The secret must be relentless incremental improvement driven by rigorous engineering economic analysis of the various hardware/software combinations. Since all of the energy input comes from gasoline, that would be a ripe area to optimize. I agree the engine is awesome.

 

I would suggest the secret sauce is the Hybrid Synergy Drive which consists of the two motor generators and the planetary gear system, or e-CVT. This system allows them to decouple the ICE rpm from the road. As you have found you cannot rev up the engine in idle, but the HSD can rev it up and do it while you are driving. It does this to optimize the rpm and efficiency of the ICE. The freedom to do that independent of road speed and gearing is what I consider to be the refinement that others lack.

That said, I will admit that I have not researched the Hyundai system all that closely. The obvious difference is the 6 speed auto vs the e-CVT. In my initial research I found that Toyota was by far the most experienced (Prius 1996?) hybrid manufacturer. And that they controlled about 75% of the hybrid market share when you included the licensed products with Nissan and Ford. When I saw the gas mileage of the Hyundai, and the not so attractive price of their hybrid, it was dumped from my short list. And Honda's version of the hybrid is very primitive, so it didn't even get a first look.

Remember in a hybrid all the energy comes from gasoline. The battery is just a buffer, and even a source of loss. It only makes sense to use the battery as much as needed to optimize ICE efficiency, and store regenerative braking energy. If you were seeing the battery fully charged all the time, that would be a sign that the battery is too small. I don't see it, but it does run higher in the cold than it does in the summer.

When LiIon is proven for reliability, I think it may offer some more power, but not likely fuel efficiency. In electronics products I have not been impressed with LiIon for life. Right now I think that is the big question mark.

 

I agree. I'm a ham radio operator and the idea of depending on a LiIon battery pack's longevity scares me. First, they are more delicate, and I wonder what the temperature extremes they will see in a car will do to them. Also, I was always led to believe they have a limited lifespan even when not in actual use. And there have been a couple cases of spontaneous LiIon combustion in laptops, and perhaps one instance in the Volt. (OK, I'll admit the longevity of the NiMH technology concerns me a bit, too -- I guess I'm a natural worry wart -- but it doesn't concern me nearly as much as relying on a LiIon traction battery would.)

The e-CVT is really an amazing design -- quite simple and elegant. Toyota really thought outside the box on this one.

 

The NiMh high amp cells that I have worked with in model planes drawing up to 30 amps for up to 3 or 4 minutes at a time seem to be the reliable workhorse battery. They are not that sensitive to overcharging and dissipate heat rather easily. In comparison, the Lithium cells are very sensitive to overcharging and could be a overheating problem depending on how they are cooled. Years ago I read where many companies were working to create a Lithium battery that was more forgiving on being so sensitive to these things.

I'm sure in time they will perfect the LiIon for traction battery use, or the possibility of some unknown new battery may come along that would be even better.

When and if toyota starts using the LiIon batteries in 'all' their hybrids, then I would not be worried at all about them.

Now that I think of it I never heard of any problems with the '07 or newer TCH with the traction batteries. Maybe a few with a weak cell which would be very rare till the car gets over 200K on the clock.

restamp, your mention of the e-CVT transmission was the second reason I bought the TCH knowing it would run part time on battery power. I was tired of owning cars that auto shifted gears.

 

Thanks for your responses. Alot of good feedback here. I like the comment about integration of all the systems. The instant, torquey power you get is something I really like, even in eco mode. Touch the gas and it throws you back in the seat. This is not something I would expect from a car that delivers such good fuel econ. The eCVT gives that immediate response, but the battery also jumps in to boost the gas engine for power and going up hills.

It sounds like the Hyundai is slow off the line, and when we test drove the Prius hatchback, I found this to be the case as well. At least with the Prius it delivers even better FE.

 

Not sure how gasoline provides energy, when you are rolling down the hill and the battery is being charged by the force of gravity, then by electromagnetic cohesion between the driveshaft and generator, with engine gas supply completely shut down, and at the bottom of the hill you simply go into EV mode and keep driving on battery power, just supplied by the above mentioned, but hey, I am full of strange questions.

