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Old 09-04-2009, 08:10 AM   #1
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What's Reasonable Fuel Economy and EPA numbers.

Ive got a couple of questions. What's reasonable fuel economy from various types of vehicles? Also does the EPA Test over-estimate the mileage of smaller engines and automatics while under-estimating the mileage of larger engines and manuals? Ive repeatedly seen cars with larger engines and manuals beat the estimates by a large margin while smaller engines and automatics struggle to make them.

We have two vehicles. My commute is very short (2.6 mi) which does not allow for proper warm-up but is impractical for a bike or foot (narrow shoulder-less road in the dark).

2007 Accent Hatchback Automatic
24 Mpg City (Driven without specific FE techniques), Have not tried idle reduction.
32 Mpg Highway (70 mph actual), 34 Mpg Highway (65 mph Actual)

2007 Mustang GT Manual with 3.55 Performance Rear Axle Ratio
20 Mpg city (Without FE techniques), 22 mpg City (Turn off at redlight and drivethru).
29 Mpg Highway (70 mph actual), 31 Mpg Highway (65 mph actual)

Note: Cruise Speeds for both are GPS Speeds and Odometers corrected per the same measured 200 mi (according to mile markers) course.

Just seems like their should be a more than 3.6 mpg combined (60/40) difference between those two cars.
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Old 09-04-2009, 09:04 AM   #2
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You're getting quite decent fuel economy from the Mustang GT. I'm going to guess that you only use the Accent for that commute, and the Mustang gets longer trips?

Given the same route and driver, I'd expect a little bit more difference, but maybe not a lot. If you drive with fuel economy as at least a vague afterthought then you'll shift the Mustang pretty low and the manual transmission will be a HUGE advantage.

Some newer automatics are as efficient or better than a manual driven by an average driver who doesn't care about fuel economy, but I wouldn't expect a 2007 Hyundai automatic to be anywhere near as good as an economically-driven manual. The difference is enough to almost even the score.
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Old 09-04-2009, 09:14 AM   #3
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When it boils down to it, it takes about the same energy to push cars with not substantially different cDAs (coefficient of drag x area) down the highway at the same speed.
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Old 09-04-2009, 02:40 PM   #4
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very true. just like in todays cars, a 2.2 liter cobalt gets better FE on the freeway than a 1.5 yaris or fit. but it has .7 more liters and more hp, tq to go along with it. in city, the cobalt sucks though.


the thing that i see is that most manuals,its easier to get better mpg than the epa rating, due to enigne braking and better shifting points for fe.
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Old 09-04-2009, 02:50 PM   #5
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4.6L V8 FTW!

Only 4mpg city and 3mpg highway better in the little 4 banger hatchback... I'm at a loss for words.
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Old 09-04-2009, 05:45 PM   #6
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My Echo is consistently getting 53 MPG with a manual. It wouldn't be close to that with an automatic. The AT transmission shift controls do not let the engine stay in a low enough RPM range. I installed a simple vacuum gauge so I could accelerate at less than 1 inch of manifold vacuum at low engine speeds.

It would be neat if someone could reprogram the AT controls to allow a hypermiling operational mode where you could keep the RPM low and manifold vacuum low to maximise the effective compression and keep the engine operating in its sweet spot. It would be fairly easy to either have two modes or one that was controlled by throttle position.

As long as you stay under 75% throttle position the tranny would stay in the lowest practical gear and up shift quickly to keep manifold vacuum low. Then if you needed greater acceleration just go past the 75% throttle position and get a more performance oriented shift program.

regards
gary
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Old 09-04-2009, 07:26 PM   #7
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Bike it instead

Quote:
Originally Posted by Tightwad View Post
...My commute is very short (2.6 mi) which does not allow for proper warm-up but is impractical for a bike or foot (narrow shoulder-less road in the dark)....
You're just not thinking right about that commute. It's entirely do-able by bicycle. You probably won't even have enough time to break a sweat (unless it is all uphill).

Leave the cars. Buy good lights for your bike. Take the lane.
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Old 09-04-2009, 10:14 PM   #8
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Quote:
Originally Posted by striegel View Post
You're just not thinking right about that commute. It's entirely do-able by bicycle. You probably won't even have enough time to break a sweat (unless it is all uphill).

Leave the cars. Buy good lights for your bike. Take the lane.
I dunno about that...I've seen quite a few roads where I'd never take a bike. Some of them I did ride a bike on when I was about 15 or so...at that age, you bounce a lot better than you do when you are over 50...
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Old 09-05-2009, 04:03 AM   #9
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Quote:
Originally Posted by R.I.D.E. View Post
It would be neat if someone could reprogram the AT controls to allow a hypermiling operational mode where you could keep the RPM low and manifold vacuum low to maximise the effective compression and keep the engine operating in its sweet spot. It would be fairly easy to either have two modes or one that was controlled by throttle position.
I was thinking of doing exactly that with my GMC, but I don't drive it enough that the increased fuel economy would pay the $200 it would cost. It comes from the factory with two shift programs, a normal one and one for heavy towing. I figured the normal one could be reprogrammed for FE and the towing one could be left alone; if I needed to go faster I'd just press the button or downshift.

Quote:
As long as you stay under 75% throttle position the tranny would stay in the lowest practical gear and up shift quickly to keep manifold vacuum low.
Don't you mean highest practical gear?

It would also need to lock the torque converter pretty aggressively, I think. All that early upshifting could result in wastefully sloshing the ATF.
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Old 09-05-2009, 05:45 AM   #10
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Quote:
Originally Posted by R.I.D.E. View Post
My Echo is consistently getting 53 MPG with a manual. It wouldn't be close to that with an automatic. The AT transmission shift controls do not let the engine stay in a low enough RPM range. I installed a simple vacuum gauge so I could accelerate at less than 1 inch of manifold vacuum at low engine speeds.
The Echo that was in the family here, a 2005 I think it was, was an auto and got pretty damn close to 50... think it had a decent highway ratio. Wasn't all that on top of mpg because I only drove it a couple of times. It got written off when rolled into a ditch avoiding deer at 60mph, driver got out without a scratch.
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