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When you have only 4 cylinders running it is more efficient. Due to heat, right? Each cylinder is running more load and hotter. Less losses. Yes, the injector pulsewidth has increased. If you look I don't think it is >= 2x though. I am sure you could even have a special tunable intake manifold like on the 3.9L V6 which closes off part of its self. I can't really think of how to phrase this such yet. I am sure that DOD does a good job for what is possible. The reality of it says that 4 cylinder engines don't get much better fuel econ than V8's in a car-car situation. Look at the fuel milage of an Ecotec Cavalier and a C5 Corvette. Not a huge increase in MPG on the highway compared to the loss in HP with the Cavalier. So GM is just trying to level the playing field even more. If it was built into all V8's it could be made even more affordably and GM could continue the North American V8 market. Which, is pretty much the only v8 market left for the general consumer. |
GM is putting into most of their daily driver V8s. . . Tahoes, pickups, etcetera. . . |
This may be the engine/tranny combination that we use for our Ferrari 308. http://www.exoticperformanceplus.com...Car.php?car=45 If we do, we will rebuild the engine and add good rods and pistons. If we're lucky, we'll find the room to install an ATI ProCharger. Bob |
Originally Posted by Exotic Performance Plus This may be the engine/tranny combination that we use for our Ferrari 308. http://www.exoticperformanceplus.com...Car.php?car=45 If we do, we will rebuild the engine and add good rods and pistons. Your article mentioned a LS2, assuming you're going to use a LS4 with that 4T65E. There are a few of us that also want a non DoD camshaft, are you guys looking at removing the DoD as well? Can you PM me your LS1 F-Body packages? Thanks! |
Originally Posted by Kazmaniac Can't believe 16 seconds!!! Your article mentioned a LS2, assuming you're going to use a LS4 with that 4T65E. There are a few of us that also want a non DoD camshaft, are you guys looking at removing the DoD as well? Can you PM me your LS1 F-Body packages? Thanks! PM me your e-mail address, and I'll send you some quotes. Thanks! Bob |
I spoke with a woman last week, and she said that you guys are not working on any LS4 cars right now. Has this changed or maybe she didnt know about you being on this site? I am looking for someone to do programming/tuning on my car while its on the dyno and also remove the DOD from my car. |
Originally Posted by BigMikeGXP
(Post 5322427)
Displacement on Demand (DoD) General Information The original name was Displacement on Demand (DoD). For the start of the 2006 model year GM renamed it Active Fuel Management (AFM). 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. Mike, I found this pretty good video on the AFM (DoD) system at Chevy's website: http://www.chevrolet.com/pop/avalanche/2008/afm_en.jsp |
Originally Posted by Taz34SS
(Post 7374739)
I spoke with a woman last week, and she said that you guys are not working on any LS4 cars right now. Has this changed or maybe she didnt know about you being on this site? I am looking for someone to do programming/tuning on my car while its on the dyno and also remove the DOD from my car. Give us a call and ask to talk to Brent. I am sure we can tune your car for you. http://www.efilive.com/supvehicle.aspx 260 244-4808. Thanks. Bob |
Bob, sorry but I have moved to Indy since then. Sorry. |
I'd appreciate it if somebody would please read this entire review on the '08 Buick LaCrosse Super: http://www.forbesautos.com/news/auto...ick-super.html Ques: Does anyone have any idea what those guys at the GM Performance Division, specifically Jeff Boike's team, did when they tuned the car's exhaust to make it quieter? I would love to have it re-tuned to the Impala SS and/or Grand Prix GXP's specs so that my exhaust would be a little bit louder, like a V8 should. Right now it sounds like the V6 in my wife's Regal. A wild guess would be to tweak something in the car's computer system (ECM?) that controls exhaust sound, since Boike said they had to give up 3 hp in order to make it quieter (they probably compared it to the Impala SS). I don't know for sure, but since it was built at GM's Oshawa 2 plant, I suspect the entire exhaust system is the same one used for the Impala SS (since the engine, tranny, and exhaust parts would already be available in building the LaCrosse Super). Some people have suggested removing the resonator, but I want to leave that as a last resort. Plus I was told doing it wouldn't gain back the lost 3 hp. I would appreciate any thoughts or suggestions on this matter. |
Does anyone have the part number for the VLOM? |
Some more LS4 info http://media.gm.com/us/powertrain/en...Car/08_LS4.doc |
Sooo...you mean the GXP isn't tuned for good fuel economy between 75 and 80 mph? Damn. I believe I am getting 18 city/25 hwy. Unless my right foot gets a little frisky, then it's 16 city/23 hwy. I have a few mods, thinking about others...checking the posts on the forums to see what's been tried and works, etc. |
Awesome info, Defently good to know all this! |
Disabling the DOD system? I have a 2006 Monte Carlo SS and want to disable the DOD, what is the best Tuner to do it?
Originally Posted by BigMikeGXP
(Post 5322427)
Displacement on Demand (DoD) General Information The original name was Displacement on Demand (DoD). For the start of the 2006 model year GM renamed it Active Fuel Management (AFM). 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. |
anyone got any info on the GMPP posi for the 4t65ehd? |
Replacing the transmission If going to replace this transmission, what would be the best trans to upgrade to so I wont have these problems and in the near future be able to upgrade the performance and not affect the trans. |
Originally Posted by mikee21089
(Post 15822888)
If going to replace this transmission, what would be the best trans to upgrade to so I wont have these problems and in the near future be able to upgrade the performance and not affect the trans. |
We recently picked up a used 2007 GXP for a daily driver family car. So far I really like the DoD feature. We sold our 3800 GP after putting 200,000 miles of trouble free miles on it. Best car we ever had. Although a 5.3 version obviously gets less mpg than the v6, we were surprised at the mileage it DOES get on the highway. Not really going through much more fuel than we used to. Probably because my wife always had her foot way into it with the old 3800. http://i1227.photobucket.com/albums/..._8341574_n.jpg |
GXP thirsty for Oil Any ideas if lets say something wasn't working right if when DOD is enabled it caused the car to use oil or extra crank case pressure? My wife's 06 GXP at first seems to be thirsty for oil cause around 2000 to 2500 it wants another quart. I have a catch can on the system and it fills up pretty fast even when it's just vented out. It doesn't hold a lot but I'd say 600 miles it's just like 3/4 full. I'm going to disable the DOD first see if that makes any changes if that doesn't help my choices might be checking cylinders, but it is a bit odd doesn't smoke like using oil at all, Just wondering where all this oil going, lol Any ideas are appreciated. |
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