Hi there, I'm new to the racing game and have been soaking up all the bits of information I can that might of use in my latest interest. I understand that Avgas has advantages over pump fuel, one of which is that it has got lead in it and as a result, a lubricating effect, benefiting the valves. What I'd like clarified is which fuel burns the hottest and are there any negatives in using the higher octane stuff?...thanks
Bazza, Please go to the web site I am listing in this post. I work for a major oil company and was surprised about the info I read. By the way this info was previosly posted by another BritBike member. My '66 A65L runs excellent on unleaded 93 octane once I got the carbs, plugs & timing correct according to spec & from tips found here on this forum.
...Wow, great site thankyou, so now we know, not much difference if any between the different companies products. I guess it's the same story in my part of the world. Looks like I'll be doing what Dig advised in a previous post and adding a little Avgas to my tank of pump gas to provide a little lead and assist with reading the sparkplug...cheers, Barry.
Re: Aviation gas verses pump petrol#4695 09/12/052:24 pm09/12/052:24 pm
A couple of years ago we discovered the UK "4 Star", gas was crap. I/we were thinking it was the 'good' fuel to use in our Goldies. I was having strange symptoms and hard starting using the stuff. By chance I met up with a retired petro engineer on the IOM up at Creg na Bah while 'kicking tires'. He asked me if we were getting along with the UK fuel as he knew it was a different 'brew' from the US gas. I mentioned the hard starting problem I had. He explained the "4 Star", was actually a lower octaine than the "No lead", and was made available for the older engines in the UK that still had cast iron ie non insert valve seats. Because of it's higher cost was seldom being used. Consequently the fuel in the station tanks was old/stale and out of date which made it all the worse to use in a high perf engine. So we used premium 'no lead' with no further issues.
I sure prefer using "Race gas", vs "Av gas", in a racer. We use Sunoco 100 octane with good results here. Kinda expensive at US$5+/gal, but ....
The US "100 octane Low lead", AV gas actually has a higher lead content than the older leaded gas we could buy from the pump in the olden days. But as it's formulated for low compression and slow turning aircraft engines it actually burns slower than no lead pump gas and perhaps makes less power??? hmmm I do know some/many(?) guys mix it with pump gas for racing and high compresh road bikes.
Alcohol would be the fuel of choice if permitted as it runs so cool and makes more power with the proper set up. But a hurrah purging the fuel system as Must be done after every event, as it's nasty and corrosive.
dave - NV
Re: Aviation gas verses pump petrol#4699 09/13/0512:42 am09/13/0512:42 am
Bazza, I used a 3 to 1 mixture of 93 octane pump gas and 110 octance leaded racing fuel. That probably made my octane about 97. The bike (1966 A65L)would pink miserably without it. I upgraded to a Boyer ignition and new carbs and it does just fine on 93 octane. The Boyer has a less agressive advance curve when compared to the 4ca points which were cumbersome to time both cylinders.
Re: Aviation gas verses pump petrol#4700 09/13/052:52 am09/13/052:52 am