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Are these things really worth it? - What if you made a regular car with all the tricks of a Prius?
Hybrids definitely do work -- we're not refuting that -- how well they work is open to debate, however, especially in light of the revisions to EPA mileage numbers. So, let's examine the Prius. Amazingly engineered vehicle, that's for sure. The way they got all those different systems to work as a team and perform smooth handoffs between functions is pretty incredible. We're not going to bother with the electric powertrain portion of it for now. Have you ever poked around the gasoline engine in the Prius? Interesting stuff, lots of little tweaks to boost efficiency. We're wondering, having looked over the Prius, whether you could realize most of the gains without the batteries and motor.
More after the jump
The first thing Toyota did was fit the Prius with an Atkinson-cycle engine. The Atkinson cycle leaves the intake valve open for part of the compression stroke. While that seems counter to efficiency gains, it keeps cylinder pressures in check and allows longer burns, ensuring more complete combustion and extracts more work from the intake charge. The lower cylinder pressures reduce NOx emissions by keeping temperatures down. We'd be curious to see the 1NZ-FXE engine in the Prius fitted with Toyota's trick "dual-injection" system. The dual-injection system uses both direct gasoline injection, into the cylinder, and indirect injection, into the intake port. The reason for the seemingly redundant systems lies in optimizing swirl and atomization. Teaming the two methods together allows more optimal tuning across the RPM range, resulting in better efficiency and performance.
Sticking to the engine, there's an insulated canister fitted to the Prius that works like the vacuum flask we fill with fine coffee every morning (lest we have to stoop to store-bought swill). Warm engine coolant is held in the canister and then re-used to speed engine warmup. This is a really slick trick and would likely bump every engine's MPG rating a hair, as time spent warming up would be greatly reduced. Another thing to consider for colder climates would be gasoline-fired coolant heaters. These are pretty commonly fitted to vehicles in Scandinavian countries. They consume a fraction of the gasoline used by a running engine and are a far more efficient way to pre-warm your coolant. It'd also mean an end to our neighbor's seemingly endless idling at 4AM. WIth the coolant pre-warmed, the engine is able to get into it's most efficient mode of operation much faster.
An automatic transmission (or CVT like the Prius) is undoubtedly the way to go for emissions control. With fly-by-wire throttles, the conditions of shifts can be tightly controlled so that the engine management isn't chasing the driver's input like less integrated systems have to do. The throttle plate can be feathered, timing optimized, fuel delivery exactly metered, all to ensure a perfect shift as cleanly as possible. Team the transmission with a steep final-drive ratio, and program it to short-shift, keeping the throttle plate open wide, and pumping losses are brought down. We're not sure what the current state of throttle-less gasoline engines is, but the last time we checked, it was difficult to get them to meet emissions targets. While it would seem great to just run the thing as lean as possible, cleanliness suffers. With a lean mixture, there's not as much fuel to absorb heat in the cylinder, leading to excessive cylinder temperatures and very high combustion pressures. Those lead to increased NOx, which is one of the more difficult internal-combustion byproducts left to control; engineers have done a great job figuring out how to tame most of the others.
A low coefficient of drag can have a marked effect on MPG at elevated speeds. The Prius has a low .26 Cd. Lessening the wind resistance through body shape has to be the most maintenance free way of lowering consumption and thus emissions. Those savings last for the life of the car (provided it's repaired after any crack-ups). Tires that offer low rolling-resistance are also a proven way to reduce fuel consumption. The tradeoff is typically that ride and handling suffer, but we're not sure how true that is anymore. A lot of it comes down to tuning the car for its prospective audience, and efficiency-geeks don't typically feel the need to go whipping around corners (though you could do it, and be efficient at the same time!).
Lastly, weight reduction is a huge factor. Cars today are heavy. Using composites and aluminum where possible helps, and safety equipment isn't light, either. Not only that, vehicles are expected to come full-boat loaded. Power everything, nice stereos, HVAC that'll roast marshmallows in the winter and chill sodas in the summer, etc. The Prius really shines at delivering a remarkably normal driving experience for all its technogeekery. We're just curious how the Prius would do without the weight of the battery pack and electric motor, and a little more gumption from underhood (perhaps throw a supercharger on the engine, making it a Miller Cycle).
Let's make sure we're clear here - this is not Prius hating. We're just wondering out loud about possible solutions that would yield across-the-board efficiency gains for all the cars that are not blessed with Hybrid Synergy Drive. We can learn some new tricks from the hard work that the Prius team has undertaken, and we'd love to see Toyota lead the way applying bits and pieces across their entire line of vehicles.
