Race Gas

[2002 Busa SE]

going back to the track, have a grudge race against a buddies Gixxer 1000, looking for every last HP, what gas is going to give the most bang..Nutec???

[ZXLNT]

MR9 Or Nutec

[2002 Busa SE]

no nutec, going to run 87, it will be ok, i geared it down and lowered the back 4", I shoudl leave him at the line, he isnt lowered and launching a stock wheelbase 1000 is a handful, I can just leave at 2000 and screw the gas on

[Ducman851]

Unless you have a way to make the correct fuel/air or timing changes then race gas will only make your bike smell funny. Heres a link to an article written by someone FAR smarter than me.

By Dr Rob Tuluie

In many high-performance situation, riders clamor for higher octane fuels, thinking this will give them additional horsepower and, thus, an advantage over the competition. But this is not the case--adding higher-octane race fuel to your motorcycle may actually produce less horsepower. Here's why: Octane, an arbitrary number which is calculated as the average of the Research Octane Number (RON) and the Motor Octane Number (MON), and is only an indic ation of a fuel's sensitivity to knock, which is typically pressure-induced self-ignition. (Of these two ratings, MON is more applicable to racing fuels as it is measured under high load and high speed conditions.)

Octane, as you can see, is not a measure of how much power--or, more correctly, specific energy--is contained in a fuel. And remember that leaded high-octane race fuels burn slower than most unleaded fuels, and may reduce performance in stock or lightly modified motorcycles. A high octane rating itself, however, does not mean that the fuel is slow burning. Hence, it has no direct bearing on the power characteristics of the fuel.

The knock tendency (and hence, the Octane rating) of a fuel is a function of the amount of free radicals present in the fuel prior to ignition and can be reduced by the addition of tetra ethyl lead, aromatics and other additives.

Although some racing organizations still use maximum octane number as the discriminating factor for fuel legality, it is really not appropriate for racing purposes.

Instead one should look at the amount of energy (heat) released in the burning of a particular fuel. This is described by the specific energy of the fuel. This quantity describes the amount of power one can obtain from the fuel much more accurately. The specific energy of the fuel is the product of the lower heating value (LHV) of the fuel and molecular weight of air (MW) divided by the air-fuel ratio (AF):

Specific Energy = LHV*MW/AF

For example, for gasoline LHV= 43 MJ/kg and AF=14.6, while for methanol LHV= 21.1MJ/kg (less "heat" than gasoline) and AF=6.46 (much richer jetting than gasoline). Using the above formula we see that methanol only has a 10% higher specific energy than g asoline! This means that the power increase obtained by running methanol, with no other changes except jetting, is only 10%. Comparing the specific energy of racing and premium pump gas you can see that there is not much, if any, difference. Only alcohol s (such as methanol or ethanol) have a slightly higher specific energy than racing or pump gas.

Other oxygen-bearing fuels, besides the alcohols and nitromethanes, such as the new ELF fuel, will also produce slightly more power once the bike is rejetted. However, at $15.00 to $20.00 at gallon for the fuel the reportedly minor (1% - 2%) improvement is hardly worth the cost for the average racer.

The real advantage of racing gasolines comes from the fact that they will tolerate higher compression ratios (due to their higher octane rating) and thus indirectly will produce more power since you can now build an engine with a higher compression rati o. Also, alcohols burn cooler than gasoline, meaning even higher compression ratios are possible with them, for even more power.

The bottom line here is that, in a given engine, a fuel that doesn't knock will produce the same power as most expensive racing gasolines.

However, it sometimes happens that when you use another fuel, the engine suddenly seems to run better. The reasons for this are indirect: First, the jetting may be more closely matched to the new fuel. Secondly, the new fuel may improve the volumetric e fficiency (that is, the "breathing") of the motor. This happens as follows: Basically a fuel that quickly evaporates upon contact with the hot cylinder wall and piston crown will create additional pressure inside the cylinder, which will reduce the amount of fresh air/fuel mix taken in. This important--but often overlooked--factor is described by the amount of heat required to vaporize the fuel, described by the 'enthalpy of vaporization' (H), or 'heat of vaporization' of the fuel.

