Winter Reawakening of Subaru 2.5

[dunc]

After trouble-free extensive flying last summer, my RAF was basically hangared until now, at low humidity, 6500 MSL. It understandably always had better performance during cooler months of lower DA. e.g. a 60 kt cruise was achieved at 4700 rpm in early spring, which took 4900 rpm in summer when the field DA at 90F approaches 9500 ft. Always achieved 5200 rpm WOT at takeoff. Yesterday's flight was done at about 20F, much colder than any other recent flight. WOT only achieved 4800 rpm.

Pre-rotation speed was also significantly lower. Removed, thoroughly cleaned, and re-lubed the Bendix w/ LPS2, cleaned sheath and shaft, and the shaft received light dose of moly-graphite. Dressed the PR clutch and brake pads with 160 grit too. PR engagement was much better, although PR rotor rpm did not benefit much. Since PR is done a much lower engine rpm, I don't think whatever engine problem is holding back on WOT rpm would affect PR rpm, but maybe wiser minds can offer explanation and help in both areas,

Low WOT engine rpm, and low PR rpm help needed.

Gonna inspect plugs, compression check, and borescope today. I have a potential neighbor looking to buy, and don't want to make a grumpy neighbor.

 

[Vance]

In my experience dunc, automotive fuel has a short shelf life.

My Ford E350 often sits for months at a time and does not run well until I have put some fresh gas in it.

I have enough excess power where it is not particularly noticeable.

Same thing with my lawn tractor.

We have particularly bad gas in California with lots of peculiar additives in it so this may not be applicable to your situation.

If your engine is fuel injected and you run leaded gas usually the oxygen sensor has a short life.

 

[dunc]

Thanks for the ideas, Vance. I only burn 92 octane no lead, no ethanol. It was last refueled after last flight in late September.

Borescope look OK, still see cross hatched honing marks, and 150 psi cold compression on all four cylinders.

Plugs show lots of soot, so I am removing and checking sensors now. Already checked the fuel pressure regulator vacuum reference line for possible diaphram fuel leak.

 

[WaspAir]

We have particularly bad gas in California with lots of peculiar additives in it so this may not be applicable to your situation.

In Colorado, our auto gas is seasonally blended for Reid vapor pressure control in temperature regimes that change significantly.

Winter officially started this afternoon, and at my place we are expecting to go from a high of 47 F today to a high of -5 F tomorrow. Overnight it will drop to about -13. Guess the atmosphere was checking the calendar.


(We'll be back to +50 by Christmas.)