Octane rating

[aiki]

Thinking on the fuel prices, why is it we are set on the higher more expensive octane fuels. I have checked my info on my bike, and it is recommended fuel over 87 rating so 91 should do well. Look at this site for some interesting facts on fuel. http://www.leeric.lsu.edu/bgbb/7/ecep/trans/b/b.htm
My bikes compression rating seems perfect to use the 91 completely.
Any wise souls who know better are welcome to let me know.:sherlock:

[Motu]

Because there are a lot of vehicles on the road that require a higher octane fuel.These people have the right to keep these vehicles on the road,and so therefore have the right to be supplied with a fuel that allows them to run efficiently.You may think they are stupid,and that such old or modified vehicles should be banned from our roads.If so,I suggest you join the Labour Party and put the legistation in place - although I think they have it well in hand.

[Ixion]

Alfatoy is 2001, so not exactly old, warns in NO uncertain terms, in the drivers manual, in the boot, and behind the fuel filler cap that you MUST use minimum 95RON fuel ONLY.

[Motu]

Well the octane rating for that car is far too high - please surrender car and keys to your nearest police station....um,hang on,I have a faaaaar better idea.....

[aiki]

Why is it my post topics bring out the loonies :blip: who can't see the wood from the trees, often simple questions have simple answers.
The reality is likely we put the wrong octane in our tanks thinking it will perform better.

[Motu]

I don't think anyone does that,most shop on price alone.

[skidMark]

Why is it my post topics bring out the loonies who can't see the wood from the trees, often simple questions have simple answers.


now i think you are missing the point....

this is kiwibiker....

WE ARE ALL LOONIES :doobey: :woohoo: :eek: :bleh: :kick: :slap: :baby: :wari: :thud: :shutup:

[Quartida]

I don't think anyone does that,most shop on price alone.

This is the problem....I persist in filling my '89 Lancer with 95 or above as it has a large sign in RED AND WHITE LETTERING that insists

"USE 96 OCTANE FUEL ONLY"

(OK, I do use 95, but that's because 96 doesn't exist any longer.)

And people laugh at me as they tell me that it actually "doesn't matter that much".

But as some caring people have explained to me, it DOES matter. And besides, I cannot ignore signs. I just can't.

So I shop according to what is "best" for my car.

[skidMark]

rip the sticker off and put 91 in it......

once i put BP 98 octane in my gpx among every other bike ive ever owned i have tried it in just once to see how it goes.....they advertise smooter acceleration yer it was bloodey smoother alright thats cus thier was none! it has made every single one of my bikes a gutless pile of poo (yes more than usual) when i put 98 in i put 91 in and they perform so much better

[scumdog]

This is the problem....I persist in filling my '89 Lancer with 95 or above as it has a large sign in RED AND WHITE LETTERING that insists

"USE 96 OCTANE FUEL ONLY"

(OK, I do use 95, but that's because 96 doesn't exist any longer.)

And people laugh at me as they tell me that it actually "doesn't matter that much".

But as some caring people have explained to me, it DOES matter. And besides, I cannot ignore signs. I just can't.

So I shop according to what is "best" for my car.

Just stand near an intersection on a hilly part of town and listen to the cars 'pinking' as the drivers lug them up the hill in too high a gear on too low an octane fuel.. I shudder to think what it's doing to piston tops etc.

I could run 91 in my 10.5 to 1 comp.ratio 429 V8 - IF I retarded the timing by about 10 degrees!! Then it would run like it was 3 litres instead of 7 - BUT use the 7 litres worth of fuel.!!!
i.e. running a fair bit of advance and expensive high octane can be more fuel eficient than sticking to cheaper fuel but less timing advance...

Go with what the 'book' says - and if you feel like playing then advance the timing and use the more expensive fuel - I know I can tell the difference in horsepower.

Modern 'puter controlled engine do the adjusting for you - only they don't advance the timing for high octane fuel so much as retard it for poor quality
(low octane) fuel.

[Quartida]

That makes me feel better.
My argument has always been - I am a typical girl. I know little or nothing about engines and fuel, except you need one to keep the other going. Therefore, I shall follow manufacturers' suggestions as they know more than I do.

I always suspected there was a good reason for using the right fuel, so I am glad that I now understand the reasoning a lot better.

Now all I need (don't worry, you don't actually HAVE to explain it to me, I'll find out from someone who has many hours of free time) is exactly HOW the octanes work and WHY it makes the engine run less/more efficiently.

Then I will have achieved "petrol harmony". And I can wiggle my tongue at the naysayers.