Reader Comments (Page 1 of 3)
SherbornSean 9:13AM (12/28/2006)
What about those skinny tires? If you're willing to trade grip for economy, that's the first place to start.
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sp 9:40AM (12/28/2006)
If that was true, then people would produce petrol Camry's that get 50 mpg, wouldnt they? Wouldnt GM love to have an petrol car that does 50 mpg?
And you suggest to put supercharge in it? Yeah... so much about being serious publication...
As to the EPA revisions, all it will do is bring Prius down to more normal 50 MPG, which still cant be reached by other cars... it will also simply kill the city mileage of small cars, or any car for that matter.
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epilonious 9:44AM (12/28/2006)
I'd think a better question to ask is what can you NOT duplicate in a regular car versus a Prius:
1. Full Planetary Gear Transmission: The Prius is the only car that has this because the Prius's motor is actually powerful enough to drive the car on it's own. I've always felt that the greatest technological feat of the Prius is the transmission that has less clutches, belts, and other power-losses and instead chooses to simply route power directly to the generator, wheels, or motor depending on the drive mode.
2. An electric motor powerful enough to move the car: This isn't an "electric booster" like in the Honda Hybrids or the "green line" GM cars... it's a big motor that can actually scoot around and leave the engine completely off (as opposed to sitting at idle until your foot is off the brake). So far the ONLY cars that have city mileage better than highway mileage are the hybrid synergy powerplants and it's because of the big motor.
Really, the simplest, closest thing you can do to achieve prius-esque efficiency is buy a diesel... but they will be stinky because deisels are logical extension of inscrutably-high compression and high temperature burns.
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Vince 9:47AM (12/28/2006)
Imagine what kind of efficiency Toyota could get out of a diesel engine...
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Mark 9:50AM (12/28/2006)
I don't know if the EPA revisions will kill city mileage for small cars. I drive a 5 speed Protege5 and regularly get 30-33mpg in the city. The EPA sticker is 25 city, 30 hwy. So how does that figure?
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Mike McDermott 9:49AM (12/28/2006)
Not just skinny tires, but properly inflated tires. How many extra gallons of gas are burned every year because people don't manage their tire pressures?
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Steve C 9:53AM (12/28/2006)
SP, a supercharger is not a blue-sky, out of the question idea for this hypothetical Prius. A supercharger coupled with a turbocharger is what VW has developed for its Golf sized autos in the near future. It gives great power and economy of a diesel. It maybe one of the engines of the future.
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Bonita 9:54AM (12/28/2006)
Squeezing more efficiency out of a Prius is kind of like putting lipstick on a pig. There is one word for this car's looks: FUGLY.
If you like the Prius, buy one while they make them since 2008 will be its last year. Since the Corolla is going hybrid in '08 next to the also-homely Camry, there will be no need for 3 hybrid sedans similarly sized.
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Dale Waller 3:10PM (12/28/2006)
Another viable tool for any car is Orbital Corporations Air-Assisted Gasoline Direct Injection. It seems to me that it would be more efficient than the Toyota "Dual-Injection" system.
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JR 10:33AM (12/28/2006)
Toyota already has diesel engines in use abroad. Don't think I've ever heard talk of them bringing 'em to the US. From the UK Corolla (www.toyota.co.uk):
The 2.0 litre turbocharged D-4D engine* - 114 bhp, maximum torque 280 Nm, maximum speed 116 mph, acceleration to 62 mph 10.6 seconds, fuel economy on the combined cycle 49.6 mpg, emissions 151 g/km.
* Figures based on Corolla 5-door with manual transmission.
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Oliver 10:45AM (12/28/2006)
Who cares?! Are people really that broke? Must we count each MPG? Seriously guys.
Oliver
(Yes, the one who drives the 10 MPG Range Rover Supercharged)
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Zo 6:19PM (12/28/2006)
#3 - you had me until you talked about the diesels. Modern diesels do not have the smell of the original diesels and the new low sulfer fuel will have less of a stink. In the EU there are diesels that are getting 40 and 50mpg. Too many people are hung up about what desiel used to be that they can't see the advantages. Get behind even a 06 TDI and you don't smell anything.
Most all of fuels saving of any hybrid is in city driving or heavy traffic situations where the electric motor can run.
On country roads, highways or hilly areas the hybrids have nothing on standard cars. This is why desiels are a better solutions -- they do much better on mixed mode driving than a hybrid.
