[Harsay]

Some race fuels have a lower specific gravity, and require mapping to run on that type of fuel... your bike already runs lean from the factory, so additional leaning is not a good strategy. Higher end fuels are even oxygenated so they would be lean much more so requiring proper mapping.

As the octane is the resistance to detonation, the additives replacing actual fuel may not be beneficial to produce the best power for a stock compression engine.

My 1098R on the other hand, has 15:1 and like the VP110

 

[wigster]

Wigster my manual on page 4-16 says: "Your Yamaha engine has been designed to use premium unleaded gasoline with a pump octane number [(R+M)/2] of 91 or higher, or a research octane number of 95 or higher." Maybe that's where your 95 comes in place?

Ah, of course, two different standards - I really should have realised that!

 

[wigster]

As a footnote on this, I ran three tanks of 97 RON through. Saw no difference in performance or economy, only in how much I had to pay!

Sent from my HTC One_M8 using Tapatalk

 

[porsche996]

User the lowest octane rated fuel that doesn't cause premature detonation (pinging/knocking) in the engine for the best performance, best mileage. That's because the higher the octane rating, the harder the fuel is to ignite under compression. For the best performance, you want the fuel to be easily ignited, but not so easy it self-combusts like a diesel engine...

 

[dougied]

The higher octane does nothing for performance unless you actually need it. In fact your bike will make less power with higher than needed octane due to the higher octane fuel actually burning slower. We use high octane because it's more resistant to detonation. Unless you're using nitrous, a turbo, or very high compression, the added octane will only hinder performance rather than improve it.

100 % correct answer. It (91-93) burns SLOWER than 87. There's a little more science in there but suffice to say it's ALWAYS best to run what the manufacturer recommends you run!

 

[LouG]

One strange thing I've noticed, KevXTX told me this, I was running E10 98 fuel in the bike, that company doesn't do 95 of any sort. When I mentioned to him that the throttle had become more twitchy, he recommended not using E10 as he'd struck issues with O2 sensors on that fuel.
I'm now using straight 95 and it does feel better.

 

[Emporer Zurg]

Reviving this thread because I've noticed my Gen3 MT09 runs smoother and the throttle is livelier using Shell V Power, which is 98 RON here in HK, imported from Singapore. The regular unleaded is 95 RON. The difference with others experience might be the absence of any ethanol in the fuel here?

 

[LouG]

I noticed the same when we had V Power, but I don't think it had anything to do with it's octane rating. More likely it's the additive package Shell uses because V Power was rated at 95 here like every other premium brand
Using anything above 95 RON on an 09 is just wasting money.

 

[Emporer Zurg]

I'm lucky that the Shell stations here sell V-Power at the same ludicrously high price as regular on Wednesdays so it's no extra cost. I probably wouldn't even have tried it if they did not.

So the bike gets 98RON unless I cannot wait until Wednesday to fill up - and when that happens I notice the 95RON (minimum advised by Yamaha) is not the same juice and it is obvious - like a diet version

I wonder if the gen3 ecu has any way to alter timing based on sensor readings? if it can adapt to different fuel octanes, then it would fully explain my experience.

The other thought is that the 98 is actually 95 and 95 is like 93 or something. Seems unlikely but it's perhaps another way to explain.

 

[LouG]

Modern engines are designed to operate as efficiently as possible with a certain octane fuel, with a safety margin to prevent detonation and pre-ignition. Boosted engines like my EA888 VAG engine can run on 95 instead of 98, but that's because the ECU is reducing timing, and power, to suit. ECU's do not increase timing in the same way.
To take advantage of a higher octane fuel you would need to modify it. More compression, greater volumetric efficiency, different fuel and timing maps etc. Simply using a higher octane fuel makes no difference on a stock engine.

 

[Emporer Zurg]

It depends on the engine design - knock sensors are used to adjust timing to suit octane.

YouTube has a video of dyno runs showing higher octane produces some tiny amount more power/torque - 1% iirc - in an Accord with no modification. Of course, the ecu was advancing the timing because the engine has sensors, although the video didn't show this.

Another video of a Mustang showed even less gain and concluded the engine needed a tune for the different octane. I don't know if that car has knock sensors.

There's another I saw where they modified a Golf TSi (it has knock sensors) to run two cylinders on one fuel and the other two on another and they also fitted pressure sensors to measure the change because of the fuel - they found pressures are much higher with the higher octane. They then reversed the cylinder arrangement to show this pressure increase wasn't because of differences between cylinders or any other changes - just the fuel. IIRC this video showed the change in timing too.

So different fuel does make a difference but it seems that this either needs a design that can make the most of the change or it needs advanced timing.

Circle back -
I wonder if the gen3 ecu has any way to alter timing based on sensor readings? if it can adapt to different fuel octanes, then it would fully explain my experience.

The other thought is that the 98 is actually 95 and 95 is like 93 or something. Seems unlikely but it's perhaps another way to explain.

One thing that might make a difference in 09 owner experience - my gen3 bike has a straight through exhaust - no cat or noise reduction chambers and piping.