Hi Octane fuel

[Panda]

Hi all,

Noticed the III was running quite sluggish. By accident, I put in premium petrol, (only because the garage had run out of the cheap stuff.)

Straight away, it seemed to run like the wind. The difference was quite remarkable. Is this just a coincidence, or goes the premium good stuff make such a difference.

As a further experiment, I put in some Wynn Octane booster prior to filling her up today (which seems to make it run even better, if that's possible.)

However, was then advised too high octane can blow the engine. Any thoughts?

Thanks,

Panda

[Fusion]

the higher the octane the more bang you get for your buck . I think normal ulp is 91, ethanol is 94 and premium is 98 . It does make a difference but for premium up pay through the nose for it and ethanol is normally 4 cents cheaper than ulp . Hope it helps ;)

[discowhite]

it could just be that your timing is out.

cheers phil

[PhilipA]

the higher the octane the more bang you get for your buck
I wish it were so!
Generally Octane only refers to the ability of the fuel to resist "knock" on a test rig.
The oil companies claim that their 98 octane fuels are more dense therefore give better mileage.
This may be so, but I reckon would only be on an engine with closed loop feedback, which would lean off to 14.7 :1 or whatever is set, if the denser fuel showed a lower AF ratio at the sensors.

Their claim of better performance only really applies to engines with knock sensors which retard if they hear knock. If they are fed high octane fuel, the computer advances to the maximum programmed extent if no knock is heard, thus giving better power and economy.
An old engine is so crude that little of this would apply.
In fact I found when I tried 98 in my 3.9 14CUX, that the engine stalled just before becoming fully warm, as high octane fuel is less volatile than low octane fuel.
Regards Philip A

[rovercare]

I wish it were so!
Generally Octane only refers to the ability of the fuel to resist "knock" on a test rig.
The oil companies claim that their 98 octane fuels are more dense therefore give better mileage.
This may be so, but I reckon would only be on an engine with closed loop feedback, which would lean off to 14.7 :1 or whatever is set, if the denser fuel showed a lower AF ratio at the sensors.

Their claim of better performance only really applies to engines with knock sensors which retard if they hear knock. If they are fed high octane fuel, the computer advances to the maximum programmed extent if no knock is heard, thus giving better power and economy.
An old engine is so crude that little of this would apply.
In fact I found when I tried 98 in my 3.9 14CUX, that the engine stalled just before becoming fully warm, as high octane fuel is less volatile than low octane fuel.
Regards Philip A

So you just manually advance the timing and make the most of the high octane fuel:D

[Panda]

Thanks Phil,

I have no idea what "closed loop feedback" is or "knock sensors", but I'm guessing none of this would apply to my basic 6 cylinder Landy?

Thought it was too much of a coincidence, maybe it was just wishful thinking. I've also noticed it seems to run better in colder weather? Any substance to that do you think?

Thanks for your input, much appreciated.



I wish it were so!
Generally Octane only refers to the ability of the fuel to resist "knock" on a test rig.
The oil companies claim that their 98 octane fuels are more dense therefore give better mileage.
This may be so, but I reckon would only be on an engine with closed loop feedback, which would lean off to 14.7 :1 or whatever is set, if the denser fuel showed a lower AF ratio at the sensors.

Their claim of better performance only really applies to engines with knock sensors which retard if they hear knock. If they are fed high octane fuel, the computer advances to the maximum programmed extent if no knock is heard, thus giving better power and economy.
An old engine is so crude that little of this would apply.
In fact I found when I tried 98 in my 3.9 14CUX, that the engine stalled just before becoming fully warm, as high octane fuel is less volatile than low octane fuel.
Regards Philip A

[Panda]

I had the timing done a few weeks back, but will wait til Tony returns from the UK to do it again! I too thought it may have had something to do with the timing ...

Thanks Phil


it could just be that your timing is out.

cheers phil

[rovercare]

I had the timing done a few weeks back, but will wait til Tony returns from the UK to do it again! I too thought it may have had something to do with the timing ...

