gas

I can assure you VP doesn't oxgenate fuels to reduce emmissions. They all but promise a 6% power increase with their oxygenated fuels. And as most racers will tell you...VP knows their stuff.

When you spend 30 or 40 hours in the seat of the same race bike you get a pretty educated butt when it comes to how the engine is running. I can without a doubt tell you after a race if the bike had pump gas, race gas (Sunoco) or VP in the tank. Probably half of the street bikes I've owned responded very noticably to race fuels like CAM2....I don't claim the difference was due to octane though. The other half would run the same...or worse.

Presently I plan on switching from VP C12 to VP U4 specifically to get a lower octane. In the case of my race engine with only about 10:1 compression I'm probably giving up some power running 108 octane VP C12. The U4 is around 94 octane.

The major difference I've seen between pump fuels and race fuels is that in almost every case the race fuels will see more complete combustion during a race...almost always indicated by a plug that begins to run more lean. Race fuels often require jetting up a size for the plug to read the same as with pump gas.
JohnnyB

All I can say is....if a person needs an opinion on race fuel....they should talk to a racer. If they want an opinion on street fuel...talk to a street rider.
I'm not much for theory when experience is available. And to be honest...I have the experience when it comes to racing the same engine, at the same track, in the same conditions, with different fuels. I've also got about 50 dyno runs on this engine...but while none of them were done to specifically test one fuel to another. I am pretty good and comparing my seat of the pants dyno to actual dyno readings.
You can ask any of the guys here I race with, they will tell you I am not one to believe in untested theory, rumor or conjecture. I am rabidly anal about actual and real performance and my results on the track show it.
In most instances reading or guessing about how fuel might work in a particular instance is no replacement for the actual experience of running 100's of laps on various fuels and noting the differences.

You've quoted a couple of sentences off the VP site discussing particular fuels...VP makes about 50 different fuels. Oxygenating leaded race fuel is not done to reduce emissions, whether that is a by product of the process or not. Leaded race fuels are not known for being friendly to the environment. The two fuels you mention are both unleaded street legal fuels that far from the same as the specialty leaded race fuels we are discussing.

While I'm no chemist....I CAN tell someone how a particular fuel will most likely perform in their race motorcycle. Not by guessing, but based on my experience with these fuels.

And while mentally unstable pilots may have fantasies about their engines. I assure you I didn't build what is probably the fastest Honda 175 race bike in the country based on my imagination
JohnnyB

quote: how much of the need for race fuel is dictated by other factors such as flame front speed and combustion chamber shape at higher RPM than a stocker runs on the street?

Click to expand...

A lot.
The first time you see a bike come into the pits after a race with condensation dripping off the float bowls full of C12 you realize there is more at play than just octane.

I've personally never seen ANY vintage bike run worse with race fuel in a Road Race situation. It's not often you run a street bike at WOT, 10-12,000 rpm for 20-30 minutes straight. The racing environment cannot be compared to the street. Pump fuels are just plain not made to operate under these conditions, street fuels have to be formulated for easy starting, cold weather starting, good idle, low emissions, minimal valve deposits, tolerance of moisture, non-corrosive etc etc etc. Race fuels do not. If you ride your bike on the street....use street fuel. If you race it on a track...use race fuel.
I promise you the three guys standing on the podium will be using race fuel.
JohnnyB