Power Mist Race Fuel?

[MightyDuc Racing]

The bike originally had 12:1 J&E Pistons in it.  It was over-revved and had a rod put through the piston before I got it.  The previous owner then put in Wiseco 11:1 pistons so the bike could run on pump gas (that's what I was told) when the motor was repaired.  I know very little about engine internals, etc, and am trying to learn as quickly as possible about all of these racing things.  Thus all the questions here.  When talking to Bruce at BCM (the original builder of the bike and one of the top Ducati builders in the country), I told him the jetting that was in it and he suggested I change it.  I obviously did what he suggested.  Maybe it was a bad piston, maybe it was a combination of all the changes, maybe it was...who knows for sure?  My main goal here is to get it back basically as new and do everything right so it doesn't happen again anytime in the near future.  If that means going back to a 175 jet instead of a 165, or running race fuel, or whatever...that's what I want to find out and do.  I really appreciate your time reading and answering my questions that never seem to end.

Thanks,
Bryan

[Super Dave]

Ok, so you basically have a changed motor that we really don't have a perfect answer on.  

I think the best thing to do would be to go to a shop that has a Factory eddy current dyno.  There are about four of them in Florida.  They can actually give you a consistent answer about where you're at.  I think that would be money well spent.  Find out where it's at jetting wise and go from there.  Get that thing dialed in.

11:1 doesn't seem to high, but you've got big pistons.  A lot of distance to cover without a lot of time, compared to a weenie little 600 four.

So, I can't say you NEED race gas.  That would be contingent upon the combustion chamber shape, etc.  A leaded fuel will tend to have a bit more complete combustion, given that the fuel is chemically engineered to burn quick enough.  T111 should work really well for what you're working on.

[tzracer]

Yes Dave I am a physics instructor now, but at one time I did work at Buell Motor Company (1986-1990). I was the production manager, technical writing staff, warranty department, test rider amoung other duties.

What you may be interpreting as a condescending tone, is that my posts are written (hopefully) for all to understand, so I may add things that you understand, but other readers may not. My intent is to get to the truth and hopefully help/educate others on the board.

The reason I ask is because I always heard the opposite, such as the following quote from http://www.leesracing.com/articles/a2.html


"The general rule of thumb is that if we are moving from a higher SG gasoline to a lower SG gasoline, we need to richen the mixture by going to larger jets. On the other hand, if we are moving from a lower SG gasoline to a higher SG gasoline, we need to lean the mixture by going to smaller jets.

How much leaner, or how much richer?? Here is some ballpark information to get you started. If the new fuel is lighter (lower SG) than the old fuel, richen the mixture by one jet size for every 0.0 10 difference in SG. If the new fuel is heavier (higher SG) than the old fuel, lean the mixture by one jet size for every 0.010 change in SG. This will only work if the carburetor was correctly jetted for the old gas. If we are out to lunch with the old gasoline, we may still be out to lunch with the new gasoline. "

This article was written by a Union 76 fuel engineer (Tim Wusz).

I have also emailed several race fuel companies asking their opinion. I will follow up after (if) they reply. I sent the following message:

"If I switch from a lower to a higher specific gravity fuel, all else being equal, would I need to go richer or leaner with my jetting?"

Just checked, this is the reply from VP

"Going to a higher specific gravity fuel will automatically make the engine richer.  So you will have to lean it down."

[MightyDuc Racing]

I think I'll try some T111, but I will wait for the opinion of the actual engine builder before trying to decide what my final decision will be on the jetting.  Thanks again for all of the advice, and I respectfully reserve the right to continue asking far too many newbie questions and hoping for more answers from you guys.   ;D

[Steviebee]

Thats one thing that i thought of (race gas)  then visited VP's web site,  and then decided that i was glad 93 pump gas from shell would suite me just fine !!.


FYI  i lived in West Palm Beach for 5 years,  i miss it.  ( I used to work at P&W  across from Moroso)  Say hi to it for me on the way by !

[Super Dave]

I think I'll try some T111, but I will wait for the opinion of the actual engine builder before trying to decide what my final decision will be on the jetting.;D

Which is the best way to go.  Get it on a good dyno, if possible.  Intuition will carry you and the engine builder only so far, then you need to check it on something that can give you information.  

[Super Dave]

Thats one thing that i thought of (race gas)  then visited VP's web site,  and then decided that i was glad 93 pump gas from shell would suite me just fine !!

Race gas is only really necessary for a couple of reasons...

One, the motor has necessary loads on it that require a different fuel.

Two, the rules body requires certain fuels.

Three, there are power gains to be had from fuels.

A motorcycle road racer needs to get effective use of his bike before it is necessary to look for power gains.  Pump gas is relatively inexpensive, even though it has gone up, and still burns quite quickly in our application.

Rules wise, CCS has stated rules.  However, they are not enforced.  As the rules are written, street gasoline is NOT legal.  In fact, all unleaded racing fuels are illegal, along will all oxygenated racing fuels.  There is no way to necessarily say that a given race gas at a race track would be legal also.  Hence, why CCS does not enforce that rule.