Thanks Phil

Advance it till it pings, then back it off a touch:o

[Panda]

Hi Mick,

I had a look at the manual which reckons the timing should be 2 ATDC with 90 octane, 6 ATDC 85 & 2 BTDC with 83. All very confusing. What's the difference with ethanol? I thought ethanol was the same as premium (yes, I know, showing my ignorance but hence I seek all your expert advice!)

So what should the timing be set at for premium? Are different premium petrols (e.g. Caltex, Shell etc) all the same octane levels, or are some higher or lower?

What does more "bang for your buck" mean? Does that mean it fires/ignites better?

Thanks


the higher the octane the more bang you get for your buck . I think normal ulp is 91, ethanol is 94 and premium is 98 . It does make a difference but for premium up pay through the nose for it and ethanol is normally 4 cents cheaper than ulp . Hope it helps ;)

[rovercare]

Hi Mick,

I had a look at the manual which reckons the timing should be 2 ATDC with 90 octane, 6 ATDC 85 & 2 BTDC with 83. All very confusing. What's the difference with ethanol? I thought ethanol was the same as premium (yes, I know, showing my ignorance but hence I seek all your expert advice!)

So what should the timing be set at for premium? Are different premium petrols (e.g. Caltex, Shell etc) all the same octane levels, or are some higher or lower?

What does more "bang for your buck" mean? Does that mean it fires/ignites better?

Thanks

Advance it till it pings then back it off, but inconsistancy's in fuel and swapping from premium to standard stuffs this up, the ultimate timing, is just before preignition, so whats in the book is a good "base" to start with, but not always the best

[Fusion]

Hi Mick,

I had a look at the manual which reckons the timing should be 2 ATDC with 90 octane, 6 ATDC 85 & 2 BTDC with 83. All very confusing. What's the difference with ethanol? I thought ethanol was the same as premium (yes, I know, showing my ignorance but hence I seek all your expert advice!)

So what should the timing be set at for premium? Are different premium petrols (e.g. Caltex, Shell etc) all the same octane levels, or are some higher or lower?

What does more "bang for your buck" mean? Does that mean it fires/ignites better?

Thanks

Mate . I cant really help you with the timing side of things as i am not a mechanic (blknight is ;) ) but more bang for your buck means that it ignites better giving that bit more power .
The ethanol fuel is normal ulp with 10% ethanol which has a slightly higher octane and is 4 cents cheaper than normal ULP . premium is the same everywhere at 98 octane . The servo's just have all these stupid names for it . hope this helps .

[beforethevision]

Octane is the ability to resist detonation, allowing higher compression or more adavanced timing. (both = more power).

Energy density is what they dont tell you, but claim anyhow. The higher, the (potentially) less you need to add to get the same HP.


Ethanol has a higher octane and a lower energy density to ULP. So it wil lbe less HP/mileage per litre unless you have an engine that can take advantage. (as mentioed before, either high compression, or good advance systems).

Premium, often badged '98', is /typically/ denser, and has the high octane.

Cheers!

[PhilipA]

Just to throw another spanner.
Ethanol has only 60% of the calorific value of petrol, so 10% ethanol should yield 4% poorer fuel economy than straight petrol.
So the price difference of 4 cents is really nil.

BUT just to add to the subjective nature of the argument, I cannot say I have noticed any reduction in fuel economy using E10, which I have tried a couple of times.

AND re the LR 6 cylinder. They have such a low CR that I doubt they would ping until VERY advanced, and if you didn't hear it, severe damage could be done to what is now a totally obsolete engine. So I wouldn't advance it too much.
Regards Philip A

[beforethevision]

Thanks Phil,

I have no idea what "closed loop feedback" is or "knock sensors", but I'm guessing none of this would apply to my basic 6 cylinder Landy?

