Race Fuel - Worth It?

[Bonz]

That's false. The octane (itself) has nothing to do with burn rate. As a good example, Sunoco SR18 (118 octane) has a faster burn rate than 93 octane pump fuel.

Higher octane simply means a longer timeframe before auto-ignition of the end gas occurs which is not related to the flame speed.

The resistance to combustion (burning in the engine) is what keeps high octane fuel from causing knock and ping. Fuel is burning too quickly, early in the combustion cycle, when you have knock/ ping. High octane fuel keeps this from occurring.

I will edit it causes the back of exhaust valves to get covered with carbon, potentially, because premium/high octane air/fuel mixture combusts slower in the engine and if the engine isn't designed for premium you potentially have that issue due to the fuel finishing its burn as the exhaust valves are further into opening. The spark ignites the fuel at the same time whether it's high octane or lower octane. It's how long it takes the fuel to combust from that point that is whether you get undesireable results or not.

 

[RDY4WAR]

The resistance to combustion (burning in the engine) is what keeps high octane fuel from causing knock and ping.

No. The resistance to auto-ignition (uncontrolled ignition of end gases) is what keeps high octane fuel from causing knock and ping.

Fuel is burning too quickly, early in the combustion cycle, when you have knock/ ping. High octane fuel keeps this from occurring.

This is a common fallacy based on a misunderstanding of what happens during detonation. Detonation is an uncontrolled ignition of the air/fuel mixture that's not related to, and works against, the spark-ignited flame propagation. It is caused by the entrainment of gases that become considerably hotter than their surrounding air/fuel mixture due to a lack of combustion turbulence. The chamber shape is the largest factor in preventing detonation.

Let's take a 93 AKI non-ethanol pump fuel and slowly add TEL (lead) to it. We will see nice jumps in octane, but no changes in specific gravity, distillation, heat of vaporization, stoich AFR, carbon ratio, etc... and therefore no change in burn rate. Burn rate is more about how well the fuel remains atomized, how well it vaporizes, and the concentration of light aromatics in the fuel. If you look at the specifications for race fuels, you'll notice the fuels advertised as "quick burning" fuels or fuels for NA engines tend to have a lower specific gravity and lower, tighter distillation curve. Alcohol fuels being the exception as they do their own thing.

I will edit it causes the back of exhaust valves to get covered with carbon, potentially, because premium/high octane air/fuel mixture combusts slower in the engine and if the engine isn't designed for premium you potentially have that issue due to the fuel finishing its burn as the exhaust valves are further into opening. The spark ignites the fuel at the same time whether it's high octane or lower octane. It's how long it takes the fuel to combust from that point that is whether you get undesireable results or not.

Once again, the ability to resist auto-ignition is not related to the flame speed.

 

[Bonz]

Alrighty!

 

[Cujet]

I think the OP's question is whether race fuel is "worth it". In my case, the answer is yes. Locally, non Ethanol pump fuel is about $4/gal. C9 is $8/gal at the local pump. So it's twice the cost of the local NO-E fuel that lasts no longer than 5-6 months with a dollars worth of Stabil added.

Yes, I know Costco sells 10% ethanol 87 and 93 for $1.90 and $2.08 locally. Neither Cheap choice is a bargain when compared to the mechanical costs of fuel shut off valves that fail, carbs that overflow and diaphragms harden into uselessness, not to mention the incredibly rapid degradation and gummed up float bowls. I tried the cheap fuel in my JD garden tractor and was rewarded with a massive fuel leak on my patio. Followed by a two day long repair.

So I use C9, and the problems went away, the fuel lasts forever and my equipment is ready at the next season, plus everything runs better (really) . Costs me about $60 more per year. It's worth it to me.

 

[mattwithcats]

I get Sunoco 260 GTX at the local racetrack. $6 a gallon, no ethanol, no metallic additives, no lead...

98 Octane...

Cheaper than Tru-Fuel...

260 GTX: 98 Octane Unleaded Race Fuel | Sunoco Race Fuels

www.sunocoracefuels.com

 

[TheBig2003]

As already stated by others, there is no befit with racing fuel, just run premium 91+ without ethanol and you will better off.

 

[2strokeNorthstar]

If you want to pay 3x the price for a good smell it is. Otherwise it’s a waste.

 

[KneeGrinder]

All of that said... you could probably put the cheapest E10 87 AKI pump fuel in that thing, beat the snot out of it, and it would be none the wiser. I wouldn't worry about it. On the point above, it'll like the E10 more than E-free as far as response and power is concerned because of ethanol's low BP and high heat of vaporization.

I have read all of [U]RDY4WAR's[/U] posts in this thread. He has a very good understanding of fuel, not that others do not have valid verified points on why they prefer to use Racing fuel, I always did in my Race bikes. In a "Worked" or Race type motor the answer is yes, it will benefit almost always with some exceptions.

