Hybrids less efficient than ICE
 

Energy Efficient Technologies

Okay, so that's the very mild Hybrid is less efficient than a direct injection (with a turbo or blower). Just a tinsy little lie to grab attention. And then subtract the 7.5% boost from forced air injection.

But I really thought it was the fact that CVTs got a 6% boost and a dual clutch got a 7% boost that stood out most! Is that unicorn poop or due to the frictional losses common to CVTs.

Also if cylinder deactivation is so cool, could we see v4s and w3s? Guess not because Direct Injection means you don't need separate banks to do the job.

Most DCTs don't have torque converters and don't need them.

Some CVTs, particularly those built robust enough to survive being mated to powerful engines, use torque converters, which hurts efficiency and it's probably what brings the average down. But the most efficient CVTs are just as good or better than DCTs... and lighter, too. But they're very fragile.

I have long considered mild hybrids to be made of unicorn poop.
They cost far more than their non hybrid counter parts, their milage usually can always be matched by a non hybrid. Then to top if off you have all that hybrid stuff that is going to break some day and need to be repaired.

The only time they seem to offer an advantage is if you are going to be driving a lot of city miles and sell the car before some part of the hybrid systems breaks.

The electronics aren't usually the problem though right? I know batteries tend to go frequently. That aspect of hybrids is definitely stupid, batteries have very limited cycle lives and hybrid operation requires them to cycle like crazy.

IMO a hybrid should either be something with a very large and durable battery pack (if that exists lol), or only short term energy storage (flywheels, ultracapacitors, hydraulic).

Depends on what exactly you consider a "mild" hybrid. If the 1st gen Insight fits, there is a heck of a lot of real-world experience (some of it mine) proving you wrong.

But to the topic, a hybrid probably is less efficient than a pure ICE of the same size. The point is that with the hybrid you can downsize the ICE, using one which by itself would barely allow the car to get out of its own way.

The Insight-I is in a class by itself - 2-seater, great aero, etc. - and can't be easily compared to any other car, except an Insight-I with the hybridization turned off. MetroMPG is driving one of those and is getting milage comparable to "healthy" Insights with hybrid drive.

It would be better to compare two similar cars with different (hybrid and non-hybrid) drivetrains. For example, the Civic, only the non-hybrid version should also get the goodies from the hybrid (rear lip spoiler, lower suspension, etc.).

The problem is that in many cases the electric engine is just an addition to the ICE, without downsizing. Take the Peugeot 3008 Hybrid4 for example: the ICE is a 2 liter turbodiesel with 120 kW/163 bhp, which is probably more than enough already, plus a 27 kW/37 bhp electric engine to make flooring it even more fun:rolleyes:

An interesting data point on this is the X-Prize Knockout Round:

The FVT is a serial (aka series) hybrid, and it did not use the genset at all in the X-Prize. It only used the battery power, so while it carried the weight of the genset around, it still managed 152.5MPGe.

The ICE powered cars all were very light -- the only one that weighed close to the hybrids and electrics was the BITW diesel Metro. So, weight matters less than drivetrain efficiency. But, when an ICE is involved, it may be that low weight trumps the small efficiency gains of a parallel hybrid? Of course the very low aero drag of the four Edison2 VLC cars also greatly improves the average of the 6 ICE powered cars, and advantage that only a couple of the electric cars could match.

Obviously, hybrids are better in most real world situations, with the crop of cars on the roads today. Another point is that the really efficient ICE cars are veeeery slooooow.....

I almost 100% agree with this post. Where I differ is, if you are going to use a very large battery pack then it should be battery powered exclusively.

A genset and a smaller battery would allow much greater range.

Regeneration should be by capacitive means with efficiency of at least 80% far beyond that of a sytem like the Prius which can not regen at more than half that percentage.

regards
Mech

But he's willing to tolerate its inability to get out of its own way without hybrid assist

Sure, but you'd also have to make sure they have equal performance, especially acceleration.

From what I've read, my Escape Hybrid accelerates about as fast as a V6 Escape, while being rated to get 30-50% better fuel economy.


I think the CVT category should be split in two, planetary based (Prius and some other hybrids) and belt/chain based. I would be willing to bet that planetary based CVTs are more efficient.

Aren't planetary gears simply... one gear?

The electric CVTs of Toyota and Ford suffer when one of the motors needs to provide torque near 0 RPM. The electric motor efficiency there is low. Belt type CVTs have some slippage.

I think the Lincoln MKZ is a fair example, but the V6 is substantially quicker than the hybrid, 0 to 60 in 7.2 for the V6; 8.7 for the hybrid. The EPA combined is 21 MPG for the V6 and 39 mpg for the hybrid. (The list price is the same.)

-mort

a planetary gear has a few gears:
1 sun gear-which is typically the drive gear
2 (or more) planet gears-which connect the sun to the planetary gear
1 planetary gear- which is a large ring that touches the planet gears.

So there is a tiny gear, surrounded by more similar sized gears, wrapped in a larger circle.

