dmp
Senior Member
I'm transcribing this from a Road and Track Magazine...I thought some of y'all may enjoy the read. Know that i'm picking and choosing parts of the piece.
Aero vs A/C
The importance of aero has given rise to a good folk legend: You're better off, so goest the myth, running with your car's Air Conditioning (AC) on and the windows up, rather than invoking the added drage of what we used to call "440 a/c" (that is, 4 windows down, 40mph).
The tradeoff is car-and velocity-sensitive, but my sources tell me that it's generally not beneficial at anything resembling legal speeds. Air conditioning can be as much as a 20-percent hit in fuel consumption. Unless heat and humidity call for it, you're better leaving the AC off and the windows rolled down (Purely as an aside, do young people wonder why we "roll down" a window?)
There's a corollary to all this concerning a climate control's Defrost setting. This mode typically activiates the AC as a dehumidifier and is certianly essential in clearing the windshield and side windows. Once they're clear, though, you're better off switching the system from Defrost to Heat; otherwise you may be running the AC all winter long.
Revs aren't Free - and alas, Neither is Speed
It's only in racing - and with execptions even there- that "revs are free." In fact, entertaining though they may be - and sonorous though they may sound - revs pay a penalty in fuel consumption and in wear.
Also, among the things under your control, one with a most profound effect on fuel consumption is your car's speed. Power requirements gro with the square of vehicle velocity (e.g., double the speed, quadruple the required power). And, obviously, power demand is directly related to fuel consumed.
Whatever is an enthusiast to do?
When I'm canyon running, corner strafing or, just for the fun of it, beating that fellow next to me across the intersection, I think of my earlier comment about 'Liquid entertainment'. And certainly we have the least expensive gasoline anywhere I'd want to live.
On the other hand, a lot of my motoring is rather more mundane. And there's genuine satisfaction in performing it efficiently.
WOT/Short-Shifting
Remember Coah Grimbly's dictum about "driving with an egg under your foot"? Forget it. The most efficient way to reach cruising speed is wide-open-throttle (WOT) short shifting. That is, not only do revs cost money, but so does prolonged motoring in lower gear, when throttling and pumping losses are at their greatest.
WOT/Short-shifting can save as much as 20 percent in city driving, worst to best case. In actual practice, rarely does traffic allow full WOT, but it's certianly fun - and efficient as well - to accelerate briskly through the lower gears to whatever the ambient speed happens to be.
Once there, the appropriate choice of gear is one that offers modest RPM with relatively large (and constant!) throttle. Here, Coach Grimbly is vindicated. Dithering the accelerator is a pure waste of fuel, as is a slice-and-dice driving style. Read the traffic and go with the flow. Said one of my sources, "In fuel-economical mode, never request more power than is necessary to get to the next deceleration." There's a good enthusiast message here: Once up to speed, maintain it.
And, of course, avoid last-instant braking that wastes both fuel and brake hardware. A word on hybrid braking; It's useful to 'shape the stop', that is, not to overwhelm the instantaneous capacity of regeneratvie braking. What's optimal is a relatively gentle initial pedal, followed by increased pressure as speed diminishes. Some hybrids have regen gauges that help in perfecting this technique.
Last, a lot of this is manual-shift-oriented, but thoughtful mimicking with an automatic can yield benefits as well.
I've got this neat fuel-saving gizmo!
What of fuel gizmos? Briefly, save your money. Noted one of my sources, "The engine burns fuel with 99-percent efficiency. The inefficiencies are heat-induced, not related to fuel burn." Said another, "Such gizmos enhance the financial transfer from your pocket to the seller's."
Automakers have tremendous incentive to improve their products. Anything with legitimate cost/benefit ratio - and thus, real advertising advantage - would be accepted in an instant.
For example, driving aids, gizmos giving information that aguments fuel frugality, can be of real benefit. One example is tire-pressure monitoring. Another is a hybrid's regen meter to help the driver optimize braking techniques.
Aero vs A/C
The importance of aero has given rise to a good folk legend: You're better off, so goest the myth, running with your car's Air Conditioning (AC) on and the windows up, rather than invoking the added drage of what we used to call "440 a/c" (that is, 4 windows down, 40mph).
The tradeoff is car-and velocity-sensitive, but my sources tell me that it's generally not beneficial at anything resembling legal speeds. Air conditioning can be as much as a 20-percent hit in fuel consumption. Unless heat and humidity call for it, you're better leaving the AC off and the windows rolled down (Purely as an aside, do young people wonder why we "roll down" a window?)
There's a corollary to all this concerning a climate control's Defrost setting. This mode typically activiates the AC as a dehumidifier and is certianly essential in clearing the windshield and side windows. Once they're clear, though, you're better off switching the system from Defrost to Heat; otherwise you may be running the AC all winter long.
Revs aren't Free - and alas, Neither is Speed
It's only in racing - and with execptions even there- that "revs are free." In fact, entertaining though they may be - and sonorous though they may sound - revs pay a penalty in fuel consumption and in wear.
Also, among the things under your control, one with a most profound effect on fuel consumption is your car's speed. Power requirements gro with the square of vehicle velocity (e.g., double the speed, quadruple the required power). And, obviously, power demand is directly related to fuel consumed.
Whatever is an enthusiast to do?
When I'm canyon running, corner strafing or, just for the fun of it, beating that fellow next to me across the intersection, I think of my earlier comment about 'Liquid entertainment'. And certainly we have the least expensive gasoline anywhere I'd want to live.
On the other hand, a lot of my motoring is rather more mundane. And there's genuine satisfaction in performing it efficiently.
WOT/Short-Shifting
Remember Coah Grimbly's dictum about "driving with an egg under your foot"? Forget it. The most efficient way to reach cruising speed is wide-open-throttle (WOT) short shifting. That is, not only do revs cost money, but so does prolonged motoring in lower gear, when throttling and pumping losses are at their greatest.
WOT/Short-shifting can save as much as 20 percent in city driving, worst to best case. In actual practice, rarely does traffic allow full WOT, but it's certianly fun - and efficient as well - to accelerate briskly through the lower gears to whatever the ambient speed happens to be.
Once there, the appropriate choice of gear is one that offers modest RPM with relatively large (and constant!) throttle. Here, Coach Grimbly is vindicated. Dithering the accelerator is a pure waste of fuel, as is a slice-and-dice driving style. Read the traffic and go with the flow. Said one of my sources, "In fuel-economical mode, never request more power than is necessary to get to the next deceleration." There's a good enthusiast message here: Once up to speed, maintain it.
And, of course, avoid last-instant braking that wastes both fuel and brake hardware. A word on hybrid braking; It's useful to 'shape the stop', that is, not to overwhelm the instantaneous capacity of regeneratvie braking. What's optimal is a relatively gentle initial pedal, followed by increased pressure as speed diminishes. Some hybrids have regen gauges that help in perfecting this technique.
Last, a lot of this is manual-shift-oriented, but thoughtful mimicking with an automatic can yield benefits as well.
I've got this neat fuel-saving gizmo!
What of fuel gizmos? Briefly, save your money. Noted one of my sources, "The engine burns fuel with 99-percent efficiency. The inefficiencies are heat-induced, not related to fuel burn." Said another, "Such gizmos enhance the financial transfer from your pocket to the seller's."
Automakers have tremendous incentive to improve their products. Anything with legitimate cost/benefit ratio - and thus, real advertising advantage - would be accepted in an instant.
For example, driving aids, gizmos giving information that aguments fuel frugality, can be of real benefit. One example is tire-pressure monitoring. Another is a hybrid's regen meter to help the driver optimize braking techniques.
