Sender: <marv@lancaironline.net> (Marvin Kaye)
To: flyrotary
Date: Thu, 27 Mar 2003 10:59:03 -0500
Message-ID: <redirect-2088354@logan.com>
From: John Overman <mooneydryver@yahoo.com>
Subject: Re: [FlyRotary] Re: boost control?
In-Reply-To: <list-2088081@logan.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii


--- Marvin Kaye <marv@lancaironline.net> wrote:
> Posted for <13brv3@mchsi.com>:
> 
> [It has been my plan all along to incorporate a
> manually-actuated turbo on
> my
> 13B installation, and redlining the MAP at 34"hg...
> this equates to (about)
> 2psi boost on a standard day, so I think we're
> singing the same tune.
> 
> Indeed we are.  I've also considered using a manual
> control, but dismissed
> it.  Now, you've got me re-thinking again.  
> 
>    I understand you can find a pop-off valve that
> installs in the intake
> manifold
> that vents excess pressure to the atmosphere.  I had
> intended to install one
> on my intake manifold to prevent me from
> inadvertently overboosting.  
> 
> In a classic turbo installation, the popoff valve is
> supposed to be a safety
> device only.  In other words, it's not supposed to
> be used to control boost.
> That's the reason I dismissed the manual wastegate
> control in favor of a
> wastegate actuator.   I just re-read the control
> section in the Maximum
> Boost book, and they state that the popoff valve is
> an effective way to
> limit boost, but should not be used as the "primary"
> boost control.  Hmmm,
> as the human wastegate actuator, I guess I would be
> the primary boost
> control, and the popoff valve would be there to save
> me if I screw up. 
> 
> I had planned to have a popoff valve all along, but
> was also planning to
> have a blow off valve, and wastegate actuator.  Now
> I'm starting to see that
> I can manually control the wastegate for my intended
> usage, and the popoff
> valve will keep me honest.  I've also realized that
> for our purposes, the
> popoff valve will perform the duties of the blow off
> valve too.  This all
> just got a whole lot simpler :-)


Could you guys possibly be making this more involved
than it needs to be? 
   In the intended application, a car, the usual
method of accelleration is to "stomp" on the
accellerator. this scenerio requires elaborate means
of controlling overboost. In an airplane we smoothly
apply power on takeoff and smoothly reduce to cruise
power when we get to altitude. I had intended to see
if the wastegate could be eliminated entirely, and
control boost strictly with throttle adjustments, ie
if the engine is running at low power ,Idle, the
throttle is almost closed thus eliminating the amount
of fuel mixture burned thereby controlling exhaust gas
pressure and controlling turbo speed. On takeoff, you
would not use full throttle and the restriction at the
throttle body would reduce boost in the same way. I
think you would quickly learn about how much throttle
to use and make needed adjustments after becoming
airborn. In many production planes you have to reduce
power after takeoff so no big deal,
   However, I have purchased a standard exhaust
manifold and it looks like the wastegate would have to
be cut out and the hole welded shut so I quess since
it's already there I'm going to put a manual control
on it. If that doesn't work maybe more elaberate
measures  will be in order. "KISS".
   One man's opinion.
                        John  


__________________________________________________
Do you Yahoo!?
Yahoo! Platinum - Watch CBS' NCAA March Madness, live on your desktop!
http://platinum.yahoo.com