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Driving with a Load

  #21  
Old 09-01-2004, 12:38 AM
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Hi Basjoos:

___I canít answer your questions directly because I donít have a non-lean burn stick but I have seen to many game gauge miles to think all cars do not act similarly. The stick in the Insight whether lean burn or not still shows the fuel savings w/ the ďDWLĒ technique. I am not always in lean burn as you can well imagine. Now, I donít know what exactly your ďboost and coastĒ technique is but a sudden acceleration in any automobile is a fuel economy killer no matter when or where it is applied. F=MA simply canít be worked around as even a very efficient electric motor still has to come up with the extra F to overcome any unneeded acceleration. I am not speaking of sitting in first and second gear for 1.3 minutes as there is a problem with that but slowly and ever so delicately working your way up to speed takes the A to minimum which also brings about a minimum F which via a lower throttle opening over a given distance which in turn gives more fuel economy over said distance.

___Good Luck

___Wayne R. Gerdes
___Hunt Club Farms Landscaping Ltd.
___[email protected]
 
  #22  
Old 09-01-2004, 06:31 AM
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Originally posted by xcel@Sep 1st 2004 @ 2:38 AM
Now, I donít know what exactly your ďboost and coastĒ technique is but a sudden acceleration in any automobile is a fuel economy killer no matter when or where it is applied. F=MA simply canít be worked around as even a very efficient electric motor still has to come up with the extra F to overcome any unneeded acceleration. I am not speaking of sitting in first and second gear for 1.3 minutes as there is a problem with that but slowly and ever so delicately working your way up to speed takes the A to minimum which also brings about a minimum F which via a lower throttle opening over a given distance which in turn gives more fuel economy over said distance.
I think boost and coast means you get up to speed quickly and go to neutral and let the car coast. And ideally, you shut the engine down while you're coasting.

This technique might look bad from F=MA point of view, but what is more relevant here is work--force over distance. In the case of boost and coast, you apply a very large force over a very short distance and use the kinetic or potential energy you built up to carry you the rest of the way. In the case of DWL, you apply a very small force over the whole distance you need to go.

In the ideal world where engines are 100% efficient, I guess it doesn't matter either way. But in the real world, whether DWL or boost and coast is more fuel efficient overall depends on whether the engine is more efficient under low or high load. The impression I get is that it's usually the latter, but I'm not sure if it's still the case with lean burn.

Andy
 
  #23  
Old 09-01-2004, 09:38 AM
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Hi Accwai:

Originally posted by accwai@ Sep 1st 2004 @ 8:31 AM

In the ideal world where engines are 100% efficient, I guess it doesn't matter either way. But in the real world, whether DWL or boost and coast is more fuel efficient overall depends on whether the engine is more efficient under low or high load. The impression I get is that it's usually the latter, but I'm not sure if it's still the case with lean burn.
___Let me describe the MDX. It is a 4,500 # 4WD semi-lux SUV. It has a 260 HP, 250 Ft-Lbís of torque 3.5 L ICE Automatic without lean-burn. Itís 4WD is engaged at all times when accelerating from a stop up to 18 mph at which time the electric clutches release for 2WD mode unless slip is detected.

___Seeing the FCD in the MDX sit in the 0 - 5 mpg range while accelerating for maybe 15 - 20 seconds and finally popping up to 30 + mpg when it reaches a steady 55 mph is an absolute fuel economy killer! The much less aggressive 5 - 10 mpg from 0 to maybe 15 mph and watching the FCD steadily rise past 20, 25, and then 30 + mpg at the same final cruise speed always gives the MDX a much better final fuel economy number over any distance. I see this after a refuel as its an ~ 5 mile drive home and the way to punch that monster up into Hypermileage range is very slow and steady acceleration. We are speaking of an automobile that receives 12 mpg per CRís in an all-city environment vs. the EPAís lowly 17. It isnít even close in fact with a ďboostĒ method if that is what is being described. The former gives you 10 mpg w/ an at best, 15 mpg readout after 2 miles. The latter gives you a 25 - 30 mpg after the same 2 miles. Fast acceleration is never going to be recovered in that automobile nor the Insight. Fuel economy with faster acceleration was not recovered in the LE Sabre or the Mercury Mountaineer I drove back from the U of I last year either. Both had rudimentary game gauges.

