Why I'm not sold on the air box mod (a discussion)

Huey130 · 11-02-2004, 07:23 AM

Imagine a pool full of water.
On one end is a giant grate. Behind that grate is a HUGE pump.
On the other end of the pool (or somewhere in the middle, or pointed right at the grate, or not) is a pipe.
The pipe ensures the "level" of the pool never gets below the level of the grate nor below the "volume" that the pump can pump out.

The pump starts sucking. Water flows through the grate. It does so at the entire surface area of the grate. The pipe continues to pump water into the pool.

That's an airbox. It's always full of air. The engine sucks the air out all the way across the filter. The tube from the fender well ensures the airbox is always full.

It's not like the pool isn't full of water and the hose is supplying "only" what the grate needs. If that were the case then yes, the drawing of the pipe pointed directly at the filter would be true. It would be the equivelant of having an empty pool and the water spraying straight from the pipe into the grate. But that's not the case. The airbox is full of air just as a pool is full of water.Think of the airbox as a huge resoivor, Not just a box that a single stream of air from a pipe passes through.

I think the reason it's pointed down is the exact reason people say it's restricting flow. I've seen it said that because only the bottom of the filter is dirty then that's the only place that's getting air. I suggest that's the only place that's getting air in a bee line from the pipe and thus is why it's only "really" dirty BUT all of the filter is pulling air. The bend "protects" the filter... Yet it's still supplying all the air the filter needs by ensureing the airbox is full.

PS: I'm an ME but dropped fluid dynamics twice! Hahahaha

juma · 11-02-2004, 07:30 AM

"The pipe continues to pump water into the pool."

the pipe doesn't pump - its just an inlet.

the airbox isn't full to a certain pressure - so at full throttle the air pressure is lower in the box. less air than possible flows into the pump and the right amount of fuel for the air in injected. but if you got more air, you'd get more fuel and more power.

Liquids (hydrostatic) pressure doesn't vary pressure to the degree that air pressure does under suction. but, it will vary volume and again, the air box won'tbe full.

juma, MBA, CPA, CISA, CFE

morpheoussc400 · 11-02-2004, 11:35 AM

Quote:

Originally Posted by juma

"The pipe continues to pump water into the pool."

the pipe doesn't pump - its just an inlet.

the airbox isn't full to a certain pressure - so at full throttle the air pressure is lower in the box. less air than possible flows into the pump and the right amount of fuel for the air in injected. but if you got more air, you'd get more fuel and more power.

Liquids (hydrostatic) pressure doesn't vary pressure to the degree that air pressure does under suction. but, it will vary volume and again, the air box won'tbe full.

juma, MBA, CPA, CISA, CFE

Yea, what he said!!! And on a side note since we were originally talking about water, grates, and tubes, imagine that if the "pump" were suddenly required to pump at maximum volume there by emptying the reservoir completely and pulling water through the tube. If said tube were pointed at a wall which deflected the flow toward the nearest corner of the greate, even though the primary chamber may be refilling any debris in the water would be trapped primarily in that corner. Which over time would reduce the overall flow. Changing the angle of deflection or removing it completely so that the flow were spread over the entire grate..... Well you get the picture.

juma · 11-02-2004, 11:42 AM

I will add this though -- the mod is only worthwhile to redneck pretenders who think they need a truck but don't. What I mean is the tuning of the box is to provide a certain airspeed at a certain range of rpm. You won't notice it if you never haul anything. but if you load up your truck with a trailer or 1500 pounds of dirt, it will take a bit more pedal to move it than it would with a stock aribox. me? I'm a pretender. my truck will never pull anything but a bag of mulch or 4 tube sands.

juma

morpheoussc400 · 11-02-2004, 11:49 AM

Quote:

Originally Posted by juma

I will add this though -- the mod is only worthwhile to redneck pretenders who think they need a truck but don't. What I mean is the tuning of the box is to provide a certain airspeed at a certain range of rpm. You won't notice it if you never haul anything. but if you load up your truck with a trailer or 1500 pounds of dirt, it will take a bit more pedal to move it than it would with a stock aribox. me? I'm a pretender. my truck will never pull anything but a bag of mulch or 4 tube sands.

juma

This applys to me as well. I'm a pretender... Matter of fact, I just ordered an ARE tonneau, so I won't be hauling anything much more than luggage....

juma · 11-02-2004, 12:05 PM

HMMMMMM....Let's ask ekool for a "pretender's section!"

