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post #1 of (permalink) Old 09-10-2000, 01:59 PM Thread Starter
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I recently moved from Arizona (3500 ft. elevation) to Northern California (2000 ft elevation). After the smog station got done tinkerling with my '86 Samurai to past the smog test, the gas mileage dropped from 33 mpg to 28 mpg on the hiway. The mechanic said they adjusted the idle and timing. They then charged me $120.00 for it. Would a more experienced mechanical type tell me what the optimum timing should be for gas mileage and for power? The only engine mods are K&N filter and Thorley Headers with 2" exhaust. Thanks.

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post #2 of (permalink) Old 09-10-2000, 03:42 PM
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The factory service manual says 10 degrees BTDC @ 800RPM + or - 50 rpm

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post #3 of (permalink) Old 09-10-2000, 09:20 PM
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advance the timing as far as possible, just to the point where you start to get spark knock. that point, in general, will give the best economy AND best power. just be careful, because you may not hear continuous spark knock at highway speeds. also, the engine will run hotter the more you advance the timing. if you're really into it, you could switch permanently to premium fuel, and set it up for that. the higher octane is there to prevent the knock and you could potentially get even more power and economy with that fuel, and timing adjusted to take advantage of it. it may be best to watch your economy every fillup to get a running average, and then try playing with changes, to see if there is any measureable difference.

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post #4 of (permalink) Old 09-10-2000, 11:37 PM Thread Starter
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Thanks Paul, that is the type of advise I was looking for.

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