___Here is another piece of anecdotal evidence. So many Hybrid forums including Insightcentral.net say fast accelerations on the pack and ICE to reach cruise speeds is the best way to achieve the highest fuel economy. This is absolute bunk as anyone watching their game gauge(s) over any distance can tell its BS given what they will receive after such a short distance as well as the pack recharge that takes many miles to recover from. I can usually hit EPA highway estimates (70 +) in the Insight before I hit the highway from a cold start. This is through 2 stop signs, 3 stop lights, and through the back of a huge Mall encompassing an ~ 2 mile distance. The same when leaving work with 3 stop signs and an overpass climb out. The only way this is accomplished is by slow and steady acceleration/deceleration vs. the much more aggressive 1-2-5 method many in the Insight community use. Again, this is not running first and second gear accelerations for 1.5 minutes to 30 and climbing out in third, fourth, and fifth afterwards but a slow and steady acceleration to whatever the speed limit is in maybe 40 - 50 seconds. That is if traffic allows.

___The Prius IIís might be different but in my short time behind the wheel, it was not. I shall see once I get some more time behind the wheel of one. In my experience, fast acceleration is a huge killer of ones fuel economy under any and all circumstances whether itís on the pack, an ICE, or both depending on the automobile (Hybrid or not).

___Good Luck

___Wayne R. Gerdes
___Hunt Club Farms Landscaping Ltd.
___[email protected]
 
  #24  
Old 09-01-2004, 10:34 AM
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Originally posted by xcel+Sep 1st 2004 @ 11:38 AM--></div><table border='0' align='center' width='95%' cellpadding='3' cellspacing='1'><tr><td>QUOTE (xcel @ Sep 1st 2004 @ 11:38 AM)</td></tr><tr><td id='QUOTE'>___Here is another piece of anecdotal evidence. So many Hybrid forums including Insightcentral.net say fast accelerations on the pack and ICE to reach cruise speeds is the best way to achieve the highest fuel economy. This is absolute bunk as anyone watching their game gauge(s) over any distance can tell its BS given what they will receive after such a short distance as well as the pack recharge that takes many miles to recover from.[/b]

But the point is you get low mileage for a short distance, then you get very, very high mileage for a much longer distance. Purely from an mechanical eneregy transfer point of view, it doesn't make sense that there should be huge difference between the two techniques, as long as the car carries the same kinetic + potential energy at the end.

As for anecdotal evidence, so how come those Mileage Marathon cars that get thousands of mpg's are always pulse driven, if the technique is such a mileage killer?

<!--QuoteBegin-xcel
@Sep 1st 2004 @ 11:38 AM
___The Prius IIís might be different but in my short time behind the wheel, it was not. I shall see once I get some more time behind the wheel of one.[...][/quote]
Well the Prius is different. First, it does have the hardware and logic to shutdown the engine on the run, as long as you're not faster than 42mph. So at city speed, you do get infinite mpg while coasting (or gliding in Prius lingo). And when load is low, the control logic drives the engine higher than necessary to obtain higher efficiency. The excess output goes to the battery. While this gives you better overall efficiency than you would have gotten running the engine low, it's still not good in absolute efficiency term.

As for taking miles to recharge the pack, on a Prius, how much assist you get depends on how heavy you step on the gas. You can accelerate without assist if you keep things moderate. In case of really slow acceleration, you can even recharge while accelerating. So that is not an issue.

Andy
 
  #25  
Old 09-02-2004, 01:32 AM
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Hi Accwai:

Originally posted by accwai+ Sep 1st 2004 @ 12:34 PM--></div><table border='0' align='center' width='95%' cellpadding='3' cellspacing='1'><tr><td>QUOTE (accwai @ Sep 1st 2004 @ 12:34 PM)</td></tr><tr><td id='QUOTE'>But the point is you get low mileage for a short distance, then you get very, very high mileage for a much longer distance.[/b]

___Not in the MDX and not in the Insight. The high fuel economy comes right from the start and continues on. That 3 mpg or less for 20 or so seconds with hard acceleration kills the MDX and no matter how many miles you drive at 30 + afterwards, you canít make it up as fast as the slow acceleration allows you from the start. I have driven her more then a few times from the fuel station to have missed this fact. Remember that in both cases, the MDX receives far better fuel economy with the slow acceleration then the fast one and her highway fuel economy is worth 26 - 27 mpg (23 EPA) according to CRís. In both cases, I take her up to 50 mph with the slow acceleration giving me the much higher fuel economy to my door. I used to be a very active member of the Acuramdx.org forums and do you know how many people in the world have achieved even 25 in the city or 30 mpg + from one on the highway? Not a single one that I have read and there are thousands of members over there. They simply drive normally with fast accelerations. My normal from the gas station is 25 - 29 mpg. My highest was 33 after almost 200 miles of mostly highway and that was driving in lower 50 degree temps from a peak of 35 mpg while it was in the upper 60ís loaded with my sons college collection of mostly junk after graduation last spring to home.

