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Hi all,

My name is Wim, I'm 30 years old, physicist by training. But very interested in all sorts of things, technical and other. I found this great resource after just 2 minutes of googling for a more efficient style of driving.

I don't own a car, and don't want to own a car, as long as I don't absolutely need it. I use the cleanest transportation possible... I cycle!

Nevertheless, I'm interested in hypermiling... for my job. I just started to work at Ecolife (http://www.ecolife.be), a Belgian organization which does various campaigns for a more environmetally sound life style. It will be extremely interesting... the campaign I will work on is for a more efficient style of driving.

For myself, I want to know and understand as much as possible about the various techniques, enhancements to the car, choice of car, choice of roads, hybrid technology etc.

For the campaign's target public, I want to greatly simplify things, and assume they will stick with a normal (too luxurious, too heavy, non hybrid) car. However, I can safely assume a manual transmission. In Europe, it is common knowledge that automatic transmissions are less efficient, and most drivers prefer to have that control over what their car is doing.

I will do some more reading. But some hints and/or opinions are already very welcome!

My job description says I am to build a simulator in order to teach small groups of people a more efficient driving style, with various hardware and software components already available. See Het Nieuwe Rijden (http://www.hetnieuwerijden.nl) for a similar project in the Netherlands. (All links in Dutch unfortunately)

However, the first things I want to get clear for myself are: what are the most important things to change, assuming a normal manual car. Which of these things can we teach people, in such a way that they (1) understand the reasons and (2) will actually adopt them?

I feel it is necessary that they understand them, otherwise thay will just forget what they've learned.

I would also like to be able, preferably from my own experience (which I could possibly gain with my girlfriend's Toyota Yaris 1.3), to give numbers on how much money one can save by allowing say 5 or 10 minutes more time for the same drive etc.

Any comment is welcome! I expect to be on these forums regularly.


One question I already have at this point. I gathered that an efficient way of travelling at higher speeds, is to build up speed to a certain limit (could be the speed limit), then make sure the engine stops, and repreating that cycle. Very good for hybrids obviously, but not quite so easy for normal cars. Do people succesfully do this anyway? I suppose it is illegal, because one loses brake and steering power. Even though I quite agree that neither is absolutely necessary, especially for light cars.

Thanks, and talk to you later!

Wim

You don't have to shut off the engine to see gains in fuel economy, it just allows you to coast longer, which helps out even more with efficiency, but... the whole point of accelerating to some speed, coasting down to another speed, and repeating, is to decrease your engine's brake specific fuel consumption (BSFC). From this BSFC map

http://www.histomobile.com/histomob/internet/techniqu/135-2.jpg

we can see that the engine is operating most efficiently at ~2/3rds throttle, from 2000-3000rpm. Most cars have engines that produce way more power than is usually needed. Because of this, when driving, the engine in most gasoline powered cars is operating very inefficiently, somewhere around 400-600g/kwh. Now if we break up driving into an acceleration and coasting phase, we can increase our engine efficiency by maximising the amount of throttle and minimising the amount of time the throttle is engaged. So if we're using the map above, and only need ~6kw to cruise at 100km/h, then by pulsing half the time while maintaining a 100km/h average speed, we are effectively doubling the amount of power over half the time, which reduces the BSFC (200-300g/kwh) and increases engine efficiency.

In cars with manual transmissions, no power steering, and power brakes, putting the vehicle out of gear and stopping the engine allows for a longer coast because the engine isn't pumping air. This helps out even more with efficiency and isn't very dangerous because the car can be started by engaging the cluch in gear, or the starter, doesn't need the engine running for power steering, and can still brake effectively for short periods because the fluid is still pressurized. On automatic cars with power steering, turning the car off can be a bit of a pain because power steering goes, and the only way to start it is with the starter, which can lead to quite a bit of wear on the starter, also possibly on the automatic transmission, since moving between nuetral and drive a lot more than normal may lead to problems I'm not familiar with. Hybrids are especially suitable for pulse and glide because they are designed for plenty of stops/starts, and their engines are usually designed with much larger BSFC ovals, if that makes any sense. They can usually operate at peak efficiency with much less throttle, and are easier to get into the minimum BSFC area. Anyway, a driver doesn't have to shut down the engine and coast out of gear to see an increase in fuel efficiency, it just helps.

