Giday
Just curious to whether it is bad for a engine to run a higher octane (Bp 98) in normal engine like a old civic or bluebird etc.
I mean can it be dangerous to run a higher than normal octane in a normal old car?
Cheers
Running high octane...
Started by
_01dencwe_
, Apr 07 2006 05:11 PM
16 replies to this topic
#2
_draglc_
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Posted 07 April 2006 - 06:15 PM
No not at all, infact it will probably run better, ie clean out the engine, and u might even get better fuel economy.
A1
A1
#3
_Herne_
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Posted 07 April 2006 - 06:43 PM
Cost could be a factor to maybe consider? Yesterday I paid $149.7/litre for Shell Optimax.. I don't normally use Shell but was low and my fav filling station was packed out.
I didn't put much in at that price... Luckily i dont need a car everyday.
Cheers
Herne
I didn't put much in at that price... Luckily i dont need a car everyday.
Cheers
Herne
#4
Tiny
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Posted 07 April 2006 - 07:05 PM
The octane of a fuel is in massively simple terms its bang. ( also resitance to pre-detonation or pinging).
Old engines were all designed to run on 95 odd octane fuel and thats what the manufacturers tuned and designed them for.
Unleaded fuel was dropped to 91 octane, and you'll notice a drop in compression ratio as well as power output in earl ULP cars as they came to grips with the new crap fuel.
Putting high octane juice in an old car ( non EFI especially) will give cleaner burn, slightly more power if the engine is tuned for it, and a much greater resistance to pinging.
In short.. No.. it cant hurt!
Alot of hi performance guys ( myself included) MUST run premium fuel cause of high compression ratios and other factors in their hi-po engines.
Hope this info helps!
Old engines were all designed to run on 95 odd octane fuel and thats what the manufacturers tuned and designed them for.
Unleaded fuel was dropped to 91 octane, and you'll notice a drop in compression ratio as well as power output in earl ULP cars as they came to grips with the new crap fuel.
Putting high octane juice in an old car ( non EFI especially) will give cleaner burn, slightly more power if the engine is tuned for it, and a much greater resistance to pinging.
In short.. No.. it cant hurt!
Alot of hi performance guys ( myself included) MUST run premium fuel cause of high compression ratios and other factors in their hi-po engines.
Hope this info helps!
#5
_01dencwe_
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Posted 07 April 2006 - 08:31 PM
What if the engines are not tuned for it I mean.
Won't the fuel ignite to quicky?
Won't the fuel ignite to quicky?
#6
_CHOPPER_
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Posted 07 April 2006 - 08:37 PM
No. The higher the octane, the slower it burns.
#7
Tiny
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Posted 08 April 2006 - 04:46 PM
No, if the engine isnt tuned for it, it just wont use it to its maximum capcity. You can tune it for premium to gain more power, but if you need to use regular you'll find troubles!
#8
_finer70_
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Posted 10 April 2006 - 06:28 PM
Lets get one thing very clear. Octane rating has got absolutly and positively nothing to do with POWER, BURN RATE or CLEANER BURNINNG. These are all aspects of the fuel itself.
Octane rating is a rating of compressability of the fuel before it will spontaineously combust.
So compression ratio has everything to do with why differing octane ratings are used.
Low compression say 87 octane. High compression 100 octane. Unleaded 91 so compression ratios came down. The fuel did not change, only the octane rating.
Aircraft still use AVGAS which has lead. It is not more powerful. It just handles high compression better. The fact it has lead is why it is not legal on the road.
TEL (Lead) was found during the 2nd WW to have a marked influence in the octane rating of fuel.
You need high octrating fuel in high compression motors simply to stop pre ignition (Pinging)
To get more BANG as has been suggested you need a fuel with a higher calorific value. That is more energy. OCTANE is not ENERGY.
Why is it that the general opinion is that octane = energy. Well if you run low octane in high compression you need to retard the spark in an effort to prevent pinging. Obviously this kills power from the engine.
With the correct octane rating for the given compression, the spark can be
advanced to its set point and hence give optimum output from the engine.
