Almost reach 3000rpm when travel at constant 100km/h

[Jolie888]

Does that means those car having less rpm at 100km/h saves more petrol while traveling long distances?

 

I don't think so.

 

To achieve a lower RPM for any given speed, you'd need a higher torque to be developed on equivalent RPM.

 

To achieve that, you'd need a larger capacity NA engine, or a forced induction engine ... both ways, you will need to burn more fuel for equivalent km travelled, at the same speed.

 

Nothing comes for free in this physical world of energy and mass conservation.

[Bluepica]

I don't think so.

 

To achieve a lower RPM for any given speed, you'd need a higher torque to be developed on equivalent RPM.

 

To achieve that, you'd need a larger capacity NA engine, or a forced induction engine ... both ways, you will need to burn more fuel for equivalent km travelled, at the same speed.

 

Nothing comes for free in this physical world of energy and mass conservation.

 

hmmm... some say yes, some say no.... whatabout compare apple to apple... I mean for a given 1.6AT/CVT ... one RPM 2k 100km/h , another RPM 2.8k 100km/h... definitely the latter saves more right?

[Alechi]

More gears ... lower rpm @ high speed ... more fuel economical

[Ben5266]

Yes. When the engine capacity is bigger and more powerful, the highest gear ratio can be lowered further to achieve lower rpm and the car can go faster.

But if the engine is small and less power, having too low ratio will give no power to pull/push the car.

4AT will have limited ratio number to play with because if put to low, the car will have no power to accelerate. Put too high (close to 3rd gear) will limit its top speed.

[Joseph22]

hmmm... some say yes, some say no.... whatabout compare apple to apple... I mean for a given 1.6AT/CVT ... one RPM 2k 100km/h , another RPM 2.8k 100km/h... definitely the latter saves more right?

 

you mean the former saves more right?

[Joseph22]

Yes. When the engine capacity is bigger and more powerful, the highest gear ratio can be lowered further to achieve lower rpm and the car can go faster.

But if the engine is small and less power, having too low ratio will give no power to pull/push the car.

4AT will have limited ratio number to play with because if put to low, the car will have no power to accelerate. Put too high (close to 3rd gear) will limit its top speed.

 

actually for smaller engine, if you have a gear box specially tuned for it, it is still possible to save more fuel and at the same time with the correct power pull to the car. Take Polo for example. if they set the first 2 gear ratio to that of a normal AT4, it can still pull off at the same power. but as it reach higher speed, switching to a higher gear will not required it to need as much power as we think.

Edited January 8, 2010 by Joseph22

[Bluepica]

you mean the former saves more right?

 

ops... yup

[Ben5266]

1.6 4AT 2.8krpm @100km/h will consume more fuel.

1.6 CVT 2krpm @100km/h will consume less.

 

1 rpm means, 1 fuel and air intake and an explosion per minute. Then, the 2nd cycle will be to push out the waste.

So, 2k rpm, 1000 explosion per minute.

2.8k rpm, 1400 explosion per minute.

So, if the engine capacity is the same, burning fuel 1000 times is less than burning fuel for 1400 time in 1 minute.

[Peaceracer]

1.6 4AT 2.8krpm @100km/h will consume more fuel.

1.6 CVT 2krpm @100km/h will consume less.

 

1 rpm means, 1 fuel and air intake and an explosion per minute. Then, the 2nd cycle will be to push out the waste.

So, 2k rpm, 1000 explosion per minute.

2.8k rpm, 1400 explosion per minute.

So, if the engine capacity is the same, burning fuel 1000 times is less than burning fuel for 1400 time in 1 minute.

 

Thats a very good way to make layman understand. Never thought of explaining it that way before.

[Peaceracer]

Mine:

 

Idling: 500 RPM

100 km/h: 1,800 RPM (flat road)

 

3.0V6 7A/T.

 

So low?? Surprising. Maybe i suaku never sit in a big engine car b4.

 

Anyway my 1.1M getz is abt 3000rpm at 100kmh, and 2500 at 70kmh. Somehow i which i had a 6th gear. Quite heart pain to hear it work so hard.

 

BTW anyone knws why auto gearing is most of the time higher than the equivalent manual gearing? Shouldnt there be lesser losses in manual and thus able to use higher gearing thn auto for the same make and engine cap?? This puzzles me for a long time le...

[Joseph22]

So low?? Surprising. Maybe i suaku never sit in a big engine car b4.

 

Anyway my 1.1M getz is abt 3000rpm at 100kmh, and 2500 at 70kmh. Somehow i which i had a 6th gear. Quite heart pain to hear it work so hard.

 

BTW anyone knws why auto gearing is most of the time higher than the equivalent manual gearing? Shouldnt there be lesser losses in manual and thus able to use higher gearing thn auto for the same make and engine cap?? This puzzles me for a long time le...

 

4 gear as opppose to 5 or 6 gear??

[Levinx]

My 1.5L auto fit hovers around 1900RPM-2000RPM at 100km/hr..

Edited January 8, 2010 by Levinx

[Jolie888]

So low?? Surprising. Maybe i suaku never sit in a big engine car b4.

 

Not 'so' low. Idling rpm is a strong function of engine capacity and tuning.

 

The Merc's 3.0 V6 7A/T:

Idling: 500 rpm

100 km/h: ~1800 rpm

 

Previous Lexus 2.0 IL6 4A/T:

Idling: 700 rpm

100 km/h: ~1900 rpm

 

Previous BMW 2.5 IL6 5A/T:

Idling: 800 rpm

100 km/h: ~2000 rpm

 

Weight is a factor too. My BMW was an SUV.

 

Compare that with my previous VW 2.0 IL4 Manual:

Idling: 1000 rpm

100 km/h: ~2700 rpm

[Peaceracer]

4 gear as opppose to 5 or 6 gear??

 

Hmmm, tat makes sense too.

[Peaceracer]

Not 'so' low. Idling rpm is a strong function of engine capacity and tuning.

 

The Merc's 3.0 V6 7A/T:

Idling: 500 rpm

100 km/h: ~1800 rpm

 

Previous Lexus 2.0 IL6 4A/T:

Idling: 700 rpm

100 km/h: ~1900 rpm

 

Previous BMW 2.5 IL6 5A/T:

Idling: 800 rpm

100 km/h: ~2000 rpm

 

Weight is a factor too. My BMW was an SUV.

 

Compare that with my previous VW 2.0 IL4 Manual:

Idling: 1000 rpm

100 km/h: ~2700 rpm

 

Ya, mine is abt 800 w/o AC and 900 with A/C. Really appreciate if the car can idle and criuse at low rpms. The trip will be much more comfy.

[TangoElite]

My 1.5L auto fit hovers around 1900RPM-2000RPM at 100km/hr..

 

 

must be CVT

 

wild guess, u driving axio? allion?

 

 

[Fcw75]

must be CVT

 

wild guess, u driving axio? allion?

 

Alamak bro, he said he driving fit oready leh.

[TangoElite]

Alamak bro, he said he driving fit oready leh.

 

 

 

opps

 

my csi

Edited January 8, 2010 by TangoElite