Does 100 octane make a difference???

[bzakk]

I have an 05' yz450 and I was wondering if it is worth the extra money to 100 octane. The manuel calls for 95 but pump gas doesn't go that high. What do you guys think? ?

[noslo98]

I run VP U4 in my 03 it runs awesome but theese bike runs fine on pump gas. If you do run high octane gas dont go too high i tried VP C12 once and the bike ran like [@#$%&*!].

[flyinguitars]

No. Octane # is the resistance to detonation. Higher compression requires higher octane. If your bike requires 95, then youre just wasting money paying for a higher octane gasoline. Many people think that higher octane means better quality....again octane is just a resistance to detonation rating. Many people swear by race gas and avaition 100LL, but I believe that is because those fuels are more consistant and enable fine tuned jetting.

Mike

[Aaron]

your manual will also specify that the 95 figure is for 'motor octane', not the average octane you see on a pump. that means that the 91 stuff is okay.

[grayracer513]

By itself, increasing or decreasing octane of your fuel won't make any performance difference as long as it stays high enough to prevent knocking and detonating. The confusion gets started because some (by no means all) of the things used to increase octane also add to the engergy content of the fuel. This is typically the case with racing gasolines. In many of them, the oxygen content has been boosted in such a way that they will provide an increase in power, but the increase in octane isn't directly responsible.

In the research method, chemists examine the fuel and assign it an octane rating based on its formulation compared to other known fuels. In the motor method, the fuel is run in a teast engine with a variable compression ratio and the compression cranked up until it starts making funny noises. The testers assign the octane rating based on what the fuel put up with.

California requires that an average of these two be posted on the pump.

Ultimately, it's your motorcycle that will tell you if the fuel is good enough, but most pump premiums are adequate for your YZF.

[Fastest1]

If you run a race gas, it usually isnt oxygenated for pollution and it is consistent. The higher octane doesnt help but it doesnt hurt either. When I run pump gas of different brands I get different results. I run 110 because I dont burn much, I get it at a fair price and it smells good ? The bike runs crisp always with race gas.

[grayracer513]

Your points are mostly correct. The increase in oxygen content in racing gas and the "oxygenation" of pump gasolines that is done seasonally in some states should never be confused. They are done by entirely different means and for completely different reasons.

There is some difference in pump gas as to quality, but maybe not just like you think. In the San Diego area, the gasoline going to all retail outlets is shipped to a "tank farm" where it is stored in the same 3-4 tanks. You can watch as trucks with all different brand names pull up to the same hoses coming from the same tanks, fill up and leave. The only difference is the additives that were put into the tankers before they left their own yards. Dirty little secret. The quality variation is usually an age issue, and is even more important while the "oxygenated" gas is around.

For a whiff of the good old days, try a teaspoon of racing castor in your next tank.

[Rich_Rohrich]

In the research method, chemists examine the fuel and assign it an octane rating based on its formulation compared to other known fuels. In the motor method, the fuel is run in a teast engine with a variable compression ratio and the compression cranked up until it starts making funny noises.

Just a minor correction here.

Both the Research (RON) and Motor(MON) method tests are performed in a CFR test engine using the ASTM D2699-92 procedures. The major difference between the two tests is the Motor method is done at a slightly higher speed, an ignition advance that varies with compression ratio, and depending on the altitude the test is performed at, the intake air temp will also usually be higher with the motor method.

A lot of countries outside the US use the RON number at the pump which I think is the reason the japanese use an RON number as a minimum rating recommendation.

No question that in most cases a properly tuned YZF will survive just fine on pump premium, but it will be far from optimized. ?

[SSpeeDEMONSS]

what is racing castor?

[Rich_Rohrich]

what is racing castor?

Click this link : http://www.planetkarting.co.uk/castrol.htm

[WR426madness]

flyinguitars is correct the higher the octane the less combustionable the fuel is so run the lowest high grade fuel you can run without ping for max power. ?

[Rich_Rohrich]

flyinguitars is correct the higher the octane the less combustionable the fuel

The octane rating has nothing to do with it. The hydrogen/carbon bonding of the fuel's components will determine how easily the fuel can be reacted and it's ultimate heat release.

Once you meet the engine's basic octane requirement, which in the case of the YZF is pretty much met by premium pump, the fuel's distillation (aka vaporization) curve is the single most important spec you should be looking at. The specific energy of the fuel is important as well, but if you can't vaporize the fuel the energy can never be released so it takes a back seat.

