'03 5.3 in 4cylinder mode? (1st Post)

[tclaiborn]

Friend is getting only 13mpg in their '03 Envoy XL with the 5.3 V-8. Is there a way to update the engine / computer in the 5.3 to go into the 4 cylinde rmode like the new engines? They were shocked to hear my '06 4.2 gets 21 mpg.

[rbarrios]

i have not heard anything about updates to make older engines into Active fuel management. I think it may even require parts......
I believe in these cars- the computer is also able to control the alternator and such.
With an envoy XL- im sure they also have more weight from all the fancy stuff. but 12 is low... lead foot?
i too am up in the 18-19 MPG I6 territory... on a good long drive 23 is doable.

[tclaiborn]

I was thinking it would be heads, plumbing and computer. "Displacement on demand" used oil pressure to activate / deactivate the lifters on the affected cylinders, and the computer shut off the fuel charge. I'm guessing this hasn't changed.

[Envoy Fan]

Don't think it can be done. DOD is the Gen IV engine. He doesn't have the Gen IV engine.

[ScarabEpic22]

Don't think it can be done. DOD is the Gen IV engine. He doesn't have the Gen IV engine.

It cant, lots of different parts, programming, etc.

[canadianbacon]

as some people have already mentioned,you can't do it...requires alot of hardware besides just an ECU swap...here read this link:

http://www.findarticles.com/p/articles/mi_m3012/is_12_183/ai_111617012

this is the interesting part if you don't want to read the entire article:

"GM's first production applications of Displacement on Demand (DOD) will find its way onto the fourth generation Vortec 5300 small block V-8, standard on the 2005 Chevrolet Trailblazer EXT, GMC Envoy XL and Envoy XUV, as well as a DOD-equipped Vortec 3900 V-6, which will debut in the Pontiac G6, the Grand Am replacement due this spring. A version of the 5300, sans DOD is available now in the Buick Ranier and a non-DOD automotive application of the 5300 will debut later this year in the '05 Corvette.

The brains behind DOD is the E40 engine controller. The controller monitors such things as oil temperature, rpm, coolant temperatures and throttle position and determines when to drop cylinders and vice versa.

The seamless shifts occur through the activation of two-stage hydraulic valve lifters. In normal mode, the inner and outer lifter sleeves are held together by a pro. DOD is activated by delivering high pressure off to the lifters, which depress the pin and allow the outer portion of the shaft to move with the cam lobe while the inner portion doesn't move, holding the pushrod in place. The electronic operation is achieved through the lifter oil manifold assembly (LOMA), mounted in the engine valley. The LOMA is equipped with solenoids that trigger the switching lifters.

Oil circulation and pushrod length are the same for all cylinders while camshaft lobes are customized for the deactivated cylinders.

Because of the change in acoustic dynamics and vibration with the switch from four to eight cylinder mode, engineers added a pressure-activated valve in the muffler that automatically switches with the engine, adjusting the exhaust path to deliver the appropriate noise reduction.

DOD-equipped engines also have specially-tuned exhaust and engine mounts.

The engine's electronic throttle control is designed to increase manifold pressure in DOD mode to maintain engine torque."



and down at the bottom it also mentions this:

"The new block casting has redesigned oil galleries to meet the oiling requirements needed for DOD. The knock sensors and camshaft sensor have been moved to provide room for the new oil galleries. A higher capacity oil pump and larger coils on the coil-near-plug ignition are also need for DOD. All models now feature electronic throttle control for improved throttle response and DOD signaling. The transmission now has its own controller due to the demands that DOD puts on the ECM."

[tclaiborn]

Thanks all. Looks like I just need to offer them my supplier discount so they can trade it in.