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Date: Mon, 19 Nov 2012 08:23:22 -0500
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Subject: Re: [LML] Unusual LIVP Manifold Pressure Reduction with Altitude Climb: Why so much?
From: Ronald STEVENS <Ronald@sdc.com>
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Hi Jeff

What is your engine (TSIO550 type E or C?) and your prop?=20

thanks -- Ronald

On Nov 18, 2012, at 8:33 AM, jeffrey liegner wrote:

> On a recent flight to Chicago, my MAP during WOT climb was normal and =
ample all the way to cruise FL220, at which time I pulled throttle back =
to 31.5", dialed down RPM to 2350 (which increases MAP some, so =
readjust) and "Big Mixture Pull" to LOP 16.4gph.  All very normal.  =
Cabin Pressure 5 psid.
>=20
> On my return, departing during 30*F temps and cleaning some overnight =
rain-ice off the wings (via hanger heat), I climbed out of Chicago WOT =
and had full MAP at departure, but then observed a decreasing MAP during =
climb (numbers are below).  Details below.
>=20
> I leveled off at 17,500 and observed WOT ~31" MAP and RPM 2690, 32.3 =
gph, all engine parameters normal.  I did not reduce throttle, I dialed =
back RPM to 2350, and observed MAP reduce to 24" (and cabin altitude =
climbed with 1.5 psid).
>=20
> T/O 		WOT 38.5" 	RPM 2670 	FF 43 gph
> 8000'	WOT 37"	 	RPM 2670 	FF 41 gph
> 12000'	WOT 36"	 	RPM 2670 	FF 38.5 gph  	Cabin =
4.1 psid
> 15000'	WOT 34"	 	RPM 2680 	FF 35.1 gph
> 16000'	WOT 33"
> 17500'	WOT 31.8" 	RPM 2690 	FF 32.3 gph
> 	adjusting into cruise settings:
> 17500' 	WOT 24"	 	RPM 2350 	FF 23.9 gph	Cabin =
1.5 psid
>=20
> At home, I pulled the cowling, inspected everything, pressurized the =
induction system, inspected the already clean filter, check the Alt Air =
Door, checked turbos and waste gate controller (on bench), checked =
compressions: everything normal and in great working condition.
>=20
> Today I test flew back to 17,500' WOT max RPM (full rich) and observed =
the same behavior.  This excludes intake ice or frozen alternate air =
door.
>=20
> Also found that if I diverted incoming bleed air (feet vs defrost), =
the MAP remained same.  As expected, if I occluded incoming air, MAP =
increased to 28" but cabin (of course) climbed to >12,500'.  If I =
selected HOT air, MAP remained same; if I selected COOL air, MAP rose =
0.5".  None of this is surprising, siphoning off the Upper Deck =
pressure.
>=20
> Interestingly, while at 17500', there was no change in MAP when the =
throttle cable was moved from WOT (all in) to more than 2" throttle =
pulled out.
>=20
> Descending back to 8000', the numbers were as above for that altitude, =
with access to 37" MAP WOT and higher cabin psid.  The plane has =
historically been able to maintain >36.5" MAP WOT up to FL210 (or maybe =
a bit higher) before MAP would start dropping off as turbos were max'ing =
out.
>=20
> What suggestions can you make regarding this engine =
performance/behavior issue?
>=20
> Jeff L
> LIVP
>=20
>=20
>=20
> --
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