Matt - RPM's vs MPH

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

 

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

 

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. ) I
wonder if it's still worth the $3200 I sold it for!!!! (

Tom

 

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?

 

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

 

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.

 

Wouldn't know it occurred if didn't look at the tach.

 

Well, that makes me feel better. I was beginning to believe I was numb as
well as senile. )

 

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.

 

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

 

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.

 

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.