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Re: Bypass Valve operation - the basics first
In a message dated 97-11-13 04:16:00 EST, you (oh boy, here we go) write:
<< The valve on the K24 app is not opening because of a Density problem,
That little turbo is a heat pump above 10psi in the 10V and 20V app.
Your not doing your homework here Scott, and in lot's of other places
A k24 maximum flow and pressure are achieved at under 2000 rpm. Hmmm that's
hard swallow given the above.
>Do this experiment correctly with a gas and you'll get a higher Density
>at low temp than high temp. Pilot's worry about Hot and High situations,
>Why? Hotter air has less density, less density = less lift and less
>power. You can go to extremes in the other direction and get too cold
>and too dense, Siberia for instance where an engine will actually make
>less power, This can be proved with Topping charts for helicopters.
>Pretty basic stuff here... Again.
>IF you understand it, which by example your showing that you
>don't......... BTW wanna try to impeach my info, get the books first and
>read up. "The Art And Science Of Flying Helicopters" by Shawn Coyle has
>a very succient section entitled "Helicopter Engines And Their Controls"
>page 71 and 72 will be of particular interest to you.
>BTW if it's not a density issue why was water injection developed? I'll
>even give you the answer, it's used primarily to increase the DENSITY of
Yes UNDERSTANDING, the key here, me thinks.
Using this whole density argument to your example and "theories," ARE you
SURE you didn't hook up the original valve backwards? Let's understand
first how the "stock" bypass valves work before I go buying books on
Helicopter lift. The bosch valve (per audi) is hooked up the following way:
Manifold pressure (Pb-Pv) on the top of the diaphram. Opposite the diaphram
is the turbo inlet pressure Ptv ( mild vacuum ALL the time) or Po (open to
atmosphere) . 90 DEGREES to turbo inlet pressure and 90 DEGREES to Manifold
feed Pressure is Boost Pressure from the turbo. So HOW exactly, are you
BLOWING the valve open? The valve OPENS 90 DEGREES to the Boost Pressure
with VACUUM in the manifold . Maybe I should clarify my "rating" post before
this gets just plain whirly.
Testing has shown that above 15psi, the stock k24 bosch valve has "function"
problems. What is that exactly? Someone here claims that is "blows" open at
9psi, not if the valve is hooked up correctly. With the turbo spinning at
full bore 15psi+ there is NOT enough pressure and flow (Pb + spring pressure
@ oriface) on the TOP of the bypass to overcome the pressure and flow the
turbo is generating 90 degrees to the valve. So, either: a) the valve takes
longer to close, or b) the valve sometimes closes cocked over, creating a
leak. So LIFT and DENSITY have NOTHING to do with the operation of the
valve, when the valve is closed on boost, it's closed, we are talking about
the opening and shutting of the valve between lift (manifold Pv) and Boost
So when we speak of "rating", that is the ability of the valve to overcome
the side pressure forces of turbo boost and flow. A stiffer spring helps the
effective spring pressure on the top of the valve (Effective Spring Pressure
on the top of the diaphram = Boost Pressure + Spring Pressure), since BP will
be constant regardless of turbo, application or "density". So, the S4 valve
can overcome the turbo pressures up to 15psi (boost), the sport q up to about
18-19psi (boost), and the Aluminum valve up to 25psi (boost). Each of these
valves accomplish the EFP the same way, adding SP only. Flow is constant,
Boost is constant, diaphram is the same size, ports are the same size. The
HKS Sequential Bypass Valve does the following: Increases EFS, and increases
FLOW by increasing the port diameter. So two valves with the same EFS will
perform the same relative to the PRESSURE, the only difference is FLOW.
Multiple valves with the same effective port area can accomplish the same
Conclusion: Assuming one to hook up the valve correctly, by definition, you
AREN'T blowing the valve open. Hence my question.
S.O.c, let's put this "helicopter" example in perspective to your own posts.
The bypass valve isn't blowing open, cuz the valve isn't hooked up as you
propose. But the WG is hooked up EXACTLY as you describe. You have been
known to claim that you see 26psi Pb from the STOCK WG spring in your car.
How bout applying the EXACT same "whirlybird" principle to the WG on your
car? Boost pressure on the bottom (your claim "were talking DESINTY here..."
-exact quote), % control of manifold pressure on the other. So why then
doesn't your WG blow open too with a stock spring? HELLO?
Appreciate the "long" post, relatively. Even if the "lesson" is exactly
incorrect. This isn't rocket OR helicopter science. I sure am dizzy tho.