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Old 08-21-2008, 11:30 PM   #1
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First Hypermiled tank completed, a few questions.

Well, I'm officially a hypermiler with the fillup of my first tank hypermiling. I'm proud to say I broke the EPA estimates by almost 4 MPG. A few things I've noticed, but correct me if I'm wrong:

Weight makes a big difference. I filled up about 9 gallons and my average trip MPG dropped from 45.5 to 43.5, same driving habits, same speed, same bit of highway, for over 30 miles each way.

Staying at somewhat higher RPMs during city driving seems to be ok. I tried always getting to 5th gear ASAP by shifting at 2000 rpm, but it seems like its more efficient to let it go up to 2500 rpm at least.

Hills are a good place to coast, but I found even pulse and glide on level ground was good enough to take my trip mpg up about 0.5 mpg.

Sometimes city driving seemed more efficient that highway driving due to the amount of DFCO I could do.

So here's a few questions:

What are your recommendations for city driving? It seems that if I DFCO to less than 40 mph, I need to open the throttle more for 5th gear acceleration. Should I shift into a lower gear to get more power?

Should acceleration be swift or gradual and slow? It seems like if I do it quickly, the faster I get to a point where I can start P&G.

When should I stop gliding and get back up to speed? I'd prefer not to shift down, but maybe that's a good idea when I get under 40mph. However, that generally lets me only glide from 55 to 40mph. Should I get back up to speed quickly or gradually in 5th gear during the pulse?

Thanks, and I hope someday to break the 40 MPG barrier soon (that would be 10 mpg over EPA)!
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Old 08-22-2008, 10:23 AM   #2
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Quote:
Originally Posted by FLAteam View Post
Well, I'm officially a hypermiler with the fillup of my first tank hypermiling. I'm proud to say I broke the EPA estimates by almost 4 MPG. A few things I've noticed, but correct me if I'm wrong:

Weight makes a big difference. I filled up about 9 gallons and my average trip MPG dropped from 45.5 to 43.5, same driving habits, same speed, same bit of highway, for over 30 miles each way.
Yup, every 100lbs of weight can reduce MPG up to 2% or so


Quote:
Originally Posted by FLAteam View Post
Staying at somewhat higher RPMs during city driving seems to be ok. I tried always getting to 5th gear ASAP by shifting at 2000 rpm, but it seems like its more efficient to let it go up to 2500 rpm at least.
True, the most efficient engine RPM's are actually in a range ... something like 2000-3000 RPM is the best point to shift. I also aim for about 2,500

Quote:
Originally Posted by FLAteam View Post
Hills are a good place to coast, but I found even pulse and glide on level ground was good enough to take my trip mpg up about 0.5 mpg.
Yeah speed up going down hills, and coasting up the hill helps a lot. P&G works but is a huge PITA with a non-hybrid I think. Unless you install a kill switch I don't think it's worth the hassle and aggravation to other drivers around you.

Quote:
Originally Posted by FLAteam View Post
Sometimes city driving seemed more efficient that highway driving due to the amount of DFCO I could do.
I can get some of my best MPG in city yep.

So here's a few questions:

What are your recommendations for city driving? It seems that if I DFCO to less than 40 mph, I need to open the throttle more for 5th gear acceleration. Should I shift into a lower gear to get more power?
I just accelerate slower and my MPG are be better.

Should acceleration be swift or gradual and slow? It seems like if I do it quickly, the faster I get to a point where I can start P&G.
Debate on that one, I've read it's better to accelerate 50-60% throttle, but my ScanGauge says accelerating gradually and keeping my GPH (gallons per hour) under like 1.5G is better.

When should I stop gliding and get back up to speed? I'd prefer not to shift down, but maybe that's a good idea when I get under 40mph. However, that generally lets me only glide from 55 to 40mph. Should I get back up to speed quickly or gradually in 5th gear during the pulse?
I do it gradually

Thanks, and I hope someday to break the 40 MPG barrier soon (that would be 10 mpg over EPA)! [/QUOTE]

You're well on your way. Their is a ton of info on this site.
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Future MODS = Removable lower grill block, Clear fog covers, 195 deg. therm, Rear spoiler, Full belly pan
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Old 08-22-2008, 12:41 PM   #3
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Congratulations on your success!

