91 octane VS 87 octane

[Skidood]

[whisperquiet]

Use this oil always.

[whisperquiet]

And don’t forget the best chain lube.

 

[Shizzle]

I would use, if at all possible, what the owners manual calls for. Premium Unleaded

[Ride On]

Don't forget... the Owners Manual also calls for, "After extensive tests, only the tires listed below have been approved for this model by Yamaha".  And those tires are, drum roll please... the stock tires. 

There's a lot of other b.s. stated in the Owners Manual, another such item is chain tension requirements.

No doubt one can adhere to every statement made in the Owners Manual, but life experience often leads one to acceptable, even better, alternatives.

[GTO MIKE]

Ok let's put the manual aside and get to the real issue at hand. The CP3 being a high compression motor requires premium fuel to perform properly and avoid the damages that lower grade fuels can cause. The main one being preignition or fuel ignighting before the piston has reached top dead center. Lower grade fuels actually burn quicker which causes this to happen and can cause damage that you don't even hear. Sure you run what you want and don't lug,rev,or ride it like it was made for. TO PERFORM. not me ill put in the best I can get and enjoy it like it was ment to be enjoyed.       MIKE 

[Ride On]

Agreed.  The real issue is engine knocking (preignition).  If your engine is knocking you need a higher octane fuel.  If it isn't, you don't. 

 

[betoney]

I've Got Gas! Should it Be High or Low Octane Fuel for My Motorcycle?

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Over the years, I’ve heard a lot of conflicting views about which fuels to use...

I called 2wheeldynoworks (forum vendor and highly regarded engine tuner here in the PNW) and asked about fuel recommendations for the CP3 motor.  They told me specifically that based on the compression ratio of the CP3 motor, they develop the fuel map for their ECU flash on the dyno using either Shell or Chevron E10 Premium. 

When asked about E0 or non-ethanol fuel (for everyday riding) they told me that depending on elevation or barometric conditions, E0 will run richer.  Feel free to run what you like in your bike. 👍

[peteinpa]

There are atmospheric conditions that cause knock. You can get away with lower octane if you don't combine all at once.  

Run hard at sea level (or below) at high ambient temps, at high baro. press. at high engine temp. and it will knock. You can't always hear it.

I suspect 2WDW advances the ignition timing in their tune for more power. 

[texscottyd]

3 hours ago, betoney said:

... they (2WDW) develop the fuel map for their ECU flash on the dyno using either Shell or Chevron E10 Premium. 

Good to know, and exactly what I run 98% of the time.   Thanks for the info! 

[Ride On]

The CP3's have been out quite a few years now.  Not a dead engine yet from 87 octane.  91 octane seems to cure a "problem" that does not exist in the CP3.

I ride at near sea level elevations and sometimes on hot days, with a passenger, running hard, on 87 octane.  Stock engine.  No knock.

As long as the combustion chamber temperatures (piston, head, valves, spark plug, carbon deposits) remains below the autoignition temperature of the fuel then there's no preignition, no knock.

Compression ratio, timing advance, air/fuel ratio, spark plug heat range, density altitude, intake air temperature, engine cooling and exhaust efficiency all effect combustion chamber temperatures.  Mess up on any combination of these and you can get preignition, on any grade of pump gas.  In a stock engine though, the experience of many, and the test of time has shown 87 octane won't harm it.  If it does, where are the dead engines? 

 

 

[PhotoAl]

Unless knock is substantial damage will not be an immediate destruction of the engine but rather a slower degradation of performance.  I'm under 1,000 feet elevation but always run Shell premium E10 - that's what is close.  When on a long trip elevations carry but can be 2,000 to 3,000 feet and occasionally cannot find 91 when I need gas.  Before next trip will get some octane booster.  All the variables like elevation, temperature and humidity can vary significantly.  IMO the cost savings are insignificant - already getting 40 to 50 MPG.  

As for the manual, it is kind of like the internet.  Some good stuff and some written by lawyers - trick is figuring out the part written by engineers - IMO fuel rating written by engineers.  Tire section written by lawyers with supervision by the marketing department.

[betoney]

14 hours ago, Ride On said:

As long as the combustion chamber temperatures (piston, head, valves, spark plug, carbon deposits) remains below the autoignition temperature of the fuel then there's no preignition, no knock.

Compression ratio, timing advance, air/fuel ratio, spark plug heat range, density altitude, intake air temperature, engine cooling and exhaust efficiency all effect combustion chamber temperatures.  Mess up on any combination of these and you can get preignition, on any grade of pump gas.

This is good info and I appreciate your point of view but with so many variables I don't want to have to use a scientific calculator or a barometer to determine octane needs for a fill-up.  (kidding, but still...)

I live in a mountainous region with greatly varying barometric pressure in each half of the state, I can go from sea level to over 5,500' and have crossed mountain passes with temperatures varying from low 90's on one side to low 40's at the summit and back to low 90's on the other side, all within 90 minutes.  WAY too many variables, I prefer to just keep it simple and use premium, when available.

[CottonTop]

Lucas offers these small one fill-up size bottles of octane booster for about 3 bucks.   Throw a couple in your tank bag and problem solved. 

[Shizzle]

Doesn't make sense to go cheap on fuel if premium is available just to say hey look at me I saved 50 cents. Not even worth the argument. If your going to be traveling and only 87 is available I'm sure the world will continue to turn as will your engine. But yep these fuel threads are as bad as oil threads.