Mechanics

HOW TO CHANGE GEARS FOR FUEL

2010 All Other Makes All Other Models

I have a tata nano petrol. The gear ratios are
1st 3.45
2nd 1.95
3rd 1.26
4th 0.83

if you could please tell me how to change gears at what speeds to gain best fuel economy and best millaege.

its a 625 cc engine 2 cylinder.
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Nadine_kerman
April 9, 2011.




Gnerally speaking, the harder you press the gas pedal, the more fuel you are usuing. So it is more to accelleration speeds than shift points. And the lower the rpms you can shift at and still maintain acceptable accelleration speed the better the gas mileage. You may get honked at alot by tryng to save on gas!


Tiny
Fixitmr
Apr 9, 2011.
YOU CAN INSTALL A VACUUM GAUGE ON YOUR DASH---PLAY THE GAME..."HOW HIGH CAN I KEEP THE VACUUM GAUGE NEEDLE!" (ACTUALLY MEANING, HOW LOW YOU CAN KEEP VACUUM)! IT'S SORTA FUN, KEEPING IT AS HIGH AS POSSIBLE WHILE ALSO TRYING TO MAINTAIN ACCEPTABLE DRIVABILITY! IT ALSO ALERTS YOU AS TO PROBLEMS WITH YOUR ENGINE.....I HAVE ONE ON THE DASH OF BOTH OF MY JEEPS (MAINLY FOR SEEING PROBLEMS, THE NEEDLE WILL BE HIGH AND STEADY IF ALL IS FINE,.......IT MAY WIGGLE, GO HIGH/ LOW, SHAKE, ETC. IF SOMETHING IS WRONG...SEE THIS http://www.secondchancegarage.com/public/186.cfm AND THIS http://www.youtube.com/watch?v=MBYVZLRyQjk THIS CAN BE PERMANENTLY MOUNTED OR USED LIKE MY DIAGNOSING ONE (LAST 3 PICS). ---IN MY '77 JEEP IT IS THE TOP RIGHT GAUGE (22 INCHES [Hg] AT IDLE)--IN MY '46 IT IS THE BOTTOM RIGHT (20 INCHES [Hg] AT IDLE) GAUGE---LET ME KNOW WHAT YOU THINK!!-THE MEDIC


CJ MEDEVAC
Apr 9, 2011.
Sorta Cool! I just wanted to see what your car looked like, I have seen similar ones here and there, in my region, I didn't know what they were called. With your 2 cylinder car you are trying to really save on the fuel! What is your KPH or MPH NOW? What does gas (petrol) cost in US currency, in your region? Definitely not good around here now, Last I saw was $3.55 per gallon ($.92 per liter). In the 1st Jeep (1st pic) of mine I get about 18 Miles per gallon (7.64km per liter, if I converted correctly!), It is a 6 cylinder. What do you think about using a vacuum gauge, for a guide for Accelerator Pedal Management, now that you have seen the video(s)? Please respond, this is really interesting!--The Medic


CJ MEDEVAC
Apr 10, 2011.
Hey so this might be a bit technical, and although I'm a newbie at engine maintenance, power and torque are something I understand pretty well. As your RPMs increase in your engine, your torque and horsepower increase almost linearly. Eventually, though, they start falling off because of friction and other opposing forces that occur at high RPM. The point is that there's a peak. Typically the torque curve falls off faster than the horsepower curve (see picture). Engineers will design transmissions so that the engine operates somewhere within this optimum power band.

Although horsepower gives you the "kick" into the back of your seat, torque is what you're actually driving. Torque is your engine's ability to rotate your wheels. In order to maintain maximum gas mileage, you always want to operate your engine at peak torque. That's why diesel engines get so many more MPGs that gasoline engines - they have WAY more torque! Horsepower is your engines ability to create kinetic or "movement" energy. Although your horsepower might be peaking, your engine isn't operating at it's optimum efficiency. Medic, that's why your vacuum will peak too. The intake vacuum is a function of the efficiency of the engine.

If you're a race car driver, you want to operate your engine so the RPMs are at peak horsepower. If you're a penny pincher, you want to operate you engine at peak torque. You should be able to find a torqe-horsepower curve for your model and engine. These curves will change as your engine ages. You could go to your nearest university and get some nice engineer (like me) to run a test for you if you want an accurate curve. Simply operate your engine at the RPMs as close to possible to your peak torque. That's why they have those fancy double clutch engines and expansion gears so the engine spends more time at optimum RPM.

If you want to know EXACTLY what speeds to shift your transmission to maximize gas mileage (maximize torque), there could be a way to optimize the RPM at which you change gears by integrating the torque over the time spent there at a certain speed. I know, I just talked about calculus on a car forum. If you want me to run the optimization for you, let me know. All I'll need is your torque vs. RPM curve.
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Tiny
Hang em hi
Jun 22, 2012.

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