[skidMark]

Just stand near an intersection on a hilly part of town and listen to the cars 'pinking' as the drivers lug them up the hill in too high a gear on too low an octane fuel.. I shudder to think what it's doing to piston tops etc.

I could run 91 in my 10.5 to 1 comp.ratio 429 V8 - IF I retarded the timing by about 10 degrees!! Then it would run like it was 3 litres instead of 7 - BUT use the 7 litres worth of fuel.!!!
i.e. running a fair bit of advance and expensive high octane can be more fuel eficient than sticking to cheaper fuel but less timing advance...

Go with what the 'book' says - and if you feel like playing then advance the timing and use the more expensive fuel - I know I can tell the difference in horsepower.

Modern 'puter controlled engine do the adjusting for you - only they don't advance the timing for high octane fuel so much as retard it for poor quality
(low octane) fuel.

how much hp would one expect to gain on a 40 hp gpx 250 if one was to advance the timing and put 98 octane in her?

[BeakerRAT]

Go with what the 'book' says - and if you feel like playing then advance the timing and use the more expensive fuel - I know I can tell the difference in horsepower.

Modern 'puter controlled engine do the adjusting for you - only they don't advance the timing for high octane fuel so much as retard it for poor quality
(low octane) fuel.[/QUOTE]

I agree - and note the fuel we get here is often of poor quality. They use all manner of additives to get the octane rating to the levels quoted.

[Ixion]

That makes me feel better.
My argument has always been - I am a typical girl. I know little or nothing about engines and fuel, except you need one to keep the other going. Therefore, I shall follow manufacturers' suggestions as they know more than I do.

I always suspected there was a good reason for using the right fuel, so I am glad that I now understand the reasoning a lot better.

Now all I need (don't worry, you don't actually HAVE to explain it to me, I'll find out from someone who has many hours of free time) is exactly HOW the octanes work and WHY it makes the engine run less/more efficiently.

Then I will have achieved "petrol harmony". And I can wiggle my tongue at the naysayers.

Very wise. There is more nonsense talked about octane rating than any other topic. Your engine, and any other engine, is designed to work with a certain octane rating. Some engines will be designed for a higher rating , some for low. Stick with using the fuel which your engine was designed for.

The simple simon explanation of how octanes work.

Engines suck in air/fuel mixture, then squeeze the mixture, before the spark plug ignites it and makes it burn. It is the burning of the fuel which produces power.

Some engines are designed to squeeze the fuel mixture more than others. The amount of squeeze is called the compression ratio.

But if you squeeze too hard, the mixture may EXPLODE instead of burning. This can cause major damage to the engine.Explosions do that.

Fuel with higher octane eating is less likely to explode than lower rating.But, conversely, higher octane fuel burns slower than lower octane. Other factors being equal, the faster the fuel burns the more power you get.

So if you have an engine designed with lots of squeeze ("high compression ratio"), you need higher octane rating . Or your engine may be damaged.

But if you have an engine with less squeeze ("lower compression ratio"), and you use high octane fuel, the fuel wont burn fast enough, and the engine will have less power. So you lose on power and pay more too.

Putting high octane fuel into your low squeeze engine won't give more power. it will give less.

simple rule:
More squeeze, more octane.
High squeeze, low octane = bad.
Low squeeze high octane = bad.

How do you know which octane rating you need. Read the handbook!

Remember, that just because someone else reckons HIS engine runs fine on 91 , yours may not - they may have different compression ratios. And vice versa. Follow the manufacturers recommendation. It is just possible they know something about the engine they designed.

Of course, it's far more complicated than that.It always is, isn't it. But that's the principle of it.

[Quartida]

Ixion, sometimes I feel like you know everything.

Thanks :D

[inlinefour]

When I brought my new bike i was specifically told by the dealer to only put 91 into it. I was told that any fuel with a higher octane rating would be detrimental to the bikes well being. Considering I still want to have the bike when Im retired, I listen.

[ZeroIndex]

So I shop according to what is "best" for my car.
who cares what's best for your car? sell it.. you've got a bike.. that's all the transport you need.. :yes:

[grandpa_dave]