A high value of H will improve engine breathing, but the catch is that it leads to a different operating temperature within the engine. This is most important with two-strokes, which rely on the incoming fuel/air mix to do much of the cooling--even mode rn water-cooled two-strokes rely on incoming charge to cool the piston. For two-strokes a fuel that vaporizes, drawing a maximum amount of heat from the engine, is essential--the small variations in horsepower produced by different fuels is only of second ary concern.

Also important is the flame speed: Power is maximized the faster the fuel burns because the combustion pressure rises more quickly and can do more useful work on the piston. Flame speed is typically between 35 and 50 cm/sec. This is rather low compared to the speed of sound, at which pressure waves travel, or even the average piston speed. It is important to note that the flame propagation is greatly enhanced by turbulence (as in a motor with a squish band combustion chamber).

The most amazing thing about all this is that you can get the relevant information from most racing gasoline manufacturers. Then, just look at the specification sheet to see what fuel suits you best: Hot running motors and 2-strokes should use fuels wit h a value of "H" that improves their cooling, while more power (and more heat) is obtained from fuels with a high specific energy.

By the way, pump gas has specific energies which are no better or worse than most racing gasolines. The power obtained from pump gas is therefore often identical to that of racing fuels, and the only reason to run racing fuels would be detonation probl ems, or, since racing fuels are often more consistent than pump gas--which racers call "chemical soup"--a consistent reading of the spark plugs and exhaust pipe.

[gixxum6]

I'm pretty new to the sport but I've heard from a couple of people that burning a really high octane actually decreases performance because it's a slower burning fuel. I ran out of gas the other day and didn't have anything but some 87 and I hardly noticed a difference from the 92. So I'd look into it a little more before you drop $10/gallon.

[Matt Sterbator]

Busas run well on 87 octane.

[2002 Busa SE]

yes, I was trapping at 143 mph, with 87

[jstyle]

If you really think it will make a huge difference go with who ever sells the most expensive crap. But ask all of the guys I kill in CCS unlimited classes with my r6 if their ducati 999 makes them faster than me.

[sungwei]

Man thanks for that information. I am going to direct my friend who is "octane obsessed" to this link cause he keeps telling me to run 93 instead of 87. The only reason 93 makes me run faster is cause it makes me lighter by removing more money out of my pockets!

[12RPilot]

I wonder if that guy knows what he's talking about. He pretty much covered what I already thought to be true but I might have misconceptions. I suppose since all my research hasn't contradicted what he was saying, it's safe to assume it's all accurate. Proof is in the pudding, I reckon.

[Ljolivia]

Compression needs octane.

Go to the local airport and get some 100LL Avgas. Around $3/gal. Cheaper than "race" fuel.

[boostnsrt]

when i was going to MMI we did an experiment with high octane fuels. proven gains between 93 and 112 were 8 hp and 6 lb ft. also the higher the number the higher the resistance to detination, but if you don,t have your bike tuned specifically for race gas you don't want to have your bike pingin the rev limiter. it will cause valve float and your pistons will kiss your valves

[smooth]

Have you tried VP fuels? they make high-octane fuels for high compression engines, but they also make low-octane oxygenated fuels for racebikes (as in roadracing). MR1 and MR9 are both high as hell and AMA legal, but you can get VP U4 for a little less, it's oxygenated and make better power. I use it in my race bike and can tell a difference (although slight) between it and pump gas. mostly just a better throttle response and it seems to pull a little stronger

by the way, I'm new here so . . . hey ya'll!

[smooth]

one last thing. in the latest issue of RRW, they tested several race fuels in a gixxer 750 and VP U4 made the best power gains

by the way, have you a power commander or some way to adapt your FI? that's the best way to get the most from whatever gas you run

[Naughty76]

dang..... i really didnt have an idea that octane got this comples