AV gas opionions 100 octane low lead

Mac

Mac

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I have found I can purchase AV gas 100ll at my local airport $4.10 a gallon. Not a bad price compared to race fuel. I'm considering mixing 50/50 premium and 100. I run a Viper 780 with mega power heads @152-153 PSI and .050 squish. I am looking for a little extra protection from detonation. I'm thinking premium fuel only with ethanol at this compression will detonate. Any thoughts? Any concerns?
 
Pros + Cons to Remember about 100 LL AV Gas:

Cons:

-it has a lower specific gravity then pump fuel[means your engine will run leaner the more pure AV gas/ pump fuel ratio you run]
-it is designed and blended to run in engines that have "coffee can" sized pistons and cylinders at a max RPM of less then 4000
- it is VERY high lead content[it gets its octane primarily from the tetraethyl lead] and can leave deposits on plugs ect
-it was designed to be used in air cooled 4 strokes not 2 strokes
-sleds, bikes, boats, cars, ect don't start as well when using AV gas...especially in the winter

Pros:
- it is a very high quality fuel[ super premium from back in the leaded fuel era]My 1970 Mach 1 loved this stuff!!!
-it is 100 octane minimum...guarenteed
-it blends well with normal pump fuels

Recommendations[from experience using it]:

-don't run 100% AV gas in a 2 stroke. [My 81 SRX Mod actually will not run properly at high RPM on pure AV]
-50 % blend AV to 91 Octane pump fuel is the max I would suggest...that gives you better then 96 octane...BUT JET ACCORDINGLY
-The blend I have had very good luck with is - 2 gallons AV 100 LL to 3 gallons premium[91 octane NO ETHONAL] that ends up at about 94-95 octane[ R+M/ 2 ] but again WATCH YOUR JETTING

JM.02c
 
just adding to bobs post,most people don't know that leaded fuel will extend two stroke engine life. The connecting rod big end bearings last twice as long on leaded fuel.

One simple trick is to mix unleaded auto gas with AVGAS 50-50 or so. Resulting in about 1g lead per gal (that's enough).

Lead can form deposits in the combustion chamber and spark plugs, so fouling becomes more of an issue with leaded fuels. Make sure not to use too much lead if your engine is prone to fouling. Otherwise, you are good to go.

AVGAS is a fantastic fuel for certain applications. It works very well in larger two strokes. Plus, it contains NO ALCOHOL. So engine life, jetting and performance are all properly managed using AVGAS.

However, it does not provide the worlds best throttle response in smaller, high RPM two strokes. There are many reasons for this. But, larger engines, like sno toys will do perfectly well on AVGAS,TCP can be added to leaded fuel to minimize combustion chamber deposits if you are running it long term. Just a spike of leaded, or one run of leftover race fuel is nothing to worry about. There is a lot of info on the web about leaded fuels. Personal plane sites are a good start.
 
My buds run avgas in there modded to the nutz big bore 975 cc mach Z,s. No detonation failures in 2 winters.
 
Just a side note[if my memory serves me well]...the 1977 SRX 440 factory fuel recommendations were: [unblended] 100/130 AV gas premixed at 16:1. My 1979 SRX did not mind this but my 1981 SRX does not run well on pure AV gas!??
 
Thanks for the reply's everyone. Tony " 100% use it" are you saying use AV gas full strength or are you saying you agree 50/50 mix.
 
daman said:
I would not run full strength,performance could slack,id cut it 50/50 60/40 MAX!! $.02
Click to expand...

I agree...unless you are running higher then 13.0:1[thats high for trail use] uncorrected compression ratio, the 50/50 blend should be good. If you have a higher uncorrected comp ratio then that you probably should be looking at race fuel. JM.02c
 
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