 MPG v.s Speed (rpm), General question |
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 Sep 27, 2004 - 1:01 PM
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 Enthusiast  Joined Aug 30, '02 From Austin Texas Currently Offline Reputation: 0 (0%)  |
Ok here is the Situation:
You car gives 30 Miles to a Gallon at 70Mph. At 70mph ( last gear ) you are in the middle of your powerband. The distant you have to travel is 33 Miles. You have only 1 gallon of fuel in your car. What do you do? Do you slow down your car burn less fuel? OR do you speed up? All road and air conditions are ideal. |
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Sep 27, 2004 - 1:06 PM
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 Enthusiast Joined Aug 20, '03 From Annapolis, Md Currently Offline Reputation: 5 (100%) |
You go as fast as you can, cause A: you run out of gas, you can put in N an drift a good amount, or get pulled over an a cop could get you some gas, an it would be fun....
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Sep 27, 2004 - 2:10 PM
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Enthusiast Joined Jul 7, '04 From charlotte N.C. Currently Offline Reputation: 0 (0%) |
im pretty sure your going to get more mpg at 2k than at 5k
-------------------- Former: 96 GT 5 speed (i/p/e) Fate- rear ended by mack truck
00 GTS 6 speed (i/ Bored TB 63mm - 68.5mm w/ butterfly/ Ported IM/ IMG/ PFC/ Commander/ datalogit/ Ported & heat wrapped Header/ Decat/ UEGO/) 193FWHP 14.2(1/4mi) @98mph, 2.12 60ft (just intake, unbolted Exhaust, and gutted) Fate- side swipped by 18 wheeler at 75mph. Next: maybe an elise |
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Sep 27, 2004 - 2:10 PM
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 Enthusiast Joined Sep 10, '03 From Santa Barbara, CA Currently Offline Reputation: 0 (0%) |
I think you would slow down to lower rpm but keep it in 5th gear.
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Sep 27, 2004 - 2:21 PM
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 Enthusiast Joined Aug 26, '04 From Vancouver, WA Currently Offline Reputation: 0 (0%) |
From what I was told you get your best gas milage at your peak torque. Whitch is around 3k rpm if i remember correctly for the ST, not sure about others.
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Sep 27, 2004 - 2:26 PM
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Enthusiast Joined Jun 2, '03 From Annandale VA Currently Offline Reputation: 0 (0%) |
Peak is 3600 I believe. I get the feeling you will get the best mpg around 2800 rpms
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Sep 27, 2004 - 6:04 PM
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 Enthusiast Joined Jan 8, '04 From LA Currently Offline Reputation: 0 (0%) |
skooled by 97, incorrect info removed
This post has been edited by shid: Sep 27, 2004 - 9:44 PM |
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Sep 27, 2004 - 6:29 PM
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Enthusiast Joined Aug 30, '02 From Anaheim, CA Currently Offline Reputation: 0 (0%) |
not really depending on speed and gear and the powerband of the engine maintaining low rpms is harder, requiring mroe throttle work and putting more load on the engine the result is burning more gas even though you are at a lower rpm get a vacuum gauge and hook it up. then maintain 2000 rpms in fifth gear, look at the reading on the gauge, then try cruising at peak torque and look at the gauge. the closer to 0, the worse the mpg, cruising at peak torque makes it very easy to maintain your speed, which means less work has to be done by the engine, which equals best mpg you can get. -------------------- 1994 Celica GT4 WRC Edition
@gt4.wrc on Instagram |
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Sep 27, 2004 - 6:57 PM
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 Enthusiast Joined Sep 4, '03 From Twin Cities MN Currently Offline Reputation: 2 (100%) |
erm... I say slow down- increasing enigne speed also increases rate of consumption. even though in theory you may get peak fuel economy at peak torque, who is to say you are required to use ALL that power to mantain speed? All that happenes when you maintain peak torque is use excessive power in most cases, and keep the engine closest to a set point without much deviation if you did need that power... It increases fuel economy much in the same was cruise control would- you keep the car at a constant. If you were to get best fuel economy at peak torque, 5th gear would be geared higher in out GT's. 65 mph in a GT is 3200 rpms- 1000 or so rpms below peak torque. Of course there are certain variables to consider- reducing rpms also reduces speed, and there will be a point where the reduction in speed will result in longer periods of consumption, and so on. Remeber- a basic concept of physics is the the more energy somthing puts out, the more energy it consumes.
-------------------- Car #3: 98 Accord LX- purchased 5/06, totaled 8/06
Car #2: 95 Celica GT- purchased 8/03, current daily driver Car #1: 01 Focus ZX3- purchased 5/01, sold 8/03 |
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Sep 27, 2004 - 7:03 PM
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Enthusiast Joined Sep 14, '04 From SaN DiegO, CaLi Currently Offline Reputation: 1 (100%) |
i say you always make sure you have a full tank before you go anywhere...lol
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Sep 27, 2004 - 10:25 PM
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Enthusiast Joined Aug 30, '02 From Anaheim, CA Currently Offline Reputation: 0 (0%) |
BINGO -------------------- 1994 Celica GT4 WRC Edition
@gt4.wrc on Instagram |
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Sep 27, 2004 - 11:02 PM
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 Enthusiast Joined Dec 25, '02 From Pittsburgh/Clairton, PA Currently Offline Reputation: 1 (100%) |
i still would say lowest RPMs youcan run in 5th gear w/o having any acceleration.
based on Saleeka's thread, i agree that you only should need as much torque as to keep the car going against air resistance, and engine resist. hitting a max torque would most likely help the efficiency of the engine, but the surplus of power would bring this overall down a few notches... just a hypothesis --------------------  |
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Sep 29, 2004 - 2:07 PM
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 Enthusiast Joined Aug 22, '04 From Menomonie, WI Currently Offline Reputation: 0 (0%) |
i should ask this to my physics teacher tomarrow if i remember....or you guys should get me some stats on this....mpg at different speeds, ect, and ill made a graph according to it, and it will tell you the best way....but its all just theoretical....
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Sep 30, 2004 - 4:08 AM
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Enthusiast Joined Aug 16, '03 From Bay area Currently Offline Reputation: 0 (0%) |
remember the oil chrisis in the USA during the vietnam war? well they lower the highways speeds to save gas. so i assume lower rpm will save more gas.
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