How Come???
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Senior Member
Joined: Feb 2004
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From: Texas
How Come???
I have a stupid question.
How come there is a huge diference between the octane levels and performance.
For example why is a 93 tune better than an 87?? what makes the difference??
How come there is a huge diference between the octane levels and performance.
For example why is a 93 tune better than an 87?? what makes the difference??
Senior Member
Joined: Aug 2005
Posts: 262
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From: My House
The 91/93 octane is slower to burn, so your engine can be made to run faster/hotter without pinging or early combustion. The 87 octane may combust before the spark when you have your engine tuned higher.
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Joined: Mar 1998
Posts: 13,385
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From: Virginia
Hi FX4,
No, that is NOT a "stupid" question - not at all!
SEARCH - there you will find all those answers, as all of this is very basic & have been covered many many times.
In short, no, higher octane does not burn "slower" - it simply takes longer to INITIATE the combustion process (in teal time and in degrees of crankshaft rotation), but once lit, the flame front propagates itself across the combustion chamber at about the same rate. But in general, many people DO express this much more simply in terms of saying that it burns "slower."
It has a much higher resistance to knock threshold (detonation), and due to that, and the fact that it takes much longer to START it burning, more timing (spark advance) not only can be used, but it MUST be used for the motor to run correctly and get proper energy release from the same volume of fuel.
And with more timing, up to the point of detonation and MBT (whatever spark is actually required for maximum brake torque on any given motor, as you can over-spark a motor and drop power but NOT go into actual detonation), you get more power - pretty simple, really.
But reading up on it in detail is fascinating, so please do consult the SEARCH feature here to retrieve & read past posts on these topics, you'll find a lot of good info there.
Hope that helps for now, for a short quickie type answer!
No, that is NOT a "stupid" question - not at all!
SEARCH - there you will find all those answers, as all of this is very basic & have been covered many many times.
In short, no, higher octane does not burn "slower" - it simply takes longer to INITIATE the combustion process (in teal time and in degrees of crankshaft rotation), but once lit, the flame front propagates itself across the combustion chamber at about the same rate. But in general, many people DO express this much more simply in terms of saying that it burns "slower."
It has a much higher resistance to knock threshold (detonation), and due to that, and the fact that it takes much longer to START it burning, more timing (spark advance) not only can be used, but it MUST be used for the motor to run correctly and get proper energy release from the same volume of fuel.
And with more timing, up to the point of detonation and MBT (whatever spark is actually required for maximum brake torque on any given motor, as you can over-spark a motor and drop power but NOT go into actual detonation), you get more power - pretty simple, really.
But reading up on it in detail is fascinating, so please do consult the SEARCH feature here to retrieve & read past posts on these topics, you'll find a lot of good info there.
Hope that helps for now, for a short quickie type answer!
