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Shift RPMs vs MPG. 4x4 AC

Discussion in '4 Cylinder' started by Speck, Jun 25, 2014.

  1. Jun 25, 2014 at 8:09 AM
    #1
    Speck

    Speck [OP] Well-Known Member

    Joined:
    Mar 13, 2013
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    Tejas
    Vehicle:
    07 2.7 4x4
    I'm curious about the relationship between RPMs, shifting, and MPG. When I first got my truck, I shifted around 2000 as much as possible, thinking that the lower the RPMs the better the MPG. I got around 20-21 MPG (mixed) and a have a camper shell, access cab, and 4x4.

    The past several tanks I've been a bit bored, and shift now around 2800-3000. The MPG hasn't really changed at all... most recent tanks of ~75% city driving were all around 20.5. It seems like shift RPM doesn't matter as much as I thought it did.

    Is there any explanation for this in terms of the 2TR FE running more efficiently at these RPMs to balance out for working harder?
     
  2. Jun 25, 2014 at 10:14 AM
    #2
    tooter

    tooter play every day

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    Greg
    Los Angeles
    Vehicle:
    2012, std cab, 5 lug, 2.7, 5 speed
    Built for maximum low end torque, tooter II.VII intake manifold spacer, LCE long tube header, Injen long tube intake, 2,900 rpm torque peak.
    I average 23 mpg shifting my 2.7 at 2,000-2,500 rpms and see no reason to take it over 3,000 rpm. After all, 3,000 rpm is 90 miles an hour in 5th gear on the freeway, which is more than fast enough. My engine has been modded to hit peak torque at 2,900 rpm, so taking it over that is just a waste of gas.


    Greg
     
  3. Jun 25, 2014 at 7:09 PM
    #3
    iroh

    iroh Well-Known Member

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    michigander
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    07 AC SR5 2.7 5MT 4x4
    tonneau
    I've noticed a similar trend. The last couple tanks I've shifted typically between 3000 rpm and redline depending on how fast I've wanted to scoot and I'm still hovering just below or above 25 mpg.

    Maybe the engine is just efficient at high rpm as well as low. Some engines are just like that. An example of this would be the first gen Honda Insight; it was very efficient when keeping it around 2000 rpm, but that little 1.0L made the most power for the least fuel at 4500 rpm near 90% load, making a 5000 rpm shift point just about the same mpg-wise.
     
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