Goede Morgen, Wim. You will find much of what you are looking for here at CleanMPG.com Hobbit has been working on some of these same ideas for a leaflet he wants to distribute in the Boston area. Also, the Elite Hypermilers here have much that you can learn from. It won't take long for you to get enough information to keep you busy. :) In the meantime, I've been checking out the Nieuwe Rijden website and enjoyed the "Dukes of Hastelt" commercials. This is the kind of public service announcement that we should be broadcasting on our televisions here in the states. It's odd that we don't. Good luck with your job and veel plezier met uw ontzoeken!

I seem to have confirmed what you mentioned above. I have been a heavy user of P&G in my '97 Saturn SL1 with M-5 transmission. For one day I tried accelerating at 1/4-1/3 throttle during the pulse portion thinking that I would use less fuel. My Scanguage2 showed me that my mpg actually went down by doing this.:( In a segment that I can routinely get 72-75 mpg, it dropped to 65-68mpg. I will be paying even more attention to the TPS reading during the pulsing phase from now on.:) And, by the way, welcome to the site WimW! It sounds like we may learn a lot from you.

Thanks for the warm welcome guys!

Diamondlarry, I don't quite understand what you changed. You used P&G and it worked well (manual transmission non-hybrid car). Could you tell me more about that (what top speed, at what speed do you restart the pulse, at what throttle, engine off or not)? Those are already VERY good numbers!

HyChi, thanks! I actually hadn't noticed that commercial yet...

Lyeinyoureye, thanks! I think I understand the diagram and your information, except for one thing. I don't quite see how P&G helps if you're not switching the engine off. You still waste loads of energy compressing air, right? I suppose during the pulse you take the engine around the square I drew, or something similar? So you pass a region of very low efficiency...

http://users.skynet.be/wimwoittiez/BSFC_map_arrows.jpg

By the way, I suppose the first and most important thing is to lower ones speed. Does anybody have any number work on that, that he wants to share? I'll do some searching myself of course.

Wim

I'm not quite sure...
When I'm coasting, the throttle plate is closed, and I'm assuming the injectors aren't firing (I don't see why they would be). There is a certain amount of air already in the intake manifold, which will be drawn into the engine. During the intake stroke, the difference in pressure between the crankcase and expanded cylinder will result in negative work. During the compression and combustion stroke, there should be no change in work because there's no combustion and change in pressure, and during the exhaust stroke, as the cylinder is going up, the intake valve opening should actually result in air in the exhaust being drawn in with the result being less positive work than if pressure differential between the crankcase and cylinder had stayed constant. Eventually there should be some relatively steady state pressure in the intake manifold that depends on what the CR of the engine is...

So... Hmm. I'm not sure if the energy needed to pump the air in and out of the exhaust is more than the energy saved by having the engine operate more efficiently a certain percentage of the time. Naturally the throttle plate isn't perfect, so some air will get past, as well as friction losses, so I'm not quite sure about the sum of everything. I think the best bet would be to have someone with a scanguage do a few bidirectional runs cruising at 80km/h, and a few P&G'ing with an average speed of 80km/h. One caveat is that I may have no clue what I'm talking about, so what is really needed is a test... ;)

Welcome to CleanMPG!

As far as a steady cruise goes, the best speed is probably going to be your highest gear just above the lugging speed.

Hi WimW:

