Avgas octane rating?

**thorns** · 7th January 2015, 13:43

Have a 2 stroke that has been run/jetted for straight AVGAS. What is the typical AVGAS ocatne rating in NZ? I seem to get varying numbers between 100 and 110 octane.

How much of a difference would it make if I ran it on 98?
Or as a alternative, what about 98 with an octane booster if 98 wouldn't be great for it?

**scott411** · 7th January 2015, 13:55

Originally Posted by thorns

Have a 2 stroke that has been run/jetted for straight AVGAS. What is the typical AVGAS ocatne rating in NZ? I seem to get varying numbers between 100 and 110 octane.

How much of a difference would it make if I ran it on 98?
Or as a alternative, what about 98 with an octane booster if 98 wouldn't be great for it?

i always got told it was 100, but not really sure, i ran some of my 125's on 50/50 mix of avgas and 91, you run the avgas to get the lead in it that is very good at preventing detonation, and the 91 to get the burn rate up, (avgas is designed to run at low RPM's,

it can be a bit of a trick to get a bike back running on 98, but it you are not hammering it, then it might not make a difference,

EDIT:

more info
http://www.shell.com/global/products...-30071515.html

looks like it is 100 MON rating,

**thorns** · 8th January 2015, 07:41

Thanks Scott.

Found there is a helicopter depot near work which sells AVGAS, so will try my luck there and see if they can hook me up, I figure I may as well stick to what the bike has been running if I can find a reliable source.

**scott411** · 8th January 2015, 08:57

we were lucky in pukekohe as one of the gas stations sold it, (and put it as deisel on the fuel card)

some places will nto sell it, and some require you to produce a race licence to prove you are not using it on the road, but most are ok if you are putting it into gas cans

**FJRider** · 8th January 2015, 19:04

http://www.shell.com/global/products...pes/avgas.html

Your welcome ...

**neil_cb125t** · 9th January 2015, 07:37

Originally Posted by thorns

Have a 2 stroke that has been run/jetted for straight AVGAS. What is the typical AVGAS ocatne rating in NZ? I seem to get varying numbers between 100 and 110 octane.

How much of a difference would it make if I ran it on 98?
Or as a alternative, what about 98 with an octane booster if 98 wouldn't be great for it?

Everything on this thread is correct - the reason you heard between 100 and 110 octane is becuase there actually is 100 and 110 octane rated av gas.....hahahaha

NZ doesnt stock/use 110 octane Avy as far as I know....

The 50/50 blend in theory is good. octane booster will make you go faster, becuase your wallet will be lighter.

**Flip** · 9th January 2015, 08:11

Jetted for AV gas...... Really?

The air fuel ratio for all petrol is the almost exactly the same and well within the ability of any carburettor to maintain.

**scott411** · 9th January 2015, 13:14

Originally Posted by Flip

Jetted for AV gas...... Really?

The air fuel ratio for all petrol is the almost exactly the same and well within the ability of any carburettor to maintain.

in my expereince 2 stroke motocross bikes that are in a high state of tune (noramlly raised compression from standard) can be quite a bit differently jetted for 98 unleaded to av gas, AV gas is much easier to get rid of the detonation, but you can do it with 98 if you want,

**pete-blen** · 9th January 2015, 16:36

Avgas = 100 octane...
NO fuel / gasoline can have more than 103 octane unless it is
blended with something ealse...

Petrol = gasoline mixed with oil.... ie 2 stroke mix...
Gasoline for 4 strokes...
Petrol for 2 strokes....