Brady Posted July 12, 2007 Author Share Posted July 12, 2007 My point is that peak torque has nothing to do with peak fuel economy. I was commenting that IF you properly spec'd an engine for best fuel economy, you'd want to choose an engine that was small enough that the full output was required to run at peak power to maintain about 50 mph. Ultimately, we don't need 250 hp to go 55 mph ... maybe more like 50-60 hp. Link to comment Share on other sites More sharing options...
DriverX Posted July 12, 2007 Share Posted July 12, 2007 I have an '06 SE. On my trip to the Jersey Shore (lot's of cops, if you can do 60mph on these 55mph roads you take it) I have had the computer show 34.7 mpg on a round trip (120 miles) Link to comment Share on other sites More sharing options...
rporter Posted July 13, 2007 Share Posted July 13, 2007 Remember that peak power is a purely mathematical equation for torque over time, and will not get you the best mileage. Peak torque is the most efficient RPM. Nonetheless, cars that are geared to run like the Corvette may not be running at their optimal efficiency at 1800 RPM versus peak torque, but the lower wind resistance, mechanical and tire losses, etc, can give better rmileage. The peak power number will never give the best mileage under any circumstances, unless it was an odd engine where torque and HP occurred at the same RPM. Which doesn't seem even remotely possible if you look at the HP equation, unless there were no more RPM available. Ron Link to comment Share on other sites More sharing options...
Brady Posted July 13, 2007 Author Share Posted July 13, 2007 Remember that peak power is a purely mathematical equation for torque over time, and will not get you the best mileage. Peak torque is the most efficient RPM. Nonetheless, cars that are geared to run like the Corvette may not be running at their optimal efficiency at 1800 RPM versus peak torque, but the lower wind resistance, mechanical and tire losses, etc, can give better rmileage. The peak power number will never give the best mileage under any circumstances, unless it was an odd engine where torque and HP occurred at the same RPM. Which doesn't seem even remotely possible if you look at the HP equation, unless there were no more RPM available. False. Just plain false. Honestly, I don't have the energy to try to explain this and dig out all the laws of physics on this. I guarantee that peak power will yield the highest efficiency ... it's my job. However, in a vehicle (automobile) the engine needs to be designed to do more than be efficient at cruising speed. It also needs to be able to accelerate. I also assure you that operating a motor at peak Torque does not yield peak efficiency. Link to comment Share on other sites More sharing options...
dr_sharp Posted July 13, 2007 Share Posted July 13, 2007 I also assure you that operating a motor at peak Torque does not yield peak efficiency. +1 But again it depends on your definition of efficiency... of course not textbook efficiency. If efficiency were determined by quickest time from a to b then peak torque is what you want lol Link to comment Share on other sites More sharing options...
ZinFreak Posted July 13, 2007 Share Posted July 13, 2007 Ultimately, we don't need 250 hp to go 55 mph ... maybe more like 50-60 hp. Brady, At 55 mph, it is going to be more like 25 hp required to maintain steady state speed on a flat road, bumping that up to 70 mph, it jumps to about 40 hp. "Wind" drag goes up with velocity squared, which is illustrated directly by the numbers above. It is amazing to realize that the energy required to keep a 1-ton car moving at highway speeds (55 mph) is the equivalent of about 9 hair dryers. [ 1 hp = 745 W] -Zin 06 LGT LTD GRP 5MT 07 FXT LTD OBP 4EAT Link to comment Share on other sites More sharing options...
700watts Posted July 13, 2007 Share Posted July 13, 2007 Am I the only one who floors it when I pass one of those "Speed Limit 35 / Your Speed ___" ? Just to see if spedometer is working correctly of corse. NOPE, your not the only one..... Link to comment Share on other sites More sharing options...
Brady Posted July 13, 2007 Author Share Posted July 13, 2007 Brady, At 55 mph, it is going to be more like 25 hp required to maintain steady state speed on a flat road, bumping that up to 70 mph, it jumps to about 40 hp. "Wind" drag goes up with velocity squared, which is illustrated directly by the numbers above. It is amazing to realize that the energy required to keep a 1-ton car moving at highway speeds (55 mph) is the equivalent of about 9 hair dryers. [ 1 hp = 745 W] Is it really that low?! I was trying to over-estimate just so no one accused me of exaggerating low numbers! Link to comment Share on other sites More sharing options...
gfxdave99 Posted July 13, 2007 Share Posted July 13, 2007 Is it really that low?! I was trying to over-estimate just so no one accused me of exaggerating low numbers! You might be coming up with the highest number of miles If everything seems under control, you're just not going fast enough. - Mario Andretti Link to comment Share on other sites More sharing options...
D_J Posted December 25, 2007 Share Posted December 25, 2007 Well, I re-upped .... 480.2 miles on one tank ... http://burnedimage.afraid.org/lgt/gas1.jpg http://burnedimage.afraid.org/lgt/gas2.jpg http://burnedimage.afraid.org/lgt/gas3.jpg Looks like about the same results as boomshnka except I pushed a few more miles and used about the same amount of gas. Not bad. Did you consistently get 30.9 mpg? The highest so far I got was today. Just a couple days after an oil change...went an average of 70 mph on the freeway, mixed in with a substantial amount of city driving. My best average mpg is 27.9 on a 50 mile trip. That is actually the highest overall mpg I got so far. Fuel efficiency is poor until the engine gets broken -in from what I hear on newer vehicles. Link to comment Share on other sites More sharing options...
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