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Old 03-29-2008, 04:08 PM   #1 (permalink)
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Driving the Scanguage for FE

A few days ago I hooked up my new Scanguage II and am trying to learn how to get the most out of it in order to help maximize FE on my 04 Camry 4cyl automatic. Of course, since this is an automatic, it's more difficult.

I'm pretty new here, so this is just a part of my overall learning to drive for better FE.

What readouts do you find are most useful for learning to max FE? What is the best way to use them?

I have it set to display current FE, Average FE for the trip, LOD, and speed.


When accelerating from a stop, or from a low to higher speed, how do you determine the optimum rate of acceleration?

On the highway, I have been experimenting with bleeding off speed uphill and making it up on the downhill. How do you use the scangauge to help optimize this process?

I was quite surprised at the wide range of instanteous MPG readings that I get on the scanguage. Starting from a stop, readings are in the single digits. Cruising at 60 mph on a very flat section of road, it can be around 50 mpg. On a slight downhill at 60, it can top 60mpg, but on the uphill leg, mileage drops dramatically. Up a modest incline at 50mph, FE can be around 22. The mpg is extremely sensitive to very tiny changes in throttle.

My sense, confirmed by readings on this forum, is that slow, very gentle acceleration, is not the best for FE (though it probably helps to minimize wear and tear). Rather, it seems sensible to try to have the engine and transmission operating at a point of high effeciency. Where is that point? Can the Scangauge point to it?

Thanks,
Harry

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Old 03-29-2008, 04:17 PM   #2 (permalink)
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Welcome to ecomodder Harry!

I don't have any instrumentation on my car, but you sound like you've got a pretty good idea of the setup. The current FE, average FE and such are what I'd want to be looking at.

The basic idea should be to keep your current FE as far above the average FE as long as you can, and minimize the time spent below average FE.

As for accelerating, it is allegedly more efficient to accelerate at a certian RPM range at close to WOT. The specific RPM you're shooting for, however, varies from car to car.
So if you'd like to find out what that is, look for your car's BSFC (brake specific fuel consumption) chart. Unfortunately BSFC charts are notoriously hard to find, even with Googles help.
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Old 03-29-2008, 04:25 PM   #3 (permalink)
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Welcome to the forum, Harry.

The challenge, as you've pointed out, is that you're driving an automatic. That makes it more difficult to accelerate as efficiently as a manual because you have less control over engine RPM / gear selection.

Generally I think it's good advice to advise people with automatics (who aren't doing P&G) to accelerate gently.

Andrew's spot on with the advice for hills (also known as Driving With Load): the idea should be - where traffic permits - to monitor your instant mpg at that time, and modulate the throttle to keep it above some arbitrary MPG that you want to maintain. Depending on how aggressive you are with your target will determine how much you play (lift) the throttle and lose speed on the incline.

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Old 03-30-2008, 02:41 PM   #4 (permalink)
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trying various things

Thank you Andrew and Darin - you gave me some good ideas to think about and play with.

As you say Andrew, a BSFC map would be about impossible to come by for my 4 cyl camry. But it seems fair to guess that the BSFC ratio would be best with RPMs somewhere around 2K, and the throttle fairly wide.

And doing that immediately kicks the automatic into a lower gear. So the game I have been trying is a brisk acceleration, followed by light throttle to promote upshift. Depending on speed goal, this may then be followed by as much throttle as possible without causing downshift.

I have also tried a related strategy on a rolling highway. The car seems to cruise with good FE at around 60 mph. So going downhill, I try to gain some speed with light throttle, but try to keep the FE above a floor level of around 33. On the uphill, I try to continue to maintain the FE above the floor level, which means fairly constant throttle. But as speed drops this becomes impossible. At that point, I lighten the throttle to keep the fe above the floor, but speed tends to drop fast.

And here is the funny part:
I give it lot of throttle - as much as possible without causing a downshift. The theory is that I am putting gaining kinetic energy from a part of the BSFC map that is more efficient. I think this is workable because the camry has a reasonable cd of around .28.

Anyway, I have gotten just over 36 mpg on the highway with this strategy. But as it turns out, that is just what I get on my control run using more of the constant throttle method! Oh well. Still, the second method got me around the run at a higher overall speed...

The auto does make this experiments difficult. I wish there was a way to easily change the shift points. My 1985 Camry, which I will soon sell, had a switch to change the transmission shift strategy to economy. With that vehicle, and no eco driver's ed, I was averaging 34 mpg on drives that had a fair amount of highway. And I was doing it at speed! Ok, I did blueprint the engine a couple of years ago...

Harry
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Old 03-30-2008, 10:48 PM   #5 (permalink)
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Higher avg speed with the same fuel consumption is a good thing!

I'm sure you're doing this already, but if you're not, I'd also encourage you to start a fuel log and track your consumption. Nothing like looking back at past performance for motivation.

You'll need to create a garage entry for your Camry to do that here. (Feel free to create an entry even if you're not planning to keep a log!)
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Old 03-31-2008, 06:00 AM   #6 (permalink)
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Monitor FE, FF and TPS

Quote:
Originally Posted by AndrewJ View Post
The basic idea should be to keep your current FE as far above the average FE as long as you can, and minimize the time spent below average FE.