Doesn't the higher octane rating mean the fuel burns SLOWER and because it burns slower it is PUSHING on the piston (during the power stroke) for longer thus producing more power.
But yeah, the fuel exploding is bad. It should burn in a controlled front from the spark plug through the cylinder, PUSHING the piston down rather than exploding and SHOVING it down, this is when some of the little (sometimes important) bit inside your engine can get bent.
If said engine is tuned to run on 91 and you chuck 98 in it for instance the fuel will still be burning after the power stroke and leave all sorts of nasty deposits on its way out of the engine. However if you switch back to 91 these should burn off again without causing any problems, although prolonged running on the wrong fuel will eventually (and we could be talking 1000's of k's) cause problems or excessive wear and tear.
Avgas has an octane rating over 100 (110 I think from memory) and still has lead in it, so if your engine is tuned to run it you will get SIGNIFICANT power gains from running it, but if your engine is tuned to run 91 you will have all sorts of problems. (Lead in petrol is a whole other, quite interesting, story-Check the "dog and lemon guide" for cars to see just how the petrol companies have everyones best interests at heart)

[aiki]

I'd like to know what the USA gas octanes are as my handbook says to use 87 octane. Now is that like 4 below our 91 or does the US use different gradings like when you compare US and UK shoe sizes.

[FlyingDutchMan]

Doesn't the higher octane rating mean the fuel burns SLOWER and because it burns slower it is PUSHING on the piston (during the power stroke) for longer thus producing more power.
But yeah, the fuel exploding is bad. It should burn in a controlled front from the spark plug through the cylinder, PUSHING the piston down rather than exploding and SHOVING it down, this is when some of the little (sometimes important) bit inside your engine can get bent.
If said engine is tuned to run on 91 and you chuck 98 in it for instance the fuel will still be burning after the power stroke and leave all sorts of nasty deposits on its way out of the engine. However if you switch back to 91 these should burn off again without causing any problems, although prolonged running on the wrong fuel will eventually (and we could be talking 1000's of k's) cause problems or excessive wear and tear.
Avgas has an octane rating over 100 (110 I think from memory) and still has lead in it, so if your engine is tuned to run it you will get SIGNIFICANT power gains from running it, but if your engine is tuned to run 91 you will have all sorts of problems. (Lead in petrol is a whole other, quite interesting, story-Check the "dog and lemon guide" for cars to see just how the petrol companies have everyones best interests at heart)

As long as the gases don't escape past the rings or valves, the pressure will remain in the piston, pushing it down. At high revs, you'll need a faster burning fuel.

Petrol has almost the same calorific value per litre regardless of octane rating. AFAIK higher octanes have slightly lower calorific values. Methanol has about 1/2 the calorific value of petrol, even though it has a much higher octane rating. As long as the stochiometric ratio is kept (12.7 parts air to 1 part petrol by mass) the maximum power output of an engine is deterimined by the amount of air that goes into it (more air = more power). This applies to internal combustion engines, jet engines, ram jets, and good old oxycetelyne torch. If you don't put more air in, you can't get more power.

On the other hand as mentioned earlier, high compression ratios or turbo'ed engines, the use of higher octane fuels is required to stop the petrol from exploding.

[Wolf]

Well, according to the specs, I'm supposed to use low octane fuel in my bike and that has been borne out by others who ride the same model - nothing but grief using high octane.

I noted that some of my old bikes ran like a haunted shithouse if I put super in them and performed so much better on regular - thanks to Ixion's "Octane for Dummies" post, I now know why.

As 91 is significantly cheaper than 95/98, I'm quite happy that my bike is supposed to run on lower octane.

I'm a bit concerned as a bloke in the States was saying his bike had issues running at 92 Octane - their "Premium" (compared with their "Regular" at 87).

Does this mean our modern 91 and 95/98 octane fuel is worse for our vehicles than the old "Regular" and "Super" fuels we had back in the leaded petrol days (which, I recall, both had lower octane than our modern counterparts)?

[Motu]

RON and MON,the octane twins.

[Skunk]

I'd like to know what the USA gas octanes are as my handbook says to use 87 octane. Now is that like 4 below our 91 or does the US use different gradings like when you compare US and UK shoe sizes.
Yep, octane ratings in the US are different to here. As Motu says MON and RON. Google it.

[Wolf]

Yep, octane ratings in the US are different to here. As Motu says MON and RON. Google it.
Thanks. Did google it and found out that the US octane is PON - Pump Octane Number - the average of the RON and MON ratings whereas ours would seem to be RON, same as Europe and Australia.


87 octane fuel, the "normal" gasoline in the US and Canada, would be 91 in Europe.

I also found a table that informs me that 95RON is 91PON, 96RON is 92PON (no wonder that American's bike was running like shit on "92 octane" and runs better on 87) and our 98RON is the equivalent of 94PON in the USA.

[Motu]

Oh,so it's the octane triplets now,I might of known.Huey Dewy and Louie.

[pritch]

Why is it my post topics bring out the loonies

LOL That's a couple of fairly senior (and knowledgable) "loonies" you have there.

