100 Octane

[skotty]

Just filled 100 Octane today. I heard somewhere that its good practice to run 100 Octane once in a while. Thought I'd put that to the test.

It seemed like it ran smoother, and the gas mileage has shot up from 38 to 43 in the city. At $7 a gallon, its not cheap, cost a total of $27 to fill up that tank

Thats the most I have ever spent to fill up my tank

Anyone else use 100 Octane occasionally?

 

[Busa505]

does it make more power ?? like in the upper rpm range ??

 

[skotty]

Havent got to test it out yet. Got two speeding tickets in the last few months

- one in the car and one on the bike. So I am a little wary of speeding.

 

[WWJD]

higher octane on stock engine is less power. your engine has to be tuned for higher octane to be helpfull in teh power department

 

[skotty]

(WWJD @ Sep. 10 2007,07:46) higher octane on stock engine is less power.  your engine has to be tuned for higher octane to be helpfull in teh power department

Wow, didnt know it would produce less power.  Either way, I wasnt looking to gain power, I thought of it more as a cleanse.  Is that true?

Oh and by the way, what is the optimum Octane level for the Busa?  I think I saw somewhere it was 87.

 

[ks-waterbug]

87... Thats correct

 

[tinbender0]

higher octane doesnt mean higher detergent.....................

 

[skotty]

(tinbender0 @ Sep. 10 2007,08:25) higher octane doesnt mean higher detergent.....................

Thats the answer I was looking for. Thanks

 

[Wag]

Just after I had bought my Busa, I ran a couple tanks of 100+ octane and it ran like crap and the mileage sucked. 87 or 88 is the way to go!

--Wag--

 

[WWJD]

I attribute the RUNNING SMOOTHER effect of higher octane to it running TAMER.... less power to be so herky jerky on takeoffs and throttle twists. my unprofessional, not documented, unscientific perspective.
I think running different octanes make shake things up a bit and maybe keep things cleaner - but I don't really know

My engine is stock and I run 87 - did a LOT of reading to come to that... there's a lot here and a lot on the net. Essentially, wrong octane creates more "carbon buildup" from improper burner IE Slower burn than the engine expects? Help me out, grease monkeys.... does higher oct help clean anything out by varying the chemical breakdown timing?

 

[kawiboy11]

if it's tunned for 100, run better, if it's not, stick with pump gas, but man.....it does smell good!

 

[memorex]

A High octane is only good for high compression engines. 13 to 1 or higher. It keeps the air fuel mixtire from pre igniting.

 

[Mr Bogus]

Octane is simply a fuel ability to "resist" burning. (You can see this by putting a bit of 87 octane gas and some 100 octane gas on the ground and lighting them with a match. The low octane fuel will "flash" and the high octane will ignite with a slow steady flame front)

Detonation (preignition, detonation, pinging) is the collision of 2 flame fronts converging at a common spot. High compression engines have the ability to create spontaneous combustion (like a diesel). This spontaneous ignition creates the second flame front that collides with the primary flame front from the spark plug. The resultant pressures can exceed 10 times normal pressures in the combustion chamber and also push temps well beyond the melting point of the piston. Blown head gaskets, melted pistons, hammered bearings and bent rods are often the direct result of this problem. If you want to make more power by dumping something simple in the system read below...

High octane fuels are not needed in stock compression motors. If you have a turbo, run nitrous or have an elevated compression ratio, then you may have a need for this fuel (higher initial combustion chamber pressures). Compression ratios numbers are only part of the combination. Combustion chamber design, chamber flow, heat transfer, cylinder head composition are all part of the formula. A motor running aluminum heads can typically run a full point of compression more than a cast iron head by the nature of heat exchange. The flow patter in a cylinder head also makes big differences. So a specific compression ratio is not really a very reliable indicator of which fuel you need to run (unless it is a known combination. We have run 15:1 BBC gas motors on 93 octane fuels.

The Nitromethane we run in our fuel motors use alcohol to up the octane (nitro is literally liquid explosive that creates its own oxygen when burned) It also reduces the "percentage" of the nitro to "race legal levels"

The octane is raised with up to a 10% methanol addition. (if you want more power, add some water and do not get caught, there are rules against water as well as a number of other oxidizers we have used over the years)

Running 100 octane fuel in a stock Hayabusa motor will do nothing with the exception of make it run worse if the ignition system is weak or the plugs are borderline.

This running high octane fuel is an old wives tale that started in the early days of hot rod cars.

In a new car, running this fuel can screw up your cars tuneup. Many new cars can adapt to fuel quality and running this high octane fuel will make the car learn a much more aggressive timing curve. When going back to regular 87 octane fuel, this can result in detonation issues for a period of time.

Save your money......

If you want to clean your system or make more power, use water/methanol injection system. The water will clean the combustion chambers and valves quite nicely over time.

A simple water injection system can add measurable power to a motor by a couple aspects. Gasoline has around a 700:1 expansion ration when burned. Water has a 1500:1 expansion when converted to steam. It also cools the combustion process and allows more aggressive timing curves and/or lower octane fuels.

