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· Premium Member
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you do realize that higher octane actually hurts performance right?

You want to run the lowest possible octane an engine can run on without knocking.

The higher the octane, the slower the burn, and cooler the flame.
 

· GvillefloridaR1
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Discussion Starter · #5 ·
Ahhh your the machinst in ocala right? I called your shop looking for a custom NOS bracket....I scratched that idea and just spent the extra money on exhaust and pc3usb... thanks for the advice
 

· Premium Member
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Huh..where did you get this info from.. first I have ever heard of that... Its says on the tank NO LOWER than 93 octane gas...

There are several threads about this on here...then again, I build engines for a living. They put 93 for being safe, but I always run that, what Im saying is higher octane will actually lower performance.




Ill explain......


OK, you piston comes down, sucks air/fuel in while the intake valve is open, now the piston heads back up, at a certain point before TDC, the plug ignites the compressed air/fuel..this is where the octane comes in, gasoline when compressed can ignite on its own, so the lower the octane rating the easier it ignites, so if the fuel ignites before the piston is close to TDC the explosion tries to push the piston down, while the crank pushes up(this is bad)

Now if you have to too high octane, the piston comes up, the spark ignites, but the flame is actually slower and does not burn as fast which is not creating the biggest bang to slam the piston back down.
 

· NESBA Mid Central
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High Octane Not Slower

Higher octane gas does NOT have a slower flame propagation, NOR does it have less joules of energy per unit volume than lower octane fuel. It only prevents early dentonation. In thermodynamics, the Ideal Gas Law states that, PV=nRT where P is pressure and T is temperature. Thus when pressure goes up (read high compression ratio), the temperature goes up and premature detonation is more likely. That is why high octance becomes necessary.

He's getting just as much or more power by running 100 octane vs. 91.
 

· Ghostrider Squadron
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race fuel in stock piston R1... i can tell u what is does and same with gsxr1000. okay i run nitrous in stock motor. so for safety i ran VP c-16 fuel. on motor it hurt power in bike, on nitrous is was safe. so i tested it to see at track with back to back passes. the race fuel slowed bike down .3 of second over super unleaded. had buddy try it in his gsxr in 1/8 mile track. he is big guy, but went from running 6.60 in 1/8 to 7.35 just adding fuel. now it does depend on what octane fuel u run. 100 octane wont hurt bike if any very minimal. higher octane fuels burn slower to prevent detonation. so it takes more pressure(higher compression) to get good clean burn. on my old poor gsxr600 won jug of howell 003 fuel..dunno octane. poored it in straight.. bike wouldnt pull past 9k rpms and ran 11.71. dumped it out, went to truck stop, got some regular, bam next pass... 11.17. doesnt sound like couple tenths is much.. but at dragstrip a single tenth can be 4-5 bikes lengths.

now oxygenated fuel is little different. most if it is low octane. like U4 or MR9 is less than 100 octane. U4 is like 92 octane i think. these have 4% or greater oxygen in them and are good for 4-7 more hp just adding fuel and tuning it to fuel. but at $15 a gallon and u cant leave it in tank for more than day/... or it turns to rust and kills fuel system.

run what u want. i dont think 100 will slow bike down, but anything over that prolly will and ur just burning money that u dont have to in cost.
 

· THE MAN
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3,750 Posts
The only thing octane tells you, Please listen to this, is a FUEL's ABILITY TO RESIST BEING LIGHT BY HEAT OR PRESSURE.

Thats it. It is not directly tied to power production, and for 100% sure more octane is NOT BETTER, and often times worse.

If you actually take the time to learn about fuel, and you should, you will find that with pump fuel you should always use the LEAST octane that does not knock or ping.

I would bet money that will be less than 93 octane on your bike. That sticker is there as a cover there ass sticker. They have no way to know what quality of fuel you will use, nor how you will use the bike. 93 most likely will not make the best power for the bike, but it will for sure keep ping at bay.

The good race fuel makers have very good RACE fuel in octanes from 87 on up. If you really test it you will find that the 100+ octane stuff, while possibly making more power than pump fuel, will make less power than a race fuel with a proper octane rating for your application.

You have a very small window in which to push down on the piston. Octane has a GREAT deal to do with this. It is important to use the correct octane if you want to make the best power and have the least ammount of engine deposits.

The 87 octane race fuels smell just as cool as the 100 octane stuff believe me, and they will work better in a stock compression sport bike.

I built an 07 G1K with N20 for a customer. It runs a 50 shot on stock compression. WE use MRX01 (98oct) when on spray as a saftey net. 98 oct is way way over kill for a stock compression bike with no power adder.

