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I supported Toymods
Location:
south of the big smoke
Registered:
May 2002
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what uses more fuel?
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Wed, 31 December 2003 02:56
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was driving along today and i got thinking
what uses more fuel
doing 80km/h @ 3000rpm in 4th or 2200rpm in 5th?
see when ya in 4th ya dont have to hit the accelerator as much, but since its reving harder the stroke that more fuel is injected is more frequent
in 5th it isnt reving as hard but you have to push the accelerator harder??
lets say for this scenario im going up a slight hill
cheers
craig
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Location:
Sydney
Registered:
May 2002
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Re: what uses more fuel?
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Wed, 31 December 2003 02:57
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are u accelerating ???
or just maintaining speed ???
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I supported Toymods
Location:
south of the big smoke
Registered:
May 2002
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Re: what uses more fuel?
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Wed, 31 December 2003 03:16
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lets say both
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Location:
Kita-Ku, Sapporo, Japan
Registered:
January 2003
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Re: what uses more fuel?
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Wed, 31 December 2003 04:05
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depends on a whole bunch of things (obviously) but comes down to efficiencies (also depends on mapping etc etc)
higher rpm lower throttle has more friction.
lower rpm with more throttle has less pumping losses.
for a turbo car with small cam overlap, higher gear, more throttle will be better, as long as you are not too far below where the turbo is actually doing something.
for an NA car with large overlap cam, you don't want to drop below your cam efficiency.
as a very general guess, best fuel efficiency will be where your rpm and pumping losses are both minimised, and you will probably be close to the motors 'part throttle torque peak'. this is assuming things like 'closed loop AFR control'
blah blah etc etc 
Cya, Stewart
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Location:
Blacktown, Sydney
Registered:
December 2003
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Re: what uses more fuel?
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Wed, 31 December 2003 04:09
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ive actually been wanting to ask that question for quite sometime now ... and since my throttle isnt as responsive i actually have to step on the pedal alot more and wait till the rev goes up and then maintain certain speed ...
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