As for accelerating, it is allegedly more efficient to accelerate at a certian RPM range at close to WOT. The specific RPM you're shooting for, however, varies from car to car.
Mine seems to follow suit quit well with this. I strive for flat level to keep instant FE above 42mpg. I too believe granny acceleration serves to only decrease FE for that acceleration stretch. No BSFC numbers. I use TPS and FF for that. I try for 20-25% TPS, which usually yeilds 1.25-1.75gph depending on grade and whether I was at dead stop or not. That puts the Civic shifting crisply (2250-2750), then at 40mph, I feather the throttle to get it into OD and set FE and FF from there. Once I'm at speed (55mph), I cut the throttle for 500msec then bring it back in to ensure I'm not accelerating on false hill. Rountinely on my routes, I found level sections that I can cruise at 55mph at 0.9-1.1 FF and average ~52mpg. These sections aren't level, but always have appeared so until monitoring.

On hills, I accept a higher FF going into the hill in order to build inertia, then set TPS for first half. Approaching crest, I roll it back to try to be at my target MPG at the crest. Once you get the TPS feel, monitoring Fuel Flow (FF) and FE is the easiest for me during accel.

Trying to deadeye the TPS and FF would be benifited by hand control which I'm considering. Prestage -Stage - Lights come down. Just to think, last year, I was getting 1.4gals/mile in the Coronet.
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Old 03-31-2008, 10:07 AM   #7 (permalink)
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I ordered the scangauge yesterday. I wonder the effect it will have on the intuitive FE driving which has taken me from 32.5 to 40.04 over the same 26 mile course I've driven for the last 2 month in a 2007 Aveo. Though I'm happy with the progress. I have a lot of questions that I think the gauge may answer, like most efficient rpm in 5th gear on level. My course is almost traffic free so I have a lot of latitude to chose a speed. I set a goal of 40 mpg and have already reached it so anything the gauge gets me will be gravy, but this is an addicting pastime and I find myself spending a lot of time thinking it over. Current driving times are 5-7 minutes longer the previous, but I find the trip very relaxing and considering I drive about 25,000 miles a year, it will have some cash benefits. Good luck with FE. I plan to check out the Honda CR-V automatic which is the weekend ride.

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Old 03-31-2008, 11:29 AM   #8 (permalink)
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Quote:
Originally Posted by homeworkhome53 View Post
most efficient rpm in 5th gear on level
I'll bet you a donut that on a level road, your most efficient 5th gear constant speed will be the slowest you can drive without lugging.

Congrats on ordering your "game gauge". It adds a whole new dimension to the fun.
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Old 05-23-2008, 01:25 PM   #9 (permalink)
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Quote:
Originally Posted by MetroMPG View Post
Welcome to the forum, Harry.

The challenge, as you've pointed out, is that you're driving an automatic. That makes it more difficult to accelerate as efficiently as a manual because you have less control over engine RPM / gear selection.

Generally I think it's good advice to advise people with automatics (who aren't doing P&G) to accelerate gently.

Andrew's spot on with the advice for hills (also known as Driving With Load): the idea should be - where traffic permits - to monitor your instant mpg at that time, and modulate the throttle to keep it above some arbitrary MPG that you want to maintain. Depending on how aggressive you are with your target will determine how much you play (lift) the throttle and lose speed on the incline.

Darin
Now this was exactly my thinking, but over on gassavers, I was chided for not looking at things correctly. I'd pointed out that by slowing down on the upslope, I was able to maintain at least 22 mpg verses around 9 mpg with cruise which was taking the engine right to the borderline between boost and vac in my saab. But I was told to not put so much stock in instant mpg which left me wondering why I bought a scangauge???

http://www.gassavers.org/showthread.php?t=7539
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Old 05-24-2008, 02:09 PM   #10 (permalink)
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When I drive my automatic truck, what I do is accelerate like normal but let off the gas before it revs too high, so that it shifts into the next gear early, then press down on it a bit again. I watch my tach and I usually let off around 2000 so that the revs stay between 1700 and 2000 usually. Any comments?

Here's my newbie's suggestion for Harry, you smarter folk can pick it apart if you like!

On an empty flat road with preferably no wind, start from zero speed and reset your avg mpg, then do a "granny acceleration'' test, so accelerate to 60mph really slowly, and make note of where you reach that speed, and what your avg mpg is at that spot. Then go back to your starting position, reset your avg mpg, and do the test again with fast acceleration, up to 60 mph, then when you reach that spot, make a note of this test's avg mpg. Of course, this time you'd be cruising at 60mph for a bit. And you'd want to do each test several times. The driving style that has a higher avg mpg would be better for you to use!

This isn't very exact of course, but it could give you a rough idea on how fast you should be accelerating. I'm not that familiar with scanguage, I still need to get me one of those, but do they show fuel flow? If they do, use that to make sure each time you do each test is the same.

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