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SVT Shelby GT500
Rumor has it GT500 make 638 rwhp with mods
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<blockquote data-quote="Black2003Cobra" data-source="post: 3143907" data-attributes="member: 3159"><p>Just a few brief comments on fuel efficiency.</p><p></p><p><u>Obviously weight is bad:</u></p><p>Higher weight means more energy to accelerate to a given speed, KE = 0.5*m*v², which requires more fuel. (This KE is then lost in the form of heat energy when you hit the brakes.)</p><p></p><p>Rolling resistance loss is also directly proportional to weight, so higher mass = lower mpg here, too.</p><p></p><p>Aerodynamic drag is directly proportional to Cd <em>and</em> frontal cross section area, so both of these can ping mpg.</p><p></p><p>Higher mass also means a greater road inclination loss, (going up hills). So again…lower mpg.</p><p></p><p><u>Then there’s perhaps the not so obvious.</u></p><p>Moving a given mass at a given speed requires a given amount of power to overcome the “road load”, (i.e., rolling resistance, aero loss, road inclination loss, etc.). And to make a given amount of indicated power takes a given mass fuel (and air) flow rate. But because a larger engine is going to have a lower mechanical efficiency, (due primarily to higher pumping* and frictional losses), this means a lower brake power for a given mass fuel rate. Therefore, to generate the required brake power with a lower mechanical efficiency means a higher amount of indicated power, which means a higher mass fuel flow rate. Ergo, lousy mpg again.</p><p></p><p>The lower static CR of a blower engine reduces the thermal-conversion efficiency of the motor. This means a lower fuel-conversion efficiency (compared to a higher compression NA engine), which once again means a higher fuel consumption.</p><p></p><p>*Pumping loss is the energy required to pump air in to, and exhaust out of the engine. Since a larger engine will be throttled back more to make a given amount of power, this means a higher pumping loss. Larger frictional losses with a bigger engine should be obvious.</p></blockquote><p></p>
[QUOTE="Black2003Cobra, post: 3143907, member: 3159"] Just a few brief comments on fuel efficiency. [U]Obviously weight is bad:[/U] Higher weight means more energy to accelerate to a given speed, KE = 0.5*m*v², which requires more fuel. (This KE is then lost in the form of heat energy when you hit the brakes.) Rolling resistance loss is also directly proportional to weight, so higher mass = lower mpg here, too. Aerodynamic drag is directly proportional to Cd [I]and[/I] frontal cross section area, so both of these can ping mpg. Higher mass also means a greater road inclination loss, (going up hills). So again…lower mpg. [U]Then there’s perhaps the not so obvious.[/U] Moving a given mass at a given speed requires a given amount of power to overcome the “road load”, (i.e., rolling resistance, aero loss, road inclination loss, etc.). And to make a given amount of indicated power takes a given mass fuel (and air) flow rate. But because a larger engine is going to have a lower mechanical efficiency, (due primarily to higher pumping* and frictional losses), this means a lower brake power for a given mass fuel rate. Therefore, to generate the required brake power with a lower mechanical efficiency means a higher amount of indicated power, which means a higher mass fuel flow rate. Ergo, lousy mpg again. The lower static CR of a blower engine reduces the thermal-conversion efficiency of the motor. This means a lower fuel-conversion efficiency (compared to a higher compression NA engine), which once again means a higher fuel consumption. *Pumping loss is the energy required to pump air in to, and exhaust out of the engine. Since a larger engine will be throttled back more to make a given amount of power, this means a higher pumping loss. Larger frictional losses with a bigger engine should be obvious. [/QUOTE]
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Rumor has it GT500 make 638 rwhp with mods
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