OT: compression ratio and octane rating
06-21-2002, 01:16 PM
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OT: compression ratio and octane rating
How do auto manufacturers decide what grade of fuel to recommend? Is it strictly a function of compression ratio (in normally aspirated cars, of course) or is there more to it?
06-21-2002, 03:06 PM
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Yeah, probably from experimental testing and monitoring the knock/detonation level. Even before they start designing the engine, they probably have some possible compression & octane requirements in mind.
06-21-2002, 03:20 PM
#3
Race Director
[quote]Originally posted by ****:
<strong>How do auto manufacturers decide what grade of fuel to recommend? Is it strictly a function of compression ratio (in normally aspirated cars, of course) or is there more to it?</strong><hr></blockquote>
I'm sure octane rating is decided upon based upon whether the car is being considered a performance model or not. Whatever octane rating they decide upon, they then have many parameters to adjust during the design and development phases. There are certainly design elements that affect knock (such as combustion chamber design). Certainly the easiest things they can do is adjust the fuel and spark maps. Adding fuel helps to control detonation which is why most OEM maps tend to be a bit on the rich side.
<strong>How do auto manufacturers decide what grade of fuel to recommend? Is it strictly a function of compression ratio (in normally aspirated cars, of course) or is there more to it?</strong><hr></blockquote>
I'm sure octane rating is decided upon based upon whether the car is being considered a performance model or not. Whatever octane rating they decide upon, they then have many parameters to adjust during the design and development phases. There are certainly design elements that affect knock (such as combustion chamber design). Certainly the easiest things they can do is adjust the fuel and spark maps. Adding fuel helps to control detonation which is why most OEM maps tend to be a bit on the rich side.