|
6
Nerd-Its
|
|
article
by Hybrid. Bio-Diesel. Hydrogen. We've heard them all. As the world rushes to find alternatives to our current fossil fuel sources, the everyday American is caught somewhere in the middle. Matthew Vea, an avid off-roader, was not satisfied with the current fuel alternatives as none presented him with the capabilities to fully explore the unpaved world around him. Rather than abandon his current Jeep platform, he optimized it ... and himself.
This extensive article walks you through the tools and methodology one can use to assess an engine's performance as well as one's own driving habits. In the end, you'll improve your driving, do a little less damage to Mother Nature, and save yourself a few dollars at the pump.
Add a Comment (83)
Email This
Message Author
I got a better way. Why don't we build tiny nuclear reactor to power every automotives in the nation. It's very efficient, it saves natural resources, and it may kill us all, but most importantly it's cheap.
The analysis looks quite reasonable, though the drafting benenfit results from a decrease in density seems iffy. Air near room temperature below 200 mph is pretty much incompressible -- there won't be a density change. Though, I admit, I don't know how to model drafting either other than the lower pressure cause by the wake of the lead vehicle means less pressure drag. Check out Anderson's <i>Aerodynamics</i> if you get the chance.
I just skimmed through the article and it looks good. However, there are some inaccuracies. I believe the Engine Mass Airflow equation is missing both the gas constant and the engine displacement. Also, the power required curve is cubic, not expontential -- as the equation above it shows. And the equation for drag force, while correct, looks as if area is squared, rather than velocity.
--Nathan
The drafting section is very wrong.
The density is constant. The effect of drafitng is a reduction in your air velocity. It's crude simplification considering the turbulence of the wake behind the lead vehicle, but nevertheless a velocity reduction is far closer to the truth than the density dropping.
This doesn't result in a penalty for the lead truck or car. You get something but they don't lose anything that they wouldn't have lost without you. The turbulent wake behind the truck is a region of low pressure which causes a light suction on the truck. This is where most of the drag comes from. If you drive further behind, the turbulent air settles and gets churned up again by you. You both lose.
I also feel you are slightly incorrect about your conclusion on acceleration. Slow acceleration is not the key. Low revolutions are. Accelerating with 1/4 throttle is slow acceleration. Close to full throttle but low revs shouldn't be called slow acceleration. Many people interpret it wrongly and drive like fuckwits.
Your explanation for the fuel inefficiency of high revs isn't quite right. More air being sucked in means more power which means less time accelerating. However, the high revs result in much more power lost to internal friction, a slightly richer mixture (depends on the car but this is common), and more breathing inefficiency in the engine.
While hard to find, graphs of power per flowrate of fuel vs rpm are available. These show that the efficiency drops with increasing revs. If this wasn't the case, full throttle high rev acceleration would be as efficient as low rev acceleration and it would be quicker. The quicker acceleration would offset the large flow rate during acceleration. Unfortunately this constant efficiency engine doesn't exsist.
BTW, regarding the above post, my credentials are aerospace engineer (stress analysis) with a love of cars.
I also feel you are slightly incorrect about your conclusion on acceleration. Slow acceleration is not the key. Low revolutions are. Accelerating with 1/4 throttle is slow acceleration. Close to full throttle but low revs shouldn't be called slow acceleration.
Can you clarify this a little more? I don't quite see how you can have low revolutions at high throttle and vice versa. When I gun the engine, the RPMs skyrocket. When I slowly increment the throttle, the RPMs rise slowly.
Slow acceleration is not the key. Low revolutions are
I don't quite see how you can have low revolutions at high throttle and vice versa
With a manual, you can (and I do). Is your car an automatic? If so, that would explain your experience.
Geronimo
However, there are some inaccuracies. I believe the Engine Mass Airflow equation is missing both the gas constant and the engine displacement. Also, the power required curve is cubic, not expontential -- as the equation above it shows. And the equation for drag force, while correct, looks as if area is squared, rather than velocity.
There might definitely be some inaccuracies - other than knowing how an engine worked, prior to this, I really didn't know anything about the details of it's operation. On the other hand, I think the equation will still be accurate because the measurements are based on data at the MAP sensor prior to entering the engine - therefore, the fuel should be roughly equivalent to the air passing that sensor based on the stoichiometric ratio. Also, changing engine compressions will result in a change in drawn air (which will in turn change the fuel draw). You're right the drag force equation is supposed to have velocity squared - somewhere in the transition from PowerPoint, the equation got skewed and the exponent slid to the left (it was a layered graphic).
Very interesting article. I'll start using my cruise more when it is safe.
You did forget about exhaust modifications. I recently had to put a new exhaust on my Cherokee. I decided to put the best on, 2.5 inch Borla performance exhaust. The increase in power was unbelievable. So if you then drive at the same speeds as before, you'll use less fuel (which I have noticed on the highway). Course I some times push the gas harder to feel the power which negates the fuel savings.
