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SmallPackage:

You’re right, I forgot about belt driven cam engines as I don’t use one myself.

My parents was the last in our family to have a timing belt in their car.

Thankfully that one never snapped the entire time they owned the car. It was a nice car though. 1992 Dodge Spirit.

 

AModelCat: I remembered that article about the Cummins camless engine.

Interesting read.

What’s next? Solenoid driven pistons?

 

If you think about it, fluids are virtually incompressible. If you could eliminate the piston rods/bearings in favour of a fluid, that would further reduce the internal friction of an engine. As to how the hell one would do that? Beats me lol.

 

Cummins is still working on it so they can get to cylinder deactivation during low load demands.Cummins demos cylinder deactivation tech in its X15 engine

 

Wonder how that'd work with the aftertreatment systems? Probably make less heat.

I remember GM having oil consumption issues with the displacement on demand in their 5.3L Vortecs. I wonder if that was due to cold cylinders or if they alternated the "dead" holes to keep the cylinders evenly heated?

 

I think the idea is put greater demand on activated cylinders to get better combustion to improve emissions in cylinder.

 

I guess that makes sense. IIRC high combustion temperatures make more NOx but less particulates. Less demand on the DPF and just convert the NOx in the SCR.

 

The oil consumption issue was 2 issues. The pcv orfice is a tin deflector that is riveted and sealed to the valve cover with a silcone sealer. The sealer would degrade and pcv would allow ingestion of oil.

The other issue was the oil pump relief valve was part of the oil pan, when it was relieving it sprayed oil all over the bottom of the cylinders. Cure for that was a deflector

The gm system actually "shut off" the valave train with oil pressure solenoids for each cylinder that shuts down. It was designed to trap an exhaust charge in the cyl. They did have issues when the cyl would reactivate, the sudden temp change would cause the spark plug ceramic to crack.

The pins that held the lifters engaged would also wear, allowing the lifters to collapse when not intended to..

 

Good to have clarification from a GM tech. Thanks!

I heard of the oil consumption problem on those engines and opted for the 4.8L being under the impression it was directly related to the DoD system.

 

Absolutely, also invites moisture to a closed pvc system and dirtier oil. But hey gained some mpg! Er or kpl?