Aviator 902S

Yup, the primary purpose of lead in fuel is to boost octane, but also provided the added benefit of lubrication for valves and anything else it came in contact with. It boosted the octane rating of premium avgas to 130 (rich mixture) and 100 (lean mixture), hence the designation "100/130. The lower compression engines typically used 80/87. But the blue 100LL was the fuel formulated to replace 100/130 as the preferred fuel for all aircraft piston engines, including higher-compression engines.

In fact, both 80/87 and 100/130 are rare these days. Most if not all airports only supply the 100LL, which in spite of its "low lead" designation, contains about three times as much lead as regular leaded automotive fuel used to have 30 years ago.

This is sufficient to provide adequate octane rating for higher compression aircraft engines, yet is still compatible with lower-compression aircraft engines since these engines have the same larger running clearances as higher-compression aircraft engines. These running clearances allow lead deposits to flake off and be expelled rather than clog rings and valves. Spark plugs still have to be sand-blasted regularly though.

Hyper4mance2k

iTrader: (40)

so would lead be bad for a rotary? and would kerosene ignight if mixed with gas. I'm gonna make a super fuel. It'll be gas, redline 2-stroke, kerosene, and some lead additive.

Aviator 902S

LOL... Yes, lead would be bad for a rotary. Plugs everything up and fouls spark plugs. Sorry, but the aviation community beat you to the punch with your "super fuel." It's called Jet B and it's a mix of Jet-A (kerosene-based) and avgas.

rotary emotions

If lead was bad in a rotary, wouldn't pre-unleaded cars (aka all first gens etc) have had problems? I'm not sure about the USA, but overhere unleaded fuel is available since a limited time only (well, what's limited... 15-20 years or something,, I don't remember ), so before, we all HAD to use leaded. When unleaded became available, many people driving older cars had to keep using leaded. So undoubtly, many rotary owners simply kept using the leaded stuff aswell. Many 12A engines overhere have many kilometers on them, and I'm pretty sure a lot of those have been ran on leaded. If this was really bad, they couldn't do 150k miles or more, would they?
I'm sure it's not really all that important. It's useless to pour in leaded fuel, for sure, but not really bad. As a matter of fact, unless you are running high boost levels, a rotary will cope with about any fuel. Wether it's 80 or 105octane, leaded or not, it simply doesn't really matter. Later EFI and turbo engines will have some more problems, but our old carburated 12A and 13B engines will keep going as long as you put something in there that looks and smells like gas, and change the oil from time to time. Without a doubt a 12A is the most reliable rotary engine ever.

Aviator 902S

Yeah, rotaries in the 70s ran on leaded fuel, albiet, the lower octane stuff with less lead than premium had back then. They didn't officially switch to unleaded until after Mazda got rid of the thermal reactors used on the SAs and replaced them with catalytic converters. But premium leaded automotive fuel at that time still only contained about a third (if even that) the quantity of lead that is found in 100LL aviation fuel.

Still, even this reduced amount of lead in auto fuel at that time would leave deposits on plugs and in seals given enough time, but would still run fine with routine maintenance. Lead deposits didn't accumulate fast enough to become a major problem, and much of this lead would eventually end up going out the exhaust ports.

But aviation fuel even now contains enough lead to quickly overwhelm the internals of not only rotaries but also modern closer-running-clearance boingers. I know of two Diamond Katana light aircraft powered by Rotax 912 engines (with the same close running clearances as most auto engines) that cratered en route to Victoria, BC from Vancouver several years ago. A steady diet of 100LL caused the pistons to seize at the bottom of the stroke. The rotating engine mass then proceded to push them upward anyway, ripping the jugs right off the engine. Fortunately the flight instructor (the same one in each incident) managed to dead-stick the plane into Victoria International.

These engines had for years run on auto gas in homebuilt aircraft and had an excellent reputation for reliability and economy, and were even certified for use in production aircraft later on. But a steady diet of 100LL changed everything. Many flying clubs that use these aircraft now run them on auto gas most of the time, with one fill-up of avgas per week. This is legal as long as the aircraft is properly STC'd.

Hyper4mance2k

iTrader: (40)

so in theory this fuel will make more power than pump gas?

Clearkut

iTrader: (1)

92 with 10% ethanol, the car just doesnt seem the same without it

Aviator 902S

"In theory,"yes--- given that jet-A fuel contains more BTUs per given weight. But like deisel fuel, jet fuel is kerosene-based. Until deisel rotaries are produced that can handle the associated high compression without detonation we're stuck with gasoline, natural gas and maybe hydrogen fuels for all spark-ignition type internal combustion engines.

Pele

iTrader: (28)

Can Kerosene and gasoline be mixed to increase octane for boosted engines?

Kerosine seems to light easily in the little home heaters. Why's it so hard to light off with a spark plug?

Manntis

In the hierarchy of refined petroleum products from highest to lowest (from a gaseous state, then liquid, to solid) are: natural gas; "wet" natural gas; high-octane aviation gasoline; automotive gasoline; finished kerosene; home heating oil; diesel fuel; industrial fuel oil; finished lubricating oils; waxes and paraffins; gas oil; coke and finally asphalt. Also moving from highest to lowest, the viscosity, or stiffness, of the refined product increases. For example, at room temperature, automotive gasoline flows much more freely than finished lubricating oils.

Unlike # 4 Diesel Fuel, which is thick, Kerosene is too thin to work well as an engine fuel (notice it comes before diesel in the hierarchy). The thickness of the diesel fuel itself acts as a lubricant to prevent wear of the engine's fuel injectors, which is why some oldtimers still refer to it as "Diesel Oil." Adding a common lubricant to Kerosene usually decreases its ignition quality.

Thus running a kerosene based fuel in a GSL-SE would be a bad idea (possible seized injectors) and in a 12A is no great shakes either.

Aviator 902S

Reminds me of a thread a month or so ago in the 1st gen specific forum. A guy in Washington state had just filled his car and only made it a few blocks before the car began running rough and then quitting altogether. I asked if it were possible that he may have inadvertently filled up with deisel. That turned out to be exactly the case.