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Old 07-06-2013, 05:04 PM   #1 (permalink)
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Default Hypermiling Techniques

OK Larry, need advice. Was out testing my new FAS circuit this afternoon. Near perfect conditions here in Richmond, except for the hills of course. On the interstate, target 50 MPH, was getting 118-120MPH - no MIMA. Good, but not in your league

I have a question about best way to reengage LB after a hill or purge. I have been giving it just enough gas to light 3 bars of assist, then easing up. That "seems" to reengage pretty quickly, but I honestly don't have anyone here in Richmond to talk it over with, so don't really know. What is your method of reengaging
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Old 07-06-2013, 05:53 PM   #2 (permalink)
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Quote:
Originally Posted by jime View Post
OK Larry, need advice. Was out testing my new FAS circuit this afternoon. Near perfect conditions here in Richmond, except for the hills of course. On the interstate, target 50 MPH, was getting 118-120MPH - no MIMA. Good, but not in your league

I have a question about best way to reengage LB after a hill or purge. I have been giving it just enough gas to light 3 bars of assist, then easing up. That "seems" to reengage pretty quickly, but I honestly don't have anyone here in Richmond to talk it over with, so don't really know. What is your method of reengaging
Those numbers look about right for 50 mph. As for getting back into lean burn, if it is just a normal purge event, in most cases it will automatically go back into lean burn. I usually do what someone on here suggested when lean burn drops out at the beginning of a purge, and that is to drop back on the throttle a bit until lean burn returns. I try to keep the mpg as close to 100 mpg as I can while it's purging.

As far as reengaging after a hill, that can be a little trickier. I will drop back on the throttle enough to get the FCD to read 100+ mpg and it usually reengages fairly quickly. I usually do the throttle drop fairly quickly to avoid losing too much speed...and then pray the next hill doesn't come along too quickly. One thing the Right Lane Cruiser told me that is helpful, is if you are ascending a hill and it becomes apparent that speed will drop below 50 mph, dropping to 4th before going under 50 mph will usually allow lean burn until you can reach the top of the hill and level out again. Of course, this is assuming you are in the far right lane of the interstate when letting the speed fall that far.
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Old 07-06-2013, 09:20 PM   #3 (permalink)
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As far as reengaging after a hill, that can be a little trickier. I will drop back on the throttle enough to get the FCD to read 100+ mpg and it usually reengages fairly quickly. I usually do the throttle drop fairly quickly to avoid losing too much speed...and then pray the next hill doesn't come along too quickly.
I'll give that technique a try tomorrow. I think I am definitely losing a bit of fuel with the press and lift method.
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One thing the Right Lane Cruiser told me that is helpful, is if you are ascending a hill and it becomes apparent that speed will drop below 50 mph, dropping to 4th before going under 50 mph will usually allow lean burn until you can reach the top of the hill and level out again. Of course, this is assuming you are in the far right lane of the interstate when letting the speed fall that far.
Yeah, he told me that also, but I must say that I still don't really have the timing exactly down pat, along with the judgment. Some hills one can ascend in 5th without dropping lean burn, some hills will slow too much and drop LB. One has to look a long way forward and judge the hill, along with the current speed and deacceleration. AND, here in Richmond area, some of the hills are steep enough to hit the FAS button. That really makes the MPG sail. I still need practice

Thanks for the tips.
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Last edited by jime; 07-06-2013 at 09:43 PM.
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Old 07-06-2013, 10:07 PM   #4 (permalink)
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Jim,

I use FAS most of the time, except in the winter, so I have a lot of experience with it.

Before arbitrarily FASing however, you need to ask yourself "If I FAS now, how long can I maintain it?"

I am not sure the exact reason (*1), but if I FAS too often and especially over a short distance, sometimes my mileage will go down rather than up. This is because once I start the engine back up, it seems that it takes a while for me to reach lean burn again. Sometimes as long as 15 seconds or so.

So the question becomes, "Do I FAS with the engine on and have immediate lean burn when I engage a gear, OR do I engine off FAS, and risk more time without lean burn". "Is the distance long enough to make up the difference?".

Good question, and I don't have a real good answer for you.

(*1) My guess is that the O2 sensor has something to do with the long delay to get lean burn again. Maybe it has to warm back up after shutting off the engine?

