Quote:
Originally Posted by AZCobra12
. There is not much timing advance as it is detuned to under 1000hp/1000trq already.
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Pulling timing lowers Hp, and that's fine to lower the Hp some. If you go too far, in my opinion, that is a poor way to kill power. If you get to the point that you are lighting the fuel so late that a lot of un-burned fuel is going out the exhaust this will make the O2 sensor believe you are lean when you are not. The ECU may compensate and make you burn rich while thinking it is spot on. High over lap cams can do the same thing at idle.
Burning a bunch of fuel after the exhaust valve is open, is a waste of fuel, which might explain your poor fuel mileage. I'm not certain but it might heat the exhaust valve too.
It would be better to tune the engine to run right and just limit the throttle to not open all the way.