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Re: FAA Swft 702 Fuel Test
Report
From a pilot/engineer friend of mine:
Pass this along to the LML recipient list if
you'd like. I read through the whole test report and I looked through
most of the graphs although I really concentrated on the results of
the TIO-540 engine since it is the one that most closely resembles the
Continental in our airplanes. It looks like a workable alternative to
100LL with the caveats noted below as far as energy/lb and
elevated EGTs.
The first thing that struck me is that none of
the tests of the Swift 702 fuel got the engine to run LOP. Even
at the lowest power test which was 60%. I believe this is
because the TIT hit redline (1650*F) as they leaned so they terminated
leaning before going LOP. The 100LL at 60% tests went LOP because the
TITs were 50 degrees lower and they didn't hit 1650*F before they went
LOP. So there is no data so far how this fuel will perform LOP.
Specifically how power drops off as you move further LOP. We know that
with 100LL power drops off about 10% when one moves from 100*F
ROP to 50*F LOP. What will Swift 702 do? Since max TIT is 1750*F on
the Continental TSIO-550 engines (with a 1850*F limit for 30secs max)
this may allow us to find peak TIT and lean properly to a reasonable
LOP. Going too far LOP actually causes an increase in BSFC with fixed
timing with 100LL.
The other big question is what does CHT do? We
know EGTs are higher with Swift 702. Higher EGTs do not necessarily
mean that CHTs will be higher also(except in the immeadiate vicinity
of the exhaust port). Advancing timing lowers the Swift
702 EGTs close to what they are with 100LL. This is
explained as being due to the slower burning of Swift 702. I know from
my experience that advancing timing as they did to try to lower EGTs
actually increases CHTs. I did not see detailed data on CHTs in the
report when they tried this.
The detonation margins with Swift 702 were
higher so compression ratios could be higher to take advantage of
this. If done this would lower EGTs. Increasing compression ratio
increases thermodynamic efficiency because it allows the capture and
conversion to work of the expanding gases to occur over a wider
expansion ratio. That is primarily why the Diesel cycle
is more efficient than the Otto cycle and why diesels have lower
EGTs than gas engines.
The other big question is altitude testing.
None was done in these tests and induction air temps go up quite a bit
at high altitudes in turbocharged engines, so this is another
important question to answer.
----- Original Message -----
From: Jeffrey Liegner,
MD
To: Recipient List
Suppressed:
Sent: Monday, March 23, 2009 9:28 PM
Subject: Fwd: FAA Swft 702 Fuel Test
Report
To: lml@lancaironline.net
Date: Mon, 23 Mar 2009 12:59:09 -0400
From: "Colyn Case at earthlink"
Subject: Re: [LML] FAA Swft 702 Fuel test report
It's worth reading the
summary section on page 29. It's only 2 pages
Highlights:
- swift fuel weighs 21% more
but only increases range by 8%
- if you are weight limited
for fuel you will only get 89% as much range.
- if you are gallon limited
for fuel you will get 8% more range
- egt's increase by 50 dF.
On my installation that would mean having to back off the mixture an
additional 50dF to keep the TIT's in range
- something about aromatics I
didn't understand
Overall:
It's better than not flying
but not as far or as fast as 100LL.
---------------------------------------------
----- Original Message -----
From:
To: lml@lancaironline.net
Sent: Sunday, March 22, 2009 4:13 PM
Subject: [LML] FAA Swft 702 Fuel test report
I found a link to a pdf of
the Swift fuel test report from FAA testing done last year.
Looks like there is a heat issue ( around 50F greater than 100LL) and
peak HP is about 1.3% less than 100LL.
I know very little about the
chemistry behind fuels and engine design, but if more heat is
generated, how come that can’t be harnessed and turned into
power?
http://www.tc.faa.gov/its/worldpac/techrpt/ar0853.pdf
Kevin
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