[TwoSeven]

Has anyone figured out what octane does yet ?

I would have thought reading the wikipedia on petrol would have been a good start :)

[Wolf]

Oh,so it's the octane triplets now,I might of known.Huey Dewy and Louie.
Yep.

I should have realised that "the Yanks" would use a different fuel rating than everyone else, after all, they use gallons rather than litres (and even then they're American gallons rather than real gallons), they've eschewed the entire metric system, use fahrenheit rather than celsius, their light switches are upside down and they hold their knives and forks in the wrong hands - why would they use the same octane rating system? :nya: :devil2:

(joke/piss-take)

[Motu]

Has anyone figured out what octane does yet ?


In this day and age it means absolutly nothing - the whole octane thing was developed back when motors were sidevalves if they were lucky,and running about 5:1 compression.These days it's not about balancing octane and iso heptane,it's a whole new cocktail brew.And it's not even about compression ratio,but combustion chamber design and cam profiles.

[SARGE]

the only time you need to run super high octane (race gas) or even 98 is if your compression is higher than standard or you are at hi altitude.. anything else and you are pouring good $$ down the shitter for Ego's sake

i have a high comp big bore that sounds like a caribbean steel drum on anything less than 98 ( 14.5/1 compression)

most bikes run nice on 91

[Motu]

It's not even compression ratio but combustion chamber design - my old XC Coon 250ci straight 6 had 9:1 compression,but a horendous bathtub combustion chamber with 2 huge valves.When we went unleaded it would rattle even on premium,and I had to use octane boosters to drive the thing,I was rapt when 98 came out because then I could run without octane boosters.But a modern engine on 9:1 with a pent roof chamber and 4 valves can happily run on 91.

[aiki]

Yeah, very clever loonies pity they have such trouble with forming intelligible sentences, I haven't the energy to crack their coded gems.
So please speaka da english if you want people to learn something, save your wit for your bar stool.

[aiki]

I would also like to add my thanks:niceone: to those who came up with such usefull information be they clever clog loonies:crazy: or not. I can certainly feel confident that my bike should perform just as well with 91 though Wgtn Motorcycles told me i should use 95. Maybe they have shares with the oil companies, who knows :whocares:

[Titanium]

Why is it my post topics bring out the loonies :blip: who can't see the wood from the trees, often simple questions have simple answers.
The reality is likely we put the wrong octane in our tanks thinking it will perform better.

Octane is not all about performance...... if you think it is the only factor .... yu are wrong.

Not loonies pal..... just people with a different opinion than yours.:zzzz:

[Titanium]

Yeah, very clever loonies pity they have such trouble with forming intelligible sentences, I haven't the energy to crack their coded gems.
So please speaka da english if you want people to learn something, save your wit for your bar stool.
Got to stop labeling everyone who does not agree with you a loonie....... I see an ignore list addition......:yawn:

[Titanium]

As long as the gases don't escape past the rings or valves, the pressure will remain in the piston, pushing it down. At high revs, you'll need a faster burning fuel.

Petrol has almost the same calorific value per litre regardless of octane rating. AFAIK higher octanes have slightly lower calorific values. Methanol has about 1/2 the calorific value of petrol, even though it has a much higher octane rating. As long as the stochiometric ratio is kept (12.7 parts air to 1 part petrol by mass) the maximum power output of an engine is deterimined by the amount of air that goes into it (more air = more power). This applies to internal combustion engines, jet engines, ram jets, and good old oxycetelyne torch. If you don't put more air in, you can't get more power.

On the other hand as mentioned earlier, high compression ratios or turbo'ed engines, the use of higher octane fuels is required to stop the petrol from exploding.

Wrong, higher revs require a slower, cooler burning fuel......... and of course the timing curve to complete the equation .....

It is an Octane, timing, compression ratio issue, then throw in port height and width for a 2 smoker....... oh yeah also plug temp rating once you start getting deeper in to it.

It is a common misconcetption that higher octane equal hotter faster burn.....

Just had a few years building, running 300 + horse power super stock jet skis......

The other issue is that you may not achieve the manufactures specified performace figures if you use fuel other than what is specified by the said manufacturer.


Cheers

[aiki]

I don't label people as loonies because they disagree with my opinion as I have no opinion just a question or 2, which i enjoy getting answered by people who might know the answers, which maybe is the reason for this forum in the first place. ;)

[Madmax]

115 is fine fuck that other shit though:gob:

[aiki]

what the hell does that mean madmanmax

[Titanium]

115 Octane ...... possibly......

[aiki]

Don't get me wrong Titanium I love all bikers :love: I just can't understand half of what they say.:confused:

[Slingshot]

The other issue is that you may not achieve the manufactures specified performace figures if you use fuel other than what is specified by the said manufacturer.

