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It seems 1600-2000 rpms is best for max. economy (?)

4K views 8 replies 7 participants last post by  PLP 
#1 ·
Ive noticed that at this rpm range that the average mpg seems to increase faster than at a higher rpm. Do u find this also ? I am taking into account the same road terrain and cargo . Dave.
 
#4 · (Edited)
In my 2012 Kia Rio 5, it is 62 miles per hour-100 kilometers per hour- cruise control on.Hands down best cruising speed.for me.right lane of course.
All other speeds are at the 2 and 7 mark.as in 22-27,32-37,42-47,52-57,62-67 cruise control on ,if safe.
After seventy, the mileage goes down.
All acceleration is gentle.
All city mileage ( stop and go) is horrible-in mine.
Tires inflated at 38-40 psi cold-done that for twenty years.All of my tires last longer then the warranty mileage.
 
#5 · (Edited)
That's very correct, but it is heavily dependent on engine (type: Otto or Diesel) and its condition (load/terrain).

Look here to learn more.
https://en.wikipedia.org/wiki/Brake_specific_fuel_consumption

Look for BSFC graphs. You will find many of them and all of them vary by engine. Like this one below.


Basically, you are looking for the lowest number, that is the least amount fuel for power produced in time.
As you see, it goes DOWN with increased pressure, hence (as said below) WOT is the most efficient at low RPM.


In my 2012 Kia Rio 5, it is 62 miles per hour-100 kilometers per hour- cruise control on.Hands down best cruising speed.for me.right lane of course.
All other speeds are at the 2 and 7 mark.as in 22-27,32-37,42-47,52-57,62-67 cruise control on ,if safe.
After seventy, the mileage goes down.
All acceleration is gentle. Read below, and then above.
All city mileage ( stop and go) is horrible-in mine.
Tires inflated at 38-40 psi cold-done that for twenty years.All of my tires last longer then the warranty mileage.
Acceleration does not have to be gentle.
Actually, if you could accelerate keeping low rpm at WOT (wide open throttle) you could achieve even better results. At full throttle you get the most out of your fuel. Sure, oxygen sensors are doing their best to keep it at optimum, but at WOT you allow the most air to get in (more oxygen better combustion), while keeping acceleration rate at its peak.
Then, for your city driving, experiment with engine braking. "Feel" the transmission shift points (if automatic) and see how the torque converter keeps it locked. Then, let it coast...
 
#6 ·
That's very correct, but it is heavily dependent on engine (type: Otto or Diesel) and its condition (load/terrain).

Actually, if you could accelerate keeping low rpm at WOT (wide open throttle) you could achieve even better results. At full throttle you get the most out of your fuel. Sure, oxygen sensors are doing their best to keep it at optimum, but at WOT you allow the most air to get in (more oxygen better combustion), while keeping acceleration rate at its peak.
Really?? Come on man, lol, so maybe you should let manufactures know so when they are doing all their tests and readings for fuel mileage that they should do this! When going WOT sometimes you are going into OPEN loop, which is Not fuel efficient.
 
#7 ·
You could take a look at what VW did for economy and emissions. But you have to merge with other road users and so economy is not main concern.
Although the engines and transmissions are built for more economy have the strengthened or lightened drive train to take the extra torque of running at low revs. ???
The only Kia boxes I have heard of getting noisy before 100k miles is the 1.6 CRDI where owners drive at revs below 2000 as if driving big old Diesel with max. revs of 2500. The final drive in box gets noisy .
An old car with prop shafts would be leaping and jumping with disapproval if you drove in such a disrespectful way.

Jeff
 
#8 ·
An old car with prop shafts would be leaping and jumping with disapproval if you drove in such a disrespectful way.

Jeff
What is old?
I do recall old Polish car I drove and it would not like to go below 1500 RPM in 3rd or higher gear, but that was almost 4000 lb car fitted with carburetor-ed 1.5L engine built in 1985.

My Elantra is just fine at 1200 RPM in any gear. Or even less in lower gears.
On highway, it will not go beyond 2500 RPM when going less than 70 MPH.
 
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