___I would not consider teaching P&G to new or younger driver although simulating it could be a lot of fun. DWB within any traffic or terrain constraint is a big one. FAS’ing to lights is too but again, too advanced for a new/young driver to be using. Press up the tires to a min of max sidewall, proper maintenance (low kinematic viscosity oil and clean air filter), DWB using Rabbit timing, Smart Braking, and Anticipation, DWL w/ the iFCD showing you when to apply and when to let off the accelerator slightly, and slowing down to within the speed limits as long as you are in top gear above lugging. PP with a FACE out would be crucial for maximum FE but again, it all depends on the terrain one has to face on there own daily grind. I can almost bet at 50 mph, that 1.3 L equipped Yaris is worth 60 + mpg US. Perform the speed range tests w/ a Scan Gauge or similar attached. Run a 30 mph steady state for 1.0 + miles on a relatively flat route and record, 40 mph, 50 mph, 60 mph etc. Once you have an average over 3 + runs, that is what you can model your sim to. An iFCD will show how much fuel is begin consumed at the steady state speeds let alone the aFCD’s output showing what you achieved over the 1 mile distance. Afterwards, you can model the sim to fit what you see in the 1.3 L Yaris. Keeping a steady and sustainable load at the lowest RPM in the highest gear is the safest and best way to maximize ones FE for a new/young driver. You can find a number of Hybrid’s speed vs. FE modeled in the following: Beating the EPA - The Why’s and how to Hypermile. ( http://www.cleanmpg.com/forums/showthread.php?t=1510). Save FAS’ing and P&G for a more advanced sim as they are techniques that can quickly get a not so astute driver into a lot of trouble let alone cause all kinds of havoc with those around him/her if performed incorrectly in the wrong locations.

___When it comes to P&G, you can throw out the maps because terrain is never as you will find on a treadmill let alone varying RPM’s as you accelerate from one speed to another, the ICE while accelerating is never steady state (especially with a stick) and mechanical losses in the drivetrain as well as aero effects are ever present as the speeds increase. P&G at 45 - 60 does not achieve nearly the same results as P&G’ing from 20 - 35 as just two speed random ranges with similar power outputs during the acceleration phase. One needs to start performing the advanced techniques w/ a useful tool to watch consumption through a cycle to find out a useful rate and range to maximize FE although that rate and range for a particular automobile is usually not available to you when mixed up with traffic, lights, obstacles, etc. There is the science of hypermiling and then there is the art of hypermiling. Add to that wear and tear from higher acceleration rate Pulses and the end result could be less then one would have hoped. Those that have the gift and the willingness to use it will knock the science guys down almost every time because modeling the real world exactly as it appears as well as the drivers mindset at any given period is a very tough business.

___After you have modeled the 1.3L Yaris, I hope it would be in a Windows format so most of us here can play with it too ;) I would love to write up an article on your work w/ the code actually attached for others to try as well.

___Follow the glossary links to find what the acronyms mean. It won’t be long and you will have your own skill sets improved when you do in fact have to drive for whatever reason.

___Good Luck

___Wayne

Thanks for the warm welcome guys!

Diamondlarry, I don't quite understand what you changed. You used P&G and it worked well (manual transmission non-hybrid car). Could you tell me more about that (what top speed, at what speed do you restart the pulse, at what throttle, engine off or not)? Those are already VERY good numbers!



WimW, Basically what changed was that I just started drawing out the glide portion and Wayne suggested that I shift earlier during the pulse portion. If at all possible, I shift at 1500 rpm's in each gear. This is from complete stops and during a pulse. Another thing I have done is try to make sure I don't come to a complete stop as much as possible. This can be done by smart braking and some of the other technigues such as creating buffer zones. When I P&G, I usually go from 30 mph up to 50 mph in 5th gear. Sometimes I will let the speed drop to 20 mph if there is more than a mile between stops. If I drop that low, I will bump pop the clutch in 5th gear to re-start then shift to 4th then accelerate to about 30 then shift to 5th to go on up to 50. When I accelerate I use approximately 2/3 throttle. I tried using 1/4-1/2 throttle and the Scanguage was showing that my segment mpg was actually lower. I should also note that I switched to driving rural county roads as much as possible to avoid traffic. I hope this helps. Feel free to ask more questions. If I can't answer them I'm sure xcel(Wayne) or someone else can.
EDIT: Upon closer inspection of my Scanguage's TPS readout, my normal acceleration rate is much closer to 1/2 than 2/3. This means that my light accleration was closer to 1/4 of max.

