aviation fuel

[John D.]

Here is one you will all enjoy.
At Fall Carlisle a friend and customer came up to me and asked me a simple question about Aviation fuel. He said to me. JD at what temperature does Av gas boil at?
I said why do you ask this question Joe. He said he heard it boiled at only 160 degrees.
I said that is totally impossible. No way does it boil at such a low temperature. H
He said he got it from an authority and the guy insists that 160 is the boiling point.
Well the known "authority" was correct. It certainly does boil at 160 degrees.
Now for the punch line. 160Centigrade!!!!!
My friend called me this morning and told me that. We had a good laugh.

Convert the 160 C into Fahrenheit and you get 320 degrees. If you take 90% of 320 you get 288 degrees.
That's why my FI 63, the LWC can sit there and idle like a clock in 93 degree hit without missing a beat.

The weight of the aviation fuel in an aircraft also effects boiling point as per info I got on the internet.

[Bruce B.]

Re: aviation fuel

John,
Interesting post.
Now if you want to really get into the boiling point thing then you need to take altitude into consideration.
For example, pure water at atmospheric pressure (sea level) boils at 212 degrees F.
At 5000 feet it boils at 203 degrees F.
And at 10,000 feet it boils at 192 degrees F.
Therefore gasoline should follow the trend of lowering the boilpoint with altitude.
So if you drive your 63 FI car up to the top of Pikes Peak on a 90 degree day it might vapor lock due to the depressed boiling point.
The other major factor in boiling point in gas is additives and contamination.
Bruce B

[Duke W.]

Re: aviation fuel

Any gasoline - avgas, mogas - whatever - is composed of a large number of hydrocarbon species, which have different boiling points.

THEREFORE NO GASOLINE HAS A SPECIFIC BOILING POINT!!!

The boiling characteristics of gasolines are described by their "distillation curves", and typically the 10, 50 and 90 percent boiling points (which are the points where 10, 50, and 90 percent of the components by mass are at or above their boiling points) are specified if the whole curve is not displayed.

A low ten percent boiling point is required for good starting and may be as low as 90-100F in cold winter weather. Fifty percent points are typically 160-200F, which might be called an "average", and typical 90 percent points may be 300F or higher.

Avgas typically has a higher distillation curve than any mogas blend to resist vapor lock at altitude, and for this reason it can cause harder starting in a car, particularly in cold weather, but will resist the vapor lock problem that some vintage engines have with modern mogas.

So now that you are "educated" you can explain it to your customer. It's not simple - no gasoline has a single boiling point like water or alcohol, but it's not rocket science either.

All liquids have a "vapor pressure" that increases with temperature. At 212F the vapor pressure of water is equal to standard sea level pressure, so it boils. A liquid boils when its vapor pressure equals the surrounding pressure, which is why water and other liquids boil at lower temperature as altitude increases.

So, knowing the above, what is the boiling temperature of water in outer space?

Duke

[Ian G.]

Re: aviation fuel

Does anyone know what the "typical" boiling point would be for leaded racing fuel, or would I just need to ask the station that sells it?

[Michael G.]

Re: aviation fuel

Trick question, but I'll take a shot at it: ( Thermodynamics, physics, and pchem were many years ago, so take this with a grain of salt... ) Since in deep space, pressure is essentially zero, (and space itself has no temperature) water will boil immediately at any temperature at which it has enough energy and some vapor pressure. If liquid water were expelled into deep space by a rocket ship, part of it would have enough energy to boil instantly at whatever temperature the water was when ejected. The remainder would have its heat sucked out and cool to near absolute zero, freeze, then sublimate into vapor as more energy was absorbed. Maybe...

Mike

[Duke W.]

Re: aviation fuel

Correct! Liquids can't exist (steady state) in a vacuum, but liquids with very low vapor pressure curves, like mercury, might take some time to completely boil off, where a relatively volatile compound like liquid water will boil off very fast.

If your space suit fails, your blood will boil - not a nice way to go!

Duke

[Duke W.]

Re: aviation fuel

Does anyone know what the "typical" boiling point would be for leaded racing fuel, or would I just need to ask the station that sells it?