In other words you should be looking for a fuel that has a reasonably low front end temperature range (for good throttle response) and 90% vaporization and end point temperatures low enough to allow complete vporization of the fuel at high rpm. Basic rule of thumb for high speed single cylinder engines is, any fuel with a 90% vaporization temperature greater than about 240F will make less power above 7000 rpm than a fuel with a lower 90% temp all else being equal. For the record the 90% temperature of summer gas in Illinois is in the 340-370F range. It's similar in other places.

Choose your fuel wisely boys, there is more power in good combustion and proper tuning than those most of the shiny pipes people sell.

Here's what a curve for a proper high rpm four-stroke MX race fuel looks like (blue line on graph) and how it compares to pump fuel. (Special thanks to Dave Redszus from Firepower Fuels / Precision Automotive Research for the graph data)

[ncmountainman]

how does adding toluene to pump gas work in relation to what is being said? does it just raise the octane or does it actually burn more efficiently? ?

[Rich_Rohrich]

how does adding toluene to pump gas work in relation to what is being said? does it just raise the octane or does it actually burn more efficiently? ?

Toluene will raise the octane but it will also raise the 90% and end point temperatures to a range similar to that of pump gas, along with raising the specific gravity. Depending on it's intended use the specfic gravity of good race fuel is in the .700 - .760 range, while pump fuel is usually in the .720-.770 range. Depending on it's purity commercial Toluene can range from about .850 - .890 .

Air/fuel ratio is determined by the weight of the air and the weight of the fuel, so you can well imagine how making changes to the specific gravity of the fuel will have a subsequent effect on the fuel curve .

[grayracer513]

If you want more, here's a very thorough and surprisingly readable work on the entire subject of gasolines. Part 6 addresses the issue of octane and detonation.

http://www.faqs.org/faqs/autos/gasoline-faq/

[beezer]

What fuel would you reccomend?

I have a drum of VP Red that I use with my 2 strokes. I have some high strung 2 stroke street bikes that won't run on pump gas. Should I use that in my YZ450? To be honest the bike has way more power than I can handle stock. It starts easily and runs great. Would there be any advantage to using the VP in my YZ?

[Ga426owner]

What fuel would you reccomend?

I have a drum of VP Red that I use with my 2 strokes. I have some high strung 2 stroke street bikes that won't run on pump gas. Should I use that in my YZ450? To be honest the bike has way more power than I can handle stock. It starts easily and runs great. Would there be any advantage to using the VP in my YZ?

NO!!!!

trade it out for VP U4.

That VP Red is too high in octane -

[flyinguitars]

flyinguitars is correct the higher the octane the less combustionable the fuel is so run the lowest high grade fuel you can run without ping for max power. ?

haha...thanks, but thats not exaclty what I said. I said:

No. Octane # is the resistance to detonation. Higher compression requires higher octane. If your bike requires 95, then youre just wasting money paying for a higher octane gasoline. Many people think that higher octane means better quality....again octane is just a resistance to detonation rating. Many people swear by race gas and avaition 100LL, but I believe that is because those fuels are more consistant and enable fine tuned jetting.

resistance to detonation and less combustionable can have two different meanings....detonation is spontanious combustion - an explosion - the fuel/air charge explodes like a bomb inside your engine and causes damage to the engine.....

combustion means burning...which is what should happen to the fuel/air charge inside the engine.

I was trying to keep it simple and and perhaps let the poster know that octane is simply a rating against detonation. Most people thinkthey are treating their cars to something special if the put in premeum......most don't realize that they are wasting money unless their car requires a high octane gasoline....same thing applies to the yzf's......so for everybody - in answer to the original question "Does 100 octane make a difference" NO....he wasn't asking about a specific type of gas ie: race gas or avaition 100ll. Just about the octane making a difference in a yzf...thats what I was trying to say!

[gonzo]

Wow 500 octane posts and everyone is starting to finally learn.

[ncmountainman]

how does adding toluene to pump gas work in relation to what is being said? does it just raise the octane or does it actually burn more efficiently? ?

Toluene will raise the octane but it will also raise the 90% and end point temperatures to a range similar to that of pump gas, along with raising the specific gravity. Depending on it's intended use the specfic gravity of good race fuel is in the .700 - .760 range, while pump fuel is usually in the .720-.770 range. Depending on it's purity commercial Toluene can range from about .850 - .890 .

Air/fuel ratio is determined by the weight of the air and the weight of the fuel, so you can well imagine how making changes to the specific gravity of the fuel will have a subsequent effect on the fuel curve .

o.k. so it will run richer,right if the proper jetting corrections are made(leaner) this will result in better fuel economy? and will it show any performance gains once jetted for it? i'm guess'in more air less fuel(but the same properties) will = better burn, more power(at least smoother running),no?