----[Please read http://ercoupers.com/disclaimer.htm before following any advice in this forum.]----
The higher Octane does not increase pressure, it increases the knock point,
means at what temperature the air-fuel mixture will self ignite.
Self Ignition happens when the Fuel - air mixture is being compressed.
Compression = heat generation.
With higher Octane, one can increase the compression ratio of an engine to
increase the power output. On such engines, we see increased internal
pressures. On our engines, we waste money. We are buying gas that is designed
for high compression, fuel injected engines.
Our engine' compression ratio is around 1:6, with lead you can go as high
as 1:12. That is double the compression and thus more power.
Adding to the discussion about the brass seats in the cylinders :
If these Cylinders made it 'till now and are still useable, surviving
centuries of Avgas and 100LL, doesn't that speak for itself ?
Hartmut
----- Original Message -----From: A J DeMarzoSent: Wednesday, March 30, 2005 1:31 AMSubject: Re: [COUPERS-TECH] Question about cylinders.----[Please read http://ercoupers.com/disclaimer.htm before following any advice in this forum.]----There's more lead in 100LL than in the old 80. If the new seats are harder to withstand the increased internal pressures caused by the higher octane, they should be able to easily handle the auto fuel. Go for the new and improved stuff.----- Original Message -----From: [EMAIL PROTECTED]Sent: Tuesday, March 29, 2005 12:47 PMSubject: [COUPERS-TECH] Question about cylinders.----[Please read http://ercoupers.com/disclaimer.htm before following any advice in this forum.]----I recently sent a couple of cylinders to be rebuilt.The guy doing the work called me to ask me what fuel I use.I told him mostly car gas and 100 LL when I am on a long flight and there is nothing else available.His concern was about the seats of the valves. These are the original 1946 Continentals and the seats are made of brass. He said modern cylinders have steel seats which resist the 100 LL better.So my question is:If the cylinders were made in the 60's when all 80 octane fuel was leaded and now they use steel seats to tolerate the lead in the LL fuel, the 85 octane unleaded should be worse on the brass seats, not better.Or is it not an issue with the lead?More like temperature?Or maybe it is just the sales pitch?This was the first time anyone has told me that 80-85 octane gas (Car gas) is better than 100LL and I want to know more about this.I have heard pros and cons related to the valve guides and sticking, but nothing about the seats.What do the experts say?N87333Alan Fairclough============================================================================== To leave this forum go to: http://ercoupers.com/lists.htm Search the archives on http://escribe.com/aviation/coupers-tech/============================================================================== To leave this forum go to: http://ercoupers.com/lists.htm Search the archives on http://escribe.com/aviation/coupers-tech/
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