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Date: Mon, 13 Jun 2005 09:34:22 -0400
Subject: Re: [FlyRotary] Re: normalized supercharger? Was Re: Is common
 sense dead (rant mode on)
From: Bulent Aliev <atlasyts@bellsouth.net>
To: Rotary motors in aircraft <flyrotary@lancaironline.net>
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> Here is where things get interesting.
>  
> Most automotive pop-off valves are set up and referenced to AMBIENT
> pressure. So.. at sea level, a few psi over ATM may be exactly what you
> want. The piston and spring push out against the ambient pressure and
> voila! Boost relief!
>  
> At 15,000 feet it may be in the neighborhood of 10 psi (thats WITH the
> "few psi" added in).
>  
> Aircraft automatic wastegates are referenced to a sea-level pressure
> that is in some sort of sealed chamber. Unless you get an electronic
> boost controller that is an "absolute pressure controller" and is
> referenced to sea level, or spend the $$$ to get an aircraft "automatic"
> wastegate actuator to control that blowoff valve, you likely wont get
> the normalization you are looking for.
>  
> Dave Staten

I also understand the blow-off valves are useful in car applications, where
the driver will shut the throttle suddenly after a period of high boost. The
turbo can not shut down so fast and the compressed air has no place to go.
The valve than releases the air out to prevent damage. I don't see why we
need blow off valve in aircraft?
Bulent