The REAL jewel in TCH is its driver. It does not matter how clever the system is. If you have a hypermiler that knows how to be conscientious driver, any system will work. If you have a led footed adrenaline seeker - hey, we got plenty of those here that do 32mpg and wonder, why they bought one.

IT'S NOT WHAT YOU DRIVE, IT'S HOW YOU DRIVE. Relatively, of course.

Personally, I believe that only the original hybrid drive, designed back in the 19th century, is best choice, and proof to it Jaguar Hybrid, that scores over 700 hp and yet does over 60 mpg. What we have in TCH is best they chose to give us, not the best possible. There are plenty of European ICE and diesel vehicles, that outperform what we have, but we will never see them here, or, even if you import one, mpg will drop due to EPA emissions requirements and pretty crappy gas or diesel fuel. Besides, 80 cents difference in fuel costs negates diesels mpg gain anyway.

That being said, out of 25 cars we owned since 1990 - my TCH is a keeper. It IS a very nice vehicle. Can it be improved - well of course. Will Toyota do it? No. Will I buy another one? No.

 

Not sure how gasoline provides energy, when you are rolling down the hill and the battery is being charged by the force of gravity, then by electromagnetic cohesion between the driveshaft and generator, with engine gas supply completely shut down, and at the bottom of the hill you simply go into EV mode and keep driving on battery power, just supplied by the above mentioned, but hey, I am full of strange questions.

Gas supplied the energy to get to the top of the hill. If it wasn't for the gas used, the battery wouldn't get charged.

 

You probably know that a hybrid car uses both a gasoline engine and an electric motor. But greater complexity often translates into less efficiency. So how does this combination of power sources actually cut fuel use?
The basic answer is that electric motors are most efficient for low-speed driving -- they get the car going with a minimum expenditure of energy. Since gasoline engines operate better at high speed, they kick in for highway driving. This teamwork results in hybrids that get close to 50 miles per gallon, a 25-percent improvement over gasoline-only vehicles.
Hybrids often use an Atkinson cycle engine, which is not quite as powerful as a standard motor but uses gasoline more efficiently [source: MixedPower.com].
Engineers have used a number of other design elements to increase the fuel efficiency of hybrids:

• Regenerative braking. In regular cars, the friction of braking generates heat that goes to waste. Hybrids capture that energy and use it to recharge the batteries.
• Aerodynamic design. Every car uses energy to overcome wind resistance, especially at higher speeds. Most hybrids are shaped to cut through the air more smoothly.
• Low weight. It takes less fuel to move less weight. Hybrids use smaller, lighter engines, and automakers employ materials like magnesium and aluminum to cut weight further [source: Hybridcars.com].
• Continuously variable transmission. This type of transmission, which operates on a pulley system rather than using toothed gears, allows the engine to run at optimum revolutions per minute. It doesn't have to speed up and slow down as gears shift. You get the same power while burning less gas [source: Edmunds].
• Efficient tires. The tires on hybrids are often narrower, with less rolling resistance. They are sometimes kept inflated to a higher pressure than other tires.
• Engine shut-off. When the vehicle is not moving, the gasoline engine is turned off instead of idling and wasting gas.
• Electric power steering. In most cars, belts connected to the engine run the power steering. Operating the mechanism electrically means the engine doesn't need to be running to steer easily. The same is true of the air-conditioning compressor, which is driven electrically in many hybrids [source: Edmunds].
• A choice of driving modes. Some hybrids allow you to switch to an economy mode. You sacrifice rapid acceleration for better mileage [source: Vijayenthiran].

Not all of these fuel efficiency designs are exclusive to hybrids. But because hybrid buyers are interested in miles per gallon, engineers try to add as many of them as possible to the cars' engineering.

 

When I first got my hybrid I wished that it had a larger more powerful battery so I could go even further in EV. Now I am questioning that. We've seen a couple of competitor cars come out with Li ion batts and they are a disappointment. Lower fuel econ and not greater. Here's a link to the hyundai comparison: http://www.autoguide.com/car-compar...ar-comparisons/2012-toyota-camry-hybrid-vs-2012-hyundai-sonata-hybrid-2220.html

Somewhat ironically, Im coming to the opinion that the gas engine is one of the real jewels of this hybrid. Quiet, very fuel efficient and fully recharges the battery in minutes without you even noticing the extra load!

