Can higher Octane cause Engine Damage?

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i think it should not be done, but a thought comes to mind. in some countries they have like 92+ octane. philippines has 114 octane i think and their cars are made to run at 91. other countires like britain is differnt and canada is differnt too. why do we have differnt octanes when our cars need a certain octane...isnt that too high if i have a 87 octane car running 95+ octane?? weird hu. well once in a while i pump with 89 octane for my 87. it feels smoother..i just want the smoothness and not the power hahahha..
 
If the design combustion chamber temp is too cool you'll develop deposits that over a period of time could cause problems. The higher Octane will burn cooler contributing to this anomaly.
 
disagree.
heat of combustion is the heating value of the fuel, and the mass of air and fuel in the chamber at the point of ignition.

A higher octane is the resistance to pinging and end gas autoignition of the fuel, not the flame speed or combustion temperature of the fuel.
 
Don't know how this plays into it, but regular has more BTUs per pound than the higher octane gas. Ford 4.6 engines are famous for carboning up if high octane is used in them unless they are a high compression version.
 
It is true that real high octane gas, like 110 unleaded race fuel burns slower and cooler as a result of a richer mixture. I used to have a modded turbo Eagle Talon, and every time I put unleadede race fuel in it to turn up the boost, I had to lean it out quite a bit for the best power and performance. High octane, without changing anything else, would cause a significant lowering of my exhaust gas tmeperature, and I had no detonation before, so it was burning cooler.
 
Using fuel with a high octane can have an effect similar to running with retarded timing.
Both can allow the fuel to still be burning when the exhaust valve opens. This can promote burned exhaust valves and this seems to be a result of using too high an octane fuel. Probably best to advance the timing a little if you're using Hi octane fuel.
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Why not just use the proper grade from a high quality supplier such as Chevron or Amoco?
 
Few things hear guys. High octane has nothing to do with flame speed or burn temp provided deto or pre igniotion is not present. Some of the highest octane pro stock fuels are also the fastest burning. The faster you can get the combustion event done the less chance the motor will detonate.
 
quote:

Originally posted by blano:
High octane has nothing to do with flame speed.

Not arguing with you here, but I always thought that with the 93 and higher octane you could set the spark advance to fire before the piston hits top dead center since it will take longer to burn and build pressure. Where as if you tried this with 87 octane it would fire off while the piston was still moving upward and cause the engine to knock. Is this not the way it works?
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I'm not sure if we're fighting with words or ideas. Flame speed and ignition speed are different.

From what I've read elsewhere, octane has a direct effect on ignition speed but very little effect on flame speed. (There's some flame difference, but it's due to formulation to attain the octane and not the octane rating itself.) Once high or low octane gasolines ignite the flame fronts should move at about the same speed. It'll just take more compression/heat/time to ignite the higher octane fuel. From there the other effects & methods we've talked about come into play. (timing, compression, altitude, temp, etc.)

Can the chemists please step in here?
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David
 
Don't know if there is a definition of ignition speed, but the following is a defintion of flame speed -
"Flame speed This is the speed with which a flame, possibly turbulent, appears to move relative to a stationary observer. The flame speed can be much larger than the burning velocity due to expansion of the combustion products, instability, and turbulent deformation of the flame. Flame speeds of 10-100 m/s are commonly observed for hydrocarbon-air mixtures and it is possible under exceptional circumstances to have speeds up to 1000 m/s."
Additionally, I read that turbulence is the primary means of increasing flame speed.

Some previous postings noted that fuels of higher octane quality have lower heating values. That may depend upon whether you are talking about a gravimetric heating value or a volumetic heating value as there is a difference. Gravimetric BTUs will decrease with increasing specific gravity whereas Volumetric BTUs will increase with increasing specific gravity. Since in the past, premium gasoline always had higher specific gracities than regular gasolines, they would have higher BTUs (on a volumetric basis) than those gasolines with lower octane numbers. This relationship does not apply when you have gasolines with oxygenates as they definitely cause a lowering of the heating value.
 
Ignition speed is probably an incorrect term. I only mean relative to cylinder conditions, different fuels will ignite earlier than others. My understanding is that low octane fuels have a lower flash point or change under compression more rapidly than high octane. Again, this is my caveman chemistry so feel free to use clubs.

David
 
1quart low, The properties you mentioned in your last post are a function of the fuels distalation curve and have nothing to do with octane. Poeple have mentioned that there motors require differant carb tuning or spark advance when running high octane. This can be attributed to changes in the distalation curves of the two fuels.
 
Would disagree as distillation curves are somewhat independent of fuel compostion. Since gasolines are composed of many many different hydrocarbons representing paraffinic, isoparaffinic, cycloparaffinic, naphthenic, some olefins, and aromatics, they themselves are the dependent factors in the combustion process.
 
Can you guys explain the effect of octane then? I understood it related to fuel's propensity to (pre)ignite when subjected to compression and heat. If the fuel doesn't ignite faster, and doesn't burn faster... is it burning from too many places?

Meum slow. You need use small words.
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David
 
1quart, Octane is a gasoline resistance to detonation. Pre igntiion is something altogether differant , but can lead to deto. Detonation occurs late in the combustion event and is charachterized by a smooth pressure buildup followed by a massive spike in pressure. This as you can imagine does very bad things to a motor. That being said higher octane does not burn faster it just prevents the pressure spike from occuring long enought to burn all of the combustion chambers charge.The faster you can burn the charge the less chance for detonation to occur hence squish bands on cylinder heads and ultra fast flame speed prostock fuels comprised of mostly iso octane.
 
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