I guess you didn't read my post. There is no "typical" boiling point for any gasoline blend. The question has no answer.

The blender might have a spec sheet (or it might be on the Web) that shows the entire distillation curve or at least some points key points like 10, 50, and 90 percent.

If you ask Bubba who works there, you will probably get a bubba type clueless answer.

The proper question is: What is the distillation curve - either the entire curve in graphical form or some data points, like 10, 50, 90 percent?

Duke

[Ian G.]

Re: aviation fuel

I always wondered why they say your blood would boil in outer space

Hey Duke, I did read you post, but I was hoping there's some average or typical formula they tend to use. I imagine I wont be able to tell unless I find out who manufactures that gas...

[Joe L.]

Re: aviation fuel

Here is one you will all enjoy.
At Fall Carlisle a friend and customer came up to me and asked me a simple question about Aviation fuel. He said to me. JD at what temperature does Av gas boil at?
I said why do you ask this question Joe. He said he heard it boiled at only 160 degrees.
I said that is totally impossible. No way does it boil at such a low temperature. H
He said he got it from an authority and the guy insists that 160 is the boiling point.
Well the known "authority" was correct. It certainly does boil at 160 degrees.
Now for the punch line. 160Centigrade!!!!!
My friend called me this morning and told me that. We had a good laugh.

Convert the 160 C into Fahrenheit and you get 320 degrees. If you take 90% of 320 you get 288 degrees.
That's why my FI 63, the LWC can sit there and idle like a clock in 93 degree hit without missing a beat.

The weight of the aviation fuel in an aircraft also effects boiling point as per info I got on the internet.

John-----


I don't think so. As Duke mentions, gasoline is a MIXTURE of different hydrocarbons which boil at different temperatures. However, I don't think that ANY of them, individually, is going to have a boiling point of 160 degrees C. Water boils at 100 degrees C and I would expect all of the gasoline components to boil below that temperature. It's just a guess, though.

[Tom P.]

Re: aviation fuel

I don't give a good doggone crap about any of those gasoline boiling, evaporating, thermomechanics, pchem, etc, etc, etc characteristics!!!!!!!!!
All I care about is finding a GOOD gasoline that will work compatably with my FI!!!!!!!!!!!
So far, the best I've come up with is 100LL Avgas.

[Russ U.]

Re: aviation fuel

Does anyone know what the "typical" boiling point would be for leaded racing fuel, or would I just need to ask the station that sells it?

Sunoco post the various 10%, 50% and 90% "evaporation" points for leaded racing gas blends on their website:

Sunoco Evaporation Points

Each fuel has a separate webpage (look at the links under the table). The evaporation points are listed along with a bunch of other info.

I was quite surprised by the different evaporation points for the various blends. Some of the blends are not much different than the gas you can buy at the local station. But some of the blends have much higher evaporation points.

Russ

[Bruce B.]

Re: aviation fuel

Tom,
I broke in my engine with a 4360 unit using 100LL Avgas.
Since breakin I have been using Shell premium which in my area (southern Ohio) contains no ethanol and the engine has run great, started hot and cold, for 1000 miles with no problems.

[Loren L.]

Re: aviation fuel

I don't give a good doggone crap about any of those gasoline boiling, evaporating, thermomechanics, pchem, etc, etc, etc characteristics!!!!!!!!!
All I care about is finding a GOOD gasoline that will work compatably with my FI!!!!!!!!!!!
So far, the best I've come up with is 100LL Avgas.

The Camoradi Corvette has functioned very nicely for 10 years on one-half 100 LL av gas and one=half unleaded Super Premium. I suspect the av LL has a little more "Stabil-like" stuff included/

[Tom P.]

Re: aviation fuel

No more that what I drive the 56, I don't mind too much buying 10-12gal Avgas at a time.
About every other Sat when I go to work on the plane, I take two 5gal gas cans and get them full to the cap with 100LL which will total a little over 11gal.

[Terry D.]

Re: aviation fuel

Tom
Are you going to run big or small block chevies in that old bird? LOL, just kidding, nice project, and I thought restoring a Corvette was expensive and time consuming.
Terry