Avgas

[borris]

Simple, succinct, cogent, easy to understand, not condescending. I am digging this Borris fella.

He's related to fabr somehow.

[Maxine]

If you think you need that high of an octane rating you would be better off to buy 100 octane race gas.  Avgas is not a good idea for a car, truck, motorcycle or atv engine unless the engine is modified for that fuel. 

[boltz2012]

Yeah! What they said!

[Punkur67]

So I should have no problem switching the motor over to 100 octane race fuel?

[Yummi]

Not unless you are smoking and spill some while filling it up? 

[borris]

 I had a pm earlier and I have to agree with the sender-to a point. He said he runs av gas in a high output BBC that's twin t'boed and runs at about 1300HP for hours on end at 5800RPM.He didn't say but I'm guessing in a boat.If so it's use is more like an av engine-steady state or near to it and run at mostly higher rpm.More steady state/higher rpms, av gas likes that.  He also states ,and I very much agree,that you have to tune an engine to the fuel you are using.You can't just change fuel and expect some miracle to happen. Lastly I think he thought I was saying that av gas would "hurt" on engine.I'm not at all saying that.I'm just saying that IMO av gas belongs in what it is formulated for(with a few exceptions)---an aircraft, and race fuel belongs in cars and bikes. 

[Voodoochikin04]

the people that recommended avgas for car use said that it is alot dryer than regular gas and thats the reason for the oil additive.

[borris]

Alcohol and propane are "dry" fuels also.Ya don't add oil to those. Anyway ,take a piece of hard learned advise if you wish. Don't believe all that you see or hear from "experts".Don't take what they or I say as the gospel.Do some research on their "facts" and then make an informed decision as to what you feel is right.Many,if not most, times you will find that the "experts" were full of BS.

[Punkur67]

I would rather not run avgas but I just dont want to mess with my tune too much when I change over.

[artie on edge]

Wow.... so much stuff to take in!

Ive run avgas here in Oz for years in our off-roaders BUT the engine was built to run on avgas. Also I dont know if our avgas is the same as yours (dont see why not but...). But for decades avgas was our sports std fuel. So much so that at larger events there was a tanker selling avgas direct to competitors.

Several years ago avgas was banned as competition fuel and we now use std pump gas AND the engines are built for this gas. The main reason for the banning was because of upper cylinder lubricant (read that as lead content). I am guess that that is what is diferent today, avgas has no lead content and the lubricant these guys are refering to is for valve seats etc. Thsi would be necessary for some aviation uses but not so for short life span competition engines (IMO.. of course).

When I say built for a certain fuel, this entails compression ratios (even engine gearing) and very importantly spark advance maps (particularly if using the entire rev range as a buggy does).

I come back to the fuel the engine was designed for, changing fules without consideration to other parts of teh engine can well lead to pretty quick destruction.

Good luck, if it aint broken ... dont fix it!

[fabr]

I can't disagree with that.

[fabr]

Really I think we're all pretty much in agreement here.If you want to run av gas you need to build and tune the engine for it.

[Punkur67]

I was told that the motor was setup to be run on it. I just want to run race fuel instead. I only wanted to know if I should continue to rn it or if I could switch without messing up my tune.

[artie on edge]

Punkur67, I feel for you bro... the world is full of burnt pistons, valves all telling each other that they were "told" that this would suit??? etc etc...

Mate, the only real way to be certain is to measure your engine and these is a way of doing this assembled. Let me know if you need more. Basically you need to know what the compression ratio is. Simple as that. Then you need to to ensure that the spark advance is suitable. Again as simple as that. (do you own a burette?)

When I first started to read this thread and saw some of the responses I was "wooo... why NOT avgas..." Just needs certain parameters met. No big deal. But I wouldnt run the stuff unless I was certain it was set up for it (or an other fuel for that matter).

Good luck mate..

[artie on edge]

and for those who are wondering....
swept volume (SV) plus clearance volume (CV) divided by clearance volume (CV) = compression ratio (CR).

Dont forget to take into account the head gasket area if calculating and not actually measuring.