[s-cars] "Negative Boost", Oh yes Martha its that dreaded

[Ben Swann]

Do the math - just sticking to basic algebra to get the idea, since a calculus version
would be more involved..

Let's say you are running a measly 25 PSI of positive pressure - so that is only 25
pounds per square inch of surface area - multiplied by how much surface area?

Lets see - that FilterHosen looks like it is at least 3" in inside diameter  and about
5" long  in the deformable area - so pi * Sq.diam is the cross section gives about 706
pounds of force on just the cross-section area of the tube - multiply by your length and
we have a force equivalent of a hand crushing around the pipe of some 2800 lb.
Uniformly distributed, so not as bad as it sounds, but enough to do that sort of damage
- if it were a normal rubber boost hose it would have blown out.  In this case, the
force was more of a Bernoulli suction inward, and the outside air pressure as an
equalizer, but you get the idea.

This is why the filter intake needs to be so much larger than the rest of the induction
piping.

Ben

[Date: Mon, 4 Oct 2010 19:30:47 -0600
From: Hap Maguire <captmagu at gmail.com>
Subject: [s-cars] "Negative Boost",	Oh yes Martha its that dreaded
	subject once again
To: s-car-list <s-car-list at audifans.com>
Message-ID: <5ABAD6D1-16DC-48B5-95AB-D2913B3C17B0 at gmail.com>
Content-Type: text/plain; charset=us-ascii

S-Heads

A sporadic boost issue has been driving Tufty Jones, Brendan Rudak and yours truly very
crazy for the last several months. Last week Brendan and I set about logging runs on da
computer to see if there was a software issue and everything checked out perfectly. We
even tried swapping out the Tial 44mm wastegate for a plug and play Turbosmart WG with a
minor change invloving a slightly laggier but still inconsistent boost between 10-15 lbs
due to a 7 lb vs 1 bar spring in the Turbosmart WG. Tufty and I finally decided to do an
intake tract leak check even though we knew it couldn't be that as this car has
basically a full hard pipe tract with the only silicon pieces at the joints for engine
flex. This would also eliminate the BOV as a potential source. Well as the pressure
built upwards of 30 lbs the only leak we found was from the test valve. The intake was
solid. To do the test though, we had to remove the 4" elbow that runs from the air
cleaner to the turbo inlet. As Tufty was  scratching his head yet again he took a good
look at the cleaner and Voila, we had found our "Negative Boostie". 

As you can see from this inside view, the plastic frame has broken down. This allowed
the cleaner to shrink in on itself as Da BEEG Comp turbo literally sucked the life from
its veins. You can also see the crease lines on the outside of the cleaner and visualize
what was going on. 

http://i935.photobucket.com/albums/ad199/hapster47/a-1-3.jpg

http://i935.photobucket.com/albums/ad199/hapster47/a-3-1.jpg

This air cleaner was mounted to a 4" aluminum pipe that had a 90 degree bend and the
cleaner just hung from the pipe without touching anything else. You can just see the
pipe here in this shot.

http://i935.photobucket.com/albums/ad199/hapster47/dm-63.jpg

Well mucho thanks to Tufty and Brendan for their continuing help in perfecting this
beast. Something tells me this is gonna be a long story. Throughout this all, the car
still ran beautifully if somewhat muffled because of the cleaner. I gotta see if I can
get a refund or do you think AEM will just laugh???

Hap, wit dakine "Negative Boost" nomoh not(and yes Mr Baloney that's 3 negatives) from
Evahboost, Maguire]