What about octane boosters, Av. gas or race fuel?
The higher the octane rating, the slower and more controlled the fuel burns inside the cylinder, BUT you need more compression when running high octane fuel or you'll actually lose power. This is because the burn is way too slow if you don't have enough compression for the fuel to release its energy.
Another issue if the octane is too high for the amount of compression you have, the piston might already be near or at bottom dead center (BDC) and the fuel might still be burning, thus not able to relesae all of its energy to push on the piston to make power. On the flip side, if the octane is too low, the fuel will burn too fast which causes detonation and leads to sure-fire major engine damage, such as blown head gaskets, broken pistons, holes in pistons, etc. It's just not good at all.
Aviation fuel is another no no, although a lot of people have run it and say it works fine in theor race engine.
A famous engine builder friend of mine named Dick Marchant, who built a number of top fuel engines, including ones for world record setting drag boats back in the 70s and 80s, told me a story one time about an engine that was in his shop that had major issues in the cylinders. He said; "Arron, av gas is for air planes! Where do you see airplanes at? Up in the sky! Do you see cars up in the sky? No! How does your car run when you're up in the mountains? Yeah, like crap! There's no oxygen up there. Aviation fuel is designed to be run in a low oxygen / high altitude environment. What happens to a cutting torch flame when you add oxygen to it? Yeah, the flame gets hotter and turns blue! What do you think happens to an engine in a high oxygen atmosphere burning aviation fuel designed to be run in a low oxygen atmosphere? Look right here at this engine and you'll know!"
He made a good point, although I have heard of guys running it and swearing by it. I figure it like this; race engines need high octane fuel because of the high compression and high cylinder pressures they produce. Aviation gas is high octane, but if it was meant to be run in cars, then when you went to the race track and fueled your race car up, they would have aviation gas there too, but they don't, and for good reason.
As far as octane boosters go, they're usually made of two things, either alcohol (methanol) of some sort of flame retardant. Alcohol works OK I guess, even though it is much better suited for engines with much higher compression than average street engines, AND for it to run as a stand alone fuel, it requires 2.7 times more liquid volume than gasoline, so adding an alcohol based octane booster to your gas is actually leaning out your mixture a bit.
The other thing some octane boosters are made of is a "flame retardant". You can usually tell these types because they turn your spark plugs red. It's the same base ingredient that you see getting dropped on forest fires to put the flames out or to help prevent them from spreading. I don't recommend those at all because the object is to burn all of the fuel in the cylinder, not put the fire out or "retard" it as fire "retardant" is designed to do! Sure, that stuff helps prevent knocking (detonation), but it isn't helping to make more power because the key to making more power is being able to burn more fuel contained in the cylinder. Adding retardant to squelch the flame to help prevent detonation isn't how you make more power.
The old octane boosters, (the good ones from days-gone-by), are all outlawed. The best one that I can remember was something called Aniline Oil. This stuff worked great but you had to use a fresh air mask and wear gloves when putting it into your fuel tank because it was highly toxic and it displaces oxygen. If you spilled some on your skin, it would literally turn that area blue because it sucked the oxygen out right through your skin! No wonder they outlawed that stuff. Moroso used to sell it as one of their octane boosters way back in the day (70's and 80s) if my memory serves me. Look close at the bottom of that can and the big, white DANGER warning label. Notice it's right on the front in a big, white highlighted area and not on the back in fine print like everything is now days. It was pretty bad stuff, but it worked. Now days most octane boosters are methanol blends or Toluene. Toluene is basically a solvent found in good carburetor cleaners like Berryman's B-12 Chemtool.
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