WHAT DOES variable valve timing do
05-29-2008, 10:44 AM
#1
Senior Member
Thread Starter
Join Date: 05-04-2008
Location: Stockton,CA
Posts: 295
WHAT DOES variable valve timing do
and how does it affect my milage and power I cant seem to find the thread on the search I know I read something on it a few weeks ago. And at what speed or RPM does it kick in
05-29-2008, 11:10 AM
#2
Senior Member
Join Date: 04-10-2006
Location: Simi Valley, CA
Posts: 195
In most variable cam timing systems it allows a little bit more radical camshaft profiles for better performance and mileage by retarding the cam timing (usually the exhaust cam) at low rpms and light loads......and then advancing the cam as the rpm increases. This will allow better idle and low rpm drivability while still getting good power and torque at higher rpms. This system is also "emissions friendly".
06-02-2008, 11:35 AM
#6
Senior Member
Join Date: 06-11-2007
Location: Durham, NC
Posts: 299
Technical answer...
Variable Valve Timing
A vane-type phaser is installed on the cam sprocket to
turn the camshaft relative to the sprocket, thereby adjusting
the timing of both intake and exhaust valve operation.
The vane phaser is actuated by hydraulic pressure from
engine oil, and managed by a solenoid that controls oil
pressure on the phaser. The phaser uses a wheel or rotor
with four vanes (like a propeller) to turn the camshaft
relative to the cam sprocket, which turns at a fixed rate
via chain from the crankshaft. The solenoid directs oil to
pressure points on either side of the four phaser vanes;
the vanes, and camshaft, turn in the direction of the oil
flow. The more pressure, the more the phaser and camshaft
turn.
For all its design and production efficiencies and
multitude of applications, the Ecotec 2.4L VVT succeeds
for one reason. It’s a world-class four-cylinder engine
that delivers excellent performance without sacrificing
durability, economy or smooth, quiet operation.
The Ecotec 2.4L VVT is built at GM Powertrain’s Spring
Hill, Tennessee, Engine Manufacturing facility.
A vane-type phaser is installed on the cam sprocket to
turn the camshaft relative to the sprocket, thereby adjusting
the timing of both intake and exhaust valve operation.
The vane phaser is actuated by hydraulic pressure from
engine oil, and managed by a solenoid that controls oil
pressure on the phaser. The phaser uses a wheel or rotor
with four vanes (like a propeller) to turn the camshaft
relative to the cam sprocket, which turns at a fixed rate
via chain from the crankshaft. The solenoid directs oil to
pressure points on either side of the four phaser vanes;
the vanes, and camshaft, turn in the direction of the oil
flow. The more pressure, the more the phaser and camshaft
turn.
For all its design and production efficiencies and
multitude of applications, the Ecotec 2.4L VVT succeeds
for one reason. It’s a world-class four-cylinder engine
that delivers excellent performance without sacrificing
durability, economy or smooth, quiet operation.
The Ecotec 2.4L VVT is built at GM Powertrain’s Spring
Hill, Tennessee, Engine Manufacturing facility.
12-09-2008, 05:53 AM
#9
Senior Member
Join Date: 07-17-2006
Location: Dallas, GA
Posts: 6,050
In theory, yes......
Honda has "vtec" in both the single and DOHC motors. The honda DOHC motors really wake up in the 5200-5500 rpm range.
IMO, all manufactors have tried to follow Honda with a "tec" motor. But none have had Honda's sucess. The Ecotec is a strong motor with good internals in both the VVT and non VVT variants. The VVT in the Ecotec only gained a handful of HP where Honda's vtec easily have gained 40+ HP (the original DOHC VTEC 1.6 verses the standard 1.6). Honda makes their power on the upper end of the rpm scale verses low end grunt.
Just my .02.
Honda has "vtec" in both the single and DOHC motors. The honda DOHC motors really wake up in the 5200-5500 rpm range.IMO, all manufactors have tried to follow Honda with a "tec" motor. But none have had Honda's sucess. The Ecotec is a strong motor with good internals in both the VVT and non VVT variants. The VVT in the Ecotec only gained a handful of HP where Honda's vtec easily have gained 40+ HP (the original DOHC VTEC 1.6 verses the standard 1.6). Honda makes their power on the upper end of the rpm scale verses low end grunt.
Just my .02.
12-09-2008, 07:54 AM
#10
Senior Member
Join Date: 10-02-2005
Location: VA
Posts: 1,245
The VVT doesn't "kick in" at any point. It is (as the 1st "V" indicates) variable throughout the operation range.
What some sense as a kick in point is actually the PE (Power Enrichment) coming on. It is delayed in the stock tune.
The Honda VTEC system actually transfers valve actuation to different lobes. That does kick in suddenly. Some other systems incorporate both types of valve control strategies.
What some sense as a kick in point is actually the PE (Power Enrichment) coming on. It is delayed in the stock tune.
The Honda VTEC system actually transfers valve actuation to different lobes. That does kick in suddenly. Some other systems incorporate both types of valve control strategies.