11:1 Compression Ratio, 97 Octane Gas
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Joined: Aug 2006
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From: Rugby, Warwickshire, England
11:1 Compression Ratio, 97 Octane Gas
Hi, a thread over on the uk corvette club site got me thinking.
My L46 has 11:1 compression ratio, someone suggested that this should be run on at least 101 octane, but all we can buy over here is 97 octane super unleaded
Leaded is almost impossible to get except at a tiny number of gas stations (I'd use half a tank driving to and from my nearest leaded station)
You can get 102 octane unleaded at a handul of stations too but its even rarer than leaded and costs about $12 a gallon into the bargain! So basically I have to run on 97 or nothing, I can't detect any noticeable knocking but should I retard my ignition in any case? (I'm currently at the factory spec 4º advance static timing)
Moving house to be closer to a decent gas station isn't really an option!
Any thoughts?
Pauly
My L46 has 11:1 compression ratio, someone suggested that this should be run on at least 101 octane, but all we can buy over here is 97 octane super unleaded
Leaded is almost impossible to get except at a tiny number of gas stations (I'd use half a tank driving to and from my nearest leaded station)
You can get 102 octane unleaded at a handul of stations too but its even rarer than leaded and costs about $12 a gallon into the bargain! So basically I have to run on 97 or nothing, I can't detect any noticeable knocking but should I retard my ignition in any case? (I'm currently at the factory spec 4º advance static timing)
Moving house to be closer to a decent gas station isn't really an option!
Any thoughts?
Pauly
Last edited by popkid; Aug 14, 2006 at 11:27 AM.
Race Director
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From: Waterloo ontario Canada
I ran 11 1/4 compression in a bigblock on only 94 octane with iron heads. If you are running a descent cam it will drain off enough compression at low rpm to prevent detonation. As rpm builds the bigger cam allows the engine to breath and by then detonation is not a problem.
Rather then spend a fortune on gas and LEAD is NOT required for any of our engines regardless of age just put in a little more cam.
I got away with my 11 1/4 compression with a mild 236, 244 @ .050 duration cam and iron heads.
Rather then spend a fortune on gas and LEAD is NOT required for any of our engines regardless of age just put in a little more cam.
I got away with my 11 1/4 compression with a mild 236, 244 @ .050 duration cam and iron heads.
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From: Pettis Performance 565 with two stages of Nitrous Supply nitrous 1.082, 4.61 at 155, 7.17 at 192
Originally Posted by norvalwilhelm
I ran 11 1/4 compression in a bigblock on only 94 octane with iron heads. If you are running a descent cam it will drain off enough compression at low rpm to prevent detonation. As rpm builds the bigger cam allows the engine to breath and by then detonation is not a problem.
Rather then spend a fortune on gas and LEAD is NOT required for any of our engines regardless of age just put in a little more cam.
I got away with my 11 1/4 compression with a mild 236, 244 @ .050 duration cam and iron heads.
Rather then spend a fortune on gas and LEAD is NOT required for any of our engines regardless of age just put in a little more cam.
I got away with my 11 1/4 compression with a mild 236, 244 @ .050 duration cam and iron heads.
Le Mans Master
Joined: Mar 2001
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From: Watkinsville, GA and Glen Cove, NY
Popkid, I can't answer your octane question but if your L46 is original, it probably isn't a true 11 to 1 compression. Typically the true measured compression is probably up to half a point lower. I have a buddy that runs an L46 on 93 without even having to retard timing.
Safety Car
Joined: Aug 2000
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From: San Antonio TX
You know, I've never known an airport that sells fuel to outsiders of their FBO. I've only heard of this anecdotally...a friend of a friend's uncle's brother's cousin... It seems it would be illegal since road taxes are not in place for aviation fuel.
As to his issue, we'd have to know how the octane rating is derrived for UK fuel. The American method for pump octane ratings, RON=MON/2, may not apply over there. If they do use a different method, then any advice he gets is worthless.
As to his issue, we'd have to know how the octane rating is derrived for UK fuel. The American method for pump octane ratings, RON=MON/2, may not apply over there. If they do use a different method, then any advice he gets is worthless.
Safety Car
Joined: Dec 2004
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From: San Diego CA
Originally Posted by danno12345
Not to quibble, but the sticker on US pumps is RON + MON / 2....
