Chevy Volt - Electric Car

[Simon F]

At freeway speeds you lose a lot of power from aerodynamics. Starting and stopping does lose some as the regenerative braking is not 100% efficient, but the high speed losses for aerodynamic reasons are worse for fuel economy.

With a petrol vehicle I never found that in practice. My previous car (rust its soul) had a trip computer that showed fuel consumption and it definitely achieved better results on motor/freeway journeys than city driving. Mind you, it was a VW Scirocco so probably slightly more aerodynamic than, say, a typical US brick.

 

[_xxx_]

why would you guess that? do you base that on the real-world mileage versus the epa mileage for regular hybrids?

Based on my experience working on hybrid development. That car would have to be either a huge battery pack with a chassis wrapped around it or some miracle we'll all bow to

especially when hybrids can recover the majority of that energy (AFAIK, it's ~80%).

What? You're even more optimistic than Chevy PR

Those numbers are all bogus, all just "best case" stuff which rarely ever occurs like that in real life.

Simon, freeway is definitely way less consumption than city for any car, no exceptions.

 

[Arwin]

With a petrol vehicle I never found that in practice. My previous car (rust its soul) had a trip computer that showed fuel consumption and it definitely achieved better results on motor/freeway journeys than city driving. Mind you, it was a VW Scirocco so probably slightly more aerodynamic than, say, a typical US brick.

We were talking hybrids. A regular petrol vehicle suffers from all sorts of other stuff that kills its efficiency in city driving. Compare the following differences, among others:

- no regenerative braking
- no 'engine off when not moving or not accellerating'
- no electric motor to help out with the initial accelleration from 0-20 that fuel engines are very inefficient with

Basically, a lot of the stuff that hybrids win over regular cars comes into play especially in city traffic. Which is why hybrids are better at city traffic than at highway speeds (for one, if there is no other traffic, then you have a constant speed at a good rpm, you're idling very little, no braking, etc., so there is much less to gain - though mind you the Prius for instance does still gain some, among others from running with less engine resistence, regenerating even a little from coasting, benefitting if there is hills involved, and even in the most flat of conditions 5l/100km is not bad compared to what most cars do that weigh 1275kg!).

 

[Arwin]

Simon, freeway is definitely way less consumption than city for any regular non-hybrid car, no exceptions.

fixed. Because no matter how much you may know from cars, in this case one counter-example is sufficient

 

[RussSchultz]

Simon, freeway is definitely way less consumption than city for any car, no exceptions.

So explain the inverted city/hwy numbers for the prius?

 

[Sxotty]

Why does one have to explain it? The escape and others are the normal way.

Lets look at some actual data instead of made up stuff.

http://www.fueleconomy.gov/feg/hybrid_sbs.shtml

What do you notice?
Prius 48/45 city/hwy.
looks like city is still better as was said. The better the aerodynamics and the worse the hybrid system the more it will tend to look like a normal car. So if you have a horrible fake hybrid system you will still get better hwy worse city, but a decent one should move you the other way.

 

[Arwin]

$32 to fill up the Prius in the US :| ... ugh. I can't believe it. I pay 60 euro.

 

[RussSchultz]

Why does one have to explain it? The escape and others are the normal way.

Well, he was making a claim that hwy was always going to be more efficient than city.

I showed a counter point and asked him how it fit his assertion.

 

[Sxotty]

Well, he was making a claim that hwy was always going to be more efficient than city.

I showed a counter point and asked him how it fit his assertion.

Oh I thought you were attacking the other claim that hybrids work better in the city than hwy.... silly me.

 

[Farid]

Here is a good source of info.........
http://www.gm-volt.com/

here is also a cooler Opel version, the Flextreme ........

http://car-reviews.automobile.com/Opel/concept/2007-opel-flextreme-concept/3185/

They called this car/concept-car Flextreme? You got to be kidding me...

 

[_xxx_]

Well, he was making a claim that hwy was always going to be more efficient than city.

I showed a counter point and asked him how it fit his assertion.

You showed me estimated theoretical (PR) values. I'm talking from real-life experience. Now I dunno how you drive on the freeways over there, maybe you all drive 20 mph max. and do stop and go games all the time? Don't think so, but you tell me.

You consume most fuel to accelerate and lose energy when braking. You certainly do much less of that when driving constant speed on the freeway, thus consume less fuel. The only exception is if you drive near the redline all the time, then the freeway will consume more. With any regular car.

As for current hybrids, Prius as an example doesn't really save you any serious amount of fuel unless you drive like a grandpa. The Lexus SUV hybrid consumes a bit more (super plus) fuel than a comparable diesel, while offering less torque and max speed. Tested that myself on a mixed city/freeway course in a direct comparison to an M-class diesel of about the same size.

 

[RussSchultz]

Those aren't 'theoretical', they're from tests.

Out of curiosity, does Daimler/Benz have a regenerative hybrid system?

 

[Sxotty]

Those aren't 'theoretical', they're from tests.

