The Type of octane to use?
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This is a discussion on The Type of octane to use? within the General Maintenance, Troubleshooting & Accidents. forums, part of the Tech & Modifying & General Repairs category; i was reading through ome threads and guy said he need 85 oct to run his wr sti.. i run ...

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    The Type of octane to use?

    i was reading through ome threads and guy said he need 85 oct to run his wr sti.. i run 93-95 what's the difference i thought the high the better unless i misunderstood. help if you can..thanks

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    Master Baiter EJ257's Avatar
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    You need 91+ fuel
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    Registered User MainFrame's Avatar
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    91 minimum, 93 is better.

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    would there be purpose to running a lower octane? isnt the higher octance better for your car in most areas?

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    higher or lower octane is not better or worse, it's different. High octane fuel is hard to ignite. The key is to use the proper to slightly higher octane required for your engine.

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    i thought the higher octane is the greater power when ignated therefore better perfomance in the higher torque/hp area
    Quote Originally Posted by Mf645 View Post
    higher or lower octane is not better or worse, it's different. High octane fuel is hard to ignite. The key is to use the proper to slightly higher octane required for your engine.

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    ignited**

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    Registered User MainFrame's Avatar
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    The higher the better in turbo charged cars. The lower ignition point of lower octane fuel makes it much more prone to knock, which is probably the number one killer of these engines.

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    we wouldnt want that now would we
    Quote Originally Posted by MainFrame View Post
    The higher the better in turbo charged cars. The lower ignition point of lower octane fuel makes it much more prone to knock, which is probably the number one killer of these engines.

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    Quote Originally Posted by Kevin Pedrosa View Post
    i thought the higher octane is the greater power when ignated therefore better perfomance in the higher torque/hp area


    Nope.. but with the higher ignition point the car can be tuned more aggressively before it starts knocking. Increases in timing and boost made possible by running higher octane are what produce more power.




    It's also possible to run a leaner mixture with more knock resistant fuel, which also produces more power.

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    leaner mixture? such as racing fuel?
    Quote Originally Posted by MainFrame View Post
    Nope.. but with the higher ignition point the car can be tuned more aggressively before it starts knocking. Increases in timing and boost made possible by running higher octane are what produce more power.




    It's also possible to run a leaner mixture with more knock resistant fuel, which also produces more power.

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    Quote Originally Posted by Kevin Pedrosa View Post
    leaner mixture? such as racing fuel?


    No, leaner AFR.. less fuel, more air. The leaner the mix the hotter the combustion temps get and the more power it makes.. until it knocks, or melts something.

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    what you mean by knock... like engines actually start knocking?
    Quote Originally Posted by MainFrame View Post
    No, leaner AFR.. less fuel, more air. The leaner the mix the hotter the combustion temps get and the more power it makes.. until it knocks, or melts something.

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    Quote Originally Posted by Kevin Pedrosa View Post
    what you mean by knock... like engines actually start knocking?


    Kind of. Knock is when the fuel mixture in the cylinder isn't igniting at the correct time. The factory knock sensor is basically a microphone installed in the block that listens for a particular frequency of sound associated with combustion. If the gasses in the chamber aren't combusting at the right time it can cause all kinds of damage.



    Engine knocking - Wikipedia, the free encyclopedia

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    Ill bet the guy was referring to using E85.

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