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Lead Fuel For Piston Poppers  
User currently offlineAileron11 From United States of America, joined Oct 2005, 183 posts, RR: 0
Posted (8 years 3 weeks 6 days ago) and read 2212 times:

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
8 replies: All unread, jump to last
 
User currently offlineN231YE From , joined Dec 1969, posts, RR:
Reply 1, posted (8 years 3 weeks 6 days ago) and read 2205 times:

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


User currently offlineFLY2HMO From , joined Dec 1969, posts, RR:
Reply 2, posted (8 years 3 weeks 6 days ago) and read 2203 times:

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 

User currently offlineBuzz From United States of America, joined Nov 1999, 697 posts, RR: 21
Reply 3, posted (8 years 3 weeks 5 days 19 hours ago) and read 2162 times:

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


User currently offlineKELPkid From United States of America, joined Nov 2005, 6428 posts, RR: 3
Reply 4, posted (8 years 3 weeks 5 days 19 hours ago) and read 2160 times:

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 :-)
User currently offlineN231YE From , joined Dec 1969, posts, RR:
Reply 5, posted (8 years 3 weeks 5 days 10 hours ago) and read 2129 times:

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.


User currently offlinePope From , joined Dec 1969, posts, RR:
Reply 6, posted (8 years 3 weeks 3 days ago) and read 2079 times:

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.


User currently offlinePope From , joined Dec 1969, posts, RR:
Reply 7, posted (8 years 3 weeks 3 days ago) and read 2078 times:

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.


User currently offlineN231YE From , joined Dec 1969, posts, RR:
Reply 8, posted (8 years 3 weeks 3 days ago) and read 2076 times:

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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