The exception I will point out that some people are missing yet [U]RDY4WAR[/U] seems to very well understand is that Alcohol of any fuel based type whether its corn base, or Methanol makes more HP and Torque, even at 10% Ethanol. Its been proven many times over and over. If an engine can not Detonate 87 Octane, it will not really make any more power with 93 Octane, E-10 or E-0, however, 93 Octane is normally a cleaner fuel with less contaminates in it than 87 Octane. 87 Octane is well known to have more contaminates, so that said, some may notice 93 Octane runs a little better in whatever they pour it into, but it is not going to make more HP.

If anyone is so down on E-10, I know the damage it can do to smaller engines, and it has a much shorter shelf life and if I had a choice for the same price I myself would buy E-0 every time I fill up one of my cars. Ask yourself why so many Modified Turbo cars can tune 20/30% more HP/Torque on E-85. They don't pass many gasohol stations.

I am not discussing fuel mileage here. The OP was concerned about a little more power in an atv that "Sorry to say" will not make any more power without jetting/tuning, ect.

The ratio difference for straight Methanol is 2.3/2.4 to 1 for gasoline. That means for every 1 gallon of gasoline a gas motor burns, a Methanol motor would burn 2.3 to 2.4 gallons, but the Methanol motor could probably have 17 to 1 compression and a lot more HP. Try that with gasoline. Diesel can run 17 to 1 compression with a Turbo and its a Detonation Timed ignition motor.

 

[KneeGrinder]

No. The resistance to auto-ignition (uncontrolled ignition of end gases) is what keeps high octane fuel from causing knock and ping.



This is a common fallacy based on a misunderstanding of what happens during detonation. Detonation is an uncontrolled ignition of the air/fuel mixture that's not related to, and works against, the spark-ignited flame propagation. It is caused by the entrainment of gases that become considerably hotter than their surrounding air/fuel mixture due to a lack of combustion turbulence. The chamber shape is the largest factor in preventing detonation.

Let's take a 93 AKI non-ethanol pump fuel and slowly add TEL (lead) to it. We will see nice jumps in octane, but no changes in specific gravity, distillation, heat of vaporization, stoich AFR, carbon ratio, etc... and therefore no change in burn rate. Burn rate is more about how well the fuel remains atomized, how well it vaporizes, and the concentration of light aromatics in the fuel. If you look at the specifications for race fuels, you'll notice the fuels advertised as "quick burning" fuels or fuels for NA engines tend to have a lower specific gravity and lower, tighter distillation curve. Alcohol fuels being the exception as they do their own thing.



Once again, the ability to resist auto-ignition is not related to the flame speed.

I have always believed the diameter of the piston was the largest factor for the cause of Detonation in the larger gas engines. The heat build up across the piston is a fire starter! The Big Block Chevy is a perfect example, non controlled fuel delivery system, sometimes flat top's, 9 to 1 compression they need 93 Octane. But that also plays right into "Lack of Combustion Turbulence" and hot spots. Smaller Rice burner motors can go a little higher compression on 87 Octane until they developed variable valve and ignition timing. They obviously have Technology that the BBC does not have=

 

[Surestick]

I have always believed the diameter of the piston was the largest factor for the cause of Detonation in the larger gas engines. The heat build up across the piston is a fire starter! The Big Block Chevy is a perfect example, non controlled fuel delivery system, sometimes flat top's, 9 to 1 compression they need 93 Octane. But that also plays right into "Lack of Combustion Turbulence" and hot spots. Smaller Rice burner motors can go a little higher compression on 87 Octane until they developed variable valve and ignition timing. They obviously have Technology that the BBC does not have=

It's not the heat build-up in the piston (exhaust valves are likely the hottest things in the combustion chamber, hence why indexing the plugs towards the exhaust valves can help with power. The flame kernel is less shrouded around the open side of the plug and can expand more easily so you're burning the most likely to detonate part of the mixture earlier and can gain a bit of timing advance before detonation starts), it's the size of the combustion chamber and therefore the distance the flame front has to travel which gives more time for the chemical reactions that cause the volatile compounds that cause detonation to form.

This is why a combustion chamber with more turbulence (generally due to a well-designed squish band) helps with detonation. The turbulence helps with mixing which helps the flame front spread faster. Same idea with dual plugs.

 

[RDY4WAR]

I have always believed the diameter of the piston was the largest factor for the cause of Detonation in the larger gas engines. The heat build up across the piston is a fire starter! The Big Block Chevy is a perfect example, non controlled fuel delivery system, sometimes flat top's, 9 to 1 compression they need 93 Octane. But that also plays right into "Lack of Combustion Turbulence" and hot spots. Smaller Rice burner motors can go a little higher compression on 87 Octane until they developed variable valve and ignition timing. They obviously have Technology that the BBC does not have=

For each component in the chamber on average over a 4-stroke cycle at wide open throttle... (NASCAR Cup Engine at sustained 7000+ rpm)

Intake valve is ~480*F
Exhaust valve is ~1200*F
Spark plug is ~1100*F
Piston face is ~580*F
Piston skirt is ~370*F
Piston ring (top) is ~440*F
Cylinder wall is ~360*F

In an older BBC, they have iron heads with large 115-120cc chambers, and the piston is usually >.020" in the hole with >.040" thick gaskets making for horrible quench distance (but ease of assembly). They were also carbureted with dual plane intakes that made for horrible fuel distribution. The average air/fuel ratio at WOT may be 12.0:1 but you may have one cylinder at 10.5:1 and another at 13.5:1. These engines also had heated iron intakes to keep the carb from freezing up which meant a lot of heat went into the air before it even reached the cylinder.