Thought it was too much of a coincidence, maybe it was just wishful thinking. I've also noticed it seems to run better in colder weather? Any substance to that do you think?

Thanks for your input, much appreciated.



Running better in cold weather is due to denser air, meaning more oxygen to support combustion. Meaning the burn is more thourough, or potentially more fuel is added also (EFI).

The better HP from premium on an engine with no dynamic advance control, no dynamic mixture control, etc is a tough one. Energy density would be my suggestion, but im not sure how that effects the stochiometric ratio. Burn speed is the other potential, but i dont know if premium burns faster or slower than standard petrol.

So yeah , there is probably some substance. A friend with a BMW 130i did a fairly thourough test between 91 and 98 octane from one fuel supplier. With 11.1 CR, and quality engine management, he was getting significant fuel savings. Which means more power per fuel.

Cheers!

[rovercare]

Running better in cold weather is due to denser air, meaning more oxygen to support combustion. Meaning the burn is more thourough, or potentially more fuel is added also (EFI).

The better HP from premium on an engine with no dynamic advance control, no dynamic mixture control, etc is a tough one. Energy density would be my suggestion, but im not sure how that effects the stochiometric ratio. Burn speed is the other potential, but i dont know if premium burns faster or slower than standard petrol.

So yeah , there is probably some substance. A friend with a BMW 130i did a fairly thourough test between 91 and 98 octane from one fuel supplier. With 11.1 CR, and quality engine management, he was getting significant fuel savings. Which means more power per fuel.

Cheers!

The joys of the better management systems, all they do, is advance till knock, then back it off, constantly, to maintain, good burn and economy, impressive to see it on an interface:)

[vnx205]

After hearing quite a bit of anecdotal evidence from friends and on talkback radio about how people were getting "50 kms further on a tank" and such things when they used premium unleaded, in spite of my natural scepticism, I decide to give it a trial.

I tried three tankfuls in my 1988 Camry and found (surprise, surprise) that it made absolutely no difference whatsoever. Power seemed the same and fuel consumption was definitely exactly the same as always.

It confirmed what an NRMA engineer had said on the radio. If the engine doesn't need the higher octane, it won't benefit from it.

More sophisticated, modern engines might give different results, but in mine it made the same difference as fitting a Hiclone.:p

[B92 8NW]

The vox populi seem to believe that the RON refers to the fuel's calorific value, this misinformation is a bliss to the fuel companies when Mr. DH fills his 1978 Kingswood with 98 thinking that he is making massive savings because the car "goes further".

[Slunnie]

Hi Mick,

I had a look at the manual which reckons the timing should be 2 ATDC with 90 octane, 6 ATDC 85 & 2 BTDC with 83. All very confusing. What's the difference with ethanol? I thought ethanol was the same as premium (yes, I know, showing my ignorance but hence I seek all your expert advice!)

So what should the timing be set at for premium? Are different premium petrols (e.g. Caltex, Shell etc) all the same octane levels, or are some higher or lower?

What does more "bang for your buck" mean? Does that mean it fires/ignites better?

Thanks
Firing ATDC sounds like a waste as the horse has already bolted so to speak. That the fuel is probably too good for the engine and a waste. If they are the specs you're probably better off running it on the lowest octane fuel (reg ULP) and setting the timing to suit.

Ethanol is just a fraction, or component of the fuel blend. The attraction of Ethanol also is that it is a renewable fuel, much like B10 is for Diesel (Biodiesel).

In NSW at least, there normal seems to be regular ULP at 92 octane, Premium ULP which is 95 octane and Premium 98 ULP which is 98 octane. Some Premium 98's have special names like BP Ultimate or Shell Optimax.

[beforethevision]

[QUOTE=Slunnie;712271]Firing ATDC sounds like a waste as the horse has already bolted so to speak. That the fuel is probably too good for the engine and a waste. If they are the specs you're probably better off running it on the lowest octane fuel (reg ULP) and setting the timing to suit.
[QUOTE]

Yeah, i agree, ATDC sounds waaay late. I got no idea about older engines, but with a stock yamaha r6 engine in a formula SAE car, we run up to 25deg advance at WOT (on 98 octane).

