Fuel 101

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KJShover

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The following was compiled from various websites:

Gasoline is known as an aliphatic hydrocarbon and is made up of molecules composed of nothing but hydrogen and carbon arranged in chains. Gasoline molecules have from seven to 11 carbons in each chain. Gasoline is made from crude oil. The crude oil pumped out of the ground is a black liquid called petroleum. This liquid contains hydrocarbons, and the carbon atoms in crude oil link together in chains of different lengths.

Octane
Octane is a fuel's ability to resist detonation and/or preignition. Octane is rated in Research Octane Numbers, (RON); Motor Octane Numbers, (MON); and Pump Octane Numbers (R+M/2). Pump Octane Numbers are what you see on the yellow decal at gas stations, representing the average of the fuel's MON and RON. VP fuels uses MON because this test method more accurately simulates racing conditions. The conditions under which fuels are tested using the RON method are not as demanding, thus the number is normally higher than the MON rating. This leads many other fuel companies to rate their fuels using the RON in an effort to make them appear more resistant to detonation. Don't be fooled by high RON numbers or an average -- MONs are the most relevant ratings for a racing application. Be aware, however, the ability of fuel to resist detonation is a function of more than just octane.

Burning Speed
This is the speed at which fuel releases its energy. At high RPMs, there is very little time (real time - not crank rotation) for fuel to release its energy. Peak cylinder pressure should occur around 20? ATDC. If the fuel is still burning after this, it is not contributing to peak cylinder pressure (which is what the rear wheels see).


Energy Value
An expression of the potential energy in the fuel. The energy value is measured in BTUs per pound, not per gallon. The difference is important. The air:fuel ratio is expressed in weight, not volume. Generally speaking, fuels that measure high BTUs per pound have a higher energy value. This higher energy value will have a positive impact on horsepower at any compression ratio or engine speed.

Cooling Effect
The cooling effect on fuel is related to the heat of vaporization. The higher a fuel's heat of vaporization, the better its ability to cool the intake mixture. A better cooling effect can generate some horsepower gains in 4-stroke engines, and even bigger gains in 2-stroke engines.

Gasloline Types

Regular Unleaded Gasoline
The recommended gasoline for most cars is regular 87 octane. One common misconception is that higher octane gasoline contains more cleaning additives than lower octane gas. All octane grades of all brands of gasoline contain engine cleaning detergent additives to protect against engine deposit build-up. In fact, using a gasoline with too high of an octane rating may cause damage to the emissions system.

Mid-Grade Gasoline
The octane ratings 'regular', 'mid-grade', and 'premium' are not consistent. In the United States, for example, one state may require a minimum octane rating of 92 for premium gasoline, while another may allow an octane rating of 90 to be premium. Check the octane rating on the yellow sticker on the gas pump rather than relying on descriptive labels.

Premium Gasoline
Certain high performance engines benefit from use of high octane fuel. For other engines, using a fuel with a higher octane rating than the vehicle requires sends unburned fuel into the emissions system and catalytic converter. This puts unecessary stress on the emissions system. For some vehicles, a rotten egg smell coming from the tailpipe signals use of too-high octane gas.

Leaded Gasoline
Many countries continue to use leaded gasoline, even though lead exposure has significant health and environmental consequences and the cost of switching to unleaded gasoline is relatively low. Although greatly improved, research indicates significant health and environmental effects from use of leaded gasoline remain even in countries that have switched to unleaded fuel.




The homework pretty much has been done when it comes to testing various grades & brands of race fuels in motorcycles.
In hours & hours of dyno testing & Powercommander map building several key points were discovered some we intentionally set out to test others just came about on their own:

1. Standard Race Fuel (VP C12, C14, Sunoco 104, 100LL AvGas even high octane pump gas 96 or 100) ran straight on a stock RC51 motor will actually lose horsepower. This is argued by many because the throttle response becomes crisper & is often mistaken for more performance when in truth the bike is making less power on the dyno sometimes by as much a 4-6hp. Many race fuels are designed for higher compression engines >13.0:1 & simply do not perform well in low compression motors like the RC51 (10.8:1). As has been noted many times on just about every sportbike forum on the net more octane does not mean more power! It simply means more resistance to detonation. If a higher octane fuel happens to make more power in a motor it is because of the additives in the fuel having the potential for more energy not just because it is higher octane.

What can be beneficial, but not always so is a blend of about 25/75 of race fuel & pump gas (1 gallon of race fuel added to 3 gallons of premium pump gas) which has been shown to consistently yield a horsepower or two. However I strongly urge you to stay away from the race fuels on a street bike if for no other reason than the extra contaminants it will leave in your motor. For me the cost of premature wear on the motor is not worth the negligible horsepower gains.


2. Oxygenated Race Fuels (Nutec #4, VP MR1 etc) can add 3-5hp without any fuel or mapping changes at all & 5-10hp sometimes even more on a stock motor with proper mapping & lots of playing around with the ignition timing. Some oxygenated fuels benefit from retarding the ignition while others benefit from advancing it.
The catch is that :
A. the stuff is really expensive usually about $15-$20 a gallon
B. it is highly corrosive & must be drained from your tank after each race weekend to keep it from eating parts of your fuel system.

There are also many true horror stories of racers getting a bad batch of Nutek & ruining a set of carbs or throttle bodies due to a varnish that settles onto the components that is basically impossible to remove. I have actually witnessed this myself once & could not believe how bad it actually was.
There are some newer oxygenated fuels out now such as VP MR9 & Ultimate 4 which is claimed to be much less caustic to fuel system components (o-rings, gaskets etc..). I have sampled the MR9 & was very impressed with the performance & the Ultimate 4 is just plain awesome even in a stock motor, but as the cost of gas soars, $16 a gallon is pretty hard to swallow. I've been mixing it about 50/50 on my stock engines with excellent results. Not as powerful as the MR9, but nowhere near as expensive either.

3. In testing various grades of pump gas I consistently found that 87 octane fuel makes 1-2 more horsepower than those exact same bikes ran on Premium 93 octane. We tested five liter class motorcycles (97 CBR900RR, 02 Honda 919, 2000 RC51, 2000 GSXR750 & an 02 R1) & only the R1 seemed unaffected by the octane of the fuel. Now I am certainly not going to tell you to run less than the recommended octane (92) in your RC51 as the specific needs of the motor dictate that a higher octane fuel is needed, but the results are blatant in that more octane does not mean more power.
It is only fair that I note that when testing the pump gas on some of the 600's (Yamaha R6 & the GSXR600) the inverse was true in that they did lose a little horsepower on the 87 octane vs the 93 octane. Most likely because of the higher compression ratios of the smaller motors, however the CBR600F4i gained a little horsepower.


Additional notes (not tested on the dyno):
Never add any type of octane boosters or fuel system cleaners to your motorcycle tank. Additives sold in auto stores are designed to treat anywhere from 16-22 gallons of fuel from one small bottle of concentrate & more often than not those chemicals are very hazardous to your motorcycles fuel system especially if the mix ratio is not absolutely perfect. I cannot tell you how many carb jobs I have done over the years because some yahoo dumped half a bottle (or more) of octane booster into his fuel tank. The bike runs great for awhile but within a day or two a varnish starts to set up on the fuel system components & it just gets worse from there.

Run quality fuels & stay away from the additives period.
 

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