Premium Gas

[slapnpop]

Octane rating is simply based on the fuel's knock tendancy (also called pre-ignition or pressure induced self-ignition).Knock tendancy is based on free radicals present in the fuel prior to ignition.

Octane is not a measure of power or energy but a measure of burn. Higher octanes can burn slower but may not.

Octane actually makes the fuel harder to ignite, hence it's use in very high performance engines. These engines make their power from the compression, not the octane in the fuel. An engine's power output is a funtion of the pressure created in the combustion chamber above the piston. The more compression, the higher the pressure at the moment of ignition and the more "push" down on the piston.

A fuel that does not knock (89 octane for the FJR) will produce the same power as higher octanes.

If your FJR knocks with 89, go up to 91. Other than that, it matters not. Use the lowest octane that does not knock.

Racing Gasoline and Alcohol (Methanol or Ethanol) is different and is really only needed when detonation problems are evident. Their energies are not really different from gas. 10% ethanol in pump gas is fine.

This is 100% correct.

One addition,

Standard vehicles engines can preform better with higher octane gas, but the ignition timing must be advanced as well. Some engines have a "knock sensor" that helps the computer control the ignition timing, to keep it just before the point of knocking. This kind of system can adjust to the grade of fuel on it's own, if there is any benefit to be had. The FJR does not have a knock sensor, and does not make adjustments for the grade of fuel.

 

[YukonG]

I know an honest Yamaha salesman in Oklahoma City.

I asked him every leading question I could, trying to see if he would lie.

I did not catch him lying at all.

 

[ionbeam]

I know an honest Yamaha salesman in Oklahoma City.I asked him every leading question I could, trying to see if he would lie.

I did not catch him lying at all.

I've never met a deaf, mute sales person!

:lol:

 

[ShawnKing]

I wonder how many sales are lost because of this one little screw up by the idiots on the showroom floor?

Probably as many as are made.

I was in my local dealership when I saw a mother looking at Suzuki 600's and 750's for her 16 year old son. (!) She said to the salesman, "So this 750 one has 150 more horsepower than the 600 one for only $500 more?"

The salesman said, "Yup!"

I couldn't call the manager over fast enough...

 

[ngarider]

Old tuner trick: take vehicle that runs on sub 90 octane gas (adjust for altitude of course). Add premium fuel. Add timing until it pings, then back off a couple degrees. Free power.

Knock sensor inputs that can be remapped are great -- you can tune the vehicle for middle of the road temps, and use the knock sensor to retard timing -- which would be in warmer temps.

Back on topic - running premium gas is a waste of money in the FJR UNLESS you advance the timing or if you notice any pinging on the low grade gas.

 

[El Toro]

The calorific value of ethanol is about half that of straight run gasoline, so a 10% ethanol blend gasohol will have about 95% of the calorific value of the straight run gasoline.

How long will it take for this thread to find its way to NEPRT? 3... 2..... 1.....?

 

[slowpoke]

This is why it's important to do your homework before going to the dealership...

 

[ROCK]

......

A common misconception that Premium gas is the "good stuff". Guess it is that word "premium"..high test gas does not burn as well or as fast as the other grades. It is used in machines that have a problem with knocking or preignition. That is it. All gas has additives, especially nowadays.

High performance motor? Sure, but as far as gasoline goes, you have to be over at least 11.5 : 1 compression where premium gas might be needed. High compression engines require premium grades of gas, not neccessarily High "perfomance" ones...

And you may not work for an oil company, but you have fallen for their propaganda..

KM

Well said, it is ONLY about the compressions ratio that an engine has that determine the type of grade we put in to our Engine, how fast the gas burns once a spark is present.

A second thing is, yes maybe all gas is the same, BUT it is not stored and regulated the same. The reputable stations have better regulations for in ground storage put on by themselves. Shell, for a fact and Chevron, Marathon, Amaco all regulate the amount of moisture in the ground tanks, and actually make sure that the moisture is not in the gas before we put it in our tanks. Some of the older Mom and Pop stations do not have the regulators that the newer up to date stations have.

 

[seniorbiker]

Old tuner trick: take vehicle that runs on sub 90 octane gas (adjust for altitude of course). Add premium fuel. Add timing until it pings, then back off a couple degrees. Free power.
Knock sensor inputs that can be remapped are great -- you can tune the vehicle for middle of the road temps, and use the knock sensor to retard timing -- which would be in warmer temps.

Back on topic - running premium gas is a waste of money in the FJR UNLESS you advance the timing or if you notice any pinging on the low grade gas.

Thats exactly how I used to set the timing on my 65 Corvette back in the day........rotate the distributor until it pinged under load, then back it off until it didn't.

