Today's Message Index:
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1. 04:45 AM - Re: Auto Fuel (Dennis W. Wilt)
2. 05:09 AM - Re: Auto Fuel (Randy)
Message 1
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I could be wrong and I have not researched this, but my very poor memory is
telling me that the UK and Australian method of calculating octane is diff
erent than the formula used for the US. I remember that UK octane of 91 is
equivalent to our US octane rating of around 93 or 94. Can anyone verify
this? If this is true then the use of mo-gas 91 in the UK is ok, but not i
n the US. In the US we would have to use 93 or 94 octane fuel.
Me? I use avgas and don't worry about it.
Regards,
Dennis W. Wilt, Aviation Consultant
Communications, Navigation, and Surveillance Subject Matter Expert
Program and Project Management
757-784-8113
N616DW (Arion Lightning S/N 132)
-----Original Message-----
From: Rob Turk <matronics@rtist.nl>
Sent: Sat, Jul 5, 2014 7:28 am
Subject: Re: JabiruEngine-List: Auto Fuel
Jabiru has not to my knowledge published reasons why, but lower comp
ression to make it run on poor quality, low octane fuel is an obvious on
e. This will be at the expense of HP.
They have made many other changes, and many of them without providin
g a reason (or when they did, it didn't always make sense).
On 7/4/2014 1:51 PM, FLYaDIVE wrote:
I don't know! Did they ever publish the reason why?
Bigger bore equals:
Lower compression
More volume
More HP
Maybe better burning/ignition properties?
Maybe a less expensive set of rings or piston?
Maybe easier starts
Maybe lower CHT's
So, what are the answers?
Barry
On Fri, Jul 4, 2014 at 7:39 AM, Rob Turk <matronics@rtist.nl>
wrote:
Why do you think Jabiru has increased the barrel size over ti
me from 106mm to 106.5, then 107 and now 107.5mm?
On 7/4/2014 1:15 PM, FLYaDIVE wrote:
Clive:
Tiger Moth (very old plane/engine) and many of the
1970 planes were designed to run on 80 Octane.
That is 6.5:1 compression up to 8.5:1
compression. BUT! That is 80 octane as proven
/tested by an anti-knock engine. Not a home-brew mi
xing of gas, or even the MoGas divide by two (2) met
hod. The question is: What is the compression ratio
of the Jab and is yours equal to that or any higher
? On the O-320 the case halves have been machined d
own 0.010" each (total of 0.020") so the compression
ratio has been increased to above the published 9.5
:1 ratio.
Barry
Message 2
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I believe it's the other way around (US rating of 91 is equal to UK rating
of 94-95). Anyway, have been using 91 octane (we have 100LL and 91 mogas at
my airport) for 900 hours now with no problems. It occasionally gets 100LL
when I need fuel away from my home airport.
Randy
From: owner-jabiruengine-list-server@matronics.com
[mailto:owner-jabiruengine-list-server@matronics.com] On Behalf Of Dennis W.
Wilt
Sent: Saturday, July 05, 2014 6:45 AM
Subject: Re: JabiruEngine-List: Auto Fuel
I could be wrong and I have not researched this, but my very poor memory is
telling me that the UK and Australian method of calculating octane is
different than the formula used for the US. I remember that UK octane of 91
is equivalent to our US octane rating of around 93 or 94. Can anyone verify
this? If this is true then the use of mo-gas 91 in the UK is ok, but not in
the US. In the US we would have to use 93 or 94 octane fuel.
Me? I use avgas and don't worry about it.
Regards,
Dennis W. Wilt, Aviation Consultant
Communications, Navigation, and Surveillance Subject Matter Expert
Program and Project Management
757-784-8113
N616DW (Arion Lightning <http://www.flylightning.net/> S/N 132)
-----Original Message-----
From: Rob Turk <matronics@rtist.nl>
Sent: Sat, Jul 5, 2014 7:28 am
Subject: Re: JabiruEngine-List: Auto Fuel
Jabiru has not to my knowledge published reasons why, but lower compression
to make it run on poor quality, low octane fuel is an obvious one. This will
be at the expense of HP.
They have made many other changes, and many of them without providing a
reason (or when they did, it didn't always make sense).
On 7/4/2014 1:51 PM, FLYaDIVE wrote:
I don't know! Did they ever publish the reason why?
Bigger bore equals:
Lower compression
More volume
More HP
Maybe better burning/ignition properties?
Maybe a less expensive set of rings or piston?
Maybe easier starts
Maybe lower CHT's
So, what are the answers?
Barry
On Fri, Jul 4, 2014 at 7:39 AM, Rob Turk <matronics@rtist.nl> wrote:
Why do you think Jabiru has increased the barrel size over time from 106mm
to 106.5, then 107 and now 107.5mm?
On 7/4/2014 1:15 PM, FLYaDIVE wrote:
Clive:
Tiger Moth (very old plane/engine) and many of the 1970 planes were designed
to run on 80 Octane. That is 6.5:1 compression up to 8.5:1 compression.
BUT! That is 80 octane as proven/tested by an anti-knock engine. Not a
home-brew mixing of gas, or even the MoGas divide by two (2) method. The
question is: What is the compression ratio of the Jab and is yours equal to
that or any higher? On the O-320 the case halves have been machined down
0.010" each (total of 0.020") so the compression ratio has been increased to
above the published 9.5:1 ratio.
Barry
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