larry(at)macsmachine.com
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 Posted: Fri Apr 14, 2006 5:05 pm Post subject: test flight for changing Bing main jets from 176 to 178 INN |
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Hi Guys,
It's been a month since the main jets were changed, but testing waited
for Sun n Fun and weather. Thought I should finally report the
results for those with a Stratus EA81 and Ram Performance heads.
Sunshine and tall overcast clouds were on tap today with just a few
sprinkles. About 2:00 weather was finally flyable with reported ceilings
of 3800 ft. I did preflight and twice checked the header tank for water.
Still pitched at 17-degrees, N601EZ lifted off at 2:30, climbed into the
south practice area and I observed the effects of changing the Bing main
jets from 176 to 178. A 180 main jet was tried last year and it caused
the engine to run a little rough. On climb out at high rpm the EGT never
exceeded 1400 deg F. Engine power seemed the same and it ran smoothly.
At 3500 feet I leveled off, pushed the throttle fully forward and
watched the tach reach 4950 rpm but no further. The richer mixture was
obviously cooler and yielded a little less horsepower. I adjusted
elevator trim to optimize airspeed and held a level attitude and waited.
The airspeed topped out at 128 mph, 5 less than before. EGTs settled to
1350 degrees F. and stayed there. At full throttle, oil temperature
finally reached my alarm set point of 250 degrees and the light came on,
so I backed off to 120 mph and the oil temp settled to 240 degrees F.
Cylinder head and coolant temps were 204 degrees F. Ambient air was
78-degrees F, which is hot for this time of year, but I was pleased that
the EGTs were lower with this 178 main jet. At a cruise airspeed of 120
mph, an exhaust gas temp of 1325 degrees F was a definite improvement.
Despite a slight loss of top end rpm, I'm really happy with the 601 and
Stratus Subaru at this point in time. Ram Performance said 1350 was a
good target EGT temp and Stratus said that 1500 would be a good max
EGT. So I think this 178 main jet will stay on and I'll continue to
watch it as the season changes.
The tower broke my focus with a warning for possible thunderclouds, rain
and severe convective in the area. Recalling last night's local
tornados, I immediately turned around and headed back under a much
darker set of clouds and a thick haze at 3000 feet. My landing was real
good and I used 23 to return to the hangars with 55 minutes on the
clock. With three quarters of the fuel used up, I'll probably drain the
rest and prepare for paint.
Larry McFarland - 601HDS at www.macsmachine.com
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