What I see happening over then next few years is people buying cars that are less general purpose but more purposefull. For example, people in metro-area who usually run short trips in crowded city areas may lean towards desiel-hybrids. Suburban areas will see more desiels and gas engines except for motorcycles, mopeds, classics or later models cars will slowly go away never to be seen again in the next 20yrs
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case 10:48AM (12/28/2006)
its happened many times before
check it!
http://www.theautochannel.com/news/2006/09/04/020700.html
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Bill 11:12AM (12/28/2006)
JR, #10
Remember, 49.6 Miles per IMPERIAL Gallon = 41 miles per US Gallon.
I'm a big fan of diesels, but so many people (Including car mags, NYT, and blogs) throw out those great UK diesel MPG ratings without verifying the facts.
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Johnny 11:29AM (12/28/2006)
These cars are ugly and borrrrrrinnngggggg!!!
No real car enthusiest drives one.
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Robert 10:58AM (12/28/2006)
UK fuel economy numbers will be slightly inflated (different gallon). So, that's about 40 combined. There are other companies with better diesels than Toyota.
The fact is the Prius averages around 45 for most people (if you claim you always get 50s, then I smell a lie somewhere). How much of that is battery and how much is all the tweaks? For the performance, it would be difficult to get 45. If you strip out the battery, you could have a slow trip to 60 and probably average 45+ on the hwy, but your city mileage would take a beating (probably like 30-35). So the battery adds something.
If you really want to see what the battery adds, then look at the Ford Escape or the Toyota Camry. Contrary to epilonious up there, Ford's hybrid system runs on battery only as well. (Yes, it is similar, but Ford developed theirs seperately. The Escape also has a similar CVT to the Prius because its from the same supplier).
Well, the Escape on the highway with the hybrid system has usually gotten 26-27 mpg in road tests, versus about 25 for the regular 2.3L. Swinging around a city, it has gotten about 26-28 depending on magazine versus around 20 for my rental car the other week. Not bad. Where it really shines is in stop and go where someone averaged over 50 in the Escape. You see similar numbers for the Camry. About 34-36 on both city and hwy versus EPA of 25-34 for the standard 2.4.
These cars differ in a couple areas: weight (they're 300+ pounds heavier), a CVT and an Atkinson cycle engine. The numbers you see on the highway are probably a little lower than you could get out of just the Atkinson cycle engine (because of the extra weight), but the city figures are much better, period. The Atkinson could never match that.
If you are looking for more significant increases, you'll have to wait for batteries that hold more charge and electric motors that drive cars up to higher speeds. Plug-in hybrids will add an interesting dynamic as well as the cars will be able to rely on the battery longer (assuming they can build a good enough battery). Maybe in 2009-2010 when the next gen of hybrids are due.
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AZMike 11:01AM (12/28/2006)
well, it's great to finally see the air leaving the Prius baloon.
here in Arizona, dealers have these teeny cars choking the lots. it's great to see "choose from 50", and prices with substantial discounts from MSRP. for you folks in California, that's the big sticker next to the little one with an additional $5,000-$10,000 tacked on that you must pay. being trendy certainly has a high price, doesn't it?
I just love to see all the Toyota-is-so-smart-and cares-about-the-enviornment comments. just remember their new Tundra factory in Texas; they anticipate a first year run of at least 150,000 units. that's 150,000 gas-guzzling pickups, about the same number as they sell hybrids worldwide.
it's all about the $$$, folks. as soon as the hybrid market dries up, it'll be history. for those doubters, just take a look at Honda. the Insight and Accord Hybrid are both history. just imagine what a nightmare finding parts will be in a few years.
Mike
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Andy 11:08AM (12/28/2006)
"Imagine what kind of efficiency Toyota could get out of a diesel engine..."
Lost by the added per gallon premium...
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aaron 11:19AM (12/28/2006)
like this is even news.
prius and most hybrids are garbage. 7-8 year payback period assuming no catastrophies and driving like an angel.
I'd love to know if all the nutswingers actually would man up and save their allowance to buy a hybrid.
We saw the study saying americans want more fuel efficient cars, yet the sale of hybrids is shit this year.
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Rene Curry 11:17AM (12/28/2006)
Oliver,
Actually MPG matters a lot if you have a long daily commute. I have a 110 mile a day round trip drive.
I used to buy old 70s unloved low mileage cars that have proven drivetrains. I could get them for $2-4K. If I could get 18-20 MPG with some tweaking I saved a ton of money over buying a new one. (cheap insurance & safe too on my 79 Cougar 302)
Now that formula doesn't work with present gas prices unless I downsize my car and get better mileage. I now have a $2000 1600cc Pinto stick. With taller rear tires, electric fan, electronic ignition it get 30-40 MPG depending on my driving mix & speed.
The taller tires in the back also helps because I am always going downhill :,)
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