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Date: Sat, 2 Sep 2000 18:11:44 EDT
Subject: High Boost Pump
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>>
<<  I have turned on high boost while doing my recurrency  training at lower 
altitude (2k) to see its effect on the engine normal  operation, and noted no 
perceptible change. >>

Doug:  I'd suspect you have a problem with your high boost...  The reason the 
pump should flood the engine is that it is designed to deliver sufficient 
fuel pressure in case of an engine driven fuel pump failure, partial 
blockage, or heaven forbid a leak in the supply (been there).  Your training 
should have covered this and the "possible" need to lean the engine if high 
boost is selected to keep the engine running.  


<<To clarify the questions about the low / high boost switch, if you are WOT,
inadvertently activating the high boost should have no affect.  The switch
is there in case your engine-driven pump fails.  However, if you are at
cruise (any altitude) activating the high boost would flood the engine.<<

Kirk:  You may be correct about activation at WOT, depending on what pressure 
the "Dukes" pumps are set at.  The TSIO550 Model Spec.shows:  "Desired Boost 
For Emergencies", Fuel Injection Pump Inlet Pressure  at 100% B.H.P. of 42-48 
PSIA.  Having set up a few engines, I assure you that an unmetered pressure 
that high will flood the engine at WOT, especially considering that the 
normal operation should see 32-36 PSI and pressures above 38-40 PSI cause the 
engine to stumble, belch copious amounts of black smoke and lose power.  

What are the spec's today for the Dukes Pumps for the IV ??
 
Mike DeHate
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