 

[str8]

I've tried 91 octane and in my humble opinion the fjr actually runs smoother (less vibration) and generates same level of power with 87 octane. Don't waste your money.

 

[charismaticmegafauna]

<snip>... High performance motor? Sure, but as far as gasoline goes, you have to be over at least 11.5 : 1 compression where premium gas might be needed. High compression engines require premium grades of gas, not neccessarily High "perfomance" ones...

Well said, it is ONLY about the compressions ratio that an engine has that determine the type of grade we put in to our Engine, how fast the gas burns once a spark is present.

Not quite -- intake mixture "tumble' and "swirl" all have an effect on how well distributed all the molecules are and how 'rarified' the pre-explosion mixture is.

We could never have gotten away with the compression ratios we have today and still use the octanes we use today without multi-valve heads and combustion chambers like the 4-valve 'pentroof'. Back in the day -- with 2 big valve, hemispherical, domed pistons (for compression) -- compression ratio was a really limiting factor. Today, not so much.

 

[ngarider]

Um, no. Compression affects the combustion characteristics of a cylinder, but it's FAR from the only thing that dictates the knock retard rating (octane). In fact, the compression ratio has nothing to do with ignition, pre, late, or otherwise.

NERPT in 5.....4......

Well said, it is ONLY about the compressions ratio that an engine has that determine the type of grade we put in to our Engine, how fast the gas burns once a spark is present.
A second thing is, yes maybe all gas is the same, BUT it is not stored and regulated the same. The reputable stations have better regulations for in ground storage put on by themselves. Shell, for a fact and Chevron, Marathon, Amaco all regulate the amount of moisture in the ground tanks, and actually make sure that the moisture is not in the gas before we put it in our tanks. Some of the older Mom and Pop stations do not have the regulators that the newer up to date stations have.

 

[Bounce]

re: OP's salesman

D3

iow: DDD!

 

[ionbeam]

...In fact, the compression ratio has nothing to do with ignition, pre, late, or otherwise...
NERPT in 5.....4......

I'll bet ya a Caterpillar D399 that compression ratio has something to do with ignition.

 

[ngarider]

I realize it's semantics, but CR is just a ratio (the maximum compression of . Actual compression (pressure) is the factor that affects combustion (and, for this discussion, point of ignition), not the ratio.

A 13:1 ratio doesn't necessarily need 93 (or 105, etc). I can retard the timing on a high compression motor to the point that 87 will work. Does it affect torque? Absolutely. Likewise, I can advance the timing on an 8:1 motor to run 105 and get some nice power gains to boot.

And the D399 is a diesel. I'm worrying about cetane ratings and when 'preignition' occurs -- since, as we all know, diesels actually RUN on knock. We're talking about gas motors here. If a gas motor with high compression (and, hey, lets say cylinder pressure is actually high because of misaligned or failed rings) predetonates, the compression ratio had nothing to do with it. Would you agree?

 

[Rob]

L Old wives tale.

Mine told me the same thing. I know that the Camaro that came out a few years ago the book said to use Hi Test. But it really doesn't matter in this case. The price difference between the 87 Oct and 91 Oct is minimal. If you feel comfortable using the lo test use it if not use the Hi.

We are talking about a savings of about $.50 every tank so that is a savings of $.011 Cents per mile?? It is hard to believe this post went this long for a penny a mile on a $14K bike that most have added another $2K in Farkles for.

And who's old Wife was telling Tales?

 

[Scab]

It is hard to believe this post went this long

Iggy must be out of town.

 

[Bounce]

https://www.fjrforum.com/forum//index.php?showtopic=26075

has 5 threads under the heading Octane.

 

[shredder]

In addition to the above listed posts.... I can also tell you that octane is the quiet and not well known robber of power. If you engine runs well on 87 then 91 will show less power at your rear wheel. Octane simply resists combustion. Think it's crazy? Rent a dyno and see for yourself. My old 89' stang w/ a highly warmed over 306 ci lost 8 hp at the wheels w/ 105 octane vs. 93. Keep in mind...if you need the octane to avoid detonation or "pinging" then it is the best option. Otherwise use the fuel that is best suited to making your engine function the most efficiently.

 

[wellsj]

Well I can tell you that I have a old FL Trooper car that pings like a bitch on anything but 93 octane fuel. I could have solved this a long time ago by adjusting the timing, but of course that is something only a dealer can do. It has the same compression ratio as any other Crown Vic , timing has everything to do with it. On the plus side it does get a little better mileage with the premium fuel. Thank God the FJR runs great on regular gas as thats about the only thing I use for most of my transportation needs these days.