But you're right, I think Europe uses only the RON or MON... Can't remember which... It's the bigger number though.
Dan
But you're right, I think Europe uses only the RON or MON... Can't remember which... It's the bigger number though.
Dan
Basically we need to know the octane formula used in the UK to know what to recommend.
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Thread Starter
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From: Rugby, Warwickshire, England
Hi Guys, in the UK I believe we just use the RON number, so that would mean that our 97 is probably equivalent to something lower in the US if the MON number is lower...
i.e. from your comments, if RON is 97 and MON is 93... US Octane = 95, whereas in the UK it would just be sold as 97.
Thanks for your comments, and getting fuel from airports here would be illegal due to the difference in taxation on auto gas and aviation fuel.
Pauly
i.e. from your comments, if RON is 97 and MON is 93... US Octane = 95, whereas in the UK it would just be sold as 97.
Thanks for your comments, and getting fuel from airports here would be illegal due to the difference in taxation on auto gas and aviation fuel.
Pauly
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From: Rugby, Warwickshire, England
Originally Posted by 69ttop502
Popkid, I can't answer your octane question but if your L46 is original, it probably isn't a true 11 to 1 compression. Typically the true measured compression is probably up to half a point lower. I have a buddy that runs an L46 on 93 without even having to retard timing.
Pauly
Team Owner
Joined: Jul 2001
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From: Lakeland, FL
Cruise-In IV-V-VI-VII-VIII Veteran
St. Jude Donor '03, '06, '17
97 octane in Europe is like 92 octane here. The difference between the european rating and the US rating is about 4 - 5 octane..
Racer
Joined: Apr 2006
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From: Rockford MI
As for buying the avgas from the local airport, tell them you have a floatplane and take the gas away in cans. Although you may want to be prepared to answer questions like "what kind of plane do you have?"
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From: Rugby, Warwickshire, England
Originally Posted by 78anniversary
As for buying the avgas from the local airport, tell them you have a floatplane and take the gas away in cans. Although you may want to be prepared to answer questions like "what kind of plane do you have?"
The only time I've seen a floatplane is in the movies...
I think they'd rumble me pretty quickly!
Pauly
Burning Brakes
Joined: Feb 2004
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From: Ville de la Baie Quebec. A winner is just a loser who tried again.
[QUOTE=gerry72]You know, I've never known an airport that sells fuel to outsiders of their FBO. I've only heard of this anecdotally...a friend of a friend's uncle's brother's cousin... It seems it would be illegal since road taxes are not in place for aviation fuel.
I agree that this is not a common subject at work and I am not writing this on some rumor form an unknown source. I am not telling anyone to break any laws, (I have know idea what your laws state on this matter and our taxes are probably not calculated the same way) I just mentionned this as a possible source for fuel because it is done and accepted by the airport in my region.
I agree that this is not a common subject at work and I am not writing this on some rumor form an unknown source. I am not telling anyone to break any laws, (I have know idea what your laws state on this matter and our taxes are probably not calculated the same way) I just mentionned this as a possible source for fuel because it is done and accepted by the airport in my region.
Pro
Joined: Sep 2002
Posts: 690
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From: near Memphis TN
Those commercially available octane boosters are a rip-off and only raise the octane a few tenths of a point.
You could go with the ole toloune (sp) mixes. Buy the stuff at paint stores, etc. It's been awhile since I've done this but I've experimented with it and it will work. Do a search here and on the internet and they have some recipes (i.e. - one gallon can to ten gallon 92 octane will get you to 99 octane, something like that).
You could go with the ole toloune (sp) mixes. Buy the stuff at paint stores, etc. It's been awhile since I've done this but I've experimented with it and it will work. Do a search here and on the internet and they have some recipes (i.e. - one gallon can to ten gallon 92 octane will get you to 99 octane, something like that).
Safety Car
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From: out of nowhere
Originally Posted by SpyderD
Those commercially available octane boosters are a rip-off and only raise the octane a few tenths of a point.
Pro
Joined: Jan 2004
Posts: 535
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From: Darwin, Australia NT
97RON is about 93 RON+MON/2. If you need more octane buy 44's of race fuel and a hand pump. In Australia we need to show a racing licence/membership to buy leaded fuel and if youre like me you have lots of mates racing and even crew now and again.