I built an 04 G1K with a bit over 14 to 1 compression once. It is the only engine I have built to date that pinged on pump gas. It had an overbore piston size which makes ping EASIER to acheive. That bike runs fine on 92 octane once we took a couple degrees of timing out of the low and midrange with an ignition module. See that way you still get the top end power you are after.

By using too high of an octane you are, in effect, retarding the timing across the entire rev range, and loosing power by doing it if you are not actually needing the octane to avoid ping or knock.
 

· THE MAN
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I should add VP's site has some great info about octane, as well as a list of their race fuels, their intended application, and their octane.
 

· THE MAN
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Higher octane gas does NOT have a slower flame propagation, NOR does it have less jewels of energy per unit volume than lower octane fuel. It only prevents early dentonation. In thermodynamics, the Ideal Gas Law states that, PV=nRT where P is pressure and T is temperature. Thus when pressure goes up (read high compression ratio), the temperature goes up and premature detonation is more likely. That is why high octance becomes necessary.

He's getting just as much or more power by running 100 octane vs. 91.
This is not true as I understand it. when dealing with pump gas, the lower octane fuel will have a quicker flame speed, as well as more BTU per gallon, ounce or whatever you want to use to measure it.
 

· THE MAN
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I will aslo mention that under about $15 a gallon and you are wasting money on race fuels. real race fuels cost real money.sad but true.
 

· NESBA Mid Central
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81 Posts
By the way, my 2006 R1 says that 91 octane is required. There isn't a gas station in my burb that sells 93 octane.

I assume that modern motorcycles have knock sensors that can sense detonation and retard the timing as necessary for low octane gas. These bikes are spinning at 14,000 rpm with 12.5:1 compression and certainly require high octane to make the most power; and adequate octane to prevent detonation even with the timing retarded.
 

· THE MAN
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NOPE, ALL OF THAT IS INCORRECT.

I don't know of any moder jap liter bike that has a knock sensor.

It is a misconception to think that if it has high compression it NEEDS higher octane.

Motorcycles have several things going for them in the anti kock department that cars just don't have.

They have GREAT cylinder heads. They put the best factory cars to shame. They have all alloy motors that shed heat better than most car motors, the cylinders are MUCH smaller and thats very important, and motorcycles don't use as much of their total power just to move the vehicle.

They can have higher compression than cars but run on the same octane because of this.

Most every car has a knock sensor, most modern bikes do not because they simply do not need them yet.

ping and knock is MUCH less likely to happen at higher rpm than it is at mid to low rpm. Thats in cars, trucks, or bikes.

allot of people think this way. It's a common misconception. You don't need high octane. You don't need a certain octane, you need enough octane to keep it from pinging or knocking. Thats it. More is not better. It just costs more money, makes less power, and add's more engine deposits to the combustion chamber (which can require higher octane...lol)
 

· NESBA Mid Central
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81 Posts
I take exception to the statement, "...you should always use the LEAST octane that does not knock or ping...". This approach may work satisfactorily in Ford Taurus on the way to get groceries, but is not applicable to high performance engines. It allows you to economize on fuel and is not germaine to what we're talking about here. If economy is the topic switch over to ConsumerReports.com.

If you are relying on your ears to hear the pinging you may be doing damage to your engine. I personally don't want to try to pick out the sound of pinging from the sonic assault my ears are taking while doing 175 mph and passing 3 gixers down the straight-a-way at Heartland Park on track day.

Yamaha's engineers want you to use 91 octane. That's what I use. If you're just putting around you might get by with cheaper gas. If you have a race engine, your on your own.
 

· THE MAN
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3,750 Posts
take exception all you want, it's the plain truth.
It has nothing to do with economy, or performance or non performance engines. It's a simple matter of understanding engines.

weither it's performance oriented or not, you don't want the motor to ping. Thats terribly bad for an engine. So what you want to do is use the LEAST octane that does not kock or ping. That means it it pings on 87 then you try 89. If it stops pinging then thats your fuel choise. It's not complicated.

Most every modern bike I have dealt with runs fine on 87 octane if it's stock. Not all, but most.

I have built several engines for motorcycles now that have been between 13 to 1 and 13.5 to 1 and they all have run with out pinging on 87 octane pump fuel.

You won't be hearing ping at 175mph, as that would be topped out in 6th on your bike (and a speed you won't be seeing on Heartlands front straight, though it humored me) as like I said before you will get ping at lower and mid rpms first. Its very hard to miss.

at higher rpm there is just not time for the fuel to ping. At high load and lower rpm then you get ping. You have high cylinder pressure (which is pressure and heat) and the resistance of the tall gear at an non optimal rpm for aceleration.

If you want to use 91 octane then thats fine. You are welcome to do it.

Please wave hi to the G1K's that pass you, I might have built one of their motors :) When you get back in the pits, see what fuel they are using.
 
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