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Automotive News & Views DOD engines - Why aren't more companies using this technology?
26 messages, Last post on Jul 09, 2007 at 7:09 AM
You are in the Automotive News & Views Forum. Your Hosts are steve_ & claires
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Replying to: zodiac2004 (Jun 19, 2006 9:53 am) Last year I took a trip to Florida with two friends in my 2000 Intrepid. I'd say that we averaged about 27-28 mpg in mostly highway driving. We had the trunk packed to the gills, with some luggage spilled over into the back seat and probably had the car at close to its ~4400 lb GVWR. And we had the air conditioning running most of the time. Oddly, 27-28 mpg on the highway is about what I usually get in that car when with just me aboard. So the extra ~600 pounds, roughly what GM saved per car when it went through massive a massive downsizing campaign back in the late 70's, actually had little-to-no effect on my mileage. I'm guessing that in "pure" highway driving, where you get up to a constant speed and only slow down for fuel and pee breaks, or when the cop motions you over  that weight doesn't have such a huge effect. If you're constantly accelerating and decelerating, or have enough hilly terrain that will force your transmission to downshift, then you'll see more of an effect.
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Replying to: andre1969 (May 25, 2006 7:00 am) Exactly right, andre - only in perfect conditions does it actually save you a significant amount of mileage, and perfectly flat, windless, resistance free conditions just don't exist many places. So, the reality is - you save 2-3 mpg for a more expensive motor - I wouldn't want it. You also have to deal with the complexity of the system and expense. Look, Cadillac's V 8 6 4 motor tried this before. Course, theirs never worked, and the new ones are surely more reliable. For the money, I don't want it. |
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Rented a Dodge Durango in Bozeman, MT this past weekend with the DOD. Drove it 400 miles in the wild. It got 17mpg. Wonderful - I can get that from my Explorer anytime, without DOD. Anytime I need to accelerate or climb, the DOD kicked in all 8 cylinders. IT's a fraud, IMO. Does nothing for the money.... 
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Replying to: nvbanker (Jun 24, 2007 4:06 pm) That is the purpose of DOD. If you cruise, you use 4 cyl. You accelerate, you use 8. Now, I wonder if the computers that manage DOD are fast enough to allow the 4 cyl to be cut at idle, below 5 mph. I wonder what this would do to city mpg, as you would be using half the fuel at idle, at a red light, or in bumber to bumper, crawling. |
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Replying to: nvbanker (Jun 24, 2007 4:06 pm) Fraud? DOD works on the premise of delivering full power when necessary (as during acceleration). Did you expect "4-cylinder acceleration"? DOD benefit seem to be "only" ~10% improvement in fuel economy and seen only in situations when the technology can be used (acceleration and uphill climbs won't be those). |
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Replying to: robertsmx (May 25, 2006 8:06 am) Multi-displacement System (MDS) on the 5.7L V8. Their next generation V6 will also have MDS that goes from 6 to 3 cylinders. |
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Replying to: andre1969 (May 25, 2006 7:00 am) BINGO, Andre, you nailed it. Why more companies aren't using it is because it's a joke, a hoax, and some companies probably won't invest in a fraud. In a laboratory, DOD does some good, but in my vast experience with both Chrysler and GM cars that do this, it's a total scam. They get no better mileage than their normal counterparts, because if you want to accelerate, all cylinders must work. If you run into a grade of any sort, all cylinders must be on line. If you have a slight headwind, virtually anything that causes any resistance at all, puts all cylinders online. Therefore, my truck is never shut down at all, unless I'm on a slight downhill grade at least, or decelerating, or have a terrific tailwind. Well, this doesn't happen much, and what goes down, must come back up. It's a total scam as far as I'm concerned.....  Another "feel good" smoke screen to try and justify low mileage vehicles.
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Replying to: nvbanker (Jul 06, 2007 2:44 pm)
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Replying to: gagrice (Jul 06, 2007 3:01 pm)
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Replying to: nvbanker (Jul 08, 2007 9:41 pm) |
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