HA HA....Achieve the manufacture's specifications....you gotta be kidding. Even following the manufacture's specs to the letter and in a perfect control environment, you'll never achieve manufacture's specifications...cause marketers make them up!




Has anyone figured out what octane does yet ?

Nope, but I guessing it does it eight times.

[Wolf]

i have a high comp big bore that sounds like a caribbean steel drum on anything less than 98
Can you get it to do "Yellow Bird"? That song always sounds great on steel drum.

[Titanium]

Don't get me wrong Titanium I love all bikers :love: I just can't understand half of what they say.:confused:

Keep your luving to yourself man, I am not that way inclined........ happily married ya know........ j/k

[Clivoris]

Marvelous.
I will stick to good old 95/96. Educational thread. Even the loonies loonies loonies...

[skidMark]

Keep your luving to yourself man, I am not that way inclined........ happily married ya know........ j/k

kidding about what exactly the not being ghey or the "happily"married

[aiki]

Well at least the bike looks cool {BMW 1200}:scooter:
I'd be interested to know if the fuel injected bikes out there are recommended to use 95 in their handbooks or is it again just one of those things we are told to do by the seller.

[Titanium]

kidding about what exactly the not being ghey or the "happily"married


You know heaps of one and fuck all of the other ........ get lost kid.

What has your post got to do with Octane.........

[skidMark]

what did your post have to do with octane.....

i listen to what a bmw rider has to say less than any other

except for ixion cus he knows his stuff hes an exception...you sir are just a cunt titanium

wanna play tit for tat...bring it on lets play....

[scumdog]

what did your post have to do with octane.....

i listen to what a bmw rider has to say less than any other

except for ixion cus he knows his stuff hes an exception...you sir are just a cunt titanium

wanna play tit for tat...bring it on lets play....

Stop drinking/smoking/snorting/sniffing/shooting-up whatever you're on, it is not doing you any good!!

[skidMark]

well ive had about 1.5 litres of coca cola...and i'm sick of him red repping almost every post i make just to be a smart ass

[scumdog]

well ive had about 1.5 litres of coca cola...and i'm sick of him red repping almost every post i make just to be a smart ass


So what? The world don't revolve around KB red reps sunshine!!!
Chill out.

[skidMark]

***wIrEd On CoCa CoLa***

[Gremlin]

I'd be interested to know if the fuel injected bikes out there are recommended to use 95 in their handbooks or is it again just one of those things we are told to do by the seller.
Can't comment on yamaha, kawasaki or honda (or the non-japs :D) but the suzuki 600 750 1000 all have stickers on the tank, stating specifically, nothing less than 95RON.

Call me ignorant, but when I asked what my bike would prefer, I was told 95/96, so thats what I do. There are risks (already mentioned) not meeting what a bike needs, and I for one would rather be a little poor, than know for a fact the bike doesn't like 91....

[ZeroIndex]

Can't comment on yamaha, kawasaki or honda (or the non-japs :D) but the suzuki 600 750 1000 all have stickers on the tank, stating specifically, nothing less than 95RON.

Call me ignorant, but when I asked what my bike would prefer, I was told 95/96, so thats what I do. There are risks (already mentioned) not meeting what a bike needs, and I for one would rather be a little poor, than know for a fact the bike doesn't like 91....
thank you for getting back on topic.. almost forgot what it was..
*silly mark.. real silly*

[SARGE]

well ive had about 1.5 litres of coca cola...and i'm sick of him red repping almost every post i make just to be a smart ass


what ya gonna spend the green rep on boyo?.. Spank doing a deal on KB clothes for Greenies or something ?

[FlyingDutchMan]

Wrong, higher revs require a slower, cooler burning fuel......... and of course the timing curve to complete the equation .....

It is an Octane, timing, compression ratio issue, then throw in port height and width for a 2 smoker....... oh yeah also plug temp rating once you start getting deeper in to it.

It is a common misconcetption that higher octane equal hotter faster burn.....

Just had a few years building, running 300 + horse power super stock jet skis......

The other issue is that you may not achieve the manufactures specified performace figures if you use fuel other than what is specified by the said manufacturer.


Cheers


My bike seems to run much nicer at 18,000rpm on 91 than 96 or 95. (Recomended minimum octane)

[aiki]

my manual says a minimum of 87 R+M, so i suppose that means minimum 91 over here as my bike is set for miles per and gallons etc.
Been an interesting discussion thanks to all who have helped.