Uk people - AVGas.

[PatrickIreland]

Just been speaking to a pilot fella at work about AVGas - I thought it would be an insane price, but apparently it's actually only 129p/litre - less than a third more than supermarket petrol!
Also no restrictions on buying it - just roll up to your nearest small airport with a jerry can and fill up. I might go and get some this weekend, I'm only 10 minutes from the airport... 100octane (RON, I think that's about 110 US equivalent) and no ethanol...

 

[cherrycutter]

I use 100 low lead av gas. Saw will run a bit richer than previously. 110 might be a bit too much. Contrary to some peoples belief higher octane feul or petrol as you call it is more difficult to ignite. My buddy is an aircraft engine engineer who explained to me that if your spark isn't hot enough you will gum up your combustion chamber with unburnt lead. Happy sawing

 

[PatrickIreland]

I use 100 low lead av gas. Saw will run a bit richer than previously. 110 might be a bit too much. Contrary to some peoples belief higher octane feul or petrol as you call it is more difficult to ignite. My buddy is an aircraft engine engineer who explained to me that if your spark isn't hot enough you will gum up your combustion chamber with unburnt lead. Happy sawing

Don't worry, I know all about octane ratings - car nut here! It's very low lead stuff, so will be fine once the saw is tuned for it...

 

[blsnelling]

My experience is that the saw will make measurably less power with 100LL than 93 octane gasoline.

 

[PatrickIreland]

My experience is that the saw will make measurably less power with 100LL than 93 octane gasoline.

Unless, I assume, the ignition timing is advanced?

I have a pretty limited knowledge of 2T engines, but 4-strokes I understand perfectly - does the same principle apply?

To be honest, I don't actually NEED the power anyway (although being an engine nut, I still want it!), the longer storage time and absence of Ethanol are what I find attractive.

 

[davido30093]

Backwards

"100octane (RON, I think that's about 110 US equivalent) and no ethanol..."


100 octane RON would be about 96 octane US (R+M/2)

 

[blsnelling]

To be honest, I don't actually NEED the power anyway (although being an engine nut, I still want it!), the longer storage time and absence of Ethanol are what I find attractive.

Right there is a good reason to run it, and is why it's in my oldies. I also find that it often doesn't idle as well.

 

[PatrickIreland]

"100octane (RON, I think that's about 110 US equivalent) and no ethanol..."


100 octane RON would be about 96 octane US (R+M/2)

Actually, I i'm not even sure how the AVGas is rated - I assumed he was quoting it in RON as it's the European standard - is AVGas possibly rated in MON as an international standard?

 

[PatrickIreland]

A quick flick of google seems to say that they are one and the same, no matter where it is bought - 100LL stuff has the same octane rating no matter where you buy it. Good!

 

[leeha]

I've been running 100LL for quite a while and
noticed no loss in power. But you do have to retune
the carb. High and Low side not much just a tweak.



Lee

 

[Dibbs]

AV Gas is for engines with high compression ratios, some of the MotoX/Super Moto men use it and some use Shell Racing fuel, they have a higher octane rating and can take more "squish" before it will ignite without the need for a spark plug (Pre-igniting/Pinking).
They are both very "clean" as far as fuels go when burned, but, to actually gain power from it you would need to reduce the volume of your combustion chamber/make your own two piece cylinder top/lathe your piston crown dome shaped, mill the bottom of the cylinder and modify ports and have the ability to change your ignition timing.
So gains with AV Gas would require a fair bit of work,work or work to be carried out on your saw to see any real benefit.

But...... If you did........

 

[demographic]

From reading up about motorcycles I understand that in order to get the extra power from avgas you would have to alter the ignition timing and maybe even the compression ratio?
On the bike changing the timing is a simple matter of moving the stator backplate round slightly, can't say I have even looked at my saws stator backplate as yet.
Without changing the ignition timing I thought you actually lost power.
Pretty sure thats what Rich Rohrich (might be spelt wrong but its been a long time since I was on there) posted over on Dirtridernet.

I never saw the point in all the hassle for my 500 two stroke motorbike so can't see me doing it for a chainsaw unless I was into some form of competition.

 

[rxe]

Optimax for me, all the way. Works fine, idles fine, never kept it long enough to find a problem. It's quite good in the car as well.....