gas

4130 Views 63 Replies 14 Participants Last post by jbranson, Oct 25, 2006

imslow

Discussion Starter · Oct 18, 2006

I used some MR8 at the last race. Frontierdon. Awesome. F'in unbelievable. I am now a believer. But I found out on the VP page that MR8 is for 125 and 250 2 smokes. Octane 107, leaded, oxygenated, yellow in color. I was running a 4 stroke 500 single.

The VP web page says this shit can be shipped UPS!!

I guess if it works it works. What isn't on their web page is

1. how long it lasts and
2. it says on the can not to leave in the carb/tank. But for how long?
3. I am going for a dyno test on Friday at MM. We'll see. All I know is I kept up with TK's 650 duc. (but he did say there was a "shimmy" in the steering)

I just need to get my post count up.

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kenessex

· #15 · Oct 19, 2006

As usual I will mostly agree with Geeto on this. The exception being that if you are running a stock motor, you ay bee able to take advantage by adjusting your ignition or cam timing. You may be able to gain some performance by avoiding detonation. Unfortunately, I don't think you would be able to find this hp without a dyno.I think the only other advantage canned gas would give is freedom from contamination and a consistant fuel mix. With a stock or mostly stock motor you might as well run pump gas.

Ken

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Vintage racing - old guys on old bikes

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kenessex

· #17 · Oct 20, 2006

Geeto and I are going to make a career out of agreeing with each other, cause we are too smart and too cool for the rest of you guys.
Like Imslow said if you are using a high comp piston and a lumpy cam you gotta use race gas. It isn't just for the performance either. Detonation will destroy a Wiseco 12:1 piston in a Honda XL500 engine if you roadrace it on pump gas. It will even do it twice if you don't learn from the first broken piston.
So the moral is use race gas when you need it and don't bother if you don't.

Ken

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Vintage racing - old guys on old bikes

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kenessex

· #20 · Oct 22, 2006

Don't worry Tex, I won't be offering anybody else positions until I hire you. I expect to be moving to Georgia either next year or the year after so I might have a better shot at getting you to move then. Atlanta is the hotbed of riding and racing.
Now I don't really know anything about oxygenated furls, but logic would dictate that they have to help make power in any engine. I also have never tried race gas and pump gas in a stock motor to see if there is a difference, but theoreticallythey should be about the same.
I would sure like to put a mostly stock race bike on a dyno and test it out. I wonder if old style 2 valve combustion chambers benefit from more octanes at real high RPM? I know that with a ported head and big carbs a CB350 will spin to 12000 rpm.
Good points made by Texy and JB. I guess you all are still in the superiorminds club.

Ken

AHRMA 412
Vintage racing - old guys on old bikes

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kenessex

· #27 · Oct 23, 2006

Man kinda sorry I got involved in this discussion at all. Now I am going to do my bobbing head doll act and agree with everybody.
First off, Johnny is absolutely right in that after years of racing the same machine, you can absolutely tell how it is running. The nice thing is he has dyno runs to back it up to one degree or another. I have never tried different fuels in the same race bike without other changes except my one Honda 500 single. That went from a piston breaker to a valve dropper, but ran good on race gas.(over revving causesd valve issues, octane caused piston issues.) As Johnny also pointed out, about half of the street bikes he has tried, race gas does not improve performance. I don't think there is any question that Johnny's race bike responds to race uel, but since it is 10:1 compression, 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? Which leads me o wonder what isgoing on in Tex's mostly stock motor at race conditions, i.e. heat and RPM, that makes it like race gas?

Geeto has also stated that in a stock or mostly stock street bike race gas does not improve performance and may even run worse. That is predicted by theory and somewhat backed up by empirical data.

I would really like to see some controlled experiments with a variety of stock motors and a variety of fuels. I wonder if older or newer combustion chamber shapes react differently to race gass? But I don't have a dyno or even my race bike to play with right now so I am still just having to use other peoples data and results.
However, Next season I am going to try race gas back to back with pump gas on my mostly stock 350 at a track day.

Ken ( trying to make nice) Essex

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kenessex

· #32 · Oct 24, 2006

Texy,
That is exactly like my motor except I have a ported head, too. What carbs are you running? I am running stockers and feel like they are running out of breathing on top end.
When you come to work for me you will be able to afford all the race gas you can drink.

Ken

AHRMA 412
Vintage racing - old guys on old bikes

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