Hi WimW:

___I would not consider teaching P&G to new or younger driver although simulating it could be a lot of fun. DWB within any traffic or terrain constraint is a big one. FAS’ing to lights is too but again, too advanced for a new/young driver to be using. Press up the tires to a min of max sidewall, proper maintenance (low kinematic viscosity oil and clean air filter), DWB using Rabbit timing, Smart Braking, and Anticipation, DWL w/ the iFCD showing you when to apply and when to let off the accelerator slightly, and slowing down to within the speed limits as long as you are in top gear above lugging. PP with a FACE out would be crucial for maximum FE but again, it all depends on the terrain one has to face on there own daily grind. I can almost bet at 50 mph, that 1.3 L equipped Yaris is worth 60 + mpg US. Perform the speed range tests w/ a Scan Gauge or similar attached. Run a 30 mph steady state for 1.0 + miles on a relatively flat route and record, 40 mph, 50 mph, 60 mph etc. Once you have an average over 3 + runs, that is what you can model your sim to. An iFCD will show how much fuel is begin consumed at the steady state speeds let alone the aFCD’s output showing what you achieved over the 1 mile distance. Afterwards, you can model the sim to fit what you see in the 1.3 L Yaris. Keeping a steady and sustainable load at the lowest RPM in the highest gear is the safest and best way to maximize ones FE for a new/young driver. You can find a number of Hybrid’s speed vs. FE modeled in the following: Beating the EPA - The Why’s and how to Hypermile. (http://www.cleanmpg.com/forums/showthread.php?t=1510). Save FAS’ing and P&G for a more advanced sim as they are techniques that can quickly get a not so astute driver into a lot of trouble let alone cause all kinds of havoc with those around him/her if performed incorrectly in the wrong locations.

___When it comes to P&G, you can throw out the maps because terrain is never as you will find on a treadmill let alone varying RPM’s as you accelerate from one speed to another, the ICE while accelerating is never steady state (especially with a stick) and mechanical losses in the drivetrain as well as aero effects are ever present as the speeds increase. P&G at 45 - 60 does not achieve nearly the same results as P&G’ing from 20 - 35 as just two speed random ranges with similar power outputs during the acceleration phase. One needs to start performing the advanced techniques w/ a useful tool to watch consumption through a cycle to find out a useful rate and range to maximize FE although that rate and range for a particular automobile is usually not available to you when mixed up with traffic, lights, obstacles, etc. There is the science of hypermiling and then there is the art of hypermiling. Add to that wear and tear from higher acceleration rate Pulses and the end result could be less then one would have hoped. Those that have the gift and the willingness to use it will knock the science guys down almost every time because modeling the real world exactly as it appears as well as the drivers mindset at any given period is a very tough business.

___After you have modeled the 1.3L Yaris, I hope it would be in a Windows format so most of us here can play with it too ;) I would love to write up an article on your work w/ the code actually attached for others to try as well.

___Follow the glossary links to find what the acronyms mean. It won’t be long and you will have your own skill sets improved when you do in fact have to drive for whatever reason.

___Good Luck

___Wayne

Wayne,

You have said/written in-my-opinion (IMO) a very excellent outline. Especially for the beginner on obtaining better fuel-economy (FE).

Terry (tiger)

interesting diamondlarry, i'll have to try that for myself....

all this time, i've been keeping a light throttle for my pulses so my engine loads are quite high, maybe I should lower them a bit.

I found that I need to edit my previous post. I paid closer attention to the TPS value today and found that I'm accelerating much closer to 50% throttle instead of 2/3. This probably means that I was using 1/4 or less when I was accelerating very lightly.

Lyeinyoureye, I follow your analysis up to the point where you say the air in the exhaust gets drawn in. I don't see a connection between the exhaust and the intake valve which would make that possible. In any case, it takes work to keep the partial vacuum in the intake manifold. Air gets pumped out of there and into the exhaust for no reason.

Real-world proof for that is the fact that engine braking is possible. To avoid engine-braking, one would have to disconnect it and have it run idle, which I recently saw uses 1 l/hr on an iFCD. That's a lot for not doing anything useful! Or one would have to switch it off.

Wayne, thanks! These look like very good starting points, things I can try and can also hope to teach people. Driving without brakes sounds like a very strong point (less stressy, easy to understand). I might simply reduce the "FAS to a light" to "switch off the engine whenever you can". One thing I don't understand: press up the tires "to a min of max sidewall". What does that mean?

DWL sounds like a very useful thing too. I'll look for some numbers on time to cross a crest versus fuel consumption. Do I understand correctly that it means keeping the iFCD at your target value while going up and down, and downshifting if rpms drop too low, still keeping the target fuel consumption value?