SD
You did forget about exhaust modifications. I recently had to put a new exhaust on my Cherokee. I decided to put the best on, 2.5 inch Borla performance exhaust. The increase in power was unbelievable.
Doh! I did completely forget about exhaust modifications. Maybe Geronimo can jump in with his knowledge here. From what I've learned in this experiment, though, I can make some educated guesses as to why. The improved exhaust systems are supposed to offer improved flow of exhaust gases post-combustion. By reducing back pressure, the exhaust readily exits the cylinders allowing fresh air and fuel to burn in the cylinder rather than remnants of spent fuel. This better burn will result in better engine performance. AND, since the exhaust is exactly the same, the O2 sensors should not cause the ECU to act any differently.
Of course, I still can't stand ricers that ONLY have a glass-pack noise maker muffler and no other performance mods. C'mon you silly kids ... do something legitimate!
Just a note on the cruise control piece, fully acknowledging that you stated your tests were conducted on flat ground.
Cruise control in even gently rolling terrain is detrimental to you gas mileage. I am a touch OCD when it comes to gas mileage - I know how many miles I need to have driven for each 1/8th of my tank for my goal of 20mpg - so I have done considerable informal studies. The bottom line is that the harder you press the pedal, the worse your mileage is.
For hills, you have to back off on the pedal on the way up (because you're getting less bang for your buck) and then ride it out hard on the way down (because you're getting more speed per gallon). Then you just coast back down to the speed limit. Trust me, I've tested this extensively with my Dodge Ram. If you're riding cruise control, on the way up, the computer floors the gas pedal to try to keep up with the set speed, and then backs off on the way down.
One warning for anyone that wants to do this, though - its good for your gas mileage, but your speed will vary wildly. On the back roads that are rarely traveled by anyone else on my way home from work in Texas, my "goal" speed is 60mph, going up the steep hills I slow down to as little as 45, and on the way down I routinely break 80, and then let it coast back down to 60. Coasting is great for your mileage, incidentally.
I recently had to put a new exhaust on my Cherokee. I decided to put the best on, 2.5 inch Borla performance exhaust. The increase in power was unbelievable.
Maybe Geronimo can jump in with his knowledge here
Would you, instead, settle for my jumping in with intuition? After all, knowledge is so hard to come by. (remove tongue from cheek)
As it concerns fuel mileage, I think what's important is NOT the "unbelieveable power increase." Rather, it's the ratio of Power Vs. Fuel Flow at a given rpm and throttle-opening.
The Borla could give 35 more peak horsepower and HURT gas mileage. How is this so? If it enhances the ***high-rpm*** pressure wave activity in the exhaust system, then it would do do at the expense of the lower rpm pressure wave. And, if this were the case, the 35 extra horses would be at full-throttle and top rpms... neither of which is the case with driving 60mph down the highway.
Mind you, I'm not saying the Borla DID have this lopsided effect (or hurt his mileage), but rather, I'm making the point that what's important here is not full-throttle power, but rather, how the engine runs at 10% throttle at 1,800 rpms... which I'm ***guessing*** to be the conditions of a 60mph cruise in a Jeep V-8 Cherokee.
The small throttle opening and lower rpm's found at cruise speeds are a nearly-unique set of circumstances, often related only obliquely to peak power. A performance exhaust might ENHANCE this range, or it might KILL it. Most engine mods are one side of balancing act, robbing one side to pay the other. Still, though my racing days are over, I do a few small engine mods; more for economy than power. My favorite mods are the ones that yield BOTH.
I love the "feel" of an engine with an efficient-but-reasonably-quiet exhaust system, but I'm not certain it improves gas mileage. However, it COULD. Consider this:
If the engine inhales a given amount of air, and the ECU mixes gasoline with it at an approximate value of 14.7-to-1, the resulting burn gives a certain amount of power. How could an exhaust change this equation? If the "right" amount of air is mixed with the "right" amount of fuel, then a given amount of power is produced. No exhaust system can make the combustion of a given weight of air and fuel (on a closed-loop, ECU-controlled car) suddenly "bigger and hotter." But, that's not all there is to it.
BTW: The above is food for thought only, not a challenge to the Borla'ed Cherokee's increased mileage claims. The way it MIGHT work is if it made the engine a more efficient pump. But at 10% throttle, I have to wonder.
However, the Borla can GREATLY increase the driver's sensory experience, which means his mind is on his job (driving), which--in turn--means he's much more "in-tune" with his machine. Note that the above is a big part of the list of necessary driver attributes in order to get better fuel mileage from a given vehicle. All pluses and, as long as it's not nasty loud, there are few negatives.
