In a sense you're both correct with the logic. I thought the same thing as Tim. Well, sine the new boot is 'solid' and it will not give; then the path of least resistance will come into play.. for lack of better description.
Basically that 'collapse' falls on the filter which is where the vaccum goes... which is better; but still not the best. 2 more lbs of boost a lot from this simple change; but it isn't what I do all day.
Another Point : Even MORE power gains should be had if the intake tube is increased... releaving some 'vacuum' from the filter... but that is my opinion.
peace,
john

 

Nice piece....Im thinking of putting some flames on my bazooka-tube too.........

 

I would think the filter would collapse before the boot? At least that's what supposed happened to REM's truck.

 

You are correct Cyntaxx.....power_whls has some good points....suction will find the path of least resistance..if the tube is more rigid than the filter will suffice to collapse, vice versa.....REM had the rigid tube on so the 140's only option was to take out the filter.....

 

I agree, to a certain extent. If the material, like the rubber boot, will not hold up under high suction than it will collapse no matter what. You could take the filter off and give it high boost and the boot collapse.

Cut the hose of a vacuum cleaner and insert a piece of thin plastic bag as part of the hose. I bet the plastic bag will collapse no matter where you put it in the tube.

 

That is BAD AZZ!!!!!!!!

JEFF

 

The plastic bag is a fairly extreme example, as the plastic has no rigidity at all. I mean, breathing on the bag would cause it to collapse. Here's my analogy:

You could pull 1000 CFM through a toilet paper tube if there were no restriction on the other end. If there is no pressure gradient, there is no force acting upon the outside wall of the tube to collapse it.

Now, add even a small amount of restriction on the end of the tube. It will collapse easily. Put on a big enough filter (i.e., no resistance at all), and there would again be no force acting upon the walls of the paper tube.

In Holdener's article on the Kenne Bell, he placed sensors throughout the intake tract. As soon as he noticed a vacuum (i.e., pressure gradient) between the intake and the air filter (at about 400 rwHP airflow levels), he knew that it was time to go to an aftermarket filter.

Yes, there will always be a slight pressure gradient in the intake tract. As you pointed out with the plastic bag analogy, just the resistance of getting the air straightened out and flowing through the end of a vacuum cleaner hose will create a pressure gradient sufficient to collapse a plastic bag. But we are not talking about a plastic bag here, we are talking about a massive rubber tube.

Bottom line: Remove the air filter and the boot will not collapse. Ergo, the restriction of the filter is causing the collapse of the boot.

I did not mean to suggest that adding a more rigid tube was not called for or was a bad decision. Obviously, if the boot is collapsing shut, anything is preferable to that. I was only pointing out that the problem was not solved -- the problem is still that the filter cannot flow enough air. The symptom is boot collapse. But the remaining problem is a serious restriction in the intake tract, which should also be addressed.

 

Agreed, it was an extreme example. However, we are using 12" open ended filters now. I wonder how big we should go. You are eventually going to come to a point where a filter is a restriction, by the dyno numbers with and without a filter it doesn't seem like much of a restriction.

 

how come i see so many cars at the track run without an air filter on the 1/4?

granted, these motors get rebuilt a few times a season, but is that the reason they need to run without one?

 

That is a very good point, Freeze. Curious -- there is enough of a restriction to cause a heavy rubber boot to collapse, yet removal of that restriction does not cause the dyno numbers to shoot up. Could the mass air be causing enough restriction to collapse the boot by itself?

 

Thats a great point there Mr Skelton....I theororize that the air is being sped-up by the mass air, since it has a smaller diameter....the mass air would then feel the effects of collapse but it has the greater rigidity of the filter and the inlet boot......so if the filter and the inlet boot had the exact rigidity..which would collapse first, the one nearer or farther from the vacume source......

 

Can you please elaborate. Are you referrring to the 'mass' of air? like density? or our 'mass' air setups.
I sound like an 'airhead' right now (wow- pi$poor crack).



Following that line of thinking; you should see the boot and filter 'collapse' slightly- spreading out the vaccuum over the area. ... does that make sense ...
The filter is the path of least resistance... so I'm not sure. I have to get back to work.

John
'the workin' man is a sucker'

 

If you had a straw that started at 4 inches than went to 3 inches than went back to 4 inches , your restriction would be the 3 inch section......this is the same as our inlet hose, mass air meter, and air filter.....the diameter of the mass air meter is the smaller of the 3......