And to respond to the original question. Putting High octane fuel into a motor that is not designed for it WILL cause damage through pinging over time. Unless the spark timing is retarded reducing the power output of the engine. Which would appear to defeat the reason (Need for more Power) the fuel was put in to start with.
So buy good fuel with an octane rating to match the compression of the engine.
You WILL save money and get the Best performance from your engine.
Octane rating is a rating of compressability of the fuel before it will spontaineously combust.
So compression ratio has everything to do with why differing octane ratings are used.
Low compression say 87 octane. High compression 100 octane. Unleaded 91 so compression ratios came down. The fuel did not change, only the octane rating.
Aircraft still use AVGAS which has lead. It is not more powerful. It just handles high compression better. The fact it has lead is why it is not legal on the road.
TEL (Lead) was found during the 2nd WW to have a marked influence in the octane rating of fuel.
You need high octrating fuel in high compression motors simply to stop pre ignition (Pinging)
To get more BANG as has been suggested you need a fuel with a higher calorific value. That is more energy. OCTANE is not ENERGY.
Why is it that the general opinion is that octane = energy. Well if you run low octane in high compression you need to retard the spark in an effort to prevent pinging. Obviously this kills power from the engine.
With the correct octane rating for the given compression, the spark can be
advanced to its set point and hence give optimum output from the engine.
And to respond to the original question. Putting High octane fuel into a motor that is not designed for it WILL cause damage through pinging over time. Unless the spark timing is retarded reducing the power output of the engine. Which would appear to defeat the reason (Need for more Power) the fuel was put in to start with.
So buy good fuel with an octane rating to match the compression of the engine.
You WILL save money and get the Best performance from your engine.
#9
_devilsadvocate_
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Posted 10 April 2006 - 09:44 PM
Finer 70, I don�t follow your claim of how high octane fuels will cause damage in a engine designed for lower octane fuels. How will it cause pinging? There is a difference in burn speed for some fuels, but this isn�t always related to octane rating�.which as you describe is related to its ability to ignite at particular temperatures/compression ratios.And to respond to the original question. Putting High octane fuel into a motor that is not designed for it WILL cause damage through pinging over time. Unless the spark timing is retarded reducing the power output of the engine. Which would appear to defeat the reason (Need for more Power) the fuel was put in to start with.
The RACV recently did tests on whether premium fuel with higher RON values would be beneficial to cars designed to run on regular unleaded. There results showed improvements in fuel consumption of around 1-3%....., but concluded this wasn�t worth it on the basis of the fuel being more than 1-3% more expensive Cant remember, but I believe the vehicles tested did have engine management computers that would have been able to perhaps advance the timing on the run to take advantage of the different burn characteristics of the higher RON fuel to increase engine efficiency. There was definitely no warning from the racv that this could cause engine damage. Just as back in the days of standard and super, cars that would run on standard were never damaged by running them on super.
In the early days autoignition properties of fuel were determined by establishing a scale on detonations compared to mixtures of heptane and octane, both have much the same energy content per litre but different autoignition temps, 220 and 280C respectively and basically made up the majority of the fuel. The octane rating was simplistically the ratio of octane/heptane. ie 85 was 85oct/15hept. Of course today the composition of the fuel isn�t so simple but the Relative Octane Rating (RON) remains, whether there is octane present or not.
Higher compression ratios allow an engine to be more efficient and reach higher power figures(I think everyone knows that on this site) so higher octane fuel can produce more power than lower octane fuel(when burnt in an internal combustion engine), even if both fuels have the same overall energy value. The energy value of fuels is typically done in a �bomb calorimeter� and correctly records how much heat/energy is evolved from the fuel, so if using either fuel for heating purposes there�d be no difference.
#10
Tiny
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Posted 10 April 2006 - 10:08 PM
From the magazine articles ive read, the Octane number is derived by using a vairable compression single piston engine. Its a callibrated pice of scientific equipment that allows teh sample fuel to be burnt and the compression ratio to be changed ( raised usually untill pre-dettonation occurs (Pinging.).