Best,
Geronimo
Cruise control in even gently rolling terrain is detrimental to you gas mileage.
Always been my experience, and for the reasons you state.
For hills, you have to back off on the pedal on the way up (because you're getting less bang for your buck)
A man (I assume) after my own heart... All the cruise controls I've ever used ALWAYS jam the gas pedal when climbing a hill. They sacrifice fuel in a vain effort to maintain speed when climbing hills. They do this because they're machines, and they're PROGRAMMED to act this way. How could they do any differently?
With the usual caveat of "be courteously aware of other traffic" (don't drive 45 in the left lane while climbing a hill on the Interstate with traffic backed-up behind you for 1/2 mile), I heartily endorse backing off on hills and coasting. They're the first two things you figure out when driving for best real-world mileage. The third one is for city driving, and it's, "Look ahead and try to NEVER touch your brakes."
Best,
Geronimo
A good compromise is to do your accelerating in anticipation of the coming hill.
I believe your acceleration experiment may be poorly designed (though I may be wrong since Jeeps may be more like trucks).
It is my understanding that car engines operate most efficiently usually somewhere between 3000 and 4000 rpms (for trucks, the sweet spot is usually between 1500 and 2500 rpms). Your most efficient speed, with little fuel and time trade off, should be somewhere between 50 and 80 mph. In your case, it looks like somewhere around 50 or 55 (loose guess based on your graphic). See what your RPMs are at that speed. Try keeping your RPMs near there when you accelerate (within reason consindering the conditions).
Also, try that just in first gear and compare it to idling. Measure your volume of fuel used and distance traveled. Measure over the same distance, starting from maximum idle speed in both cases. Do it again starting from a full stop.
Take a look at incremental fuel consumption over incremental speed.
0.062733333 0 to 45mph (this covers multiple gears, so doesn't compare to other numbers)
0.0966 45 to 55 mph
0.121 55 to 65
0.1653 65 to 75
It looks like you still get a very slight increase in fuel consumption for an increase in speed then you're down near 45 mph.
It would be cool to see narrower speed increments for the entire speed range of the gear.
I think it would also be good to note that this analysis ignores any time and traffic considerations. It is only relevant in conditions where you are the only vehicle on the road (your might be able so save fuel yourself, but at a cost of more fuel consumption for others).
If you really want to save fuel and still drive, stay in first gear at about 3400 RPMs and avoid stopping.
The AMC I6 "sweet spot" is typically around 2500 RPM (i.e. truck like).
It is my understanding that car engines operate most efficiently usually somewhere between 3000 and 4000 rpms
But that's (generally) the range of peak torque and, in the real world, has nothing to do with peak fuel mileage.
The rpm of Peak Torque is the most efficient ***breathing*** of an engine. This means that you're getting the most power for the amount of fuel used. Also, the RPM at which peak torque is acheived varies wildly from vehicle-type to vehicle-type. Peak torque on a Honda Civic Si occurs at an engine speed that would cause a V-8 Mustang to vomit its internal parts through the top of your hood. But to top it off, the RPM range of peak torque is the direct enemy of fuel mileage. Why? Aerodynamics!
For this reason, on a manual-transmission car, the highest fuel mileage will occur at (pardon my caps) THE LOWEST SPEED THE CAR WILL RUN IN ITS HIGHEST GEAR. This can be proved empirically, and will not vary.
The Honda Insight has the On-Board-Milage-Computer-To-End-All-Mileage-Computers, and I've spent more hours than you'd believe in testing with this car. The best AVERAGE mileage I ever acheived on my regular "real world" 100-mile loop was 113.7. I can show a 120-MPG average for most of the trip, but hills and traffic lights stop the show on one end of the loop. This mileage is acheived by driving 29 miles-per-hour in 5th (the highest) gear. This is the speed at which the Insight is idling in 5th gear. Yes, it's dangerous to try this on most highways. I have a test loop where it's safe, but in case of even moderate traffic, I speed up and abort the run. It's not safe to drive 29mph on a road posted 55.
Hours of testing showed that increasing speed to only 40mph makes it very difficult for the Insight to AVERAGE much above high-80s mpg. To show yourself how powerful the aerodynamic force is at 40mph, drive your car up to 40 and try opening the door ALL THE WAY OUT. It can be done, but only if you're dedicated to the task! And please don't try this if you're the type person who falls out of cars.
The reason peak torque RPM does not yield best (or even "good") mileage is because, in top gear, most modern cars would be running (as you stated) around 80 mph, automatically killing fuel mileage from the get-go.
So, to recap, manuals will always get best fuel mileage at the lowest speed they can run while in their highest gear.
