High octane fuel in 355?

Phil
Comments such as yours are typical and put a smile on my face.
However your experience with Elf race fuel is not relavent to this thread, my comments relate to the relationship between fuel density and octane in unleaded street fuels.
Your experience with 360 Challenge cars suggsts that the factory ignition curves are too advanced for unleaded premium fuel.

I just checked Elf 102 unleaded, it is actually the same density as 98 RON unleaded, so the performance advantage you suggest demonstrates the car is suffering from preignition on unleaded premium fuel under track conditions. As you would be aware, higher Octane fuels actually burn slower than lower octane fuels, so in themselves do not create any more power.

As an aside a friend of mine, Phil Tainton owns/manages the Shell Aust Superbike racing team. In testing, Elf unleaded race fuel (98 octane for Aust rules) produced less power than Optimax on the race bikes. This was after remapping for each fuel.

EDIT: did some further research and discovered Elf 102 is 2.7% oxygenated which is the max allowed under CIK/FIM world championship regulations. This would also help explain the performance increase.
Increased octane in itself DOES NOT mean increased power.

 

Yeah ok. I guess we're debating over fuel general make up, not simply octane rating. Terminology is the bread and butter of lawyers......

 

Sounds like this is getting more on the right track now, IMHO octane rating is just a measure of the fuels ability to resist detonation. For a specific engine design there is always a minimum required, around that minimum the ECU can typically try a few things to compensate. Using fuel with a very high octane rating has no benefit unless you plan to increase the compression ratio of your engine to take advantage of it (this is why turbo charged engines typically like high octane fuels the added boost of the turbo effectively increases compression).

What can change though is the refining process used to get higher octanes which may also change the composition of the fuel.
The key thing for developing HP (assuimg sufficient octane to avoid detonation) is the calorific value of the fuel. The calorific value (basically how much energy is released by burning it) is not directly related to octane, in some cases with some fuel companies it may increase with octane others it might not.

Interestingly when we used to race Karts we found that out of 5 oil companies that import fuel here there was one fuel that was almost a second a lap quicker - it was a 95 RON pump fuel compared with all the other 91,96, and 98 RON fuels (and blends we tried). Apparently it had a high benzene content which has a very high calorific value.

 

You may not be familiar with Union 76's 100 octane (RON+MON)/2, which I regularly used to mix 91 with 100 to get close 93 octane. This is a racing fuel and is not readily available in all areas or pump stations. I have data to show that my acceleration improves when I increase the tank's octane to 93 with this mix. What specs in the gasoline would you look for to validate or turn down the experiment results I have? Also, I have noticed in the new owners manual for 360 Modena the gas specified at 95 - 98 RON. Why do they specify a range when a minimum is sufficient in most cases? Thanks.

 

I thought Union 76's 100 was leaded?

 

No retailer in California can sell leaded gas (EPA, and ARB regulations), so no it is absolutely an unleaded gas and it is labeled as unleaded. There is also Sonoco, which has more variety, but it's only available in race tracks (there is one at Sears Point). Here's the specifications:

TYPICAL INSPECTION TESTS:
Product Code......................................................................................100E
Density, g/cm3 @ 60∞F........................................................................0.744
Gravity, ∞API...........................................................................................58.7
Color.....................................................................................................Blue
Octane Number, AKI, (R+M)/2...............................................................100
Octane Number, Motor..............................................................................96
Octane Number, Research......................................................................106
Reid Vapor Pressure, psi........................................................................6.8
Temperature @ V/L =6, ∞F.....................................................................145
Distillation, ∞F @ % Evap.
Initial Boiling Point.....................................................................100
10...............................................................................................156
50...............................................................................................208
90...............................................................................................230
End Point...................................................................................270
Copper Corrosion, ASTM D130..............................................................1A
Doctor Test, ASTM D4952............................................................Negative
Existent Gum, ASTM D381, mg/100ml...................................................1.0
Oxidation Stability, ASTM D525, minutes...........................................1,440+
Aromatics, vol %......................................................................................28
Oxygen Content, wt %............................................................................2.7
Lead, g/gal..........................................................................................<0.01
Sulfur, wt%.................................................................................................0
Viscosity, cSt @ 60&#8734;F..............................................................................0.7