Water is also cheap and easy to come by, the alcohol bump (better cooling properties) is also easy and cheap

 

[DaCol.]

Higher Octane means slower burninig, and 100 Octane means real slow burning. By the way, your not using 100 Octane Aviation Gas are you

? Because they are blended for a far different enviroment than what your driving in  

 

[skotty]

(DaCol. @ Sep. 10 2007,14:21) Higher Octane means slower burninig, and 100 Octane means real slow burning. By the way, your not using 100 Octane Aviation Gas are you

? Because they are blended for a far different enviroment than what your driving in  

Nope, I dont think it was aviation gas.

I appreciate all the input guys

 

[Mr Bogus]

Higher Octane means slower burninig, and 100 Octane means real slow burning. [/Quote]

Octane rating is not "how fast it burns" it is its ability to resist burning. (a flame front under compression and combustion chamber pressures are very close to identical with 80 octane or 100 octane) Controlling the flame front is important in any engine, higher combustion pressures create unstable environments for fuel burn.

Octane rating has no direct impact on the deflagration (burn) of the air/fuel mixture in the combustion chamber

The BIG difference in avgas and racing fuel or other high octane fuels is the volatility. (rate an liquid will evaporate)

If you take a cup of 100 octane avgas and a cup of 100 octane racing fuel, the avgas will evaporate completely before the regular racing fuel even starts to think about it.

the reason for this volatility is that when an airplane is initially started, raw fuel is forcibly pumped into the engine (priming). This fuel often runs out the exaust side of the motor, out the exaust pipe and onto the cowling or other airplane air frame parts. This as you can imagine creates something of a fire hazard. You can easily tell which avgas you have by the color.

The most common color is blue, (100 octane low lead) The key here is the "lead" lead provides superior lubrication to the valve train and so is allowed in aircraft. An easy check to see if you have av-gas is check the color (blue or green are most common) and dip your finger in it. By the time you can get it to your nose to smell it, it should be about completely evaporated from your finger.

Anyway, with av-gas, this "puddled" fuel evaporates at an incredible rate and reduces the likelihood that you are going to burn your airplane to the ground in the hanger.

Some aircraft can be certified to run on "regular" gasoline but this puddling issue has to be addressed and proven to be solved. Even so, some are still required to use av-gas for start up and ground operations. They switch over to "pump gas" only after getting off the ground.

I personally like av-gas over racing fuel as it tends to allow easier engine starts (volatility benefit) and the lead content is easier on the valve train. It is however illegal to use aircraft fuel in a car (lead). This never stopped us from filling up our boats with the stuff .

Here is one of the boats I ran on avgas before going to methanol

 

[skotty]

Nice! Is that a Busa engine on the boat?

Thank you for posting, very insightful.

 

[Mr Bogus]

(skotty @ Sep. 11 2007,06:50) Nice! Is that a Busa engine on the boat?

Thank you for posting, very insightful.

No busa powered boat (yet) I bought that hull from Denver Mullens shop (Mondos old hydro) and ran it for 3 years.

the boat is actually faster than my bike (468CI 15:1 full roller, hilborn injected on methanal and a 200hp fogger system) dyno specs were right at 1400hp on full kill. Would have been much better off using a Pontiac motor but I started with the Rat motors and changing over is not cheap.

I did not mean to come off sounding like a "know it all" on the fuel question but almost 30 years of racing has caused me to acquire a few facts

(and I am a licensed pilot on top of that)

My nitro racing was tutored by "Famous Amos Satterlee" Taught me an awful lot about how to make a nitro motor go. A few of you west coasters have probably seen him at boat/sand/land drags.

I have 20+ years of drag racing in boats and cars. A few years of Motocross, and I raced drag bikes in the late 70's/early 80's and the idea of a stock bike going into the 9's would have been considered a joke....

 

[ibified]

Ocatne Rating: the ratio of Octane to N-heptane. otane is not very flammable, n-heptane is EXTREMELY flammable. The ratings we have in the US are the Research octane (which is how they rate it in Europe, in case any of you wondered why the octane rating on fuel is higher in europe) added to the tested octane divided by 2. if you look on a fuel pump, you'll see the octane given as (r+m)/2. That's what that means.

As for running higher octane, it's been proven multiple times that running higher octane in an engine that doesnt need it will not raise your power OR your fuel mileage. if you get better fuel mileage on higher octane, then you need a tune-up.

 

[Mr Bogus]

The US does use a combined method of establishing the actual "octane" number. This is done using 2 numbers.

the formula you posted is the US octane formula

R= Research method
M= motor method

they are averaged (your formula) and then the number is the US octane.

I am unfamiliar with how the european method (I only had to deal with fuels issues in the US and Mexico)

How stuff works has a pretty good article on all this at http://auto.howstuffworks.com/question90.htm

One of the biggest issues we come across building motors is that we need to run "pump gas" it is possible to build a 10:1 motor that will not run on regular pump gas just as it is possible to build a 12:1 motor that will. Boils down to the "combination" of parts you have.

My choice of weapons is the turbo charger (we had the first 200Mph alcohol dragster at Denver) They produce the most efficient horsepower on pump gas IMO