I dont know the maths behind it all, but i was under the impression that RON stood for Research Octane Number, and is a number given to the test fuel based on its "anti knock" capability.
From my lmited knowledge i stand 100% corrected that RON or octane rating isnt related to the calorific value of the fuel... I agree with what Finer70 said.
I will say one thing though... The guy asked a simple question, and even though i gave "misleading" information, i still belive my advise to be correct for the purposes of answering that question. I'm not aware of a situation where a higher octane ( pump petrol in relation to motor cars) has caused damage to an engine by its use.
Cheers.
I dont know the maths behind it all, but i was under the impression that RON stood for Research Octane Number, and is a number given to the test fuel based on its "anti knock" capability.
From my lmited knowledge i stand 100% corrected that RON or octane rating isnt related to the calorific value of the fuel... I agree with what Finer70 said.
I will say one thing though... The guy asked a simple question, and even though i gave "misleading" information, i still belive my advise to be correct for the purposes of answering that question. I'm not aware of a situation where a higher octane ( pump petrol in relation to motor cars) has caused damage to an engine by its use.
Cheers.
#11
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Posted 10 April 2006 - 10:24 PM
From memory, there is RON and MON. Can't recall what MON is all about, but RON is the more commonly used term.
Corect. LPG is generally accepted as having a higher RON than ULP, but has ( from memory ) about 2/3 the calorific value of ULP.
From my lmited knowledge i stand 100% corrected that RON or octane rating isnt related to the calorific value of the fuel... I agree with what Finer70 said.
Corect. LPG is generally accepted as having a higher RON than ULP, but has ( from memory ) about 2/3 the calorific value of ULP.
#12
_devilsadvocate_
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Posted 10 April 2006 - 10:34 PM
I stand corrected it is Research and not relative......wrong, wrong.but i was under the impression that RON stood for Research Octane Number,
Thanks Tiny, Ill try and not make that mistake again.
.........for the purposes of what the number represents 'relative' is not to much of a distant cousin.....as the Research Octane numbers used in the test engine Tiny describes were intially based on the 'relative' octane/heptane ratios of fuel that created/prevented preigniton........
thats my excuse.........but doesnt make it right, its RESEARCH
Re energy value of LPG, the fuel is often maligned as having less energy than petrol, it depends how you measure it, per litre it has less, but per kg it has more.
Edited by devilsadvocate, 10 April 2006 - 10:40 PM.
#13
Tiny
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Posted 10 April 2006 - 10:39 PM
It's all good Devils, Were all learning here! Certainly not a pissing contest from where i'm standing!
I agree Chop.. there is a MON and RON, and i belive they are two ways of measuring the same thing.. but again i could be wrong!
Cheers
I agree Chop.. there is a MON and RON, and i belive they are two ways of measuring the same thing.. but again i could be wrong!
Cheers
#14
_finer70_
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Posted 11 April 2006 - 01:15 PM
Well with all the best of intentions I brought myself totally undone by saying HIGH when it was obvoius from my explanation I should have said LOW with respect to a motor designed for a high octane.
That little slip did put the credability of my whole explanation into question.
That little slip did put the credability of my whole explanation into question.
#15
_Keithy's_UC_
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Posted 11 April 2006 - 05:19 PM
HAHA!! Good one Mr. Finger!! AAAH HAHA
#16
Tiny
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Posted 11 April 2006 - 08:45 PM
Dont worry Finer70 i knew what you meant and everyone KNOWS i'm a dumb arse... I'm sure they understood itWell with all the best of intentions I brought myself totally undone by saying HIGH when it was obvoius from my explanation I should have said LOW with respect to a motor designed for a high octane.
That little slip did put the credability of my whole explanation into question.
Your other points were well made too so i'm sure everyone is cool!
Cheers
#17
warrenm
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Posted 14 April 2006 - 07:31 AM
MON stands for "Motor Octane Number" Check this site for a clearer explanation of the 2 octane ratings .http://www.csgnetwork.com/octaneratecalc.html
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