aileron11
Posts: 167
Joined: Wed Oct 19, 2005 5:46 am

Lead Fuel For Piston Poppers

Sat Dec 02, 2006 10:03 am

I checked but did not find any subject about why cant the piston aircraft switch to unleaded fuel. what does the leaded fuel do that unleaded cant do? Thanks who ever can help on this.
Jersey Lou
 
N231YE
Posts: 2620
Joined: Tue Jul 25, 2006 9:24 am

RE: Lead Fuel For Piston Poppers

Sat Dec 02, 2006 10:16 am

Quoting Aileron11 (Thread starter):
what does the leaded fuel do that unleaded cant do?

The lead found in Avgas (80, 100, 100LL) helps to increase the octane by allowing higher compression (thus preventing detonation), and it also redeposits itself onto various components, such as the poppet valves, thus protecting them and prolonging their life.

Here is a good read: http://en.wikipedia.org/wiki/Avgas
 
Fly2HMO
Posts: 7207
Joined: Sat Jan 24, 2004 12:14 pm

RE: Lead Fuel For Piston Poppers

Sat Dec 02, 2006 10:19 am

Tetraethyl lead prevents engines from knocking or detonating among other things. Unleaded 100 octane fuel needs additives to be added in place of lead to protect the engine. Those additives cost money. And considering how 100LL is almost $5 a gal. these days...  sarcastic 
 
Buzz
Posts: 694
Joined: Sun Nov 21, 1999 11:44 pm

RE: Lead Fuel For Piston Poppers

Sat Dec 02, 2006 2:41 pm

Hi Fly2HMO, Buzz here. You must live in an expensive neighborhood. Last weekend I paid $3.25 a gallon for 100LL at Stark's Twin Oaks, west of Portland OR.

When you do use the auto gas STC (cost of $1 per horsepower paid to the EAA) you need to be rather careful about the auto fuel you buy, much of it has ethanol as an octane booster. Good for cars, bad for the rubber seals and hoses that are often used in older aircraft.

Checking for alcohol in the fuel isn't hard, requires a calibrated container. For example, take 8 fluid ounces of auto gas, add 1 fluid ounce of water to it. If there is alcohol in the fuel, the alcohol will absorb some of the water, you won't get 9 ounces of mixed up water and auto gas.

g'day
 
KELPkid
Posts: 5247
Joined: Wed Nov 02, 2005 5:33 am

RE: Lead Fuel For Piston Poppers

Sat Dec 02, 2006 3:18 pm

Quoting Buzz (Reply 3):
When you do use the auto gas STC (cost of $1 per horsepower paid to the EAA) you need to be rather careful about the auto fuel you buy, much of it has ethanol as an octane booster. Good for cars, bad for the rubber seals and hoses that are often used in older aircraft.

Ethanol is also bad because it causes carburetor icing in updraft carburetors, amongst other things...

Most auto gas STC's usually include at least some replacement components because there is usually some material in the fuel system that avgas leaves alone, but is affected by common auto fuel additives (other than ethanol).

The most suprising auto fuel STC that I've seen? A '67 Cessna 182...I had no idea the Continental O-470 could handle auto fuel, much less the old 80 octane gas  Smile
Celebrating the birth of KELPkidJR on August 5, 2009 :-)
 
N231YE
Posts: 2620
Joined: Tue Jul 25, 2006 9:24 am

RE: Lead Fuel For Piston Poppers

Sat Dec 02, 2006 11:54 pm

Quoting KELPkid (Reply 4):
Ethanol is also bad because it causes carburetor icing in updraft carburetors, amongst other things...

I am pretty sure I read somewhere that ethanol also doesn't stay "mixed" in with gasoline at higher altitudes, which can lead to problems within the engine.

Quoting Buzz (Reply 3):
When you do use the auto gas STC (cost of $1 per horsepower paid to the EAA) you need to be rather careful about the auto fuel you buy, much of it has ethanol as an octane booster. Good for cars, bad for the rubber seals and hoses that are often used in older aircraft.

I believe the EAA is trying to get all of the states and oil companies to omit ethanol from premium gasoline (the 93 octane stuff), and allowing ethanol to stay in the regular and mid-grade to satisfy both sides of the ethanol/aviation debate.
 
Pope
Posts: 3995
Joined: Thu Mar 24, 2005 5:57 am

RE: Lead Fuel For Piston Poppers

Tue Dec 05, 2006 10:00 am

Quoting N231YE (Reply 5):
I am pretty sure I read somewhere that ethanol also doesn't stay "mixed" in with gasoline at higher altitudes, which can lead to problems within the engine.

Ethanol attracts water. The water freezes causing potentially disasterous consequences in the fuel system.
Hypocrisy. It's the new black for liberals.
 
Pope
Posts: 3995
Joined: Thu Mar 24, 2005 5:57 am

RE: Lead Fuel For Piston Poppers

Tue Dec 05, 2006 10:03 am

Quoting FLY2HMO (Reply 2):
Those additives cost money

The lead additives represent less than about 20 cents per gallon in each finished gallon of avgas sold.
Hypocrisy. It's the new black for liberals.
 
N231YE
Posts: 2620
Joined: Tue Jul 25, 2006 9:24 am

RE: Lead Fuel For Piston Poppers

Tue Dec 05, 2006 10:06 am

Quoting Pope (Reply 6):
Ethanol attracts water. The water freezes causing potentially disasterous consequences in the fuel system.

Thank you for the explaination.

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