<!--QuoteBegin-accwai
@ Sep 1st 2004 @ 12:34 PM
As for taking miles to recharge the pack, on a Prius, how much assist you get depends on how heavy you step on the gas. You can accelerate without assist if you keep things moderate. In case of really slow acceleration, you can even recharge while accelerating. So that is not an issue.[/quote]
___I am speaking of a full SOC, not just some amount. A fast acceleration will take 1 to 2 bars (20 in total) of SOC out of an Insight. A slow acceleration will take none or a very small amount (4 bars of assist, not SOC, is tough to bypass when accelerating in second gear) as you can control whether you want some assist or not. If you do use assist, you will have to hope for a minor hidden charging mode to make it back up but usually, itís a small charge that you may or may not see on the game gauge. When charging is forced, you are speaking of 75 mpg tops for a Ĺ mile or so until 18 or 19 of 20 bars appear. When no charging is evident, 100 - 110 is quite easily achievable and that is where I drive as much as humanly possible. When there is a charge toward a full pack, it is costing all of our little ICEís big time.

___As for the rest of the Prius II traits, most are common knowledge. Remember my mileage drive in the Prius II from a cold start in 32 degree temps? 56 mpg in an all-city environment over ~ 4 miles? I wasnít using the pack as a warmed up Prius II could yet still achieved better then most and that was only my second time driving one! I just donít have enough experience in a Prius II to say for certain how it acts but in my short time behind the wheel, it acted as any other automobile I have driven with a game gauge and the numbers should speak for themselves in that regard Ö

___In regards to the comps, the Japanese entry owns the World Record with > 10,000 mpg but not only are these not normal automobiles, they arenít even drivable ones. How they work there magic is beyond me but driving a Hybrid with your foot to the floor using the pack as much as possible out of the hole for higher fuel economy at larger throttle openings is bunk. It exposes you to some rather poor mileage over a short distance or long one in my experience given the recharge of the pack. This includes both Hybridís and non-Hybridís minus any pack charge of course.

___Good Luck

___Wayne R. Gerdes
___Hunt Club Farms Landscaping Ltd.
___[email protected]
 
  #26  
Old 09-02-2004, 06:37 AM
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Originally posted by xcel+Sep 2nd 2004 @ 3:32 AM--></div><table border='0' align='center' width='95%' cellpadding='3' cellspacing='1'><tr><td>QUOTE (xcel @ Sep 2nd 2004 @ 3:32 AM)</td></tr><tr><td id='QUOTE'>___As for the rest of the Prius II traits, most are common knowledge. Remember my mileage drive in the Prius II from a cold start in 32 degree temps? 56 mpg in an all-city environment over ~ 4 miles? I wasnít using the pack as a warmed up Prius II could yet still achieved better then most and that was only my second time driving one! I just donít have enough experience in a Prius II to say for certain how it acts but in my short time behind the wheel, it acted as any other automobile I have driven with a game gauge and the numbers should speak for themselves in that regard Ö[/b]

Well in that case you should get a Prius and show us how to do it. I mean the numbers you see in the database here are from people who use their car as daily driver. 700+ mile city only tank over three and a half weeks doesn't even beginning show the true potential of the car. We figure 100+mpg over 1100 miles is perfectly achievable on a well planned mileage run. It's just that none of the Prius people are crazy enough to even think about trying it, yet.

Originally posted by [email protected] 2nd 2004 @ 3:32 AM
___In regards to the comps, the Japanese entry owns the World Record with > 10,000 mpg but not only are these not normal automobiles, they arenít even drivable ones. How they work there magic is beyond me[...]
I thought the 10,705 mpg world record was set in last year's UK Shell Ecomarathon by a French team. Is there a newer record?

In any case, while these are not normal cars, they are physical objects that have engines, are driven by wheels (well, a wheel normally), can be steered and they have brakes. And they have a way to detach the engine from the wheels so they can coast free. I mean, a manual transmission car (or a Prius) has all of these. I don't see why the physical principles pertaining to the mileage marathon cars would be invalid for the others.

<!--QuoteBegin-xcel
@Sep 2nd 2004 @ 3:32 AM
[...] but driving a Hybrid with your foot to the floor using the pack as much as possible out of the hole for higher fuel economy at larger throttle openings is bunk. It exposes you to some rather poor mileage over a short distance or long one in my experience given the recharge of the pack. This includes both Hybridís and non-Hybridís minus any pack charge of course.
[/quote]
I don't believe I said "foot to the floor". If I remember it correctly, I said get up to speed "quickly". That is not the same as "as quickly as the car can". The term that is used in the Prius community for the optimal acceleration rate is "deadband". In that state, you have neither assist nor recharge going on. So battery state is not in the equation.

