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GM Expands Deployment of Displacement on Demand

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GM’s 5.3L V8 with displacement on demand for sedans.

Since first introducing cylinder deactivation (Displacement on Demand—DOD—in the GM lexicon) in the MY 2005 Envoy and Trailblazer extended SUVs, GM has been steadily increasing the number of applications of its 5.3-liter V8 DOD engines, most recently announcing a 5.3-liter DOD engine for the 2006 Saab SUV.

According to GM, using DOD in these engines results in up to 5% fuel savings in trucks and SUVs, and up to 12% fuel savings in sedans. For the 2006 Model Year, there are currently six GM SUVs and three sedans featuring a 5.3-liter V8 with DOD.

Although the company had earlier indicated it would introduce V6 engines with Displacement on Demand for passenger cars this year, it has pushed that rollout back to the 2007 model year to do additional fine-tuning on noise and vibration.

The V6 implementation of DOD will now appear first in a 3.9-liter engine on the Monte Carlo and the Impala.

GM has also announced that it will offer a 6.0-liter engine with displacement on demand in its 2007 line of full-size SUVs. (Earlier post.)

GM currently offers two versions of a 5.3-liter V8 engine with displacement on demand: the Vortec 5300 Gen IV V8 (LH6) engine for trucks, and the 5.3L V-8 Gen IV (LS4) engine for cars.

As implemented in these engines, Displacement on Demand automatically shuts down every second cylinder, according to firing order, during light-load operation.

DOD relies on three primary components:

  • Special de-ac (for deactivation) or collapsible two-stage valve lifters for those cylinders that will be shut down;

  • A lifter oil manifold assembly (LOMA);

  • And the heart, the E40 Engine Control Module.

The E40 ECM measures load conditions based on inputs from vehicle sensors and processes that data to manage dozens of engine operations, from fuel injection to spark control to electronic throttle control. DOD adds an algorithm to the engine control software to manage cylinder deactivation and reactivation.

When loads are light, the E40 automatically closes both intake and exhaust valves for half of the cylinders and cuts fuel delivery to those four. The valves reopen to activate all cylinders when the driver demands brisk acceleration or full torque to move a load.

In conventional engines, valve lifters are operated by the engine’s camshaft, and lift a pushrod that operates the valves in the cylinder head. In the DOD V8 engines, the special de-ac lifters are installed in cylinders 1, 4, 6 and 7, while the remaining cylinders use conventional lifters.

Gm_dod1
The special hydraulically-activated de-ac lifters that enable GM’s Displacement on Demand.

The hydraulically operated de-ac lifters have a spring-loaded locking pin actuated by oil pressure.

For deactivation, hydraulic pressure dislodges the locking pin, collapsing the top portion of the lifter into the bottom and removing contact with the pushrod. The result is that the bottom of each de-ac lifter rides up and down on the cam lobe but the top does not move the push rod.

Without the lifting, the valves do not operate and combustion in that cylinder stops. During reactivation, the oil pressure is removed, and the lifter locks at full length. The pushrods, and therefore the valves, operate normally.

The final Displacement on Demand component is the LOMA. This assembly is a cast aluminum plate, installed in place of a conventional engine block cover. The LOMA holds four solenoids, control wiring and cast-in oil passages. The solenoids are managed by the ECM, and each one controls oil flow to a de-ac lifter, activating and de-activating the valves at one cylinder as required for Displacement on Demand.

Because the vibration and acoustic dynamics of the engine under V-8 and V-4 modes differ, the exhaust system of DOD-equipped vehicles is tuned to compensate for the changes.

1_3_3stageivtec
The 3-stage Honda VTEC valve switching capabilities are enabled by three hydraulic circuits in the rocker arm, which enable a cylinder deactivation mode (VCM).

On a comparative note, Chrysler uses similar hydraulically-activated special lifters in its implementation of cylinder deactivation (MDS). Honda takes a different approach from GM and Chrysler in using a squirt of hydraulic fluid to deactivate half of the rocker arms for what it calls Variable Cylinder Management (VCM).

The Honda approach is a variation of its VTEC (variable valve timing electronic control) cam lobe switching scheme used for more than a decade. Instead of skipping between high- and low-lift cam lobes, VCM selects a rocker-arm alignment that delivers no valve lift at all.

