Matt - RPM's vs MPH

Discussion in 'General Motoring' started by Tom, Mar 16, 2007.

  1. Tom

    Tom Guest

    Hey Matt,
    I took a trip in the Sonata and watched the tach pretty closely so I have
    the answer to your question about RPM's at 60 MPH. How does 2050 rpm sound?
    At 65 it's about 2200.
    As I said earlier, that's on the flat. If I hit a slight hill, the rpm's go
    up to 2200 to maintain the 60 mph and as soon as I crest the hill they
    slowly go back to 2050. I can't feel the lock/unlock of the converter so
    Hyundai has really done a good job - at least on my car.

    Tom
     
    Tom, Mar 16, 2007
    #1
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  2. Tom

    Matt Whiting Guest

    That is interesting. It looks like the gearing is MUCH higher in the
    automatic 4 cylinder than with the 5 speed manual. I forget my RPMs
    exactly (I posted that here some time ago), but I think I run close to
    2500 at 60 MPH is memory serves. I think I'm around 2750 at 65 and just
    shy of 3 grand at 70.

    That may well explain why you get 1-2 MPG more on the highway than me,
    although the interesting thing is that the EPA rating is 1 higher for
    the standard on the highway. It would also explain why the standard
    shift car felt so much more responsive than the automatic. The
    automatic 4 felt pretty lethargic to me. I drove a V-6 and that was
    much peppier. I then drove the standard shift 4 cylinder and it felt
    even more responsive than the V-6, other than right off the line. The
    performance stats show that the V-6 is quicker, but the standard shift 4
    is very peppy compared to the auto 4. I can see why now as running
    nearly 500 RPM faster at a given speed would make a huge difference in
    the amount of torque available.

    Matt
     
    Matt Whiting, Mar 16, 2007
    #2
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  3. Tom

    Tom Guest

    Wow, that is an amazing difference! I'm like you - how can they figure the
    stick makes one mpg more with that big a difference in rpm's? I know it
    doesn't take much push on the go pedal to have it go up to 2200 at 60 but
    that still is nowhere near your rpm's.
    I guess it's because I'm getting to be an old fart, but I'm happy with the
    acceleration on mine. I guess I need to buy back my 69 427 vette. :eek:) I
    wonder if it's still worth the $3200 I sold it for!!!! :eek:(

    Tom
     
    Tom, Mar 17, 2007
    #3
  4. Tom

    Partner Guest

    Was that an 4 or 6? On my 2007 I4 (less than 1000 miles) at 60MPH my tach
    shows just under 2K rpms and jumps about 200 on a slight hill. I would
    assume if you have an I4 also with the same configuration, that the
    difference is within the margin of error for tachs. Anyone up for doing the
    math with the ratios and tell us what it should be?
     
    Partner, Mar 17, 2007
    #4
  5. Tom

    Tom Guest

    That's with the 4 cyl. I'm a tick over 2000 or about 2050. Can you 'feel'
    the torque converter lock/unlock when the rpm's change those 200? I can't
    feel it.

    Tom
     
    Tom, Mar 17, 2007
    #5
  6. FWIW, the V-6 is 2200 at 70 MPH.

    The ratings for the standard trans are greater but it may be skewed because
    of the unrealistic test methods. You'd probably have to look at the power
    curves to see how they compare at test speeds.

    From the EPA:
    The city and highway tests are currently performed under mild climate
    conditions (75 degrees F) and include acceleration rates and driving speeds
    that EPA believes are generally lower than those used by drivers in the real
    world. Neither test is run while using accessories, such as air
    conditioning. The highway test has a top speed of 60 miles per hour, and an
    average speed of only 48 miles per hour.
     
    Edwin Pawlowski, Mar 17, 2007
    #6
  7. Tom

    Partner Guest

    Wouldn't know it occurred if didn't look at the tach.
     
    Partner, Mar 17, 2007
    #7
  8. Tom

    Tom Guest

    Well, that makes me feel better. I was beginning to believe I was numb as
    well as senile. :eek:)
     
    Tom, Mar 17, 2007
    #8
  9. That's comparable to what I see in my manual Elanta, which makes sense
    since the 4 cylinder models use the same drivtrain.
    FWIW, at 65mph my Elantra consistently exceeds its EPA highway rating by
    2-3 mpg, at least when the weather is warm (in cold weather with snow
    tires, the mileage drops some). This seems to be pretty common with the
    manual, but the autos seem to struggle to reach their rated mileage.
    That may be different with the Sonata, however.
     
    Brian Nystrom, Mar 17, 2007
    #9
  10. Tom

    Matt Whiting Guest

    I've never yet matched my highway estimate of 34 MPH. I got above 32
    once or twice, but never close to 34. Now, I haven't taken a long trip
    in warm weather on a level interstate either. My trips have been in
    moderate weather (50s - 60s) on I80 in PA, which isn't even close to
    level anywhere.

    The interesting part is that my mileage is only marginally better on a
    trip than commuting to work. My long-term average is still pretty close
    to 29.5, but my best ever was only 32.3 (I just checked my spreadsheet).
    So the Sonata is pretty consistent tank to tank, but never close to 34.

    Matt
     
    Matt Whiting, Mar 17, 2007
    #10
  11. Tom

    hyundaitech Guest

    It's normal to design a manual transmission to run at a higher rpm in
    overdrive than an automatic. The automatic can turn off the torque
    converter clutch for additional rpm and torque. The manual doesn't have
    that capability.
     
    hyundaitech, Mar 18, 2007
    #11
  12. My Elantra consistently gets 36-37 on highway trips. I've seen as high
    as 38, but that may have been a fluke and it was on a one-way trip.
     
    Brian Nystrom, Mar 19, 2007
    #12
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