With DOD orother variable-displacement technology, what is now true is that your fueleconomy ratings absolutely have to improve unless you're driving all the timewith the gas pedal pressed flat to the floor.
If you do a lotof driving in the city or in the kind of traffic that requires lots of stopsand starts, you'll see slight but noticeable fuel economy improvements withvariable-displacement. If you do a lot of highway driving at steady speeds, youcan expect a serious (say 15 percent or so) improvement in fuel economy over atraditional engine of a similar size and power.
This was anextremely welcome development in the GMC Envoy XL (this is GMC's version of theChevrolet Suburban) on that triangular drive from Toronto to Canada's currentcapital to its original capital and back to Toronto. I dialed a speed (115 kmh)into the cruise control that kept the Envoy XL moving with traffic but didn'trequire the 5.3-litre V-8 to downshift much to handle whatever grades weencountered.
As I rolledalong in the Envoy, I regularly cycled the information centre to keep an eye onthe average fuel economy and it kept dropping. By the end of the trip, theEnvoy XL was registering a consumption rate of close to 14 litres per 100 km(which is well below what Transport Canada projects) and it was still on theway down, though slowly.
DOD can only doso much, however, so you can't push a vehicle that weighs 2,247 kg when it'sempty through the wind at highway speeds and not use a bunch of gasoline.
It always hurtfinancially to fill the Envoy XL up, but a 15 percent improvement in fueleconomy means a 15 percent reduction in fuel costs, and that's got to help overthe course of a year.
The improvementin urban driving would of course be lower, but with fuel costs over 90 cents alitre in many parts of the country, any advance helps.
It should alsobe pointed out that there is no issue with getting all of the cylinders backonline when you want or need them. Full power is there just as quickly as itwould be with a traditional engine.
This kind oftechnology is not as big, flashy and expensive as things like hybrid power, butit's extremely worthwhile and will probably work its way into more and more enginesas time progresses, and we should be glad.
photo:General Motors
If you do a lotof driving in the city or in the kind of traffic that requires lots of stopsand starts, you'll see slight but noticeable fuel economy improvements withvariable-displacement. If you do a lot of highway driving at steady speeds, youcan expect a serious (say 15 percent or so) improvement in fuel economy over atraditional engine of a similar size and power.
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As I rolledalong in the Envoy, I regularly cycled the information centre to keep an eye onthe average fuel economy and it kept dropping. By the end of the trip, theEnvoy XL was registering a consumption rate of close to 14 litres per 100 km(which is well below what Transport Canada projects) and it was still on theway down, though slowly.
DOD can only doso much, however, so you can't push a vehicle that weighs 2,247 kg when it'sempty through the wind at highway speeds and not use a bunch of gasoline.
It always hurtfinancially to fill the Envoy XL up, but a 15 percent improvement in fueleconomy means a 15 percent reduction in fuel costs, and that's got to help overthe course of a year.
The improvementin urban driving would of course be lower, but with fuel costs over 90 cents alitre in many parts of the country, any advance helps.
It should alsobe pointed out that there is no issue with getting all of the cylinders backonline when you want or need them. Full power is there just as quickly as itwould be with a traditional engine.
This kind oftechnology is not as big, flashy and expensive as things like hybrid power, butit's extremely worthwhile and will probably work its way into more and more enginesas time progresses, and we should be glad.
photo:General Motors