Cheers!

[Captain_Rightfoot]

What is the com ratio of the D3? It's possible that the stuff you were buying is very poor hence the difference on the good stuff.

[Panda]

Helps enormously, thanks Mick:D


Mate . I cant really help you with the timing side of things as i am not a mechanic (blknight is ;) ) but more bang for your buck means that it ignites better giving that bit more power .
The ethanol fuel is normal ulp with 10% ethanol which has a slightly higher octane and is 4 cents cheaper than normal ULP . premium is the same everywhere at 98 octane . The servo's just have all these stupid names for it . hope this helps .

[procrastination inc]

Our Subaru's ej20 motor likes 98

My disco ignores the stuff, no difference between normal ulp and premium.

So we fuel them accordingly

[isuzurover]

Just to throw another spanner.
Ethanol has only 60% of the calorific value of petrol, so 10% ethanol should yield 4% poorer fuel economy than straight petrol.
So the price difference of 4 cents is really nil.

BUT just to add to the subjective nature of the argument, I cannot say I have noticed any reduction in fuel economy using E10, which I have tried a couple of times.


Isn't this because Ethanol is partially oxygenated? Which means that while blends like E10 have a slightly lower (theoretical) calorific value, in practice they combust more completely....

[Panda]

Thanks to all for your very interesting & informative replies. Never knew there was so much involved in filling up!

Going to use up this tank of fuel & go back to regular & see if there's any difference. Think I'll take her up the shed & put the light on & see what the timings set at. Will ring George first, to see what he set it to. (If he remembers!).

Thanks for all your advice, learnt heaps.

Best regards,

Panda

ps I'll keep you posted as to the outcome:)

[JDNSW]

Firing ATDC sounds like a waste as the horse has already bolted so to speak. That the fuel is probably too good for the engine and a waste. If they are the specs you're probably better off running it on the lowest octane fuel (reg ULP) and setting the timing to suit. .....

......

As with most Series ignition settings, these are the static settings with the engine stopped. With the engine running the automatic advance mechanisms (centrifugal and vacuum) will have advanced the spark well beyond this, according to the designed curves relative to rpm and manifold pressure.

So the engine will never actually fire after TDC except at cranking speed - when it probably IS a good idea to prevent shock loads on the starter or kickback when starting by hand. Even when idling (although the centrifugal advance will not have started to change timing), the vacuum advance will ensure it is well advanced, while retarding it to allow smooth full throttle response from idling without preignition.

John

John

[Dingmark Jim]

"Octane level" is indeed a measure of how a fuel resists exploding suddenly, instead of burning smoothly without suddenly all exploding at once. Pure iso-octane (a hydrocarbon with 8 carbons in it and a particular molecular shape) was deemed to have an octane rating of 100. (There was some other hydrocarbon which had a very low number, but I forgot what one was used 30 yrs ago). Hence 98 octane resisting exploding 98% as well as does pure oso-octane. Using pure iso-octane in an engine would be terribly expensive to make, and it would also have problems vapourising on cold days, seals would explode and the fuel would provide no lubricity.

My D3 V8 gets about 5% better fuel consumption on 98 octane than it does on 95 octane (but the D3 has more electronic engine sensors than does NASA). Hence if the price difference is <5%, I go with 98. The higher octane fuels also have some more expensive additives, which do things like keep the fuel system cleaner. HOWEVER, if you put fuel (or crankcase oil, for that matter) which has all kinds of cleansing properties in an old, dirty engine, there's a risk of just moving dirt/deposits from some safe spot and plugging something expensive. There is a slight (ie, insignificant) increase in fuel density in premium petrol. It has to do with the fact that in making it higher octane, the hydrocarbon chains in the fuel are longer and straighter, which lets about 1% more pack into a litre. With no tetra-ethyl lead available to raise the octane, longer and straighter hydrocarbon chains are the alternative way of getting the octane up.