MY 2006 Implementations of Cylinder Deactivation
CompanyModelsEngineTechnology
GM Envoy Denali, Envoy Denali XL, Trailblazer, Trailblazer EXT, Rainier, Saab 9-7x 5.3L V8 (LH6) Displacement on Demand
GM Impala, Monte Carlo, Grand Prix 5.3L V8 (LS4) Displacement on Demand
Chrysler 300C, Magnum, Charger, Durango, Ram 1500, Grand Cherokee, Commander 5.7L HEMI V8 Multi-Displacement System
Honda Odyssey, Pilot 3.5L V6 i-VTEC, VCM
Honda Accord Hybrid 3.0L V6 i-VTEC, VCM

Comments

chris

it's funny that a 7L engine (in the 2006 Z06) is rated at 17/27. the corvette makes twice the power, and still gets better mileage than the honda S2000!! that's without vvt, variable intake, dod, mild hybrid, gdi, etc.

the LS2 also puts out 0.92 hp/lb (bare engine) while the new magnesium block bmw 3L puts out 0.74 hp/lb...and costs much more to buy. i'd say there's lots of life left in pushrods, and large v8s.

and we're not running out of energy...we're reaching the end of petroleum derivatives.

fwiw, the gm ev1 weighed 2900 lb. the battery pack was 1100 lb. if gm substituted saab's cng 1.9 tdi + 6 speed for the inverter/motor, it'd get somewhere north of 70 mpg. of course an 1800 lb car with 190 hp would also be tons of fun - think faster than a mustang gt, and nimble like a miata.

Adrian

Chris,
I don't believe the z06 is that good.
A ford F350 7l TD can get around that figure if you drive it nice, but thats a diesel.

Gary

The most important engineeering factor in vehicle design for better fuel mileage is the vehicle's gross weight. That's why a Corvette ZO6 with aprrox.gross vehicle weight of 3300lbs with one passenger can get signifificantly higher gas mileage than a Ford F350 with just one passenger with gross vehicle weight of approx 6500...your hauling around more than ton and half of extra weight just in the huge body...now add a one ton payload and figures will drop to single digit mpg.

eric

Chevrolet.com says the new Z06 is rated at 16/26, and Honda.com says the S2000 is rated at 20/25. So I really wouldn't say a Z06 gets better mpg than a S2000. Don't get me wrong, the Z06 is very impressive, and it's cheap compared to exotics with similar performance but the LS7 uses some more expensive pieces than a run of the mill LS1 or LS2.

craig

I wonder if a DOD system or a simular type system is in the works for the large displacement engines currently used in motorhomes? Dropping half the cylanders on down hills and flat lands in a V10 might at least get a gain of a few mpg. Granted most the engines I've seen used have been Ford (Triton V10 I think) and I don't think they have done anything in DOD.

DR

Guys, GM is putting DoD in the V6 they have postponed it until the next year due to difficulties with noise reduction... besides think about it on a V8 shutting down every second cyl. gives a balanced 4 cyl. A 6 to 3 is NOT a blanced system... more work to be done... I applaude GM for holding off on the release.

CamaroBob

'Things won't improve much until the horsepower race stops and efforts are put into making lighter vehicles.'

While it would be nice to have lighter vehicles to imrpove fuel economy, it is a bit more complicated then not focusing on horespower. Cars are definately heavier today then they were in the past but that is b/c there are more options placed on cars today. The first thing that pops to mind are safety features such as airbag systems and reinforced side panels. While these features can be life-saving they also add to the overall weight of the vehicle and thus reducing fuel economy. Then you start throwing in smaller features such as sun roof, power everything, sound systems, etc and the weight keeps coming up. Cars could be made with lighter materials that are just as strong but this would greatly increase the cost of a common sedan or compact car.

I think that in addition to finding new ways to power cars and trucks, auto companies should focus on continuing to improve the efficiency of there engines WITHOUT the loss of horsepower. That way everyone gets what they want. Fuel economy is important and should be a factor in every auto purchase but noone wants to drive their riding lawn mower to work.

BOB HAMME

How can GM call this new? Doesn't GM include Cadillac, and hasn't Caddy had the NorthStart for ever? And it does the same thing right? So why the hooooplaaah. Just drop the North Star in the C1500 and be done with it

ken

I have a 2006 silverado 1500 crew cab with a 5.3l. How can I tell if is DOD?

Steve Gentry

I have DoD on a 2007 Yukon and if it would just use it the mielage difference is surprising (approx 2.5-3 mpg); however, GM's implementation of DoD is way too conservative. If a 75% throttle opening was req'd to go into 8 cyl mode it would be an awesome system. Unfortunately, it only uses DoD while driving down flat roads (or declines) at speeds above approx 45-50 mph. If we all lived in Kansas that would work great, but....

Lozinsk06

Lots of talk of deactivation but I want to keep displacement on demand when i swap a 5.3 litter LS4 into my Honda S2000 Help me please what do I have to do?

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