Andy
 
  #27  
Old 09-02-2004, 08:11 AM
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Ideally to get the best mileage out of a car you will need to operate the ICE as much as possible within its most efficient output range and minimise the use of any form of braking (friction, compression, or regenerative). An ICE without lean burn runs most efficiently at 70% to 80% throttle and below 2000 RPM. But an ICE with lean burn is a different animal. It runs most efficiently at low load (10% throttle?) and low RPM, but then runs next most efficiently at same 70% to 80% throttle and below 2000 RPM as the non-lean burn ICE. So a lean burn car would get its best mileage if you kept a light foot on the throttle while watching the game gauge so you can keep it in lean burn mode as much as possible. This is what is at the heart of the DWL method. A lean burn car will get its best mileage on flat rural terrain where it can spend most of its time in the lean burn mode. But if you are in a situation where you can't stay in lean burn (climbing a long, steep hill, stuck in aggressive urban traffic accelerating away from a red light, etc), then you would get better mileage if you operated temporarily in the 75% throttle/low RPM operating mode of the ICE.

Since my ICE doesn't have a lean burn mode, I should get my best mileage if I operated my ICE in its most efficient 75%/low RPM mode. But if I did this for very long on a flat road, I would soon build up excessive speed and engine RPM. So at this point I would need to release the throttle, push in the clutch and/or put the car in neutral and possibly even shut off the ICE to allow the car to coast back down to a more reasonable speed. Then I would put the car back in gear and repeat this whole process all over again in a form of pulse driving. This accelerate/coast (or boost and coast) process doesn't lend itself to normal traffic patterns and would be difficult to do except on lightly traveled roads. But on hilly terrain this method works quite well. I can do the accelerate portion on the uphills and then coast on the downhills. It also blends well into urban driving where I accelerate away from the traffic light and then work in the coast as I approach a red light, stop sign, or slower traffic. In neither of these cases am I doing a pure boost and coast, but I try work in as much of it as I can given the existing topography and traffic patterns. In some cases I am only boost and coasting over a 5 MPH cycle. In urban driving I may boost to 45 MPH, then coast until I drop to 40 MPH before boosting again. Usually there will be enough changes in road grade and varying traffic speeds that I can work this method seamlessly into the traffic flow.

I know this method works. I have been using it since the 70's and in my current car it gives me 56 MPG on an engine that is EPA rated for 46 MPG highway when installed in the 1992 Civic hatch. And I've used it to get 26 MPG out of a 5 speed 97 Ford F150 4WD. This method works best with a straight drive where you can let the clutch in and out as needed to boost or coast. It is more difficult to do with an automatic where the transmission usually runs the ICE up to around 3500 RPM before shifting if you accelerate at 70% throttle. And all automatics I have driven also have some degree of compression braking in the coast unless you shift into neutral, which takes a second or two for the transmission to accomplish (and takes the same amount of time to put it back into drive).
 
  #28  
Old 09-02-2004, 10:12 AM
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Hi Accwai:
Originally posted by accwai+ Sep 2nd 2004 @ 8:37 AM--></div><table border='0' align='center' width='95%' cellpadding='3' cellspacing='1'><tr><td>QUOTE (accwai @ Sep 2nd 2004 @ 8:37 AM)</td></tr><tr><td id='QUOTE'>Well in that case you should get a Prius and show us how to do it. I mean the numbers you see in the database here are from people who use their car as daily driver. 700+ mile city only tank over three and a half weeks doesn't even beginning show the true potential of the car. We figure 100+mpg over 1100 miles is perfectly achievable on a well planned mileage run. It's just that none of the Prius people are crazy enough to even think about trying it, yet.[/b]

___Krousdb did just that in fact for an 85 mpg average over an entire tank. IIRC, he averaged something like 35 mph? You can see it in the achievement records. As for me, give me yours for a week and I will find out for you on real world roads and at speeds within the limits 100 mpg over 1,100 miles in a Prius? At least you would be approaching that of the Insightís usual but I have only read of a 1,000 mile tank from a Japanese guy receiving in the 80ís and with the Japanese Prius IIís bladderless tank and ~ 13 gallons in her. Why not yourself? You do drive real roads in the real world, correct?

