I was reading the service manual for a car with VVT.
I can see in the manual this:
Quote:
The valve timing control system is utilized to control intake valve
opening and closing timing. Engine coolant temperature signals,
engine speed and throttle position are used to determine intake
valve timing.
The intake camshaft sprocket position is regulated by oil pressure
controlled by the intake valve timing control.
When ECM sends ON signal to intake valve timing control solenoid
valve, oil pressure is transmitted to camshaft sprocket. Then, intake
side camshaft is advanced.
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OK - so by forcing more oil to the camshaft the pressure advances timing.
Directly below is a table.
When coolant temperature is low (warm up type), and engine speed is 1150 - 4450 RPM, and the base fuel schedule is above 3 msec, and the neutral switch is off, the solenoid is ON.
The same is also true when the engine has warmed up, the RPMs are 1150-4450 and the base fuel schedule is above 7 msec, and the neutral switch is off.
Thus timing is advanced, and valve overlap increases.
So by shifting into neutral, I'm potentially missing the ability to get more advanced timing out of the car.
I wonder if there's any merit in manually controlling that valve? If it's on, then timing could be advanced more often..
What are the thoughts here?
I can probably take direct control of it, I doubt it's pulsed on / off, and instead held on during those conditions.
I think I can remove the RPM requirement and base fuel schedule requirement and simply have it on when engine is warmed up (advanced timing when warmed up...)