Avgas

[JohnReid]

Does anyone know if the term avgas was used in WW1 or when it was introduced in advertising?Cheers! John.

[MikeW]

I think Avgas first appeared in the 1950s, a high octane fuel developed for aircraft but very useful mixed with pump petrol when used with high compression motorbikes such as a BSA Gold Star!!

In WW1 the octane rating of the petrol was very low indeed, I have a figure written down somewhere if you are that keen.


Mike

[JohnReid]

Thanks Mike!So I guess Petrol or Gasoline would be the proper terminology.Cheers! John.

MikeW: I think Avgas first appeared in the 1950s, a high octane fuel developed for aircraft but very useful mixed with pump petrol when used with high compression motorbikes such as a BSA Gold Star!!

In WW1 the octane rating of the petrol was very low indeed, I have a figure written down somewhere if you are that keen.

Mike

I, for one, am very curious as to what the octane rating of their fuels was in TGW!... Can you imagine the change in performance with those old crates if they had been burning 100LL!... Could those old engines even have been able to handle it???

"Prost!"

[Jim]

Simply going to a higher octane rating does little for an engine's performance and in most cases it reduces it since it will not burn completely at the lower compression ratios that most engines are designed for. The key to increasing performance is redesigning an engine to give it increased compression which then allows higher octane fuel to burn completely and providing an overall increase in power.

[Jim]

Modern day avgas also has dyes added to it so you know whether you have the right fuel in your tanks. One of the things a pilot does before takeoff is to draw a small sample of gas from the bottom of each tank and do three things - look at the color (red, blue, purple, green, etc.) to be sure you have the correct formulation for your particular engine, check to see that there is no water in the sample, and give it a quick sniff to make sure it smells right (you don't want to discover some bird brain filled your propellor aircraft with JP-5 or JP-8 jet fuel (kerosene) for example).

[MikeW]

Ok, up until the summer of 1917, all aviation petrol in the UK was supplied by Shell from crude oils sourced in Sumatra and Borneo, and thought to have an octane rating of around 70.

From the summer of 1917, a lot of aviation fuel started to be supplied from the USA, blended from paraffinic Pennsylvania and Mid-continent crudes. This fuel had an octane rating of 45 to 55 and caused the flying services no end of grief - precombustion and detonation giving rise to serious overheating and loss of power.


Mike

We used avgas in our M4 tanks equipped with the Continental radial engine. It didn't work so good, tho, when we put it in the gas tank of a captured BMW. It became a basket case.
A 314 Boeing Clipper used regular automobile gas on one of its stops on its west-bound trip away from Japanese capture and seemed to have no ill effects on the engines.

Jim: Simply going to a higher octane rating does little for an engine's performance and in most cases it reduces it since it will not burn completely at the lower compression ratios that most engines are designed for. The key to increasing performance is redesigning an engine to give it increased compression which then allows higher octane fuel to burn completely and providing an overall increase in power.

So, the older AC engines were designed with "lower" compression?... This I didn't know! More modern AC engines (and automobile engines), for the most part, are designed with higher compression than their older "forefathers" as higher octane fuel DEFINITELY makes a difference with regards to power output... Simple domestic example: We own an Olds Alero. When you run 87 octane in her, she'll run but she doesn't necessarily "like it" (sluggish... poor gas milage, etc...)... However, when running 100LL through her you'd think she should have been made with a set of wings she's so quick! And the same has held true for ALL of the aircraft we've owned over the years! Sure, increased compression is nothing to shake a stick at... but higher octane fuel DOES make a difference!

"Prost!"

[Jim]

I agree that higher octane definitely makes a difference, but only in an engine that is designed for it. Putting it in an engine that is not designed for it is a waste since all you get is unburned gas. I don't know about your particular model of car and the engine design, but in a typical modern auto you not only get either no increase or lower performance but you also you get the extra problem of the unburned gas getting into the catalytic converter and burning it out.