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Here's something on the subject that I sent outside of the LML. Touches
tangentially on the subject, but maybe it will get things started. There's
some stuff that isn't directly related to the subject but I'll send it along
anyway.
(My apologies to Ed Sikora)
Hi again Ed.
There's not much to choose between the 235 and 290 - if you install the
Lycoming high-compression pistons in the 235. You need to start out with the
"- L2C" version of the 235 but that's the same one used in the C-152 and
Piper Tomahawk, so they're well known from a maintenance standpoint. Plus,
there is a lot of them around, too. In fact, this is the same set-up used in
an STC'd engine up-gradefor the Tomahawk - so it's a known thing.
With the Hi-comp pistons, (I think Lyc refers to them as "helicopter
pistons" but I'm not absolutely sure on that) the O-235-L2C will produce
about 125 HP @ 2700 - 2800 RPM which is the nameplate continuous RPM for
this engine. I'm not sure what the difference in weight is, but it's got to
be something.
I have an MT electric constant speed prop on mine - 62 inch dia. - and I'm
very happy with the take-off performance - NOW - but I sure wasn't with a
fixed pitch prop. I have flown pretty heavy, out of fairly high altitude
fields, at very high temperatures (Tonapah, Neveda, around 6000 ft. elev.,
90 degree day, no wind, coming home from a fishing trip with a 203 pound
buddy and all the frozen trout and dirty clothes we could stuff in there)
and got away handily. The year before I put on the MT, I had to reject the
first try and go again while turning onto the runway at as much speed as I
could muster without collapsing the gear. Still very touch and go. All that
went away with the MT prop as I now can get 2750 RPM on takeoff which lets
me get all the HP I'm going to get at the Density altitude at the time.
I flight plan for 164 knots at 7500 to 9500 ft. In the last couple hundred
hours, this has held up admirably. Along with this, I usually get a fuel
burn, everything considered, of about 6.5 to 6.9 GPH. I haven't really
noticed all that much change in cruise speed with the MT but those takeoffs
are a lot less exciting!!! Once I accelerate to about 130 MPH, I
consistantly see over 1000 FPM climb.
On the down side, the O-235's have solid lifters (as opposed to hydraulic
lifters in 320's and up) and I think the 290 does too. I don't have a
problem with that - it just means you (or you wrench bender) have to check
and set the valve clearance about every 100 hours. I do mine at every annual
and it's no big thing - I used to drive Porsches and setting their velves
was much the same except you had to lay on your back to get to them! Not so
on the Lyc's valves, you can do it standing up. Takes about twenty minutes
once you've got the cowl off - but that's off for the annual anyway, so no
big deal. Also, after the first couple hundred hours on the engine, the
valve lash doesn't change much at all.
Hope this answers some of your questions.
I think the engine is fine (O-235) but just don't plan on winning the annual
race at Redmond since so many folks are running hopped up 360's nowadays. In
my view, it sort of misses the point about what a Lancair was meant for. 164
knots average on 6.5 GPH is what I originally bought it for - and I'm
happy!! And I regularly take the wife and dog (20 lbs) and laundry for a
week with no complaints!
Dan Schaefer
LML website: http://www.olsusa.com/Users/Mkaye/maillist.html
Builders' Bookstore: http://www.buildersbooks.com/lancair
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