if i got the overkill tune...
Monte Of The Month - February 2010
Joined: Apr 2009
Posts: 11,981
From: Pittsburgh, PA
DOD....displacement on demand
Active Fuel Management (formerly known as Displacement on Demand) is a trademarked name for the automobile variable displacement technology from General Motors. It allows a V6 or V8 engine to "turn off" half of the cylinders under light-load conditions to improve fuel economy. Estimated performance on EPA tests show a 5.5%-7.5% improvement in fuel economy.<SUP id=cite_ref-0 class=reference>[1]</SUP>
GM's current Active Fuel Management technology uses a solenoid to deactivate the lifters on selected cylinders of a pushrod V-layout engine.
Active Fuel Management (formerly known as Displacement on Demand) is a trademarked name for the automobile variable displacement technology from General Motors. It allows a V6 or V8 engine to "turn off" half of the cylinders under light-load conditions to improve fuel economy. Estimated performance on EPA tests show a 5.5%-7.5% improvement in fuel economy.<SUP id=cite_ref-0 class=reference>[1]</SUP>
GM's current Active Fuel Management technology uses a solenoid to deactivate the lifters on selected cylinders of a pushrod V-layout engine.
Joined: Nov 2010
Posts: 1,746
Which was switched to Active Fuel Management in 2007. Basically it turns 4 cylinders off when you're cruising on the highway or cruising in general, to save MPGs.
During light load conditions while in 3rd or 4th gear the ECM will shut down cylinders 1, 4, 6, and 7 to put the engine in V4 mode. The engine will not enter V4 mode while cranking, idleing, or heavy acceleration. To shut down the cylinders the intake and exhaust valves stay closed and the fuel injectors stop feeding gas. The ECM times the shutdown so that each deactivated cylinder keeps the exhaust charge from the previous combustion cycle. This pressure on the pistons keeps them from rocking around in the cylinder causing vibration and oil consumption. Complete cylinder deactivation is accomplished in about 250 milliseconds.
The engine components involved in cylinder deactivation are the valve lifter oil manifold (VLOM) and special valve lifters. The VLOM consists of 4 solenoids that control oil flow to 8 valve lifters. Each solenoid goes with a certain cylinder and its 2 valve lifters.
When DoD is commanded on by the ECM the 4 solenoids energize and allow oil to flow to the valve lifters. The special valve lifters are made of an inner lifter and outer lifter with a spring loaded locking pin holding them together. When the oil gets to the lifters the pin is pushed out of place and the inner and outer part of the lifter are allowed to move seperately. The camshaft is still pushing on the outer part of the lifter, but the inner part of the lifter is no longer pushing up on the pushrod. This keeps the intake and exhaust valve shut permanently until the ECM commands DoD off. At this point the solenoids stop oil flow to the lifters and the spring loaded lifter pins lock back into place, causing the lifters to return to normal operation.
The engine components involved in cylinder deactivation are the valve lifter oil manifold (VLOM) and special valve lifters. The VLOM consists of 4 solenoids that control oil flow to 8 valve lifters. Each solenoid goes with a certain cylinder and its 2 valve lifters.
When DoD is commanded on by the ECM the 4 solenoids energize and allow oil to flow to the valve lifters. The special valve lifters are made of an inner lifter and outer lifter with a spring loaded locking pin holding them together. When the oil gets to the lifters the pin is pushed out of place and the inner and outer part of the lifter are allowed to move seperately. The camshaft is still pushing on the outer part of the lifter, but the inner part of the lifter is no longer pushing up on the pushrod. This keeps the intake and exhaust valve shut permanently until the ECM commands DoD off. At this point the solenoids stop oil flow to the lifters and the spring loaded lifter pins lock back into place, causing the lifters to return to normal operation.
Ohh! I know about that, just clueless about the acronym. Personally, I wouldnt delete that because I use the car as a daily driver. I find myself on highways frequently too. As a young'un, I'll take all the MPGs I can get.
Joined: Nov 2010
Posts: 1,746
For a lot of cars, it ended up making oil consumption problems of its own - plus some people on LS1Tech have scanned the cars when driving and found that even though the car is only pumping on 4 injectors, they're pumping about twice as much - so in the end, they were still running just about as much fuel. It holds a spent exhaust charge to keep pressure built so it's not like dragging 4 pistons, then after a certain amount of time, it'll loose the charge and cycle through 8 cyls again to collect another charge to rebuild the pressure.
For a lot of cars, it ended up making oil consumption problems of its own - plus some people on LS1Tech have scanned the cars when driving and found that even though the car is only pumping on 4 injectors, they're pumping about twice as much - so in the end, they were still running just about as much fuel. It holds a spent exhaust charge to keep pressure built so it's not like dragging 4 pistons, then after a certain amount of time, it'll loose the charge and cycle through 8 cyls again to collect another charge to rebuild the pressure.
I didn't know that.
Monte Of The Month -- January 2010
Joined: May 2009
Posts: 8,464
From: San Jose, CA
I have an Overkill tune on my Monte, of course mine is a 3.5L V6, but as for the results, AWESOME! Made a noticeable difference in power, but even more noticeable difference in the way the transmission feels and shifts. I highly recommend. It's an easy install, and just requires a crank position relearn after, done by a shop, which is under $100.
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