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Registered
Join Date: Sep 2008
Posts: 149
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Regular Gas vs High Test
My '78 5 speed 928 has a stock motor & from what I understand, has an 8.5 to 1 compression ratio. This is a US car. Regular gas ignites quicker than high test & would not benefit a low compression motor. Low compression motors don't pre ignite as quick as high compression motors that need a gas that ignites slower (high test) I don't believe high test is necessary in this car due to the low compression, provided the timing is kept stock. It's been my experience that using high test in a motor designed for regular offers no benefit. It's not a matter money, it's a matter of what type of gas will work better. I don't want to hurt my car & I'm not looking to start a controversy, just want to know if my reasoning correct? What ever happened to the rumors of a new 928 from Porsche?
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12-02-2008, 03:30 PM
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Registered
Join Date: Aug 2006
Location: Cincinnati, Ohio
Posts: 1,019
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I would run the low octane too...should be fine. But the extra cost for higher octane pump gas just isn't that much.
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Kuhn Performance Technologies, LLC Big Gun: 1988 928S4 Twin Turbo, 5-SPD/LSD 572 RWHP, 579 RW ft-lbs, 12 psig manifold pressure. Stock Internals, 93 octane. Little Gun: 1981 928 Competition Package Twin Turbo, 375 RWHP, 415 RW ft-lbs, 10psig manifold pressure. Nikasil Block, JE2618 Pistons, 93 octane. |
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12-02-2008, 03:55 PM
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Network Native
Join Date: Jan 2007
Location: SoCal
Posts: 10,349
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Run the lowest octane that doesn't ping.
Or Run the best gas you can find and tune until it almost pings. |
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12-02-2008, 04:31 PM
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