How does VVT(Variable Valve Timing) on new 6.0 work?
12-13-2006, 10:28 PM
#1
How does VVT(Variable Valve Timing) on new 6.0 work? I'm looking at the catalog for the new 07 Silverado. It says that the VVT system on the Vortec 6.0L V8 Max engine changes the cam profile to increase performance and reduce emissions. Now we all know the cam profile can't be changed unless your name is David Copperfield so how does VVT REALLY work? I'm trying to decide if I want to get another 5.3L or move up the 6.0L Max with this VVT since my 04 Silverado was recently totaled. Thing is I now have Stage II heads, cam, lifters, pushrods, Pro Mag rockers, double timing set, headers w/ORYpipe, etc. sitting in my garage and I don't want to buy a new truck I can't put those thing on. The brochure doesn't mention DOD(Displacement On Demand), but I believe what they are calling Active Fuel management is a euphemism for DOD which means it has those special lifter so my Comp "R" series lifters will be spending the rest of their lives sitting on the shelf in my garage. Who knows how this VVT stuff works and which if any of my aftermarket parts I'll be able to use on the new 07 Silverado?
12-13-2006, 10:45 PM
#2
As far as i know, there is a hydraulic (works off of engine oil) phaser that is mounted to the front of the camshaft, and that advances or retards the cam. As far as how well it will work with aftermarket cams, I haven't heard of anyone who as tried yet!
12-14-2006, 12:47 AM
#3
After having looked more closely at the exploded picture of the engine in the brochure I realized there is a clutch type device mounted on the front of the camshaft timing sprocket. They are using this to advance and retard the cam phasing. They don't actually change the cam profile as the brochure says they do. I haven't figured out how they actuate it as yet, but I'm guessing it is an electromagnetic clutch similar to a automotive A/C clutch. The Active Fuel Management (DOD) system is a totally separate system from the VVT system. DOD has special lifters that activate and deactivate 4 cylinders so you can save on fuel when at cruising speeds on level highways. I don't know what controls the oil to these special lifter, but I guess they must hold one of the valves open and turn the injectors off during cruise mode. So with DOD and VVT I guess I won't be able to use my "R" lifters or my Rollmaster double timing set. Has anyone either done any internal mods to this new 6.0L Max or read an article by someone who has?
12-14-2006, 01:10 AM
#4
From what I have heard, the VVT phaser is infinitey variable, and adjusts advance or retard by changing the oil pressure avaliable to it. I think the Active Fuel Management deactivates the cylinders by keeping the intake and exhaust valves closed. Someone must know for sure?
12-14-2006, 06:54 AM
#5
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Looks like dropping an aftermarket cam in these engines would be a very careful ordeal. If the cam phasing was enabled still after the cam install (depending on how big the cam is) you could run into some clearance issues. I doubt it is infinetly variable, but I am sure it could phase a big cam enough to cause some problems...
The displacement on demand is controlled by solenoids that shut off the lifters on 4 of the 8 cylinders and keep the valves in those cylinders closed. Of course, the injectors are turned off as well. Because the valves are kept closed, those pistons act as a spring to help rotate the crank when they come up on compression. Pretty simple concept that seems to work well.
The displacement on demand is controlled by solenoids that shut off the lifters on 4 of the 8 cylinders and keep the valves in those cylinders closed. Of course, the injectors are turned off as well. Because the valves are kept closed, those pistons act as a spring to help rotate the crank when they come up on compression. Pretty simple concept that seems to work well.
12-14-2006, 11:24 AM
#6
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The valve timing is controlled by oil pressure coming thru the cam itself. The cam phazer would not work with aftermarket cams. The cylinder drop out and the cam phazer can be removed and all your aftermarket parts will bolt up and work from a engine mechanics standpoint, but the controller may have problems with these functions deleted.
Kurt
Kurt