Automatics will get best fuel mileage at (pardon caps again) THE LOWEST SPEED AT WHICH THE TRANSMISSION WILL SHIFT INTO "HIGH," AND THE TORQUE CONVERTER WILL STAY LOCKED UP. On my wife's Dodge Intrepid, this speed is around 40mph, but many cars are closer to 50mph.
To non-gearheads, torque converter lock-up "feels" like another gear has shifted, so don't confuse the two. To check the feel of TC lockup, get the car up to temperature and up to about 55-50mph. Then with a LIGHT throttle setting (but with SOME load on the engine), press the brake pedal SLIGHTLY, only enough to activate the brake lights. When the brake lights activate, this tells the ECU to unlock the torque converter. If the converter was locked-up, you'll feel the engine speed up a few-hundred rpms.
Geronimo
That's correct, air resistance increases load and therefor fuel consumption as speed increases. But the idea is to get the most speed out of your fuel consumption. You'd get excellent fuel milage by walking, but the trade off is time. By going the lowest speed in any gear you are lowering your fuel cost by increasing the cost on everyone else on the road in both terms of fuel consumption (increased frequency of stops and duration and frequency of speed changes, all far more important than cruising speed) and even more importantly time (ultimately you end up paying in hire prices at the grocery store, etc for both the time and fuel). People's time is worth far more than fuel. By running at peak torque, you are avoiding the higher speeds where fuel consumption begins to increase much faster than speed.
Accelerate at peak torque when you are at the front of a queue and observe the space that opens up between you and the car behind you. That's all wasted energy, think of the additional cars that could be moved through that traffic signal if they simply filled that gap. The increases fuel consumption for the individual cars is negligible. There would be more cars moving, not stopped, less time accelerating, and no change in top cruising speed. Everyone benefits.
All else equal, going lower speeds and acceleration will save you fuel, but the effect on the system means more fuel consumption in the long run.
But the idea is to get the most speed out of your fuel consumption
Well, that's a different question than the one I answered, but perhaps I misunderstood. However, the article all this is based on was about getting maximum fuel mileage so that's what my comments were geared to.
Also, all your scenarios are in city traffic, which is counterproductive to good mileage. Of course, we all have to drive in that environment (some occasionally, some often), but in an article about obtaining maximum mileage you'll note the Jeep owner tried to avoid it.
Of course, drving in city traffic also requires skill, the most important manifestation of which is VIGILANCE, which you appear to have.
It's easy to find the "sweet spot" for speed and acceleration: Just stay--more-or-less--with the traffic; it's the safest way. There's always some idiot who comes blasting by me in a large, powerful pickup truck, but I can't worry about him. I drive the best I can and take the mileage I get. But when there's opportunity, I drive for maximum mileage, even in town.
If you pay the least bit of attention to what's going on around you, then you're better than 90% of the drivers I share the road with. (in South Carolina, USA)
Best,
Geronimo
Dude...you posted as anonymous!! This would have definitely scored higher if'n you were signed in. BTW: Your posts on this topic are mucho informative and smart and-- dare I say it-- nerdy!
Dude...you posted as anonymous!
I fact that I realized perfectly well... but only after I pressed "SUBMIT COMMENT." (insert sound of egg being wiped from face)
Still learnin' my way 'round this place. (for example, I have no idea about the scoring, but have just taken notice that it's there)
Geronimo
But the idea is to get the most speed out of your fuel consumption.
That's simple: Drive as slow as you can, in as high-a-gear as you can and still get to where you're going on-time. You can overlay a chart of your engine's Specific Fuel Consumption onto the car's CD/Frontal Area and pick how much fuel you want to use. There is no "sweet spot," since ***aerodynamic drag*** increases with the square of speed... period. The importance of aerodynamics, as it applies to seeking better fuel mileage, is important to the point of dwarfing all other factors (such as the engine's peak torque rpm, etc.)... period. I don't see why there would be a certain speed range where a car can suddenly override the laws of physics (as "sweet spot" suggests).
All-in-all, your letter reads (to me) more like a rant than information, but then, that could be because I'm not certain what point you're getting at. If, as it seems, you're trying to work-in driving around with your engine in the peak-torque rpm as a reasonable fuel-saving measure, then you're pedaling backwards. The main reason it won't work is that all automobiles of which I am aware have their powerplants oversized for the work they NORMALLY do.
To get maximum mileage (for a given speed) to correspond with an engine's peak torque rpm, you'd have to figure how much horsepower is needed to push the car at that given speed. Assuming you'd need around 17hp to maintain 60mph (a generic-but-realistic set of figures), then you'd have to get an engine that produced 17hp when it was running at its torque peak rpm. Only THEN would the engine's peak torque correspond to best mileage at a (the) given speed. But of course, the problem is that you'd have no extra power for hill climbing, passing, etc..
So, out here in the real world, the best we can do is give a car excess power and sufficient gears to keep fuel-sucking Engine Friction to a minumum by keeping the rpms as LOW as possible.