Ethanol has other properties which owners need to be aware of. As any beer drinker can understand, ethanol and water mix delightfully. In a fuel system, the ethanol can pick up old droplets of water and flow it into the engine fuel injection/carbies. The problem is that water in metal causes rust/corrosion, so putting in ethanol can cause injectors or carbies to suddenly suffer plugging from corrosion. Ethanol is also a good solvent, so it can dissolve the gum lying in the bottom of the fuel tank and deposit it in the carbie/injector.

Sorry about being a bit long-winded and technical. Something about being a Chemical Engineer who worked in a refinery a long time ago. I do recall that there were something like 34 different specifications that petrol had to meet or it had to be re-run through the refinery processing units. Changing any one component or property can cause all sorts of problems, which is why industry is not too keen to change too much too quickly.

[Panda]

Thanks for that post Jim,

I spoke to my mechanic (who has worked on Series since God was a boy), & he said basically the same thing.

Reckons it will run better on the premium stuff, but not to put in the additives (as I did yesterday!), as not a good idea & can stuff the engine. He said it'll be ok as a one off, but not to put it in in future.

For a few extra cents a litre I'm definitely going to stick with the good stuff.

Man I've learnt a lot from all these posts!:) Never realised there was so much involved in petrol!

Which reminds me, did anyone see the Top Gear episode (I think it was Top Gear?) where some bloke put used restaurant cooking oil in a diesel & it ran? He added something else to it, can't remember what it was, but they had an "official" who drained the diesel prior to the experiment, primed it etc, & it ran sweet as. Apparently only cost something in the order of 5 pence a gallon. If that's the case & it catches on, won't take the government long to suss it out & put heaps of taxes on it!

[Captain_Rightfoot]

Which reminds me, did anyone see the Top Gear episode (I think it was Top Gear?) where some bloke put used restaurant cooking oil in a diesel & it ran? He added something else to it, can't remember what it was, but they had an "official" who drained the diesel prior to the experiment, primed it etc, & it ran sweet as. Apparently only cost something in the order of 5 pence a gallon. If that's the case & it catches on, won't take the government long to suss it out & put heaps of taxes on it!

Mate that is diesel not petrol. Very different beasts. Even then the diesel TD5 specifies no bio diesel.

[Panda]

Yea, I know it is diesel not petrol. I think it was a diesel Volvo. & yea, even I know they are entirely different! Just thought it was interesting.:)


Mate that is diesel not petrol. Very different beasts. Even then the diesel TD5 specifies no bio diesel.

[JDNSW]

Yea, I know it is diesel not petrol. I think it was a diesel Volvo. & yea, even I know they are entirely different! Just thought it was interesting.:)

Have a read of the posts in the AULRO bio-fuels forum - not very active, but there is some interesting stuff there, much more depth than Top Gear.

John

[Panda]

Thanks John,

Will have a gander.:)

[rick130]

[quote=Slunnie;712271]<snip>

Yeah, i agree, ATDC sounds waaay late. I got no idea about older engines, but with a stock yamaha r6 engine in a formula SAE car, we run up to 25deg advance at WOT (on 98 octane).

Cheers!

old Formula Ford 1600 Kent engines require around 45* ignition advance to work at WOT/5-6000RPM.
Poor spark plug placement is the culprit thanks to the flat head and bowl in piston chamber.
It can be overcome to a dgree, but only one engine builder I know ever did. I still have a set of plugs sitting on the shelf ;)

[Bigbjorn]

Meyer & Drake/ Offenhauser speedway midget engines, on methanol blend ( 90+%) and 14:1 to 16:1 compression ratio used around 30-35 degrees static advance with no advance/retard mechanism in the magneto.