does it REALLY need 89 octane?
10-02-2008, 06:03 PM
#11
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RE: does it REALLY need 89 octane?
pretty sure te srt8 was tested with 92 maybe i'm wrong?
carbon on the "and others say it burns away faster. "
the whole point of higher octane is that is burns slower.
the higher the octane rating the more heat or compression is needed to create combustion
more even burn across the face of the piston.
carbon on the "and others say it burns away faster. "
the whole point of higher octane is that is burns slower.
the higher the octane rating the more heat or compression is needed to create combustion
more even burn across the face of the piston.
12-10-2008, 08:27 PM
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RE: does it REALLY need 89 octane?
ORIGINAL: Carbon
I'm running 89 in my R/T and you could put 87, but you shouldn't put 91 in the 5.7
I'm running 89 in my R/T and you could put 87, but you shouldn't put 91 in the 5.7
12-11-2008, 03:11 AM
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RE: does it REALLY need 89 octane?
The little read document called the owners manual say's that 91 octane is recomended for the six speed cars. The owners manual recomends 89 for the automatic.
12-11-2008, 04:19 AM
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RE: does it REALLY need 89 octane?
ORIGINAL: sabby2000
so they say it requires 89 octane? is this correct?(I have not taken delivery on my R/T yet) anyone out there run 87??? any issues? anyone tried 87/89/super? can you tell any difference? or is this just for overall engine health?(lol)
so they say it requires 89 octane? is this correct?(I have not taken delivery on my R/T yet) anyone out there run 87??? any issues? anyone tried 87/89/super? can you tell any difference? or is this just for overall engine health?(lol)
The ECM can compensate for knocking caused by hot spots by retarding the spark so that the flame fronts don't collide but you still have a pre-detonation problem that will waste gas and hurt parts so don't rely on the knock sensor and ECM to compensate for using the wrong octane. Hot spot predetonation can be caused by using spark plugs that are too hot or by carbon build-up that super heats and acts like a second spark plug.
A lot of people think higher octanes burn faster but that is not necessarily true. The speed of the flame front may be the same as lower octane but the pressure at which the fuel explodes is higher.
12-11-2008, 12:46 PM
#15
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RE: does it REALLY need 89 octane?
Due to the combustion chamber in the 6.1 and the 5.7 they are ignited with 2 spark plugs per cylinder to allow flame travel on both sides of the raised piston. This is a big help in even flame travel. You get a complete burn and with it better gas mileage.
12-11-2008, 04:17 PM
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RE: does it REALLY need 89 octane?
ORIGINAL: epegasus
Engine knock is actually called premature detonation. The fuel mixture explodes in the cylinder as the result of a couple of things; pressure increases as the piston moves upward; and/or hot spots in the cylinder that cause 2 flame fronts that bang into each other. The problem is that the spark is timed to happen as the piston starts it's downward stroke. When the mix explodes early the piston cap is jammed against the connecting rod & crank which are still moving upward. BAD Juju and it wastes power trying to force a piston down when it can only move up. It can also kill valves and rings. So the purpose of higher octane levels is to raise the fuel mixture's resistance to detonation under pressure so that it waits for the spark timing.
The ECM can compensate for knocking caused by hot spots by retarding the spark so that the flame fronts don't collide but you still have a pre-detonation problem that will waste gas and hurt parts so don't rely on the knock sensor and ECM to compensate for using the wrong octane. Hot spot predetonation can be caused by using spark plugs that are too hot or by carbon build-up that super heats and acts like a second spark plug.
A lot of people think higher octanes burn faster but that is not necessarily true. The speed of the flame front may be the same as lower octane but the pressure at which the fuel explodes is higher.
Engine knock is actually called premature detonation. The fuel mixture explodes in the cylinder as the result of a couple of things; pressure increases as the piston moves upward; and/or hot spots in the cylinder that cause 2 flame fronts that bang into each other. The problem is that the spark is timed to happen as the piston starts it's downward stroke. When the mix explodes early the piston cap is jammed against the connecting rod & crank which are still moving upward. BAD Juju and it wastes power trying to force a piston down when it can only move up. It can also kill valves and rings. So the purpose of higher octane levels is to raise the fuel mixture's resistance to detonation under pressure so that it waits for the spark timing.
The ECM can compensate for knocking caused by hot spots by retarding the spark so that the flame fronts don't collide but you still have a pre-detonation problem that will waste gas and hurt parts so don't rely on the knock sensor and ECM to compensate for using the wrong octane. Hot spot predetonation can be caused by using spark plugs that are too hot or by carbon build-up that super heats and acts like a second spark plug.
A lot of people think higher octanes burn faster but that is not necessarily true. The speed of the flame front may be the same as lower octane but the pressure at which the fuel explodes is higher.
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