Out of curiosity, does Daimler/Benz have a regenerative hybrid system?

It could not possibly be a bias
_xxx_
Seriously do you understand aerodynamic drag? Look at the link I posted those are numbers from vehicles actually driven.

 

[ShaidarHaran]

You showed me estimated theoretical (PR) values. I'm talking from real-life experience. Now I dunno how you drive on the freeways over there, maybe you all drive 20 mph max. and do stop and go games all the time? Don't think so, but you tell me.

I'd love to do 20 mph during my morning and afternoon commute. Usually I'm stuck in stop-and-go for an hour or so doing 5-15mph most often (when moving).

 

[Frank]

The 40 miles electric-only figure sounds quite realistic to me: they carry a 16 KW/h Li-Ion pack. Theoretically, you can get up to 125 miles out of that, depending, although you'll never make that in real life and with such a car. If you count in the losses, you lose about a third, say 80 miles at a very steady constant 50 mph. So, the claimed figure of 40 miles - 60 km sound right on the mark.

Of course, if you like to floor it, that will drop.

And an acceleration of 0-60 in 8.5 seconds is quite acceptable to most people, I think.

All in all: nice car!

 

[Mintmaster]

You consume most fuel to accelerate and lose energy when braking. You certainly do much less of that when driving constant speed on the freeway, thus consume less fuel. The only exception is if you drive near the redline all the time, then the freeway will consume more.

Okay, fine, even if regenerative braking is only 50% efficient, that means that, by your own assertion that most fuel is used in acceleration, hybrids will have a massive reduction consumption in the city. On the highway, in contrast, hybrids have almost no advantage compared to regular cars. Given that a regular car only has around 30% boost in efficency on the highway, it's entirely reasonable for city mpg to be better than highway mpg for a hybrid.

Mechanical<->electrical conversion has been very efficient for many decades, especially since theoretically it can be done at 100%. The only thing that's tough is making it continuously variable to act like normal brakes, thus requiring fancy DC voltage conversion. With good electrical design, I doubt that 80% conversion is unrealistic.

 

[nintenho]

Regarding what I said previously about the Prius plug-in hybrid concept only getting 8 miles on electric-only versus the Volt getting 40, it seems that the Prius concept is using the standard Prius battery which is 12 times smaller than the Volt's batter so it's likely that the next generation plug-in Prius will get similar or better numbers.

xxx, theoretically, you could get better mileage in a city with a hybrid if it's efficient enough and I'm sure most hybrid owners would note the mileage difference they are getting in the city and on the highway.

however, the plug-in hybrid has the advantage of cheaper energy even when you're "paying" for it so that's probably why the car industry will move towards it.

 

[_xxx_]

Those aren't 'theoretical', they're from tests.

Out of curiosity, does Daimler/Benz have a regenerative hybrid system?

Like 3 or 4 different systems in development, still not decided which of those will go into series production. Still testing, benchmarking etc.

Sxoty, it's much less influence than what you think. Braking/accelerating >>>>>>> aerodynamics as far as the consumption goes, since you will rarely be able to drive with constant speed for longer periods.

And we do compare the developments to other brands out there all the time, thus I know that those nubers are bogus. Either they pulled all the tricks to make it look good or just plain lies.

 

[Arwin]

And we do compare the developments to other brands out there all the time, thus I know that those nubers are bogus. Either they pulled all the tricks to make it look good or just plain lies.

Are you also calling my personal test of my own Prius bogus? Because if so, I'd like to know your exact test parameters. I can imagine some parameters (notably cold start, shorter or longer distances) influencing the results one way or the other. I own this car, and I know what it does and at what speeds. I've tried all sorts of stuff to see what worked better, and since the thing almost drives itself, it leaves plenty of time to track consumption, of which it gives detailed graphs. I've also tracked a whole lot of miles with it.

Nevertheless, most official benchmarks (which are for the official ratings and often are linked to purchase tax and road tax) still rate the Prius higher for city traffic than for highway traffic.

 

[_xxx_]

Nevertheless, most official benchmarks (which are for the official ratings and often are linked to purchase tax and road tax) still rate the Prius higher for city traffic than for highway traffic.

Answers it right there.

Why Prius has high(er) consumption on the highway sometimes is clear, the batteries get drained pretty fast and not much is recouped during a constant drive. In the end if you ONLY drove the highway with constant speed, you will consume the same amount of fuel as a non-hybrid. If you only drive the city and are often stopped by traffic lights for longer periods, batteries will be drained at some point and the engine will start in order to compensate so your consumption will go up.

It gets better the better your batteries, so that will change (I hope). Because it's very dependent on the driving style, track, even stuff like the temperature outside, it's very hard to give any "correct" hard numbers anyway.

As for the tests, they differ but in our case there are norms and also certain internal guidelines and well known courses in all flavours of different freeway/city/land/bad road/slippery/ice and snow/desert etc. mixtures.