I accelerate reasonably briskly, and I don't dawdle around in the way of traffic. You seem to have constructed a "straw man" argument in which you think up some sort of worst-case scenario for ECONOMY driving, and then assign these horrible traits to the straw man... in this case, me. I'm not saying that's what you meant to do, but it is what you did. A little better grasp of the science and emperical data will clear all this up.
Geronimo
Accelerate at peak torque when you are at the front of a queue and observe the space that opens up between you and the car behind you. That's all wasted energy, think of the additional cars that could be moved through that traffic signal if they simply filled that gap.
Actually, I think the space opening up between cars can help to improve gas mileage in certain situations. In studying traffic phenomenon, such as backwards propagating waves, while writing Beating Traffic, I happened upon an article by William Beaty entitled Traffic Waves: Sometimes One Driver Can Vastly Improve Traffic. On one page of his article, he describes a "cure" to traffic waves in which he was able to "eat up" waves by properly timing his driving. I've tried the same thing myself and have been able to successfully mimic the effect, while also stretching fifty more miles out of a tank of gas and making my commute much more comfortable and less stressful.
Of course, there are lots of ways to get better mileage, but most of them involve going slower. This technique, however, doesn't have that effect. Whether it's on the freeway in stop-and-go traffic, while waiting through a metered on-ramp, or on residential roads with lots of signals, allowing a large gap to open up in front of you when approaching a "wave" can allow you to effectively "eat" the wave - saving your brakes and gas without costing any time.
Of course, it takes some practice. I've found that I sometimes get overzealous and begin to coast so soon when approaching a red light that I don't have time to get through it after it turns green. It's also important to take into account the factors mentioned elsewhere in this thread concerning blocking other vehicles' access to left-hand turn lanes and such, but the results are obvious and actually quite satisfying.
That's driving for the conditions, anticipating stops etc. All good, but you want to do most of your spacing closer to when you reach cruising speed. You should be able respond with the trottle by watching the cars in front of you and not need the brake. If you need the brake frequently, you're overduing the acceleration for the conditions. Not getting up to speed fast enough is what forms a backward wave, that and driving too fast (causing you to need to stop when you could just cruise through). The wave forms behind you.
For this reason, on a manual-transmission car, the highest fuel mileage will occur at (pardon my caps) THE LOWEST SPEED THE CAR WILL RUN IN ITS HIGHEST GEAR. This can be proved empirically, and will not vary.
Absolutely True. My Jeep used to get extraordinary gas mileage while cruising along at 35 mph in sixth gear (Army bases have agonizingly slow speed limits). The vehicle was just barely over idle at that speed ... enough to keep going but not enough to accelerate without downshifting.
Fuel Consumption: Speed: Delta Fuel: Delta Speed: %change fuel: % change speed: %delta fuel/% delta speed:
0 0
2.823 45 2.823 45 100% 100% 1.000
3.789 55 0.966 10 34% 22% 1.540
4.999 65 1.21 10 24% 18% 1.331
6.652 75 1.653 10 25% 15% 1.615
This looks like your sweet spot is closer to 65 mph.
This looks like your sweet spot is closer to 65 mph.
Right on the money. I've now done two trips from New York City to DC. Slowing down significantly and using cruise control the entire way changed my half tank range from 165 miles to 220 miles. For a Wrangler, that's nothing short of phenomenal, nearly 25mpg as compared to the previous 18mpg.
It really doesn't impact on other drivers either. For the most part, 65mph is the speed limit on I-95 anyway and there are enough lanes for all the speeders to not even notice me. What I found really interesting is that when I slowed down, several other cars did as well - falling in line behind me for miles. Maybe they were just looking for an excuse to drive slow without looking 'weak' on the highway.
Cool. Nice to know.
That's funny about the other drivers. There's probably something to that. In some areas in Michigan, using your signal for a lane change will cause other drivers to speed up to block you out. Just competetiveness. I sometimes catch myself creeping up over speed limit just because cars are speeding passed me when we are approaching a stoplight. I expect them to cut infront of and then hold up traffic at the light. I guess that's also due to competitiveness, I get way more frustrated than it's worth (I know it doesn't really doesn't matter whether one or another asshole is infront or behind me).
Another plausible explanation is that they figured you knew the cops were about.
For me, it's nice to sometimes pick a car moving a reasonable pace, follow, and not think about speed. Just one less thing on the mind (day dreaming while driving probably isn't very safe though).
I received many comments through e-mail, here's one outlining the dangers of driving too slow just to save gas.
The first is reduced speed, as many studies have shown that it is the difference in speeds between the fastest and slowest traffic is more dangerous than higher speeds for all. If people decide to driver 20 or even 10 mph below the rest of the traffic to save gas they need to consider how much risk they are adding to their own driving as well as others. Additionally during rush hour if people drive both below the speed limit and below safe speeds for traffic (accounting for road surface, traffic density, etc.) they can cause large traffic tie ups that consume greater fuel for everyone.
