Why dont more cars turn off cylinders when cruising on the highway
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from what I've read about that engine, the v6 mode was the main problem.. you can't just skip every other cylinder like in V4 mode. it made for some really odd NVH problems.quote:
Originally posted by XS650:
It was an all too common release of an engine for production by GM while it was still a Beta product.
The idea was OK and it but the execution was problamatic.
You cannot open any valve in any empty stroke. I also believe that the fuel during compression aids in lubricating the cylinder walls and rings. This would decrease friction and drag that would occur in an otherwise dry cycle. And it would decrease wear.
As stated before, fuel savings are minimal. If you need 30 BHP to push the car it does not matter if you get it from 8 cylinders with 8 cc of fuel or 7 cylinders with 9cc of fuel/cylinder each minute.
aehaas
As stated before, fuel savings are minimal. If you need 30 BHP to push the car it does not matter if you get it from 8 cylinders with 8 cc of fuel or 7 cylinders with 9cc of fuel/cylinder each minute.
aehaas
This is exactly why I love my turbocharged 4 cyl Saab! Economy of a 4 cyl & power of an 8 cyl.
But not in a 4200 lb car with an Automatic. A friend at work has a Magnum RT and has calculated his MPG, is getting about 25-27sh on the highway and about 23 all around in mixed driving, 60%city 40% highway. I also have a friend with a Firebird with a 5.7 with a stick and he gets about 25 MGP, but in much lighter car with standard.
DC's cylinder deactivation does not work above 70MPH and I belive just the DC cars have this! I though the trucks did not have the cylinder deactivation? Seeing how I often drive 75MPH-80MPH the CDA system would simply be dead weight!
Two examples of heavy vehicles that (can) get good mileage:
1. 1992 Buick Roadmaster. 350 cid engine, 4 speed auto (really 3+overdrive). Low 20's highway (average), 24-25 attainable if you can keep your foot out of it. 1700rpm at 70 mph.
2. 2002 Chevy Suburban, 6000cc engine, 2500HD. Easily obtains low 20's on the highway, 25 is doable if you can keep your foot out of it. Not sure of the transmission.
Compare that to my 2002 Honda Accord V6. 3000cc, 24-25 mpg average, 30-31 maximum.
Best mileage ever: 72 mpg. 1989 Honda VTR 250.
Worse mileage ever: 8 mpg. 1978 Ford 3/4 ton "Camper Special", 400cid with the auto. It had 2 gas tanks and it needed 'em.
1. 1992 Buick Roadmaster. 350 cid engine, 4 speed auto (really 3+overdrive). Low 20's highway (average), 24-25 attainable if you can keep your foot out of it. 1700rpm at 70 mph.
2. 2002 Chevy Suburban, 6000cc engine, 2500HD. Easily obtains low 20's on the highway, 25 is doable if you can keep your foot out of it. Not sure of the transmission.
Compare that to my 2002 Honda Accord V6. 3000cc, 24-25 mpg average, 30-31 maximum.
Best mileage ever: 72 mpg. 1989 Honda VTR 250.
Worse mileage ever: 8 mpg. 1978 Ford 3/4 ton "Camper Special", 400cid with the auto. It had 2 gas tanks and it needed 'em.
Jon, I bet if you compared the Buick Roadmaster and the Suburbans city milage to the Honda we would see a different picture all together!! It is not just engine size it engine size,gear ratio,lbs per HP and driveing style!Just becasue something has a small engine does not gurantee the best fuel economy!
I had a friend at work that had the same engine as a guys Raodmaster. THe roadmaster even weighted more then his two wheel drive pickup. He could not understand why the other guy got 26MPG onthe HWY while he averaged 17-19MPG. When I got into the areodynamics and gearing it all made sense.
P.S. I worked right downthe raod from wear all the Suburbans were made. I have known a lot of people that own them and they are as common up here as dirt! My B.S. meter is going off though with the 20+MPG with a Suburban of that vintage! Was this when the speed limit was 55MPH????
I had a friend at work that had the same engine as a guys Raodmaster. THe roadmaster even weighted more then his two wheel drive pickup. He could not understand why the other guy got 26MPG onthe HWY while he averaged 17-19MPG. When I got into the areodynamics and gearing it all made sense.
P.S. I worked right downthe raod from wear all the Suburbans were made. I have known a lot of people that own them and they are as common up here as dirt! My B.S. meter is going off though with the 20+MPG with a Suburban of that vintage! Was this when the speed limit was 55MPH????
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