Quote:
Originally Posted by Ecky
One thing I've wondered - most Toyota engines use offset cranks, and I'd be shocked if this were not true of the Avalon hybrid's. So, 0° on the crank is not the same as top dead center for the piston. Additionally, I'm unsure if Toyota's "0°" is the same as Honda's, or anyone else's. Is it 0° relative to the minimum advance, or 0° relative to TDC, or 0° relative to the crank?
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Good question! I was just going by what the Scangauge 2 has to say.
But in the end, the point is that there's no set idle timing on modern cars like old distributor cars. The Avalon apparently will idle anywhere between some 40° difference, depending on which side of the efficient-but-cool/non-efficient-but-warm the timing scale the ECU is shooting for.
Another example is that of old distributor cars with vacuum advance that would change from the ported vacuum advance to straight manifold vacuum when a certain thermostatic vacuum valve reached a certain temperature. This would make the engine advance at idle which would speed up the idle speed and help cool down the hot engine (mainly for emissions reasons).
Also, there have been a few car enthusiasts that would hook their distributors directly to manifold vacuum instead of ported vacuum. The result was that it would idle cooler and use less fuel at idle (assuming the idle speed was adjusted after the change). This also would increase manifold vacuum at idle.
In these two later examples, since both ported vacuum and manifold vacuum are the same anywhere from off idle to full throttle (in 95% of all cars from that time) there's no difference in timing under load on those vehicles.