The second is slower acceleration, this causes traffic tie ups and increased risk. Many times I have been stuck behind someone who not only was slower to accelerate from one light to another, but also braked slowly at the next light. As they are going straight they realize that it doesn't affect their drive time, however if they are in the left lane they can block access to dedicated left turn lanes. This can cause people to miss the light and thus spend more time in traffic or try and run the light, or hopefully left turn arrow, and thus create the risk of collision with on-coming traffic.
Both of these methods can also create road-rage (or I guess we should now call it IED, Intermittent Explosive Disorder) in those stuck behind them. The one thing that bothers me is people who are inconsiderate about how their driving affects others, fortunately I have reached that level of maturity (Ok, dammit I am getting old!) that I don't let this affect my driving.
Well now, that's why I have a 200watt public address system mounted to my bumper! You're never too old for a PA system on a Jeep.
But do you have a sign that says "Remain 50m back or you will be shot" in both english and arabic?
This might negate the safety benefits of accelerating faster.
Here's an interesting article outlining the cost of an automobile from inception to scrap heap. It includes everything from raw materials to vehicle lifespan and fuel. Interestingly, the simplicity of the SUVs and their longer lifespan rendered them "cheaper" on the environment energy wise than even the most frugal of hybrids.
That's a very interesting article. Particularly, it's interesting that the study found:
'... 62 percent of hybrid owners are dissatisfied with the fuel-economy performance of their cars given what they have paid for them. This means that when gas prices go up, these people don't rush out to buy more hybrids. "They buy a Chevy Aveo," says Spinella. "It delivers the same fuel economy as a Prius, but at half the price."'
Where have I heard that before?
One point in the article, though, seems faulty. It's obvious that cutting edge technology costs more per mile now, but once there are more hybrids on the road, the manufacturing facilities and procedures are in place and they are more "the norm," many of the extra costs will disappear. I think Ford's decision to back away from their promise to put more hybrids on the road is a mistake (albeit one that they might have had to make to keep their heads above water). The money "lost" now is an investment into the future of cars - one that can earn a place in the market of tomorrow. The longer Ford waits, the more behind the game they'll be. Then again, maybe that's their plan: build cars cheaply using old/tried technology they can buy from other companies who had to forked out the big bucks for development ten years ago.
... maybe that's their plan: build cars cheaply using old/tried technology they can buy from other companies who had to forked out the big bucks for development ten years ago.
Well, it worked for the Koreans all through the '90s in their automotive industry. Now they build the VBIED carrier of choice in Iraq!
Seriously, though, while manufacturing processes will inevitably improve in the future, the cost of those vehicles now is permanently set. And one may assume the benefit will also be found in the SUVs. I still believe that a diesel conversion in America is a necessity over electric vehicles. Or at least a mix between the two.
62 percent of hybrid owners are dissatisfied with the fuel-economy performance of their cars
TEACHING THE TEST
While every vehicle is incredibly optimized to return the best results on the (in the USA) EPA's inertia-chassis dynamometer, it stands to reason that hybrids, whose only claim-to-fame is incredible fuel mileage, are hyper-optimized, quite possibly to the point of returning less fuel mileage out here in the real world. The new EPA mileage loop test numbers are going to knock a lot of the sheen off hybrid numbers. Wait 'til you see the Prius's numbers take a real hit. I'm happy that the playing field is about to be leveled but it gives me no secret joy that hybrids are gonna "get theirs."
FEWER FORD HYBRIDS Vs. TRUE COST
The idea of hybrid (in general) and Prius (in particular) prices coming down with the acceptance of the technology is a good point, but I don't think it's gonna happen anytime soon. Why? Because my bet is that Toyota, while not exactly "losing money" on each $23k (in US) Prius sold, is making pennies where they could be making thousands. They could easily 'fix this by shutting down Prius production and making more Camrys, but that's not the game plan here. Priuses are trickling off the lines because even Toyota can't afford dedicate too much assembly-line time to a (so far) losing proposition. But, if hybrids get big to the point of widespread acceptance (and the accompanying $33k price tag), then you'll suddenly see lots more of them.
The Camrys are "paying the way" for the Prius's below-market-value selling price. Toyota can afford to prime the hybrid pump with this strategy. Ford, of course, can not since they are in such bad shape that EVERY car/truck they build has got to pay it's way... today.
Considering their respective situations, I think both companies are doing the right thing. I wish Ford were able to throw its hat in the ring, but my take is this: In this Beta-Vs.-VHS battle, hybrids are going to be a relatively short chapter. If so, perhaps Ford is wise to refrain from going toe-to-toe with Toyota, who has the whole hybrid hardware/software thing completely sewn up. All the other manufacturers have, apparently, conceded the race, and are trying to license Toyota's technology but I haven't heard lately how that's going.