Jim.
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Old 07-06-2013, 11:18 PM   #5 (permalink)
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Hi Jim,

Yes, there is definitely a strategy to FASing. As you say, it takes a while for the engine (o2 sensor?) to recover and one has to anticipate that. I also find myself mentally calculating whether I can stretch 5th and retain LB, or do the downshift and reengage while going uphill. For most hills, it seems best to do the downshift and reestablish early before significant momentum is lost. Hill length and grade also has to be evaluated before hand to get the best FE.

I think the whole thing becomes kind of an art. At least it is very complicated mental arithmetic that one has to work out rather quickly. It definitely helps to know your route and I think that is one reason that folks who commute the same route each day do so well, particularly with MIMA and a charging station. MIMA can be hugely important in nursing LB, but the battery is small so even here there are tradeoffs.

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Old 07-06-2013, 11:57 PM   #6 (permalink)
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I'd rather stay in 5th gear out of lean-burn and carry up the hill between 50-60mpg versus raising the RPM and going into lean-burn. You'll be pumping less air that way and still maintain a high engine load. By dropping to a lower gear and trying to hold lean-burn you are pumping more air and then using lean-burn to raise the engine load again. I've tried a bunch of hill climbs at about 65mpg without lean-burn in 5th gear and with lean-burn in 4th gear and I come out ahead in 5th gear but can get more power in 5th gear at 60mpg than I can in lean-burn in 4th gear. I'm not seeing the point. Remember lean-burn is there to raise the engine load and make more use of the air you are pumping. If the CVT wasn't so lossy we'd probably be in about the same place as lean-burn but having the CVT pull us down to about 1400RPM at 60mph or so and then raise the RPM as throttle input requires. The CVT Insight unfortunately runs the engine too fast to keep engine load high enough to be more efficient than it is.
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Old 07-07-2013, 12:08 AM   #7 (permalink)
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Since it's the first O2 sensor that determines mixture, and that one is basically mounted on the exhaust manifold itself, you are going to have to FAS with the engine off for a very long time before it would cool down enough to effect mpg. The main thing is to determine if the FAS will be of a long enough distance to overcome the fuel that was burnt getting up to the speed you started the FAS at.

For me anyway, the 4th gear option works best. If I'm in 5th out of lean burn, the mpg is around the 50 mpg range. In 4th in lean burn the mpg is in the 70-75 mpg range...despite the higher rpms. YMMV.
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Old 07-07-2013, 12:36 AM   #8 (permalink)
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Just a suggestion;
Install a vacumm gauge in the system and use the readings for a "guide".
8"-19" readings work for me.
It's easier to understand the gas pedal pressure also.
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Old 07-07-2013, 02:30 AM   #9 (permalink)
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Wink LB hyper miling

Grit your teeth and hold throttle pedal in the same constant position once in LB, changing throttle position upsets all the settings which takes LB time to recover.

The best hypermilers are the ones with greatest tolerance of muscle cramp in the right leg
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Old 07-07-2013, 02:38 AM   #10 (permalink)
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I've got a question about acceleration, I notice there is a pretty specific point at each RPM point where the ignition timing will drop back severely. When I want to accelerate at a decent speed I've been curious lately if there is a certain point in ignition timing that I shouldn't pass. It seems that Right Lane Cruisers recommendations, which don't include engine load or ignition timing of accelerating 25-35mph in 4th gear at 50mpg for a FAS put ignition timing in the low single digits but holding 50mpg from 35-40mph is closer to 10IGN on the Scangauge. I figured that 10 would be better than 0 but of course engine speed has a factor in how fast the piston is moving and that relates to the combustion process occuring at a specific point. I know I've read about not going below 7 in the past on this forum but only one person said it. I usually try to keep above 10IGN which usually means 55mpg and slowly adding throttle to 50mpg at about mid-30's MPG and continuing to add throttle if I go past 2000RPM. When I need quick speed usually pass in 3rd gear and getting past 3000RPM you can really dump in the engine load at 90LOD and be still be higher than 10IGN. Any thoughts on that?

"The best hypermilers are the ones with greatest tolerance of muscle cramp in the right leg" Plenty of truth to that, I've taken a 1900 mile (each-way) trip and will be doing it again at the end of next month. I might forgo lean-burn and hold the 75mph speed limit though to save on the hotel stop. I got pretty lucky on the final leg of the trip home the last time though, managed 65-75mph driving in lean-burn consistently in the flat parts of the trip. I never get that driving west up the "tilted table" though, also prevailing winds usually travel east which makes that tougher too.
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Last edited by MN Driver; 07-07-2013 at 02:42 AM.
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