As for keeping a steady, low RPM in the highest gear... this is where I'll run into trouble with the general public. The speed limit in Belgium is 120 km/h which means everybody does around 135 km/h or about 85 mph. At those speeds, and with a 5 gear car, you're in the higher rpms without other options. Of course, that speed by itself is an energy-eater. I don't think it will be easy convincing people to reduce their speed, except maybe if they can experience for themselves a *drastically* better fuel economy.

A few thought on the simulator... I don't officially start to work until the 18th, so I don't have all the details yet. However, I know a large part of the work has already been done. There is a control set consisting of pedals, steering wheel and stick shift, and part of the (by lucky coincidence) Yaris has been modeled. Not sure whether it's the same engine as my girlfriends'... it might be a diesel since those are very popular in Belgium (my guess 85% of cars), which is why every town in Belgium stinks by the way.

We also have a deal with Het Nieuwe Rijden (http://www.hetnieuwerijden.nl) to incorporate their software, which is used in the game on their website. Apart from the car, it implements roads with curves and traffic lights, and points out what they consider the main strategies for fuel economy (upshifting early enough, leaving the car in highest gear when approaching a red light, cruising at low rpm in high gear). It does not have slopes... The Netherlands are flat! Belgium, however, is not entirely flat.

Another serious shortcoming is the lack of other traffic. That's where I consider a simulator becoming really interesting. After all, a few simple rules are easy enough to teach. But applying them in a real-world situation is more taxing. Using artificial intelligence to simulate other traffic with realistic behaviour is probably very difficult, but it might be obtainable from third parties.

Another option would be to make a relatively small system of roads, and have all workshop participants (probably 5 people) share the same roads. That way the other traffic would be human controlled as it is in reality. I would prefer this option, but with some more participants, if feasible.

Diamondlarry, thanks for the details. All the feedback I get from you guys is very much appreciated. It helps me get a better view on the subject very quickly!

Later,

Wim

One thing I don't understand: press up the tires "to a min of max sidewall". What does that mean?
I believe he was talking about increasing the tire pressure up to the maximum value on the tire's sidewall as a minimum starting point. The tires on my car are inflated to 70 psi even though the tire says 44 psi max. I have noticed no problems in wear or poor handling; even in rain. I figure that I'm already driving very careful because of my quest for FE.

larry, how much improvement at 70 vs 60 are you getting. I thought up around that area the MPG gain is minimal like < .5mpg.

Are you going to lower them for the winter to help with sno traction or leave them that way?

As far as max sidewall pressure goes, in the US it is a requirement that companies display the maximum cold sidewall pressure on their tires. I don't know if this is true for other countries so it may or may not be on your tires.

larry, how much improvement at 70 vs 60 are you getting. I thought up around that area the MPG gain is minimal like < .5mpg.

Are you going to lower them for the winter to help with sno traction or leave them that way?

As far as segment FE goes, I don't seem to see any difference. I will probably lower the pressure according to how the weather goes. Last year, I think what I did was to lower the pressure on the days we had really heavy snowfall then raise it back up when the roads cleared up some. Since I tend to DWB and keep my speed down in general anyway, handling is usually not too much of an issue. It may actually cause me to refine my techniques even more in the bad weather.:)

WimW, once the throttle plate has closed, the most pressure that is in the intake manifold after the TB (throttle body) is 1 atm, assuming the TB forms a reasonably air tight seal. Given that most driving involves part load/less air/less pressure, the pressure in the intake manifold after the TB has closed is probably less than 1 atm. When the intake valve opens, and the cylinder expands, a proportional amount of air will be drawn into the cylinder, with the pressure in the cylinder being even less than the average pressure initially in the intake manifold.

The next two cycles wil compress and expand the air in the cylinder, which I suppose will result in friction losses, but no pumping losses. The pressure may go up a bit due to residual heat in the cylinder, but considering the compression ratio, I doubt it would hit an atmosphere. Otoh, the air pressure in the exhaust is going to be about an atmosphere, so when the exhaust valve opens on the exhaust stroke, we'll have low pressure<1 atm, in the cylinder, and higher pressure=1 atm, in the exhaust, so air from the exhaust should be drawn in, correct?