BTW: I am not anti-hybrid, but it's silly technology to have two MAIN methods of propulsion in one car, particularly when one of them is electricity, which--so far--lacks the necessary "magic battery" to make it work.
THE CONSUMER SPEAKS:
Why can't I buy a Subaru R1 here in the USA?
http://www.subaru.hu/topics/imgs/050330R1b.jpg
Best,
Geronimo
I agree that it's expensive to move to a Prius-like "full" hybrid, but I wonder that there aren't more "mild" hybrids (e.g., Chevy Silverado) out there. Every car already has an electric starter; why not beef it up a little bit so the engine can turn off while the car is braking or stopped? Every car wastes energy into heat caused by friction when braking; why not implement some kind of regenerative braking mechanism? These improvements can greatly increase the gas mileage (15% with Toyota's system) of the vehicle without jumping the ICE ship.
but I wonder that there aren't more "mild" hybrids (e.g., Chevy Silverado) out there
All good ideas, Brandon, but all is not as it seems.
The Silverado hybrid is a "hybrid," not for fuel-mileage (which is about 1-mpg better than the standard truck's) but so that its battery can run power tools on remote jobsites. Since it's considerably heavier than the standard Silverado, most mileage considerations are a wash. It has the "engine-shut-off" mode for stoplights and such, but if not for the inclusion of this feature, I have to wonder if perhaps the Silverado hybrid's mileage might be WORSE than the base trucks instead of a 1-mpg improvement.
Every car already has an electric starter; why not beef it up a little bit so the engine can turn off while the car is braking or stopped?
Emissions go way up when utilizing an engine-shut-off scheme. My guess is that even a warm start-up is a nasty thing on an ICE. I don't have a handle on exactly how much more pollution it makes (I left my Exhaust Gas Analyzer in my other pants) so I don't mean to come off like an expert here, but it's enough to cause great concern with the manufacturers who employ it.
The Insight and Prius are very good with this nasty re-start condition but, without my even looking, I can almost guarantee you that the 02 sensors in these cars are priced sky-high (they're about 30-bucks for my older GM car). And regardless of how long everyone thinks the Li-Ion batteries will last, you can safely assume that you will need several O2 sensors during the life of the car.
why not implement some kind of regenerative braking mechanism?
Again, good idea, but regenerative braking rewards bad driving. After all, it only works when you've misjudged the speed you needed to be going (I know, you must brake sometimes). When I tested the Honda Insight, after getting used to where (and how much) the battery pack kicked in, I never used battery power again. The average (down the page) I obtained was purely on the gas engine.
I can drive through my town (Greenwood, SC) and, if I pay close attention, I can stay pretty-much with traffic and only kiss the rotors with brake pads, and then only occasionally. If regenerative braking were really a windfall profit, wouldn't I be ahead of the game if I bought a Prius and drove around with my foot on the brakes?
Amazing machine though it is, the Prius is so heavy that Toyota had have a special tire designed just to support its prodigious weight. We're talking one heavy car here. For regenerative braking ("RB" hereafter) to work, it takes a monstrously-heavy generator device, and then there has to be somewhere to store the resultant electricity. Someone here has pooh-pooh'ed the heavy battery caveat by telling us how small the Prius's battery pack is. I don't care what size it is, I want to know its weight. Of course, any time the RB isn't working, you're paying dearly to accelerate 3/4 ton of "stuff" around.
For starters, the Prius has a (from memory) 50hp electric motor. Do you have any idea how much that weighs? I don't pretend to know, but I do know that I can't lift a 20hp electric motor.
I feel as if I'm beating-up on the Prius here, but I don't mean to be. It's just that, though the engineering is brilliant, when it comes to using this type of technology to acheive fuel mileage, I don't
Question about drafting by bradsmith :: NR6 :: on 16 July 2006
Rather than assume, I'd like to ask a question about drafting. Being a swimmer, I am quite familiar with the concept. One thing that must be said for drafting however, is that the person who is leading must exert more force to maintain his/her speed than if no one were drafting behind them. Can one assume then that any gas mileage saved by one is reduced from the other. Intuition tells me that there would be a reduction, but I am not sure if it is an equal reduction. It would be cool to have stats on that... but that would be quite an undertaking.
I did like how you pointed out that drafting could (and probably would) increase accidents if adopted by the general public. That is why I asked about the ethics of it if gas mileage were reduced on the other end of it. There was nothing I hated more while swimming laps than a lazy swimmer who just drafted off me and never offered to do his/her fair share of the leading. It's just bad manners to take but not give.
