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Old 07-01-2012, 09:29 PM   #1 (permalink)
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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.

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Old 07-02-2012, 12:28 AM   #2 (permalink)
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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.
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Old 07-02-2012, 04:11 AM   #3 (permalink)
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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.
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Old 07-02-2012, 04:53 AM   #4 (permalink)
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Quote:
Originally Posted by oil pan 4 View Post
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).
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Old 07-02-2012, 12:47 PM   #5 (permalink)
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Quote:
Originally Posted by oil pan 4 View Post
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.
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.
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Old 07-02-2012, 03:15 PM   #6 (permalink)
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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 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.).

Quote:
Originally Posted by jamesqf View Post
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 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
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Old 07-03-2012, 08:52 AM   #7 (permalink)
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An interesting data point on this is the X-Prize Knockout Round:

Quote:
So the lowest MPGe of an electric drive; the AMP'd Sky was 86.7MPGe (Tango was 86.8), while the best of a car with an internal combustion is the Edison2 #97 at 101.4. (Actually, the FVT has a ICE powered generator onboard, but did not need it *at all* in the X-Prize. It would be great to see how the eVaro does for MPGe in charging mode!) The hybrids all were all below the 67MPGe -- except the WWU at 92.5 (and the FVT).

The average of the 12 vehicles using electric drive MPGe (I'm including the FVT in this) was 134.7MPGe
The average of the 6 hybrids (not including the FVT) was 61.26MPGe (Please note, these are all parallel hybrids?)
The average of the 5 internal combustion drive cars was 82.92MPGe
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.....
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Old 07-03-2012, 09:04 AM   #8 (permalink)
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Quote:
Originally Posted by serialk11r View Post
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).
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.

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Old 07-03-2012, 01:14 PM   #9 (permalink)
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Originally Posted by Piwoslaw View Post
MetroMPG is driving one of those and is getting milage comparable to "healthy" Insights with hybrid drive.
But he's willing to tolerate its inability to get out of its own way without hybrid assist

Quote:
It would be better to compare two similar cars with different (hybrid and non-hybrid) drivetrains.
Sure, but you'd also have to make sure they have equal performance, especially acceleration.
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Old 07-03-2012, 04:38 PM   #10 (permalink)
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Quote:
Originally Posted by jamesqf View Post
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.

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