...it's all about simple mathematics:

90% = 90% (one conversion)

81% = 90% of 90% (two conversions)

73% = 90% of 90% of 90% (three conversions)

66% = 90% of 90% of 90% of 90% (four conversion)

...the fewer times you convert energy, the "...more of it (energy) you have...", or stated conversely the "...less you've lost."

Hello niky,
I saw MPGranger's post, and I didn't think it really addressed your question.
I'm assuming you know what a planetary gearset is, and you've seen or studied them for aircraft or toys or something. So yes, a single planetary gearset presents one gear ratio.

But for something like an automatic transmission, in general using planetary gears you need one planetary system for 2 ratios, plus you need an additonal planetary set as a reverser. So for a 6 speed transmission you need 4 gearsets.
Matthieu Rihn developed the "ravigneaux" gearset using 2 sun gears, 2 ring gears and 1 planet carrier. By using clutches and brake bands, you can have 2 planetary gearsets produce 3 forward ratios and reverse.

However, the planetary CVTs that vskid3 was referring to is the electrically controlled "power-split device" used in the Prius and other hybrids. It is based on the 1970s U.S patents 3,566,717 and 3,732,751.

-mort

Thanks... I'll check it out... having seen some diagrams and driven the Prius... I still can't wrap my head around the thing!

HowStuffWorks "How Automatic Transmissions Work"

HowStuffWorks "Toyota Prius: Lots More Information"

The current Hybrid technology appears to be in jeopardy of being overtaken by advances in ICE. However there is a new evolution of Hybrid technologies that could prove to be much better once critical mass of production and acceptance reduces manufacturing costs. Anything that gets away from using batteries is a plus!
Here's an article on the flywheel Hybrid advances that is worth a read.

KERS of the hybrid car:Flywheels and ultracapacitors give you a 10-second jolt | ExtremeTech

One gear, by itself, is pretty useless as a means of power transmission. To change ratios- the purpose of having gears in the first place- requires at least a second gear so that there's a gear mesh. Then there's the planetary gears, usually illustrated with 5 gears and 6 meshes.

There is no amount of improvement in an ICE that can get it to be even HALF as efficient as an electric motor. The best electric motors are about 94% efficient, and I very much doubt that any ICE (or ECE for that matter) will ever exceed 47% efficiency peak; let alone average above 42%.

So I think that all efficient cars in the future will have battery packs and plugs. The only question in my mind is whether they also have an engine, and how they use that engine i.e. in a serial or in a parallel mode.

Before you get all excited, you have to think about how an engine works best: and that is at a narrow range of RPM; and in "bursts". All those MPG contests when the cars get >1,000MPG only have a very small engine and they only run the engine in short bursts and at a very specific RPM. These cars are hardly practical in the real world.

Contrast this with the SolarWorld GT car built by Bochum University, which is relatively practical and very efficient -- it only uses solar PV panels on the car, and it is driving around the world.

Another example is the Edison2 VLC: the ICE version got 110MPGe on the EPA Combined test -- which is fabulous for a 4 seat car. But the electric version got ~245MPGe, and an AC electric drivetrain probably would be over 300MPGe, and it would be far quieter and a lot quicker, and smoother, etc.

I don't know what all this talk is about hybrids not being able to get out of their own way without the use of hybrid assist. Modern cars are way overpowered compared to the cars from the past. The 1st gen Insight (sans hybrid assist) is higher powered (67hp ICE, 1887lbs., 2 seats) than a 68 VW Beetle (54hp, 1900lbs., 4 seats). I drove a 68 bug for years and had no problem getting around in busy traffic. A hybrid without assist has about the same power to weight ratio as the typical car from the 60's and 70's, and, except the Rabbit diesels, we didn't consider them to be sluggish in traffic.

Practical experience, having owned one for what, eight years now. The worst is taking off from a standing start, especially if you're on a bit of an incline (as I have to do to get out of my side road on to the main, and at times busy, highway). If the assist doesn't kick in, I'm lucky to get going at all.

Heck try a 58 Bug with about half the 68s horsepower, or a 59 AH Sprite at about 1200 pounds and maybe 40-45 HP, but the doors would hardly stop a shopping cart.

regards
Mech

Try a Microbus with an engine no more powerful than a Bug's!

Have done: if not those exact models, then similar -I think my Sprite was a '61 model. Different gearing, I suspect. Or perhaps an engine tuned to produce more low-end torque. Anyway, they would get up and go, where the Insight W/O assist just doesn't.

Anyhow, if you think the performance of a hybrid on ICE engine only is adequate, that just means you can downsize the engine further. Same with any other improvement in ICE efficiency: add the hybrid system to it, and you increase efficiency by the same factor.

Why would ICE advances outpace Hybrid Tech? Wouldn't half the Hybrid Tech be included in ICE advances? I know the true answer is that, to keep costs down, the most radical ICE treatments don't make it on the more expensive hybrid models.

Realistically, the most practical AND efficient vehicle would be a TDI series/parallel hybrid. But this would cost a lot!