Any performance difference in Sunoco Purple?
 

Has anyone seen any differences with the new fuel this year? Performance or other wise effected? Do you need to rejet or modify timing in anyway? Any help or advice is appreciated

Re: Any performance difference in Sunoco Purple?
 

You need to be a little more specific. Sunoco is the official fuel of NHRA and IHRA, but any performance changes or jetting adjustments may depend on which brand and octane one used before as well as the engine combo. All of the same fuels are still legal as before in the sportsman classes. One doesn't have to change brands, but Sunoco will probably be easier to get.


I've used Sunoco Purple.....about forever, in brackets and IHRA, and have been happy with the performance and consistency. I'll stick with it when I get into NHRA as well.

Re: Any performance difference in Sunoco Purple?
 

Depends on which brand and octane you were running. Jetting should not be an issue going from one 110 brand to another. Or timing either. The only big difference between leading 110 octane fuels is the Motor Octane.
Sunoco 110 is 106
Vp 110 is 107
Renegade 110 is 108.5

Re: Any performance difference in Sunoco Purple?
 

Rockett 110 also has motor octane 106.

Re: Any performance difference in Sunoco Purple?
 

Better take a look at the specific gravity of each before you conclude no jetting changes are needed.

Re: Any performance difference in Sunoco Purple?
 

Going from last years official brand of 110 to this years official brand shouldn't require major changes. But here's a rule of thumb for jetting when changing brands or blends of race fuel. The rule of 10.

Example... moving from a fuel that has a SG of .710 to a fuel that has a SG of .718 would require no change in jetting.
Moving from a fuel with .710 SG to a fuel with SG of .721 would require a jet change of 1 jet size.
Moving from a fuel with a SG of .710 to a fuel with a SG of .730 would require a change of 2 jet sizes.
The same rule would apply going from a larger SG to a smaller SG.

Re: Any performance difference in Sunoco Purple?
 

Mike in your description, would you go up or down a jet size with the SG lowering? From Say a .760 to a .740?

Thanks

Robert

Re: Any performance difference in Sunoco Purple?
 

When going from a higher SG to a lower, you would increase the jet size 1 number for every .010 change. In your example you would increase jet size by 2 numbers.
As i said, this is a rule of thumb and assumes that your tune up was pretty close to begin with.

Re: Any performance difference in Sunoco Purple?
 

I loss my list of nhra accepted fuels , had all the s.g. and octanes on the list has well . Its got to be on nhra.com ?

Re: Any performance difference in Sunoco Purple?
 

accepted ducts list in rule book .....page 101 thanks

Re: Any performance difference in Sunoco Purple?
 

Quote"Mike in your description, would you go up or down a jet size with the SG lowering? From Say a .760 to a .740?"end Quote
There are 2 variables with fuel weight (SG)
The closer you get to 1 ( water) the more dense a fuel becomes.
The density causes 2 or more changes in the carb. The 2 most dramatic are the flow through a jet and the way the float "floats" in the fuel.
A lower (SG) or viscosity fuel will flow more through an orifice (jet) and a higher (SG) or viscosity will flow less.
A lower (SG) allows the float to sink into the fuel and raises the float level.
When dealing with air mixes(air bleeds) in the fuel the less dense will pick up/mix air more readily than the dense.
Below is a copy and paste of a general rule of thumb....
Density of the fuel. (a) This is the weight of fuel compared to water, water being at 1.00. If race fuel is .750 (specific gravity) it would weigh ¾ the weight of water. If water at 60 degrees Fahrenheit weighs 8.125 pounds per gallon (ppg), then race fuel at .750 will weigh 6.09 (ppg). (b) The less dense the fuel (lower specific gravity) the higher the BTU content and the better the stability of the fuel at higher RPM's. (c) The lower the specific gravity of the fuel, the more crucial the jetting becomes, and the easier it is to run the engine lean, possible causing internal damage. (d) The combustion speed is determined primarily by the pressure (density) of the fuel mixture. A lower (SG) or viscosity fuel will flow more through an orifice (jet) and a higher (SG) or viscosity will flow less.

Re: Any performance difference in Sunoco Purple?
 

One other thing to keep in mind, when you change specific gravity, always check and re-adjust float levels. That goes for even small changes in SG that wouldn't require a jet change.