Does anyone know if this method of shutting down cylinders not needed for driving, like on the newer GM products, can be retrofitted to a 04 Chev PU.

Hummmm??

It just didn't work years ago when it was tried, but seems like they got it ironed out now, what with computers and such.

I once owned a 1981 Eldorado with the 4-6-8 system. It seemed to work OK, but I never thought it was really any benefit. Biggest thing I noticed was the drastic cut in power when it dropped at first 2 then 4 cyl. Had to press accelerator to get it to shift back up to 8 when using the cruise control. And, boy when it goofed up there wasn't a tech in captivity knew what to do with it.

While never owning the older systems, I know they had lots of issues. Talking to owners of the new technology it seems that it works. They report no loss of power, seamless performance when engaging needed power, and good milage. So was just wondering if the system could be adapted to my 04.

Anything is possible. However, I would think you'd need a donor engine, PCM and wiring harness from a truck that has that technology. I'm not that familiar with GM's system, but it appears there is something internal within the engine itself that allows you to drop a cylinder.

My Dad had that Cadillac system in a Deville and he had a lot of problems with it. He didn't keep that one long. But computer technology for automotive applications has grown leaps and bounds in 30 years. Hopefully the newer system is better thought out.

I have Ford's variable timing in my truck and it seems to work okay, but Ford has it's share of problems with the cam phasers.

I do remember the Cadilac system had solenoids inside the valve covers that moved the pivot points for the rocker arms to keep the valves from opening and closing on the dropped cylenders. I would think there was a way to stop the plugs from firing too.

I got curious and looked into the system. It does use internal engine components and those components are controlled by the PCM. Here is what I found:

Displacement on Demand (DoD) is the name for GM’s latest cylinder deactivation system.

After its association with the notorious 1981 Cadillac, GM waited until 2004 to re-release cylinder deactivation. The DoD system has been initially released in the GMC Envoy and TrailBlazer SUVs.

The Envoy and Trailblazer use a Vortec 5.3 litre Gen IV V8 (dubbed LH6). The engine runs on all 8 cylinders during start-up, idle and heavy acceleration but switches to 4 cylinder mode on light loads.

Like the HEMI, the GM system employs specially developed hydraulic lifters (known as switching roller followers) for the intake and exhaust valves. The lifters can be collapsed by disengaging an internal locking pin. The locking pin is disengaged using solenoids to alter oil pressure fed into the lifter. When the locking pin is disengaged and the lifter collapses, the camshaft is isolated and the valves remain closed.

A new 32-bit ECU orchestrates the valve deactivation solenoids, throttle control, ignition timing and sequential fuel delivery (which includes cutting fuel to cylinders which are deactivated). A pressure-operated valve in the muffler also serves to maintain a suitable exhaust note in V8 and 4 cylinder operating modes.

The Vortec 5.5 litre V8 with DoD generates 224kW at 5000 rpm and 449Nm at 4000 rpm. Average fuel consumption is improved by around 8 percent – up to 25 percent in some conditions.

Gee Cajun thanks. I figured it might be some sort of computer hokus-pokus that just shut off spark, but its a lot more involved then that. Thanks again.

Never underestimate the good of QS!!