|
Message
Boy, John after reading your offer of free fuel,
room and beer - I started packing - then I remembered my gearbox is at
Tracy's for the retrofit of the 2.85 {:<( and I am not inclined to drive,
sorry.
So John, difficult to make diagnostics from afar,
but here goes. Some of this is basic so don't be offended, often times
that a good place to start.
1. You need both fuel, spark and airflow to
produce power. A deficiency in one or all WILL reduce power (usually at
the most critical time {:>)). One thing that sort of bothers me about
your installation is that without boost you should be able to get a closer to
4500-4800 rpm (A number of us get 5000 or more on take off). Now if you
have a lot of prop that of course could be part of the answer why your rpm is
lower and also why you do get that great acceleration. Actually, I am
impressed at how little power that canard takes to stay in the air. 2500
rpm at 400 MSL on an 80F day would only give you around 70 HP! without any
boost.
2. Spark is generally either there and firing
or not, so unless its some problems with fouled plugs, I would for the moment
eliminate them as a cause.
3. That leaves fuel and air. I use SCATT tube
and have never had it collapse, you do have the type with the wire in it?
If it did collapse, reducing the throttle/airflow could allow it to open back
up. Possible cause, but you would generally see it do this at maximum rpm and
boost (max airflow) and I would think there would be some indication - like
loose wire in the tube, torn around the wire, I mean try collapsing a length of
it by hand - its not easy to do! Possible, but not at the top of my
list.
4. That leaves fuel. Fuel will
certainly affect your power, anything affecting fuel flow. Two things
cross my mind. After you had coasted down and landed (giving the engine
some time to cool off in descent) I believe you found you had regained your
power. Now there are two reason that come to mind.
a. Could have had vapor lock. I read
your story two times and I could not find any place where you indicated you had
checked your fuel pressure (I might have just missed it). My experience
has been anytime my engine has had a problem with fuel its been reflected in the
fuel pressure gauge. Vapor lock generally shows up as fluctuating fuel
pressure. Could the heat generated by the climbout have caused something
like that whereby gliding back down give it time to cool down again , so
you again have throttle response on the ground.
b. Could have been mixture. I sort of
discount this one as if you are flying and everything is stable engine wise, the
fuel requirements (and therefore mixture ) does not usually change abruptly
enough to cause that kind of power loss.
If you want to discuss this further off line, just
drop me a line or give me a call 704-821-7595.
Ed Anderson
RV-6A N494BW Rotary Powered
Matthews, NC
----- Original Message -----
Sent: Tuesday, June 01, 2004 7:08
PM
Subject: [FlyRotary] Re: Power loss
diagnostics
wrong again. My caps lock was on. Sorry.
|