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**aargee** · 08-25-2011, 07:32 PM

Originally posted by kurtrules View Post

What is the recommended fuel octane rating for the CBR250R and what fuels are you folks using and why?

Regular fuel which is 91 Octane. FOR SURE. I remember reading somewhere in the manual, not sure though.

Originally posted by kurtrules View Post

I was using normal unleaded as there no diff between that and the Xtra premium apart from a few additives (Both 91 octane)

Obviously!!! See, the additives are just to take care there's less friction, anti rust etc. Other than this, it does nothing.

Originally posted by kurtrules View Post

I want to know if I am right or should look up to filling in Speed 93

If you want noteable difference, use Speed 97 (costs Rs 800/760 for 8 lts or so, not sure). The smoothness of the engine will be amazing as the detonation is deffered. BTW, is there Speed 93

What's the RON for it? 95?

**aargee** · 08-25-2011, 07:34 PM

One important question to all C250R owners - Have you guys observed if there's a small hole between the exhaust pipe & catalytic converted underneath? If you start the engine & put your hands below, the exhaust joint & silencer, you can feel the air hitting your hand. Just wanted to know, if its only for me or for everyone else.

For easy identification, test around the encircled portion on your vehicle.
Caution - Do not touch, but put your hands beneath & feel if you can feel the air gush.

**kurtrules** · 08-25-2011, 07:36 PM

Yes, its there

**kurtrules** · 08-25-2011, 07:36 PM

Originally posted by aargee View Post

Regular fuel which is 91 Octane. FOR SURE. I remember reading somewhere in the manual, not sure though.

Obviously!!! See, the additives are just to take care there's less friction, anti rust etc. Other than this, it does nothing.

If you want noteable difference, use Speed 97 (costs Rs 800/760 for 8 lts or so, not sure). The smoothness of the engine will be amazing as the detonation is deffered. BTW, is there Speed 93

What's the RON for it? 95?

RON for it is 93.

BTW, can you explain the term "detonation is deferred"?.

**aargee** · 08-25-2011, 07:43 PM

Originally posted by kurtrules View Post

BTW, can you explain the term "detonation is deferred"?.

Lol!!! I expected this...

Petrol without Octane catches up fire immediately with a mild pressure & spark. So Octane is added so that the compression can be with stood but not the spark; remember that during compression heat is also generated. More Octane, more with standing capacity of compression. Assume you've a 13:1 compression ratio & if you use 91 Octane, the moment heat increases beyond a certain limit, even before the plug fires, the petrol fires & explosion happens. This is a serious issue because, as long as FI supplies fuel the engine starts running without the help of plug or CDI

So once this happens, its almost impossible to stop the cycle.

Anyway, coming back to topic, more octane means, higher the capacity to with stand the heat from compression, which I termed as detonation is deffered.

**kurtrules** · 08-25-2011, 07:50 PM

That I understand pretty well aarge. Lower octane fuel in a high compression engine would cause pre-mature ignition owing to compression rather than spark resulting in knocking. Why I asked the meaning of the term was I thought that this is responsible for higher efficiency, but I cannot connect the two. An engine with recommendation of 91 RON would run fine with 91 RON, so how does 97 RON refine the engine?

**aargee** · 08-25-2011, 09:19 PM

^^^ It refines not on all engine, like, it messes up my Rx. It does help on LC engines where the CR is more than 10. I assume, 97 RON burns up less premature & causing less explosion & probably more effectively.

**psr** · 08-25-2011, 09:40 PM

Ji here is a useful link
Octane rating - Wikipedia, the free encyclopedia

**aargee** · 08-25-2011, 09:42 PM

^^^ Brilliant Sir

This is the key...

The higher the octane number, the less likely is the fuel to ignite prematurely in the engine's cycle and cause the engine damage

**psr** · 08-25-2011, 09:59 PM

Originally posted by aargee View Post

^^^ Brilliant Sir

This is the key...

And Higher Octane does not mean greater power...The surprise here is
" Lead in the form of tetra-ethyl lead was once a common additive, but since the 1970s, its use in most of the industrialised world has been restricted, and its use is currently limited mostly to aviation gasolin "
So there is Tetra -ethyl lead in aviation gasoline...and hence lead pollution continues..at a higher altitude..

**r13nick** · 08-25-2011, 10:49 PM

when i ride my bike more than 20km or so and then i stop it, it gives the sound like knock kncok.
what kind of sound is that..?
any help pls..

**aargee** · 08-25-2011, 11:01 PM

Originally posted by psr View Post

And Higher Octane does not mean greater power...

Ji...then, I'm trying to think which is little difficult to put here...wouldn't the firing happen a little less milli second than regular 91? Which mean the piston's position from the head will also be lower than the regular 91? Trying to think if that could lead to some power gain or loss; not sure though

Originally posted by r13nick View Post

what kind of sound is that..?

Metal compression sound after expansion; happens with all 4joke engines!!!

**r13nick** · 08-25-2011, 11:06 PM

Originally posted by aargee View Post

Metal compression sound after expansion; happens with all 4joke engines!!!

Do i need to worry about it..?

**techfreak** · 08-25-2011, 11:20 PM

Originally posted by r13nick View Post

Do i need to worry about it..?

No u should not....

Its happening with all of us alike

**MeTaL_MaNiaC** · 08-25-2011, 11:27 PM

Originally posted by aargee View Post

One important question to all C250R owners - Have you guys observed if there's a small hole between the exhaust pipe & catalytic converted underneath?

Yes. Had observed it long back and assumed it to be useful to drain out water that gets in accidently during washing or if parked in heavy rain as the muffler end is quiet big and slant.

@chicmagnet and all cbr owners: it would be a wonderful idea to meetup. Such way we can even discuss the problems faced by everyone and compare other bikes for same. I havent been lucky to attend even a single gtg yet

Eagerly awaited..

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