bp 98

[bikerboy]

Bluninja, I was refering to efficiency in relation to exhaust emissions. Oxygenates result in cleaner burning engines, cleaner exhausts, but result in less energy released. Engine management systems adjust for all variables to optimize the fuel, power, and emissions equation. Going to a higher octane level will not produce more power but MAY provide a smoother running engine and reduce emission polution.

[bluninja]

Well bikerboy, I'll just have to disagree on the comment about emissions and smoother running via higher octane. If this were so, don't you think that worldwide governments would be queueing up (prompted by the oil companies themselves) to get us on ever higher octane as a way of reducing emissions, rather than strangling vehicles with catalytic convertors ?

TTFN

[stevemac]

Interesting thread.
Yes, octane is resistance to knocking, which is why many people use aviation fuel (110 oct) in race engines. Because they have high compression ratios.
I have a feeling that the difference felt when changing from 96 to 98 octane fuel is because the 96 you are using is actually 95 or 94 or 93 (due to refining variances), and your engine is knocking inaudibly, sapping it of potential power. I have heard this theory of fuel octane ratings varying from the advertised value, but never heard it prooved.
Also, unless bikes these days (I am out of touch, been working on cars too long!) have knock sensors and O2 sensors, the only way for them to be adapted to lower octane fuels is to change (retard) the fuel mapping/ignition mapping, or alter the compression ratio. Compression ratio specs always seem the same for bikes no matter what the market, so manufacturers are obviously changing the mapping to suit the fuel, which is never going to be a failsafe method.
By the way, fuel octane in Japan is 98 - 100 for high grade, and 95 - 98 for regular. Regular is 93 yen a liter at the moment, which is about NZD$1.40.

[bluninja]

Interesting observation Steve. So if I read you right, then I could advance the timing on my bikes and change up to 98 RON and get more power. Simplistic I know, but that seems to be a conclusion of what you are saying.

TTFN

[stevemac]

Very simplisticly, maybe.

Like I said, I am only assuming manufacturers are playing with mapping to adjust to lower octane fuels. And remember, fuel/ignition mapping is a complex beast, it is not just a matter of advancing the timing.
I doubt that the power increase will be noticeable though. Like bikerboy said, the higher octane will burn more efficiently (no knocking) than the lower, so in the real world you could probably expect smoother performance, and a longer engine life due to less stress, rather than higher power.
So DON'T go and advance your timing, because you will probably cause pre-ignition and blow holes in the tops of your pistons! Maybe you could try and get a Japanese import ECU from a bike wreckers?

[bluninja]

Steve, don't worry I'm not about to mess about based on this forum. I know a little about performance and fueling...especially after I fitted a factorypro chip to my Aprilia. The chip was designed for bikes up to 00 which ran 44 psi average fuel pressure...as opposed to the 49 psi of the 01/02 bikes. I ended up with a lumpy engine that ran stinky rich. I ended up getting a fuel pressure regulator to lower the fuel pressure to get more power and the CO2 pots are now active so I have even more opportunity for screwing up the settings.

The most telling thing is that bikes and fuels are manufactured to commercial tolerances, so you can always improve the standard engine, and you can pay more to get a higher quality fuel (where the RON or PON are more accurate.

My experience is that I have seen no performance difference between RON 91 and RON 96 from the local forecourts, and the smoothness or not of the engine is totally subjective and open to psychological input (like when the mechanic says he's tweaked the widget for linear power delivery and the rider then says that the bike engine pulls smoother and better as he opens the throttle...though nothing on the bike has been touched.)

:bigthumb:

If a bike running on 91 RON suffers no pinking under normal operating, then IMHO raising the octane number will have no discernible effect on smoothness of running, longevity of the engine, or power increase. However this would change as soon as you start to tune the engine.
TTFN