Today's Message Index:
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1. 06:10 AM - Re: Cruising airspeed (Gary Casey)
2. 09:18 PM - Re: Re: plugs (kyle Ponsford)
Message 1
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| Subject: | Re: Cruising airspeed |
--> Engines-List message posted by: "Gary Casey" <glcasey@adelphia.net>
<<With info like that you can make a much better comparison.
Might be better off to tell us what your end goal is and then an expert
like Mahlon can tell you how to get there and how much $$$ it will cost.>>
I should have been clearer on my question. The question arises as I come
close to configuring my engine. I plan to turbonormalize it, but as the
project progresses I find I am running low on time and money, so I'm looking
at all the tradeoffs. My target cruising altitudes are between 10,000 and
18,000 ft. The three options seem to be turbonormalizing, leaving it
standard (fixed ignition timing), or going to high compression pistons and
electronic ignition. The first and third seem to be the most viable, but I
don't have performance data on the effect of electronic ignition (variable
timing) on performance at high altitude.
From data I have, all on certificated aircraft, there seems to be a lot of
commonality in the data. I used 8,000 ft data as the baseline just because
most engines are routinely operated at 75% power, which for naturally
aspirated engines is only available up to about 8,000 ft. When engine
conditions are held constant (rpm, mixture, etc.) I find that at constant
power the airspeed will increase at very close to 0.83 percent per 1,000 ft
altitude change. For a Naturally aspirated engine above 8,000 ft (full
throttle, constant rpm and mixture) the airspeed will decline at an average
of 0.93 percent per 1,000 ft. The only data I have is for fixed ignition
timing and I am sure that the slope of the line is partially caused by the
ignition timing being further and further from optimum as the altitude
rises. This is not the case for the turbonormalized example as it runs at a
constant manifold pressure regardless of altitude and hence a fixed timing
setting works.
I am missing information that would allow me to calculate the slope of the
speed vs. altitude line of the electronic ignition version. Also, my data
for naturally aspirated engines only goes up to 12,500 and I would like to
have reliable data up to 18,000.
<<You'll see why you don't really want to use 2500 RPM for cruise.
Jim Ayers>>
Yes, Jim, I see your point. My Cessna probably doesn't get close to sonic
tip speeds thrashing the air at 135 kts, but the real target is much higher
airspeeds than that, at which time the higher engine speeds are probably
fighting Mother Nature. I just need data at a constant engine speed just to
eliminate as many variables as possible.
Gary Casey
C-177RG N2180Q
LES N224SG
Message 2
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--> Engines-List message posted by: "kyle Ponsford" <wild_kyle@hotmail.com>
sounds like you and I are at about the same place! I too have done the same
thing except the bolt.
I have just ordered some cooler plugs to put in the back, I am running NGK
DCPR7E and I am waiting for some 9E's which will run 2 steps cooler.
This works in my snowmachine quite well so I thought I would give it a try.
I will let you know how it goes.
Kyle
>From: "Leo J. Corbalis" <leocorbalis@sbcglobal.net>
>Reply-To: engines-list@matronics.com
>To: <engines-list@matronics.com>
>Subject: Re: Engines-List: Re: plugs
>Date: Fri, 21 May 2004 09:10:09 -0700
>
>--> Engines-List message posted by: "Leo J. Corbalis"
><leocorbalis@sbcglobal.net>
>
>
> > --> Engines-List message posted by: "kyle Ponsford"
><wild_kyle@hotmail.com>
> >
> > Leo,
> > Now that sounds like a very scarry fix!
>
>OK I've tried a new left manifold,overhauled both carbs, put 2 3/16 bolts
>thru the front leg of the manifold(actually gives some improvement), max
>size main jets and metering pins in 4 notch. Still swapping plugs.
>
>Please suggest something better !
>
>Leo Corbalis
>
>
http://join.msn.click-url.com/go/onm00200362ave/direct/01/
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