Variable valve train

[bandit86]

I have spent way too much time driving and watching the scangauge, I posted previously that my car likes throttle position at 23 units.

Today I had an idea while driving, maybe you guys can help me out; cruising at 70mph I get the same instant mpg as 60, this is over thousands of miles and yes 55 is way better, but bare with me. At one pointing in the rpm range the oil pressure increases and the variable valve train goes to work to give more lift or lo get lift I have no idea. When that happens more air enters the engine, so it would work harder which would mean decreased throttle for more manifold vacuum

So which is better, more lift and less throttle or less lift and more throttle?

If changing valve train geometry is important, would changing to thinner or thicker oil benefit to change oil pressure

[Frank Lee]

I don't know you well enough to get bare.

[Occasionally6]

The variable valve switching isn't because the oil pressure changes. The ECU determines when the variable switching should occur and then uses oil pressure, via solenoid actuated valve, to perform the switching.

Can't you get the answer to the question from the Scangauge?

Changing oil viscosity won't alter the switching point. At worst it would only alter the speed of the actuation. That's of no real consequence.

[JETZcorp]

In your system, is it giving you more lift, duration, or both? Some VVT systems may also only affect camshaft advance. Perhaps, when your VVT switches over, it's going to a cam profile/timing that promotes volumetric efficiency at substantially higher RPM/throttle than you're giving it. That would mean that, because the charge in your intake system doesn't have the ramming inertia to keep filling the cylinder when the intake valve closes after BDC, it's acting more like an "Atkinson" than it was at the mild profile. If you think about it, the cam timing that Toyota calls "Atkinson" in the Prius, sounds a lot like what they use in, say, pro-stock, where they use the long duration and late closure to trap more charge at high RPM. Your engine may be trying to give you power but accidentally giving you economy in this way.