If weight is making that much of a difference, you need more practice. Basic smooth driving habits make weight removal/addition nearly inconsequential (unless you're talking about huge amounts of weight -- like 40%). If you have to brake and then accelerate (for example at a red light), you should have gone slower or timed it better so you could have cruised right through. Obviously that can't be done everywhere...

I don't understand how you found a difference in FE due to weight, though. Did you use a partial fill and a ScanGauge or built-in computer?

In my experience, mainly in my VW where I have a manual transmission and can control RPM better, I've found that lower RPM is ALWAYS better for fuel economy, even if the engine is vibrating and growling (maybe not better for the car's longevity when I let it do that, though!). For a few weeks I've allowed my shift points rise a couple hundred RPM and my FE has suffered badly. This week I've been mostly keeping it down again (shift at 1300 or 1400 RPM) and it looked promising until I had difficult traffic this morning.

However, every car is different, and perhaps your Mitsubishi is more efficient at higher RPM.

If you need to open the throttle more for the same amount of acceleration, that's probably a good thing. It's unlikely that you're burning more fuel but not accelerating more. Perhaps, if your observation is correct, the engine is getting less air and fuel; in that case, the wider throttle opening is a good thing, because it reduces pumping losses (imagine trying to breathe through a straw compared to a coffee stirrer).

If your car responded to low RPM like mine does, I'd suggest not downshifting, just accelerate however much you can in 5th. Since your experience is that higher RPM is better, maybe you should downshift.

Slow acceleration is generally more efficient, unless you're just buzzing along in a low gear at high RPM and not going any faster. With a manual transmission and some experimentation/measurement as you're doing, you can learn how to minimize the effect on your FE regardless of how you want to accelerate (snail, turtle, mild, medium, or brisk -- but not balls-to-the-wall which is always wasteful).

For P&G, just do whatever you're comfortable with. I make my P&G cycles as large as allowed by traffic and my own patience (or lack thereof).
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Old 08-24-2008, 06:47 AM   #4
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Thanks for the advice, but to answer some of your questions:

I use Scanguage for my current trip MPG (using the X-guage function). Its not calibrated in terms of the use of the "fillup" function. I was iffy about dumping $160 into this thing (I'm here to save money, dammit!) but after some car shopping and being able to read codes, its already paid for itself.

I'll continue to experiment, especially in city driving. It just seems that the instananeous MPG displayed by Scangauge dips down really hard when I shift up (10-15mpg) but if I continue to draw power past 2000rpm, I seem to get around 20mpg instantaneous. I may have to go an entire week or so experimenting.

I'm looking forward to November! I must be the only person calling the Democratic and Republican parties for political signs. Will grill-blocking really help that much if I go less than 55 mph? I was under the impression that at such low speeds, the aero drag isn't so bad.

I tried drafting a truck going 63 mph but i couldn't get it to go any higher than when I was going 55 mph, and I had to tail hard. I'm assuming this is because even if I caught a draft, it just wasn't at a high enough speed. So, would a grill block even be worth it if I'm not going above 55mph?

Thanks.
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Old 08-25-2008, 04:29 PM   #5
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The grille block works two ways:

1. Aerodynamically -- this may be effective as low as 40mph (some would say lower). Granted, its effect is far higher at higher speeds.

2. Heat saving -- it keeps more heat in the engine bay, which helps the engine run more efficiently, by raising the intake air temperature (and possibly just from the warm environment).

Your observations about gear selection directly contradict mine, but your measurement method matches mine. Some cars differ, and I guess more so than I thought possible.

The most effective draft behind a full length trailer is at two to three seconds following distance, which is convenient for those not wishing to tailgate. Take a look at the drafting link in my sig. Your Lancer probably has pretty low drag and doesn't have as much waste to lose by drafting, so it may not be easy to instantly detect a gain from drafting.
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