Intake Valve Timing Control
 

I was reading the service manual for a car with VVT.

I can see in the manual this:

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...)

What do you think you have to gain by advancing the cam timing at idle?

Inlet variable valve timing
 

From some "dyno type"measurements, monitoring petrol fuel energy usage in, and Kw generated out, A prius engine carburated is returning 17% at the 10kw level. (shaft estimated at 21%). This is run at 2000rpm, because of some other constraints, so maybe about the ball park. If anyone knows if this is so, please comment.

A switch to LPG, with a crude mixer,and regulated from BBQ bottle, enabled a 5KW run, but consumed around 3kg per hour. This came out at energy in to energy out of about 10% total, and maybe 12.5% shaft. My thoughts are further tuning, may improve this, but how about this idea.

The Prius engine shortens its inlet stroke lenght by leaving the inlet valve open for about 25% of the upward stroke. If the inlet valve cam gear was advanced on the timing chain, a higher compression ratio for the LPG could be obtained, maybe up to 13:1. Risk would be of the valve clipping the piston at the begining of the intake stroke, when in the vvt off position. Nice if this worked without a cam grind.

:rolleyes: Any Ideas?

+1 The idea behind the VVT system is to provide low to mid-range torque for an engine which is tuned to give more top end power. Without it engines like the Honda Type-R (200hp for 1.6 litres) or even my own car's 1.0 3cyl (68hp) would be undriveable in the real world.

I can't see a benefit at idle. You could of course turn the engine off instead. :snail:

Advancing the cam at low load is bad in every single way. There's a reason it's fully retarded at idle.

You may want to see this:
http://www.youtube.com/watch?v=Mvm0At-8k3s

It's VW r32 engine with turbo and variable valve timing all controlled by MegaSquirt 3 ecu. And you can change timing on the fly regardless revs, load, temp, etc.