The cylinder will move up and push out some of the air that has been drawn in, until it has reached TDC. Then the pressure is ~1 atm, and the volume of air in the cylinder corresponds to the compression ratio. During the intake stroke, the pressure between the intake manifold and cylinder will again equalize, etc...

How much energy is expended doing this I'm not sure, but I was thinking that by having a bypass for the TB position sensor, and a cutoff for the fuel injectors (just in case), coasting in an automatic with the TB closed and opened could be measured to determine the approximate losses due to air moving in and out of the exhaust, to determine if using pulse and glide while keeping the car in gear will result in better mileage.

In terms of engine braking, this does happen, but the question is, is it more than what we gain by operating the engine more efficiently. There is also the matter of drag from the transmission, etc... Drive by wire systems and variable valve timing may be able to minimize these losses by opening the throttle during coasting and retarding the opening of the exhaust valve to minimize the amount of air coming in from the exhaust. But in any event, coasting in nuetral with the engine off after pulsing will show a definite improvement compared to cruising at the same average speed, the question is, will coasting in gear stll show an improvement?

WimW, I think I found the appropriate information. Apparently, most modern EFI cars have a fuel cut-off when the throttle body is closed and the engine speed is above some rpm. In the case of modern Toyota drivelines, supposedly fuel starts being injected at 1k rpm for standards and 1.2k rpm for automatics. Some cars will inject more fuel when injection is resumed to start up catalytic converter operation, other models may pulse fuel to keep it at some temperature, and very old mechanically injected models will always try to keep the A/F ratio at ~14.7:1. It also seems to depend on coolant temperature. In terms of the proportion of drag an engine that's not in operation has on a car, it appears to be minimal... Provided the injectors are off while coasting, the majority of drag comes from the differential, transmission, and engines spinning.

So, it would seem that accelerating in the minimum BSFC region and decelerating down to a speed where injection doesn't occur, in gear, can ideally double fuel efficiency compared to cruising at the same average speed, but by killing the engine and putting the vehicle in nuetral, the driver is removing drag from the spinning driveline and insuring no fuel is injected the entire time. In the automatic I drive, I loose twice as much energy by staying gear compared to coasting in N, so it seems like minimizing BSFC and driveline losses are what makes P&G so effective.

I tried it in my car. The deceleration time, in gear, with the ignition off, was identical whether I had the throttle open or closed.

Lyeinyoureye,

OK, so apparently air compression is not what causes engine braking, apparently it's engine and drive train friction. So in order to P&G effectively, one would have to remove that, by going out of gear.

However, I tried coasting down a hill in the Yaris, at 60 km/h. The iFCD showed about 1l / 100 km, which is a lot of fuel consumption just to keep the engine spinning. It does make sense to me though, since the engine now has to overcome its own friction, and part of the drivetrain's.

But this contradicts your earlier post saying getting out of gear helps but isn't essential. I would suppose optimizing BSFC but living with the friction losses etc. is not nearly as effective as dealing with both.

I must say, it's mostly a gut feeling... engine braking is relatively strong, so it must be a big energy loss!

Hi WinW:

___How about you do a few tests of your own to show you the result of the various modes we use.

___Get up to 100 km/h let off the gas to achieve ICE braking w/ fuel cut and record speed to a given distance until you hit maybe 1,100 RPM (injectors should open to allow the ICE to fire back up to idle under closed loop ops with warm coolant between 1,000 - 1,200 RPM). Next get up to 100 km/h let off the gas while at the same time shifting into N w/ the ICE still on (NICE-On) and record speed while you pass that same distance recorded in test #1. The speed once you pass that same distance while in N far exceeds the speed while under engine braking. Considering the ICE is idling while in N, it is consuming such a small rate vs. the extra distance traveled before idle would have reinitiated under ICE braking (injectors fire up), that a NICE-On from higher speeds makes complete sense for better FE. Notice I said higher speeds. At low speeds, the ICE will be consuming fuel in either case yet you will still coast a much longer distance with the drivetrain dis-engaged while in N vs. D or any other gear you may have selected in the case of a manual transmission. There may be a small cross-over region at a lower speed above injector’s opening where overall FE over a given distance with engine braking may exceed that of a NICE-On but it would be a very small region indeed. A FAS knocks both of these methods into the dirt in terms of fuel consumption (none) while passing the same point that Engine Braking allowed before the injectors opened back up. More risk, more reward. Whether or not a NICE-On or FAS is legal in your country is another question altogether?

