Wrxblue 1st Gear October 19, 2003 Share October 19, 2003 The octane rating of gasoline tells you how much the fuel can be compressed before it spontaneously ignites. When gas ignites by compression rather than because of the spark from the spark plug, it causes knocking in the engine. Knocking can damage an engine, so it is not something you want to have happening. Lower-octane gas (like "regular" 87-octane gasoline) can handle the least amount of compression before igniting. The compression ratio of your engine determines the octane rating of the gas you must use in the car. One way to increase the horsepower of an engine of a given displacement is to increase its compression ratio. So a "high-performance engine" has a higher compression ratio and requires higher-octane fuel. The advantage of a high compression ratio is that it gives your engine a higher horsepower rating for a given engine weight -- that is what makes the engine "high performance." The disadvantage is that the gasoline for your engine costs more. The name "octane" comes from the following fact: When you take crude oil and "crack" it in a refinery, you end up getting hydrocarbon chains of different lengths. These different chain lengths can then be separated from each other and blended to form different fuels. For example, you may have heard of methane, propane and butane. All three of them are hydrocarbons. Methane has just a single carbon atom. Propane has three carbon atoms chained together. Butane has four carbon atoms chained together. Pentane has five, hexane has six, heptane has seven and octane has eight carbons chained together. It turns out that heptane handles compression very poorly. Compress it just a little and it ignites spontaneously. Octane handles compression very well -- you can compress it a lot and nothing happens. Eighty-seven-octane gasoline is gasoline that contains 87-percent octane and 13-percent heptane (or some other combination of fuels that has the same performance of the 87/13 combination of octane/heptane). It spontaneously ignites at a given compression level, and can only be used in engines that do not exceed that compression ratio. During WWI, it was discovered that you can add a chemical called tetraethyl lead to gasoline and significantly improve its octane rating. Cheaper grades of gasoline could be made usable by adding this chemical. This led to the widespread use of "ethyl" or "leaded" gasoline. Unfortunately, the side effects of adding lead to gasoline are: Lead clogs a catalytic converter and renders it inoperable within minutes. The Earth became covered in a thin layer of lead, and lead is toxic to many living things (including humans). When lead was banned, gasoline got more expensive because refineries could not boost the octane ratings of cheaper grades any more. Airplanes are still allowed to use leaded gasoline, and octane ratings of 115 are commonly used in super-high-performance piston airplane engines (jet engines burn kerosene, by the way). ↡ Advertisement Link to post Share on other sites More sharing options...
Mmythos Neutral Newbie October 19, 2003 Share October 19, 2003 (edited) a high performance engine has a higer compression ratio??? wat is the compression ratio of ur car and those exotic car? U mean lorry is it? compression ration 15:1? 'super high performance' hahaha... Edited October 19, 2003 by Mmythos Link to post Share on other sites More sharing options...
Zolidlim Neutral Newbie October 19, 2003 Share October 19, 2003 Very well said and understood.... Link to post Share on other sites More sharing options...
Wrxblue 1st Gear October 19, 2003 Author Share October 19, 2003 It refers to NA cars...for NA cars, one of the common ways is to increase compression ratio. as for lorry and buses...most of them uses turbochargered engine..so compression ratio is not so high.... if you put a bus/lorry engine in your car then..you get 'super high performance' hhaahaaa Link to post Share on other sites More sharing options...
Mmythos Neutral Newbie October 19, 2003 Share October 19, 2003 get ur facts rite, disel engine require higher compression ratio Link to post Share on other sites More sharing options...
Saaber Neutral Newbie October 19, 2003 Share October 19, 2003 (edited) good write up.......will make a copy in tips and techical folder... Edited October 19, 2003 by Saaber Link to post Share on other sites More sharing options...
Wrxblue 1st Gear October 19, 2003 Author Share October 19, 2003 (edited) oh..sorry hor!!! didnt know you are the 'master' around!!!!!!! of course i know diesel engine has high compression ratio..but it is also because they are turbocharged engines..... maybe then you can change ur petrol engine to diesel turbocharged engine and you can get..'ultra super high performance' haahahaa anyway....oh master does Octane level applies to disel fuel???? Edited October 19, 2003 by Wrxblue Link to post Share on other sites More sharing options...
Mmythos Neutral Newbie October 19, 2003 Share October 19, 2003 me master??? haha... then u grandmaster liao! regardless if the disel engine is turbocharged or not, it still require higher compression ratio... then how about the difference between petrol and disel engine? Link to post Share on other sites More sharing options...
Wrxblue 1st Gear October 19, 2003 Author Share October 19, 2003 oh..dont know leh..maybe master can enlighten us.... Link to post Share on other sites More sharing options...
Mmythos Neutral Newbie October 19, 2003 Share October 19, 2003 waiting for some grandmaster to enlighten me Link to post Share on other sites More sharing options...
Wrxblue 1st Gear October 19, 2003 Author Share October 19, 2003 hhaaha..dont dare lah...if not say wrongly kena.. haaha.. better leave it to the 'expert'... Link to post Share on other sites More sharing options...
Yttrium Neutral Newbie October 19, 2003 Share October 19, 2003 (edited) [reply]a high performance engine has a higer compression ratio??? [reply] You beg to differ? So do you mean a high performance NA engine has lower compression ratio? Edited October 19, 2003 by Yttrium Link to post Share on other sites More sharing options...
S2P2 Neutral Newbie October 19, 2003 Share October 19, 2003 you come home already ah Link to post Share on other sites More sharing options...
Yttrium Neutral Newbie October 19, 2003 Share October 19, 2003 Come home from where? I just came home from shopping Link to post Share on other sites More sharing options...
S2P2 Neutral Newbie October 19, 2003 Share October 19, 2003 i thought you travelling mah Link to post Share on other sites More sharing options...
Yttrium Neutral Newbie October 19, 2003 Share October 19, 2003 Back from where I told you I was going last last Tue.. then Wed I went another place and came back on Fri. So whole of last week I was in SG. You going HK tomorrow ah? Enjoy your trip Link to post Share on other sites More sharing options...
S2P2 Neutral Newbie October 19, 2003 Share October 19, 2003 wed to fri.....short trip, where MY ah Link to post Share on other sites More sharing options...
Yttrium Neutral Newbie October 19, 2003 Share October 19, 2003 4 hours north.. the place where they call hotels "rice shops" heh ↡ Advertisement Link to post Share on other sites More sharing options...
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