well as all the other gimmicks that are all over ebay.

SharpStick

By the way, the OEM airbox was never out of the equation. Not sure where people are getting that. It's airbox with no mods versus airbox with the stack. The stack was put into the box, just as it's shown in the story.

The used (dirty) filter is just like everyone else's. This one has about 3000 miles on it. Oh, and did anyone else notice that when I confirmed a three-run baseline and then a three-run test of the new stacked airbox, the compulsive doubters on this thread proceeded to say that that wasn't good enough either?

Also, from what I know of the Venturi effect, there's little improvement to be had by the exact shape of the tube's flared lip so long as there is one.

Ack, I'm debating minutia. Y'all can play amongst yourselves. I've got real things to do.

STICK

xxxtreme22r

What we are getting at is there is probably what a 3" gap between the original air box and that tube. How in the heck is that engine pulling it's air through the tube? I don't see a fan blowing air at the air box while on the dyno simulating the vehicle moving.

Air is gonna follow the path of least resistance. I don't see how while on the dyno that it is the sole reason why this made 8hp. I would be willing to bet if you simply left the filter in the original air box and took off the front of it, you would yield the same 8hp without that tube being there.

Some of our points are how is this a better mod than the deckplate? You state it's because of the bass tube and it's venturi effect. How do we know that? We don't.

LifeOnABoard

You guys are thinking about this too much. Gas (air) is a fluid. Removing restrictions at the filter simply reduces pumping losses, increasing Volumetric Efficiency. Sheesh. Quit it with this venturi, velocity crap.

Fink

Keep it cordial and constructive guys - this is a great thread with some good info in it, I don't want to close it down.

Fink

xxxtreme22r

well I think we got the constructive part down, at least me and Gnarly, we doing a pretty good job of pounding some heads with some big hammers. lol.

Oh BTW who said science in high school and college and in my case the military wasn't good for anything.

Fink

Everybody is doing a good job - I just wanted to throw in the occasional reminder.



Fink

xxxtreme22r

And Fink why don't ya crawl back into that little hole ya came out of. haha Nice avatar..... I think.

ok

Fink

Good ole' Rat Fink!

Fink

xxxtreme22r

I think you need to go back to 4X4 Fink he was nicer and a lot more good looking !!!!! hahahaha

Fink

Fink

dropzone

iTrader: (6)

no problem whatsoever as long as it is done nicely
I too am an old fart who have seen tons of whizbang stuff claiming all kinds of great returns for little effort/expense...