Very good link Venzoid, thanks....

 

You titled this thread: what is the secret of the camry's hybrid system?

I don't know any secrets ... and if I did, I couldn't tell them. But this I know: Toyota's hybrid system is the successful result of the corporation's making the tough decision ... and backing it up with financial and engineering commitments ... to pursue hybrid technology.

Toyota probably loses money on every hybrid vehicle it sells, but the corporation gains hybrid vehicle market share with every one that rolls off the dealers' lots. Toyota's accountants probably had seizures during their arguments with the engineers ... but the engineers triumphed. Over time, the cost of developing hybrid technology will lessen, but Toyota has been eating the costs for at the least the past 15 years. Toyota also has been racking up patents on its technology ... patents it can license to other manufacturers.

I tip my cap to those visionaries at Toyota who developed the idea of hybrid vehicles, then made the commitments to bring them to the public at prices the public could afford to pay. We're driving the biggest bargains, and some of the most efficient vehicles, in the automotive world. Everyone else is playing catch-up. We are driving proven machines ... people who buy competitors' hybrid products are buying rolling experimentation.

 

When I first got my hybrid I wished that it had a larger more powerful battery so I could go even further in EV. Now I am questioning that. We've seen a couple of competitor cars come out with Li ion batts and they are a disappointment. Lower fuel econ and not greater. Here's a link to the hyundai comparison: http://www.autoguide.com/car-compar...ar-comparisons/2012-toyota-camry-hybrid-vs-2012-hyundai-sonata-hybrid-2220.html

Somewhat ironically, Im coming to the opinion that the gas engine is one of the real jewels of this hybrid. Quiet, very fuel efficient and fully recharges the battery in minutes without you even noticing the extra load!

Ultimately, it's overall system efficiency that carries the day. And with an ICE, that efficiency peak can be 'tweaked' so the car 'crams for the test' (see Ford Fusion). In general, the higher the expansion ratio, the higher the thermal efficiency of a ICE. There are practical limits to that - and even the best designs will still reject much of them purchased energy into the exhaust or the cooling system. Converting this wasted energy into a useful form is the next frontier to dramatically reduced fuel consumption.

The thing a system like HSD gives you is incremental energy efficiency opportunity. When there is a compelling cost story, HSD system efficiency can be 'kicked up a notch' by putting in a secondary electrical generator, driven by the exhaust heat. The exact nature take whatever form can be produced at a 'good enough' price point - from a thermoelectric solid state device to a Stirling cycle device to a exhaust turbine turning a secondary generator. Such a device could increase the overall energy recovery from the current 20-30 % to maybe 40.

The hybrid system efficiency advantage over the ICE-only vehicles is in recovery of energy previously discarded as brake heat. That is the primary reason why a hybrid will get better mileage in the 'city' cycle than the much-touted Diesel vehicles - they still discard much of the purchased energy in form of brake heat. How effective any given system is in capturing this energy will be determined by inverter capacity and the batteries' efficiency at taking a high-current charge. Properly engineered, both Lion and NiHydride batteries can work - but they have different charging circuit needs to live long.

By all accounts, the '12 Camry - and the '13 Fusion - are examples of the gains still possible in improving energy recovery and system efficiency. Both discard lot of the purchased energy in the form of exhaust and cooling system heat - and that's where the next generations have the opportunity for improvement. So, what I'd expect to see as the 'next big thing':

• Increased expansion ratio, say to 16:1. This, plus the higher energy density of the Diesel fuel, is it's 'secret sauce'. The current Camry engine is only around 12.5:1. Going there will likely require stronger components - but could pay off in smaller package size.
• Tolerance for higher dynamic compression ratio (giving more power for a given nominal displacement) by going to direct injection. The current one is < 10:1, primarily to allow 'regular' fuel. This is also why the TCH engine is 'down-rated' from the ICE-only version - one would expect the higher compression to pay off in form of higher specific output.
• Secondary energy recovery devices downstream of the catalysts. This would improve the steady-state efficiency (e.g. highway speeds), and could be packaged as a muffler.
• Engineering the engines to be more adiabatic devices, discarding less of the energy into the cooling system. That's mainly a materials problem, and going with some ceramic coatings/surfaces in the combustion chamber would seem to be a viable direction. Lots of manufacturing challenges there - cost being a quite significant one.
• Continuing improvement in energy loss management through friction reduction and vehicle weight reduction. Continue the direction of cX reduction by using full underbody trays and better airflow management below and around the vehicle - active grille shutters are an example that's being used on other vehicles to good effect.