We can talk about how we got stuck some place or were made to haul an old couch around by our wives and how tough it was to park at the mall.

juma

TallTexan · 11-02-2004, 12:16 PM

Maybe we should leave the snorkle alone and install a tornado in it to create a vortex and make our truck scream like a scalded dog. Maybe some Slick 50 in the oil and couple of bottles of fuel injector cleaner will help even more. I been thinking of installing one of those fake hood scoops also to make everyone think I got ram air. Gotta go, wife taking me to Wal-Mart to buy chrome exhaust tip . Some one said could add another 5 hp.

morpheoussc400 · 11-02-2004, 12:39 PM

Quote:

Originally Posted by TallTexan

Maybe we should leave the snorkle alone and install a tornado in it to create a vortex and make our truck scream like a scalded dog. Maybe some Slick 50 in the oil and couple of bottles of fuel injector cleaner will help even more. I been thinking of installing one of those fake hood scoops also to make everyone think I got ram air. Gotta go, wife taking me to Wal-Mart to buy chrome exhaust tip . Some one said could add another 5 hp.

Ok, or maybe how about.....NOT!!!

SiMaster 2003 · 11-02-2004, 06:56 PM

I believe the tube is bent down to reduce intake noise. It's just another trick the manufacturers use to reduce noise in cars these days. The air box is not "tuned" to the computer, it's just a compromise between power, noise, size & complexity. I cut the tube out of my box the day I took my filter out and found it dirty in one spot, meaning the majority of the dirty air was going through approx. 5% of the total filter. I put a K&N style filter in and cut the tube flush with the box wall and called it a day. The only difference is a little more intake noise at higher RPM's & little more throttle response. As far as having to use more accelarator as Juma mentioned, not me. The other day I hauled about 10 2500 lb loads of 1 1/2" rock through deep mud in 4LO of course. Didn't seem to notice a loss of torque or having to use more throttle.

mtbendo · 11-02-2004, 08:43 PM

Quote:

Originally Posted by Huey130

The pump starts sucking. Water flows through the grate. It does so at the entire surface area of the grate. The pipe continues to pump water into the pool.

That's an airbox. It's always full of air. The engine sucks the air out all the way across the filter. The tube from the fender well ensures the airbox is always full.

Keep in mind that while the entire filter maybe flowing air, the air velocity at all points of the filter may not be the same, especially at higher flows. Flow will take the path of least resistance. Even in a smooth pipe, the air/fluid velocity along the walls in less than the velocity in the middle of the pipe due to surface fiction.

How's that for an engineering geek response? M.E. btw.

Hatchman · 11-02-2004, 08:44 PM

With the mod, it's definitely louder. Tows better with less throttle and fewer downshifts. That's just this rednecks experience.

juma · 11-03-2004, 02:38 AM

Quote:

Originally Posted by SiMaster 2003

I believe the tube is bent down to reduce intake noise. It's just another trick the manufacturers use to reduce noise in cars these days. The air box is not "tuned" to the computer, it's just a compromise between power, noise, size & complexity. I cut the tube out of my box the day I took my filter out and found it dirty in one spot, meaning the majority of the dirty air was going through approx. 5% of the total filter. I put a K&N style filter in and cut the tube flush with the box wall and called it a day. The only difference is a little more intake noise at higher RPM's & little more throttle response. As far as having to use more accelarator as Juma mentioned, not me. The other day I hauled about 10 2500 lb loads of 1 1/2" rock through deep mud in 4LO of course. Didn't seem to notice a loss of torque or having to use more throttle.

agree on the noise too but note that some with the mod and towing report that mileage is dramatically lower. could be natural variation and misreading but its starting to look consistent. where you would see it is on the highway with big load or tow. how it "feels" is not a good test. juma

*Squid* · 11-03-2004, 02:58 PM

I don't care how the air get's there as long as the lights come on!
E.E.

the head · 11-03-2004, 03:15 PM

You guys are going to make me spend $15 for a stock tube and another $15 to run at the dragstrip just to see the difference, aren't you?

Huey130 · 11-03-2004, 03:18 PM

Hell it's just 2 bolts and a hose clamp to swap air boxes. Just have someone meet you there.

PS see my next post.