Hi Jeff

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

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.
>
> 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.
>
> 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).
>
> 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
>
> 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.
>
> 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.
>
> 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.
>
> 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.
>
> 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.
>
> What suggestions can you make regarding this engine performance/behavior issue?
>
> Jeff L
> LIVP
>
>
>
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