AVgas, Best Long Term Fuel Storage w/o Drawbacks?

[racer12306]

Originally Posted By: lars11
and this issue with health. If you have kids around when running your ope, gennys, etc -do not- use avgas. It is a hazard to childern with no actual safe lowest exposure.

Then, do not put it in anything with a catalyzer. It will be gone basically immediately.


Guess I'm screwed because my Dad ran AVGAS in his race car for a year or two when I was a kid.

Definitely not immediately, but it will wear it out much quicker than no lead gas.

 

[Cujet]

Just a little update:

Swift Fuels now has a 94 octane unleaded aviation fuel available at certain airports. (98 R+M/2)(that's the street pump method of rating we are all familiar with)

It's approved for use in a huge number of aviation engines, it's reasonably priced (about $4.25 at Sebring airport) and it never goes bad. It is harmless to all rubbers and is ethanol free. Race car guys are purchasing it like crazy, as it is working exceptionally well in many race cars, at a fraction of the cost of race fuel.

Perfect for use in OPE. Will not gum up carbs either.

 

[Ohle_Manezzini]

Originally Posted By: racer12306
Originally Posted By: CrAlt
Originally Posted By: Best F100

* 1) Using the 100 octane, AVgas, I can expect faster startups and better throttle response.



Thats not how octane works.

Using 100 in a small engine that is designed to run on 85 wont give you better performance unless you bump the compression or make other changes.


And it will actually be the opposite effect, it will be harder to start.


Octane rating is a resistance to detonation, in resisting the detonation, you are also resisting the desired burn.


Nope, it resists pre detonation, once the spark is out, it will burn. Avgas has better light parts to assure a better start, when fresh.

 

[The_Eric]

Originally Posted By: cappilot

Over the past many years I've used unleaded auto fuel in three different airplanes that had engines originally certified to use 80/87 avgas. Routine instances of plug fouling simply disappeared, and hundreds of hours of engine operation did not show unexpected damage to valves or valve seats.

With luck, a reasonable lead-free fuel is coming in the near future for general aviation. I can hardly wait.


I've often wondered why we're still using leaded fuel in something like a plane, where reliability is critical. If it is the source of as many issues as you say, it should have been a no-brainer to remove lead a long time ago. Especially when they seem to respond so well to mo-gas or other lead free fuels. I've read plenty of chatter from other pilots who say the same as you and in fact, they're claiming their engines run better all together on fuels other than 100LL.

 

[Cujet]

Originally Posted By: The_Eric


I've often wondered why we're still using leaded fuel in something like a plane, where reliability is critical. If it is the source of as many issues as you say, it should have been a no-brainer to remove lead a long time ago. Especially when they seem to respond so well to mo-gas or other lead free fuels. I've read plenty of chatter from other pilots who say the same as you and in fact, they're claiming their engines run better all together on fuels other than 100LL.


Detonation resistance is critical in air cooled, hot running, aircraft engines, as any significant detonation leads to outright engine destruction. Remember, cylinder head temps can and do reach 500 deg F in high performance, highly loaded, big bore, aircraft engines.

Unleaded fuels, thus far, have been completely and utterly unable to provide an adequate margin of detonation resistance. While that seems like an absurd statement, consider the requirements. We can, for example use Zylene or 114 octane Toluene to raise octane into the range of acceptability. But getting it started and atomized is nearly impossible without first heating the fuel.

Swift fuels produced a binary fuel of trimethylbenzine (mesitylene) and isopentane, blended to produce about 100+ octane. It meets all of the aviation requirements for detonation resistance. However, Embry-Riddle reported that getting aircraft started on chilly mornings in Florida with 100SF was difficult. More work and tweaking may be necessary.

The bottom line is that up until very recently, it has been near impossible to produce a high octane, non ethanol, viable unleaded.

In fact, I'm still not sure there is a viable replacement.

Certainly, VP Racing fuels produces a number of high octane, non ethanol fuels. None of them are viable aviation fuels, and none of them are high enough octane under high temperature, high boost, big bore conditions. Remember that bigger bores are far more sensitive and likely to experience to detonation.

Even 100LL is sometimes not good enough in some "pedestrian" aircraft engines. I had this happen to me:

 

[The_Eric]

Cujet, thanks for taking the time to explain! I had asked this question before and didn't get what I thought was a clear answer- but this... spells it out quite nicely.

I knew that with an increase in bore (piston head area), detonation is increasingly an issue but didn't fully understand lead's role in keeping it at bay (I had always solely attributed that to octane alone). In fact I still don't but you have given me a better idea.

 

[Ramblejam]

Originally Posted By: Cujet
In fact, I'm still not sure there is a viable replacement.

Had a look at PAFI Phase II fuels?

 

[Ohle_Manezzini]

Originally Posted By: Cujet
I had this happen to me:

Were you trying to save some fuel here?
I ask because 99% of the times, this hole is result of lean operation at high output. Too much air, too little fuel. Too high CHT and EGT. Wouldn't You need to push the mixture lever a little further?
I mean, that's really a detonation result?

 

[punisher]

Don't have experience with aviation piston engines, but on automotive apps, that hole in the piston is a sign of preignition, not detonation. Detonation usually eats the edge of the piston underneath the intake valve, and eventually sticks the top ring which leads to galling, and gradual failure. Preignition is a really quick death..............usually.

 

[Ohle_Manezzini]

You can have that hole, without preignition neitherdetonation, just a higher combustion flame heat of lean operation. It melts the aluminum crown at near wot condition.

 

[Cujet]

On some aircraft engines, the middle of the piston is unable to conduct the heat fast enough. Hence the hole. The top ring land and surrounding area are often also damaged.

Generally caused by high pressures and temperatures. Once detonation starts, it is often self sustaining due to the rapidly climbing CHT and decreasing EGT.

Remember, an aircraft engine may be at full power or better stated, full BMEP (as RPM may be reduced, but not cylinder pressure) for quite some time, often for many hours. This is very unlike automotive operation.

 

[hatt]

Originally Posted By: Cujet
Just a little update:

Swift Fuels now has a 94 octane unleaded aviation fuel available at certain airports. (98 R+M/2)(that's the street pump method of rating we are all familiar with)

It's approved for use in a huge number of aviation engines, it's reasonably priced (about $4.25 at Sebring airport) and it never goes bad. It is harmless to all rubbers and is ethanol free. Race car guys are purchasing it like crazy, as it is working exceptionally well in many race cars, at a fraction of the cost of race fuel.

Perfect for use in OPE. Will not gum up carbs either.
Nice!

 

[Ramblejam]

Swift 94 is suitable for around 65% of GA. It's a transition fuel while PAFI Phase II proceeds towards authorization.