I discovered we could buy 5 gal racing fuel locally. I went over and asked for 98. They were out. All he had was 110. I bought it and tried it. Very interesting. The car (Sr dragster)does not like it. It slowed down over 3 tenths. It would obviously want some rejetting and timing correction to work. I know the car does not need a 110 fuel and I believe that is the problem. It was interesting doing the actually test though. Don
There's two sister gas stations local that sell cam II racing fuel. One has 100 octane and the other has 110. My bike really likes the 100 octane, it certainly runs ok on sunoco ultra 94 too . But the 110 makes it run kinda flat and temperamental. Might need different timing on the 110
Yep, running too much octane will slow a motor down. At least that's been my experience. Just the right octane will give it a lot of just off idle "snap". I notice my motor idles with more lope when I have it just right.. My 9.3 compression 462 Poncho runs fastest on 89 but in this heat, I use 91 on the street....
Jetting, timing, compression all play into how high a grade of fuel you need to run. Like carbs a lot of time we get the idea that bigger is better not always the case. Actually come to think of it you can also add ambient air temp to the equation. For example I have an engine that runs real well on mid grade in the winter when it is below 40 degrees out. The same engine won't run on anything but premium on 80+ degree summer days.
PORK, if your engine runs well on its minimum octane requirements, going over that minimum will not increase its performance in the majority of cases. Its a waste . Going below that minimum requirement will cause performance decrease in every case. This is a going over scenario not under of the minimum octane requirements.
The one important thing in higher octane gas is that is has less "energy per unit" than lower octane gas. I run 15:1 in my race motor, and it will not run on anything less than 114. If I had 12:1 I'm sure I could get by with 110 or maybe even 100 if I could find it. The octane rating of gas is directly related to compression ratio of the motor. IMHO
Going to higher octane in the summer has to do with my compression and aluminum heads. In the winter aside from fuel density being higher incoming charge is cooler as much as 50 degrees that combined with cooler operating temperatures makes for cooler combustion chambers. Cooler chambers lowers my octane requirements before spark rattle sets in. It could also be that the charge is somewhat diluted in the summer because of summer additives. But I am not sure that is the case. Unfortunately chemistry was not one of my better subjects so that is a question that I cannot answer. I do know that alcohol in the fuel has wrecked havoc on my tune. I have had to rejet fatter to accomplish the same goals with my engine. But alchy is a whole different story. I haven't dynoed on different fuels. We dynoed this particular engine on premium pump gas only. When we built the engine in question it was built on a bet and needed to be dailey driven and achieve a specific ET goal. So pump gas was pretty much what we were shooting at as far as a fuel to propel the vehicle. The engine being right on the edge like it is has given me opportunity to tell major differences easier with a simple change in fuel grade. Maybe not as noticable in a stock engine. Anyway I know from experience that it will run well on mid grade in the winter when it is cold but will not in the summer when it is hot. I haven't dynoed in the cold to see if there is a major HP or torque change with the change in fuel and ambient temperatures. Maybe that is something worth looking into. But I doubt that it will affect the majority of the people that I know. Combustion chamber temps are affected by compression ratio. You as well as most of the people posting on this htread already know that but maybe someone just reading doesn't. When compression ratio rises octane requirements also rise. Part of that is due to higher combustion chamber temperatures. When your combustion chamber temps rise detonation or pre-detonation becomes a problem. My understanding is that higher octain fuels require more to light the fire. Higher compression ratio as well as hotter spark becomes a requirement when running higher octain fuels. With your ratio of 15:1 there probably isn't a lot that can be done to change thigs but maybe at 12:1 if you cooled your combustion chamber you may get by with 100 octain or less by spraying it with metanonal or even water. You would probably run into a problem at the track with class rules on that one, but on a street engine you could get away with lower octane fuel on say a 12:1 and a methanol spray. At least I intend to put that one to the test real soon. That said in your situation you are probably stuck with the high priced stuff, that that it shouild be a problem in your situation. It should be a good thing. Unless your are racing a semi i'll just about bet that a neck brace is as big a requirement as race fuel.
I did play with the timing. I usnderstand fuels well. I used to teach fuel at Trade school. Higher octane a more controlled burn. Doesnt explode at high heat/ high compression but is able to still burn even and properly. I wasn't totally shocked it slowed down. It was how much that surprised me. And it did run like crap too. Engine is not quite 10 to1. It runs fine on 94 and I will stick to it. It was worth the price of a can of fuel though just to try it. And as said if I had 15 to 1 or 13 to 1 even it would have loved it. In our last pro car we had to run 104 . It worked very well on it. It was 11.5 approx comp ratio BTW we were at Mix and match night a Shannonville. You could run the drag strip or the rioad course for a flat fee. I was there with my friends. Bill and his 64 Chevelle gasser style (bumperless) Larry and his recently completed 51 Chev coupe gasser (Very period corect with a I beam front axle even!) Roy and his 49 Stude gqsser and me in the Senior Dragster. Al was there too but didnt bring his 33 Willys. Come to think of it Mike was there with me too but left his 41 hemi Willys at home. Four old lads, Four vintage style cars. Lots of run time and the track was actually decent. I sure enjoyed it. Don Don
X2...you are right on the money ! Too much octane for the compression.....slooooooows doooooown ! Octane is how fast or slow the fuel burns....Higher octane = slower burn rate.
Dolmetsch, all I see around Buffalo is Ultra 93. Is there a Sunoco Ultra 94 or was that just a typo? Art
We have Sunoco 94 over here. Sunoco is now under Petro can. If you go to their website you can get a list of stations who carry 94 . Not all do. We have one in Belleville that still does. We used to have 2. Yes it is 94. Don
Art, I looked it up for you. http://retail.petro-canada.ca/en/independent/3557.aspx?MODE=RES&R=&C=Fort Erie&PC= It doesnt say if they carry 94 but the Garrison Road one says Alternate fuels so I would suspect yes. The phone numbers are listed on that page so you could phone and ask "do they have "Ultra 94" which is what they now call it. They are both just a few minutes from where you live. However you may not need it but since you asked there it is. Don
Cool info on this fuel topic, learned something already today, thank you baby Jesus, and the H.A.M.B. ~sololobo~
Don't forget that you can mix octanes to get what you want. 50% 100 octane plus 50% 110 octane gets you 100% 105 octane. (more or less)
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