Besides Octane, What Else Should You Consider When Selecting a Race Fuel? - Engine Builder Magazine

Besides Octane, What Else Should You Consider When Selecting a Race Fuel?

It’s entirely possible to generate more horsepower with a lower octane fuel if it’s designed properly with respect to its other key properties. It’s also possible for two fuels to have the same octane rating, but perform very differently due to their other key properties.??

1.  OCTANE: Octane is simply a rating of a fuel’s ability to resist detonation and/or preignition. It is not so much an indication of a fuel’s ability to make power, but rather a fuel’s ability to make power safely, i.e., without blowing your engine. Octane is rated in Research Octane Numbers (RON), Motor Octane Numbers (MON) and Pump Octane Numbers (R+M/2).  A Pump Octane Number is the number you see on the yellow decal at gas stations, representing the average of the fuel’s RON and MON. (See below for a more detailed explanation of how octane numbers are derived and what they represent.) ??

Racing fuel companies such as VP rely on MON numbers because the MON test more accurately simulates racing conditions. Don’t be fooled by high RON or R+M/2 numbers. Many companies use these simply because they look higher and are easier to come by because of the test methods. Also bear in mind that the ability of fuel to resist detonation is more than just a function of octane.??

2.  BURNING SPEED: This is the speed at which fuel releases its energy and is partially  a function of a fuel’s vaporization qualities. At high RPMs, there is very little time (real time – not crank rotation) for the fuel to release its energy. Peak cylinder pressure should occur around 20? ATDC. If the fuel is still burning after this, it’s not contributing to peak cylinder pressure, which is what the rear wheels see. Because VP’s fuels are designed with a particular focus on vaporization characteristics, most of its fuels—oxygenated or nonoxygenated – vaporize very well. This means it cools the intake charge, burns faster and yields more efficient combustion. As a result, the “effective” octane rating of VP’s fuels is even higher than the octane test indicates, and they will prevent detonation better than competitive fuels with similar MONs.??

3.   ENERGY VALUE: Energy value is an expression of the potential energy in fuel. The energy value is measured in BTUs per pound, not per gallon. The difference is important as the air/fuel ratio is in weight, not volume.  Generally speaking, race fuels measure high in BTUs per pound and thus, have a higher energy value. This higher energy value will have a positive impact on horsepower at any compression ratio or engine speed.??

4.  COOLING EFFECT: The cooling effect of 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. The superior vaporization characteristics of race fuels such as VP’s make cooling effect one of their key advantages. A better cooling effect can generate some horsepower gains in 4-stroke engines and even bigger gains in 2-stroke engines. The cooling effect can also ensure circle track racers maintain power in the longest races and harshest conditions.  In virtually any application, the cooling effect will help extend engine life.??

Understanding these key properties of fuel will better equip you to evaluate fuels for your application. Before making a final fuel selection, you should consult with your fuel supplier and be prepared to answer the following questions:??

•    Is your engine naturally aspirated, turbocharged, blown or using nitrous oxide??

•    What is the compression ratio (CR) of your engine?

•    Does your engine have O2 sensors or CATS??

•    In what series or sanctioning body will you be racing??

•    What are their fuel rules, e.g,. are any fuels illegal or do they allow oxygenated fuels??

•    In which class will you be racing?

–Tech Tip courtesy of VP Racing Fuels

You May Also Like

Shop Solutions January 2023

Next time you have set of large journal small block Chevy connecting rods to resize, consider honing the big ends of them for a +.002” outside diameter bearing that the LS engines with fracture cap rods use.

Engine and Machine Shop Tips and Tricks

DOUBLE BYPASS

For proper block cleaning, the oil bypass valves in Gen 5 and 6 big block Chevys need to be removed. We made a couple different sized “hook” tools for a slide hammer. This tool will easily pull the valves out of the block and sometimes without damaging them.

Shop Solutions December 2022

Everyone misses occasionally, and this helps avoid dents and damage.

Jesel Certified Performance Rebuilds

Engine components are serious investments for any racer and maintaining that investment could be the difference between winning a championship and losing it.

Going the Extra Mile with Cylinder Head Porting

It’s not just the port work alone that creates spectacular cylinder head performance. The most critical areas of a cylinder head are those which pass the most air at the highest speed and for the longest duration. Your bowl area, the valve job, the throat diameter, and combustion chamber are all crucial parts. 

Tight Tolerances and Building Power

As you ascend Mt. Everest, you reach an area called the death zone. Once you climb high enough, the margin of error becomes perilously thin. That death zone also applies to engines. As the horsepower per cubic inch and rpm increase, the margin of error decreases. 

Other Posts

CNC Update: Features and Automation

Precision is key when it comes to automotive parts; the complex designs of connecting rods, pistons and rings, blocks, cylinder heads, and other parts require super tight tolerances that are getting more and more difficult to be met by hand or with other machining processes outside of CNC.

All Things Media Blasting

Engine building is a segment of the automotive industry that has always been ahead of the curve in media blasting, and no matter the engine shop, cleaning equipment is a common bond.

Engine & Hub Dynos: Necessary Tools and Additional Revenue

Being able to see the horsepower and the direct correlation to what is lost in the driveline is invaluable – dynos offer a myriad of benefits for the modern engine shop.

November 2022 Shop Solutions

November tricks and tips for the shop!