Nick1234 Posted August 5, 2006 Report Share Posted August 5, 2006 So first off how does gm make their variable valve timing work on the 3.5 and 3.9 motors. Also, how does dod work. I know the clapse the lifters, but those it switch what 4 cylinders work, because wouldn't wear be an issue? Quote Link to comment Share on other sites More sharing options...
CPSMonteZ34 Posted August 5, 2006 Report Share Posted August 5, 2006 D.O.D. Article - http://www.superchevy-web.com/technical/engines_drivetrain/accessories_electronics/0405sc_gmdod/ Basically, it deactivates the cylinder with the use of a hydraulic lifter that is void of fluid needed to produce the pressure against the rod-to-rocker-to-valve for it to open. Without the fluid, the lifter just bounces against the cam lobe. The valves being closed seals the cylinder to then take on the action of becoming an air spring. The compression inside against the cylinder is the same force acting against it on the decompression stroke. The power required for compression of the exhaust gas in one cylinder is countered by the decompression of retained exhaust gas in another. I've read that it is cylinders 1, 4, 6 and 7 for a V8. In V4 mode, every other cylinder, in the firing order, is deactivated. In a V8 engine, this means the process would affect the outer two cylinders on one bank, and the inner two cylinders on the opposite bank. I have no information as to whether it switches to 2, 3, 5, 8 in any other circumstance. I get the feeling that wear would still be even as the majority of the internal thermal temperature is based on friction. Quote Link to comment Share on other sites More sharing options...
Nick1234 Posted August 5, 2006 Author Report Share Posted August 5, 2006 that is a really good article. Now i wonder with variable valve timing, it is supposed to be a performance increase, right. Like with the honda b16 head, the intake came and the exhaust cam have 4 extra lobes, giving you 24 lobes in a 16 valve head. 1 lobe with more lift for both exhaust and intake, therefor more air going to into the cylinder. Is gm trying to accomplish this same goal or is it more of an efficiency goal. Nick Quote Link to comment Share on other sites More sharing options...
1990lumina Posted August 5, 2006 Report Share Posted August 5, 2006 that is a really good article. Now i wonder with variable valve timing, it is supposed to be a performance increase, right. Like with the honda b16 head, the intake came and the exhaust cam have 4 extra lobes, giving you 24 lobes in a 16 valve head. 1 lobe with more lift for both exhaust and intake, therefor more air going to into the cylinder. Is gm trying to accomplish this same goal or is it more of an efficiency goal. Nick probably both, efficency and more power... Quote Link to comment Share on other sites More sharing options...
jeremy Posted August 6, 2006 Report Share Posted August 6, 2006 I moved this to powertrain so it gets more attention.....DOD is available in some w-bodies now Quote Link to comment Share on other sites More sharing options...
Stevo Posted August 6, 2006 Report Share Posted August 6, 2006 Thing is with deactivated cylinders... does this mean uneven wear on plugs, wiring and associated gear? Quote Link to comment Share on other sites More sharing options...
THe_DeTAiL3R Posted August 6, 2006 Report Share Posted August 6, 2006 that is a really good article. Now i wonder with variable valve timing, it is supposed to be a performance increase, right. Like with the honda b16 head, the intake came and the exhaust cam have 4 extra lobes, giving you 24 lobes in a 16 valve head. 1 lobe with more lift for both exhaust and intake, therefor more air going to into the cylinder. Is gm trying to accomplish this same goal or is it more of an efficiency goal. Nick All I know is that the new 2007 G6s (3.5 VVT) are now rated at 224hp, previously 200hp on the regular non-VVT engine. +24hp FTW Quote Link to comment Share on other sites More sharing options...
CPSMonteZ34 Posted August 6, 2006 Report Share Posted August 6, 2006 Thing is with deactivated cylinders... does this mean uneven wear on plugs, wiring and associated gear? Actually, I wouldn't be surprised if it continuously fires the plugs anyway since there wouldn't be any fuel to burn in the air-filled cylinder. Based on everything I've read, the deactivated cylinders simply have closed off valves and non-firing injectors. I look at this practically and figure that D.O.D. isn't exactly there half the time on any drive. There's always situations when the engine load increases. One thing is for sure, people who don't know how to use gradual movement of their gas pedal will never benefit by this system unless they're in cruise control. I hate riding as a passenger with a person who is constantly heavy on the gas and the brake. Quote Link to comment Share on other sites More sharing options...
Nick1234 Posted August 10, 2006 Author Report Share Posted August 10, 2006 anybody have anything to add about the vvt. Articles or comments? Nick Quote Link to comment Share on other sites More sharing options...
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