Originally posted by [email protected] Sep 2nd 2004 @ 8:37 AM
I thought the 10,705 mpg world record was set in last year's UK Shell Ecomarathon by a French team. Is there a newer record?
___I must have missed the latest given the French team record is less then 2 months old Ö

The fuel economy world record stands at 10,705 miles per gallon and was achieved by the French Microjoule team with a petrol-driven vehicle at the Rockingham Motor Speedway in Northants last month. This topped the Japanese Fancy Carol team's record of 10,240 miles per gallon, set in 2001.

<!--QuoteBegin-accwai
@ Sep 2nd 2004 @ 8:37 AM
I don't believe I said "foot to the floor". If I remember it correctly, I said get up to speed "quickly". That is not the same as "as quickly as the car can". The term that is used in the Prius community for the optimal acceleration rate is "deadband". In that state, you have neither assist nor recharge going on. So battery state is not in the equation.[/quote]
___I did not understand exactly what you meant but in the Insight community, many are under the impression that flooring it with maximum Assist to highway cruise achieves the highest overall fuel economy and no, it doesnít. I am not sure if the Prius IIís game gauge is detailed enough to see the small changes in my short drives of one whereas the Insight definitely is. Both are different of course but seeing the game gauge in detail while accelerating and climbing, the best method imnsho is to accelerate slowly and ďDWLĒ. You can compare my own mileage with any other Insight or Prius II although the hills I encounter are less then 200í in elevation on a daily basis vs. others who get hammered by much higher then this

___Basjoos, I had that kind of mileage of an Avis owned Mercury Mountaineer w/ Auto earlier this spring (27.9 mpg off its rudimentary game gauge) that wasnít even close to setup for > 100 miles before my daughter took over for the rest of the drive home. She works for Avis so that is why we had this car for a weekend drive down to the U of I. The last time I drove the 03 Corolla LE back and forth to work for a week, I had a nice 51.8 mpg average over 751 miles. It is only rated for 38. 70% might be the optimal throttle plate opening for many ICEís but factor in wind resistance and friction as RPMís rise and it cancels out any gain. I have a friction chart of the Insight and I believe it shows RPMís on an axis. The next time I am there, I will E-Mail it back home so I can E-mail it to you. You really need to see a game gauge to see the nuances. What more can I add other then that 50% above the highest MY 2000 5-speed Insightís EPA highway estimates for every tank this summer works using the techniques exactly as I use them. The game gauges and real world mileage speak volumes and there is not better game gauge in the business then that in an Insight with the rest just letting you know you are in the game so to speak

___Good Luck

___Wayne R. Gerdes
___Hunt Club Farms Landscaping Ltd.
___[email protected]
 
  #29  
Old 09-02-2004, 10:37 AM
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___Krousdb did just that in fact for an 85 mpg average over an entire tank. IIRC, he averaged something like 35 mph? You can see it in the achievement records. As for me, give me yours for a week and I will find out for you on real world roads and at speeds within the limits 100 mpg over 1,100 miles in a Prius? At least you would be approaching that of the Insightís usual but I have only read of a 1,000 mile tank from a Japanese guy receiving in the 80ís and with the Japanese Prius IIís bladderless tank and ~ 13 gallons in her. Why not yourself? You do drive real roads in the real world, correct?
Color me a newbie and/or naive, but I cannot see how it could be physically possible to average 85 MPG over a 967 mile trip. Methinks someone is pulling our hyper-miler legs.

I myself achieved 87.8 over a 2.6 mile trip, but that is not even a smidgeon of 967 miles. Even if I had TOWED the car back to where I started and ran that 2.6 mile strip 372 more times, it is highly unlikely that I could have gotten 85 mpg.

Is there a thread on this board where Krausdb explained this incredible (seemingly impossible) achievement? I'm curious as to why no one else has approached that number.
 
  #30  
Old 09-02-2004, 10:57 AM
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Hi Lars-ss:

___The first place I remember reading about Prius II drivers receiving in the 80ís and with near 1,000 mile tanks was over at Priusonline with some Japanese members posting pics of their dashes and providing some detail. I read that Krousdb chronicled his drive in the Prius 2G or Yahoo - Prius forums? I have never visited either so donít hold me to the exact name or where they are located on the net. At least I thought I had seen these 2 sites mentioned in the Edmunds - Townhall - Hybrid forums when maximum range and fuel economy was discussed in a particular forum a few months ago. A guy going by the nick usbseawolf2000 posted Krousdbís FCD display but again, I donít know what site had hosted the pic or the details. Krousdb does update his tank over tank here but I donít remember him posting much else.

___Good Luck

___Wayne R. Gerdes
___Hunt Club Farms Landscaping Ltd.
___[email protected]
 

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