 

[Bonz]

Agreed, the lowest octane where your engine will not detonate is where you're going to make the as much power as you're going to make.

Relatively speaking air/fuel ratio with methanol or ethanol is much richer. All else equal you get more fuel in there which more than offsets the lower energy content of methanol or ethanol. The higher octane allows higher compression ratio. I believe ethanol and methanol also are more adept at absorbing heat of combustion and allow cooler running.

 

[sunruh]

Wondering if race fuel makes much of a difference in ATVs and others. I have a 2005 Honda Rancher 350cc so it is certainly not a race machine. Might be taking it to the dunes next Spring and wondering if I should use racing fuel (~110 octane or so) for a little extra power. Or maybe just use some octane booster?

define "race fuel"

its a generic term that a lot people use that has no basis behind it

 

[Nick1994]

define "race fuel"

its a generic term that a lot people use that has no basis behind it

Was my description of 110 octane not specific enough?

 

[RDY4WAR]

Was my description of 110 octane not specific enough?

There's 93 octane race fuels. The term "race" is used very loosely. I take it to mean a fuel designed around a specific application compared to the broad formulas for pump fuels. Because "race" fuels tend to focus on a specific application, they can simplify the formula. Sunoco SR18, for example, is designed specifically for big bore, naturally aspirated engines turning >8000 rpm. The evaporation and combustion properties are designed specifically for that narrow timeframe at that high rpm. Pump gas can't be specific like that because it has to be able to work in an 10:1 compression, direct injected, pentroof chambered, VCT, turbocharged, 4-valve 4 cylinder as well as a 1970s 454ci BBC in a big pickup with 7.8:1 compression, log manifolds, bathtub chambers, all iron, and poor quench.

 

[sunruh]

Was my description of 110 octane not specific enough?

no

i can buy 110 octane at the local airport.
octane is certainly NOT an indicator of being "race fuel"

as a matter of fact, citing 110 octane fuel shows you dont know what it means/does.

 

[sunruh]

There's 93 octane race fuels. The term "race" is used very loosely. I take it to mean a fuel designed around a specific application compared to the broad formulas for pump fuels. Because "race" fuels tend to focus on a specific application, they can simplify the formula. Sunoco SR18, for example, is designed specifically for big bore, naturally aspirated engines turning >8000 rpm. The evaporation and combustion properties are designed specifically for that narrow timeframe at that high rpm. Pump gas can't be specific like that because it has to be able to work in an 10:1 compression, direct injected, pentroof chambered, VCT, turbocharged, 4-valve 4 cylinder as well as a 1970s 454ci BBC in a big pickup with 7.8:1 compression, log manifolds, bathtub chambers, all iron, and poor quench.

and rvp and spec gravity and 90% boil point and oxygenated and leaded and ..........

there are a few fuels that i know of that will boil sitting in my garage during the summer
not exactly what you want

 

[Nick1994]

no

i can buy 110 octane at the local airport.
octane is certainly NOT an indicator of being "race fuel"

as a matter of fact, citing 110 octane fuel shows you dont know what it means/does.

Ok Captain Obvious, what do you think the entire point of this thread was then?

If I was a race fuel genius, I wouldn’t have asked the question.

 

[ollie]

Yes Race Fuel Is Worth It. It makes jetting and tuning consistent and simple. I can only comment to the consistency of VP fuel. You simply cannot get pump gas that can match VP fuel when you want to fine tune a motor for every last bit of power and/or homogeneous output every time you are riding.

I'm a big fan of VP U4.4 (formally U4/U2) and good old C12. When racing C12 is very consistent when jetting for temps and elevations. When riding at nose bleed elevations I run the U4.4. It compensates for elevation with high oxygenates so I don't have to re-jet.

For racing and trail riding I use the C12.

For trail riding at high elevations I run the U4.4.

When dual sporting I run pump gas and fatten up the fuel screw and leak jet due to the lean condition of ethanol based fuel. With fuel injection advancement, fuel choice is not as critical depending on system (closed loop/open loop).

Fuel injection has come so far that the popularity of race fuel has diminished. FI is getting so good that you can get consistency with just about anything you dump in the tank. The caveat to that is if you are at high elevation and want to retain HP. Then A good oxygenated fuel is your best choice.

I suggest to anyone who is going to run an engine hard for long periods to use race fuel. If not, then add an adjustable leak jet to to adjust out the lean bog that happens when running pump fuel with ethanol.

Another added bonus is plug readings are very accurate with race fuel. Our ethanol based fuels make it very difficult to get a good reading on a 4T and just a little better on a 2T.

 

[Bighorn2500]

I just use 90 octane non ethanol in my Raptor four wheeler. Only thing I ever ran race fuel in was my old KX250, 108 octane Torco mixed with Klotz R50 that it was set-up for.