___As far as ICE braking itself is concerned, some valve control is used to limit the pumping losses in the latest generation ICE’s but anytime you are compressing air and bleeding it away through the exhaust port(s), you have performed work. This is what Engine braking is mostly all about. Normal drivetrain losses are a large part of your glide distance achieved but nowhere near the huge loss in speed while the ICE is performing work by compressing the air. It is best to avoid ICE braking unless it can be controlled for DWB and/or lower wear on the brakes. Having to come to a stop ahead because of a missed or blown timing opportunity or it’s a blind stop sign as just two examples of when you should ICE brake.

___120 + km/h speed limits are ridiculous if your country considers CO2 output a major source of GHG’s. We have the same problem here where speeds and ones time are more important then ones emissions. The Europeans sound as if they can be just as hypocritical as the American’s in this regard if the types of speeds you encounter are the norm. More so in fact given 80 + is very rarely if ever exceeded by most given max limits of 75 for only a few very rural states. We can mandate/achieve a given CO2 output (FE) for a given automobile on the European Urban/Extra Urban test cycles but it makes little sense in the real world when most drive in a fashion that makes those 2 test cycles seem like a leisurely stroll around the countryside with little to no traffic to contend with. Our US EPA ratings for a given automobile are very rarely if ever exceeded by the masses because they drive above the posted speed limits, far exceed accel and decel rates of the test cycles requirements and/or simply drive like there are two pedals in the car and you had better be using them both at the same time (Brake and Accelerator) :( Higher speeds do allow more traffic to enter and share the same roadway without a traffic jam occurring but once the snarl begins; you have that many more cars on the road going nowhere while their ICE’s are idling away. I hope for both the US and Europe’s fate that we truly want to decrease our GHG emissions until we can drive EV off renewables but if an individual or country is going to drive in a wasteful manner (95 + % of the US population does), the populace does not really care. The speeds you described in your country show a similar disdain for fuel consumption and the GHG emitted while driving to and from anywhere to the detriment of us all.

___Lastly, about those speeds … This is where an alternate route can come into play. Your highways are posted at 120 km/h but the roadways through towns are not posted nearly so high. Now it becomes a race to see if your overall fuel consumption can be reduced over a similar distance (sometimes an alternate route will allow even shorter distances!) while taking another route vs. the 80 + mph speeds most drive at in your country while on the highway? There is usually a time factor to be considered here (15 miles at a steady 80 mph vs. 15 + miles at a varying average speed of 25 - 30 mph) can make a huge difference in ones time on the road or arrival but when actual time to a destination is calculated, most will find their average speeds are not anywhere near 80 + mph but a high fraction of it. With fuel costing upwards of $7.00 US in your country, I have no idea why anyone would want to travel with that high a fuel consumption rate at the higher speeds as it must cost a small fortune vs. driving sensibly? Here in the US, we get excited when gasoline hit $3.00 US?

___Good Luck

___Wayne

WimW, Both are crucial components of what is considered to be pulse and glide. By looking the BSFC map of any gasoline powered automobile, it is clear that most low load engine operation is tremendously inefficient due to pumping losses. From what I've seen, given the high power engines that are in use today, most automobile operation is at roughly half of the engine operating efficiency, if not less.
Otoh, try taking some coast down tests over a route you have using information from g-maps pedometer/google earth. You'll probably find that you'll loose a significant amount of energy (twice in my case) coasting in N compared to coasting in gear.
Ideally, pulsing in the minimum BSFC are allows engine efficiency to be doubled, and is especially easy with Atkinson cycle engines. Uncoupling the drivetrain from the wheels allows for a longer coast, with more energy saved on the glide. Both are a crucial part of any P&G, and both can be utilized seperately for better FE compared to cruising in gear.
In terms of your personal test, what rpm was the Yaris at at 60km/h? The engine may be idling the car in gear, in which case, the engine would be operating and pumping losses would be huge plus you would have driveline drag. In any event, it would be best if you wired an led is series with one of your injector grounds, so you could see when the injectors were firing and compensate by driving to avoid this. Like I stated before, modern Toyota's resume fuel injection under 1k rpm as of ~2003(?), so at 60km/h you may not be coasting with the injectors off. It would also be prudent to figure out how the iFCD works, since they may not be the most exact indicators of efficiency under all conditions.