RE: Question about drafting by Anonymous :: NR0 :: on 17 July 2006
What is the mechanism that causes the lead to have an increased load when drafting (I didn't read the full description of the method)?
RE: Question about drafting by Anonymous :: NR0 :: on 17 July 2006
By drafting you use the vacum that is behind the leader. But by doing so, you enlarge the vacum creating more drag on the leader.
However, I don't think the increase in drag for the leader is equal to the reduction for the drafter. The reduction is larger.
I personally used drafting while cycling across Canada with my wife so know the savings it makes.
RE: Question about drafting by Anonymous :: NR0 :: on 17 July 2006
One thing that must be said for drafting however, is that the person who is leading must exert more force to maintain his/her speed than if no one were drafting behind them
Faulty science.
Though the leader always bears the brunt of aerodynamic drag, everything I've ever read says that, in a drafting situation, BOTH parties benefit. I think the reason is the air (or water) is allowed to stay better-attached to the surface that's parted it.
http://en.wikipedia.org/wiki/Drafting_%28racing%29
Wikipedia says:
Drafting, or slipstreaming, is a technique in sports racing where competitors align in a close group in order to reduce the overall effect of drag or fluid resistance ***of the group*** (my empahasis)
I would assume the swimmer is confusing the frustration of being "forced to lead" in a non-workload-sharing situation with actual increased drag.
Geronimo
RE: Question about drafting by bradsmith :: NR6 :: on 17 July 2006
Thanks for clearing that up for me, that both parties can benefit. My next question would be how close must one follow to remain in the air steam without being at a distance that would create a drag on the leading vehicle?
RE: Question about drafting by VnutZ :: NR8 :: on 17 July 2006
My next question would be how close must one follow to remain in the air steam without being at a distance that would create a drag on the leading vehicle?
I think this largely depends on the size of the vehicle in front of you. From experience, I can say that you'll get some of the effect from being about three car lengths behind the target. But there is a distinct "sweet spot" even closer. Note, there is a significant danger to being this close to a speeding truck on the highway. When I approached that sweetspot, my car actually gets jostled quite a bit as the air reconverges - I can feel it being buffeted on the sides and my CB antenna began wildly banging against the hardtop. Moving in closer made the ride smooth out, wind noise became quiet and the car just kind of "sucks in behind" the truck. You really can't use cruise control this close because the wind itself will alter your speed and an RPM boost will send you right into the back of the truck.
So, long story with no actual answer. It's close, the kind of close where you need to be super alert or be a dead driver close.
RE: Question about drafting by stopgap :: NR5 :: on 17 July 2006
At least in car racing and cycling, both parties benefit from drafting:
RE: Question about drafting by Anonymous :: NR0 :: on 17 July 2006
When young and foolish I practiced drafting behind tractor trailers while on long haul interstate drives. I noticed that the benefits in terms of how much I had to hold down the throttle were quite noticeable as I approached the trailer's rear bumper to about 10 feet (very dangerous!). The airstream is rough and there is tremendous buffetting at that distance but you seem to be riding in the pocket of air turbulence just behind the trailer. My impression was that I had no noticeable effect on the semis and my hypothesis would be the decrease in the forward vehicle's gas mileage is much outweighed by the increase in the following vehicle's mileage. I'm too old to try to get the direct data with my car's OBDII data computer hookup (wife and son would kill me), so does anyone have solid data on that?
RE: Question about drafting by GeronimoPFudgemuffin :: NR0 :: on 17 July 2006
my hypothesis would be the decrease in the forward vehicle's gas mileage is much outweighed by the increase in the following vehicle's mileage
No increase in aero drag for the leading vehicle, therefore, no fuel mileage decrease. In fact, the tractor-trailer rig in this scenario would get IMPROVED mileage.
The nasty air BEHIND a given vehicle is the hardest to handle elegantly for low-drag, but it's where most of the gains can be made. This is why the drafted tractor-trailer's mileage would improve (but not by as much as it would if being followed by another T-T rig).
Cleaning up the trailing airstream is aerodynamically desirable but driving a car with a long, pointy tail is not going to happen, is it? So, they do the best they can. Look at the Honda Insight's tail. The rear-fenders pinch-in rather severely for a street car, and that's part of the magic.
Also look at the older Citroen DS series. The DSs were much-admired for their aerodynamic qualities and the Insight is, roughly, a large version of the same concept. Basically, it's like a teardrop with a truncated tail.
Geronimo
RE: Question about drafting by GeronimoPFudgemuffin :: NR0 :: on 18 July 2006
The DSs were much-admired for their aerodynamic qualities and the Insight is, roughly, a large version of the same concept.
Oops (replying to my own post)
I meant, "The Insight is a ***SMALL*** version of the same (Citroen DS) concept.
We now return you to your regular programming.
Geronimo