 

Well the Europeans have been talking about a diesel hybrid for years (concepts in the 2007 autoshows) and so far nothing. Last summer Mercedes and Toyota said they were going to cooperate (meaning Mercedes couldn't figure it out for themselves?).

Now Volvo is coming out with a v 60 diesel hybrid 400 lb/ft of torque! I don't think it is a parallel system though. Will operate like a Volt I assume. http://www.motorauthority.com/news/.../news/1080602_2013-volvo-v60-plug-in-diesel-hybrid-begins-production-u-s--bound

Here's some reasons why the promises havent panned out. http://www.greencarreports.com/news...s.com/news/1080282_diesel-hybrids-why-they-dont-make-as-much-sense-as-you-think

It seems the electric motors they are trying are about the same size as ours but the diesel engine wont start until it reaches a certain speed. Can you image that? I would say 95% of my starts from a stop light I use gas and electric, or else I would be run over from behind. A 30 hp electric motor does not allow you to accelerate with traffic.

Presumably they don't want to start and stop a diesel engine as frequently as ours. One of the key elements is the variable valve timing of our Atkinson cycle engines and the ability to change compression ratios: How can this happen in a diesel? It needs high compression all the time to run/start?

 

Now Volvo is coming out with a v 60 diesel hybrid 400 lb/ft of torque! I don't think it is a parallel system though. Will operate like a Volt I assume. http://www.motorauthority.com/news/.../news/1080602_2013-volvo-v60-plug-in-diesel-hybrid-begins-production-u-s--bound

Here's some reasons why the promises havent panned out. http://www.greencarreports.com/news...s.com/news/1080282_diesel-hybrids-why-they-dont-make-as-much-sense-as-you-think

It seems the electric motors they are trying are about the same size as ours but the diesel engine wont start until it reaches a certain speed. Can you image that? I would say 95% of my starts from a stop light I use gas and electric, or else I would be run over from behind. A 30 hp electric motor does not allow you to accelerate with traffic.

Presumably they don't want to start and stop a diesel engine as frequently as ours. One of the key elements is the variable valve timing of our Atkinson cycle engines and the ability to change compression ratios: How can this happen in a diesel? It needs high compression all the time to run/start?

I once owned a 52 hp VW diesel Rabbit. It felt equal to a 100 hp gas engine.With it's 5 speed manual transmission it would move out if you got on it. VW had designed the engine to rev up somewhat to half the rpm a gas engine would get. Driving on torque reminds me of the big cu inch V8's in the old days.

Your right, 30 hp is not much power. Looks like the '12 TCH electric power may be 59 hp or enough that I can drive up a overpass at 33 mph while in EV (ECO-on) at 60 mpg.

Edmund's description of the '12 TCH power.

ENGINE TYPE: DOHC 16-valve Atkinson-cycle 2.5-liter inline-4, 156 hp,
156 lb-ft; permanent magnet AC synchronous electric motor, 141 hp, 199 lb-ft;
combined power rating, 200 hp; 1.6-kWh nickel-metal hydride battery pack

 

As in the KungFu Panda movie, there is no secret sauce really... its all marketing with a well balanced engineering and tradeoffs created to get better MPG. To each his own, some will not accept what was sacrificed some will. But that is the package Toyota put together for their hybrids. I wont drive a Prius no matter how many more MPG it does over a TCH, but at least the TCH is comfortable for me so I bought it. Is it perfect? No, there is no such a thing as a perfect car, even if you pay $100K or more for it, you may find an issue or two that you personally do not like while someone else wont care about such.