Hi Lyeinyoureye:

___You should attempt to open your eyes wrt high pumping losses at low ICE efficiency leading to poor FE. There is too much real world data from hypermilers showing the facts as otherwise. I do not know how else to show you other then see sig or do the tests on a newer vehicle of your own w/ an SG-II. Since you have so far refused to purchase a SG or other such OBD-II based FE data display, you are in the dark. The highest gear at the lowest RPM almost always achieves superior FE to anything close to low pumping losses at higher RPM’s. Prius’ are a bit different due to HSD programming … P&G need not enter into the equation because so few will ever use it and even when the do, 2/3 throttle on up? I know the HCH-I will achieve near max FE from a 2,150 - 2,350 RPM pulse rate in a lower mid-speed P&G regiment. This is nowhere near 2/3 throttle. This is backed up by real world data. The Automotive engineers are stumbling all over themselves to achieve higher FE using data similar to your own and the hypermilers achieve so much more in the real world while supposedly running near the most inefficient region of the map.

___Good Luck

___Wayne

Wayne,

I'm not quite sure I understand your reply to Lyeinyoureye. Let me try to rephrase it... You say: when driving in the highest gear at lowest RPM, you are in an inefficient region on the map. Nevertheless fuel economy in the real world is very good, much better than... what exactly?

Still, P&G using FAS would be much better, I gather from your earlier posts.

I posted some ideas about the project I'm working on in the Fuel Economy forum.

Thanks,

Wim

Hi WimW:

___Two parts to your question … Steady State and P&G.

___If you have looked at the various hybrid articles, you will now find a steady state speed and FE received over a 1.0 mile distance with and without CC. Look at the numbers closely. Tarabell’s Adapting Basic Hypermiling Techniques to the HCH-II (http://www.cleanmpg.com/forums/showthread.php?t=1306) article shows quite clearly that the HCH-II running at a miraculously low 1,075 - 1,175 RPM’s (just above idle where the largest pumping losses can be found) is achieving near 100 mpg’s at 30 - 40 mph. If you follow any ICE map (Thermal efficiency or BSFC <-- I hate even posting that because a bench test is so far from the real world it isn’t even close), you can easily see that my statement about Steady State cruise in a very inefficient region is allowing by far the best FE. As RPM’s rise where the more thermally and fuel consumption efficient regions lye, FE falls off a cliff!

___As for P&G, what I would like you to do is start a LS (Low Speed) or HS (High Speed) P&G regiment of your own while driving any distance over 10 miles. Just do it as it will be an experiment done with you as the subject. You will more then likely become extremely dedicated like some of us here or a masochist to put it bluntly ;) You are not going to see the average driver P&G other then the very rare occasions when the traffic opens up and permits it fluently. Even though it only takes a slight movement of the accelerator pedal in the Prius II, you will find most that own Prius II’s don’t use this technique even though many know how the technique is performed. Add in a clutch and a 5 speed manual with all the manipulations and it can turn into a nightmarish amount of work with all the calculations so as to maintain momentum while DWB with a given traffic flow. Trying to use a more efficient rate or range so as to not impede others is enough to tell most that they are beyond their abilities to concentrate on all the things going on around them let alone the P&G regiment at whatever speed they are traveling. All I could ask is that you try it for yourself for a period of time and you will understand why most will not bother even if it means a huge increase in FE.

___Good Luck

___Wayne

Hi Wayne,

I wouldn't mind trying it for myself... except that I don't have a car! My girlfriend is in France with hers. Also, I strongly object to driving when it's not absolutely necessary.

Maybe I will though, when she gets back. I definitely appreciate why you want me to!

Another point: after reading a post in the FE forum, I begin to see that we will have to treat diesel and gas engines as entirely different. I think that's part of the reason for certain contradictions in my thinking. I suppose you and most other hypermilers have lots of experience with gas engines, whereas the vast majority of cars in Belgium are diesels.

Later,

Wim