The other thread got me thinking about this.

How is a "non-plug in" hybrid more efficient than a regular ICE powered car?

My reasoning is that it has to take potential energy and transform that into rotary force twice vs a standard car which does it once.

In other words, the simple equation is

(%eff Electric Motor) * (%eff Generator (ICE)) - (Regen) = %eff of hybrid

example: 85% * 70% - (-3%) = 62.5%

and regular ICE powered car

(%eff ICE) = % eff of standard car = roughly the same

I realize that the generator in the hybrid will be more efficient. However, I wouldn't think it can be more than 10% more efficient (even though it can be tuned for a certain rpm to increase efficiency).

I also realize that the regen is obviously helping with the situation. How much does that actually help? Wouldn't the weight penalty offset the regen?

All of this doesn't even take into account the inefficiencies of the battery charging and discharging.

If you take the charging and discharging into account, the equation for the hybrid looks like this:

(%eff Electric Motor) * (%eff of battery charging) * (%eff of battery discharging) * (%eff Generator (ICE)) - (Regen) = %eff of hybrid

Obviously, this is worse for the hybrid.

There are some people that get real world fuel economy gains from their hybrids. I wonder what would happen if you took a hybrid and put in a gasoline engine that would replace the hybrid system and get the same performance out fo the car.... ....would the car get the same gas mileage as the hybrid?

Feel free to blow my theory out the window!

Thanks,

Rob R.

Simple answer: They aren't burning [as much] fossil fuels and emitting toxins and particles into the air that are wrecking havoc on the worlds climate. So, no, they are not more efficient in terms of energy consumption, but more eco-friendly.

Because energy that usually gets turned into heat during deceleration instead gets recouped to be used to boost acceleration, which is where ICE vehicles use the most gas.

It should also be noted that the engine in hybrids shuts off pretty often. Our Prius will shut down when decelerating under 40 mph, and I can cruise for a mile at 35 mph without having it turn back on.

Constitutional gay slur PC Police problem with everything b4 teh lahk

You're right but you missed a lot of factors such as regen - and the biggest one, city driving. Even on top of the usual 60%+ wastefulness of an ICE, in city driving they spend a lot of time coasting and idling. The electric powertrain uses no energy for this and recaptures a lot of it via regen. This is where you get massive energy savings.

A traditional car burns fuel and converts it to heat even when no motive force is needed from it. A hybrid does a good job of keeping the engine off when not needed. Obviously it works since a Prius gets much better gas mileage than an Echo or whatever the Prius was originally based on. The question isn't whether it works but how it works.

GameboyRMH wrote: You're right but you missed a lot of factors such as regen - and the biggest one, city driving. Even on top of the usual 60%+ wastefulness of an ICE, in city driving they spend a lot of time coasting and idling. The electric powertrain uses no energy for this and recaptures a lot of it via regen. This is where you get massive energy savings.

Yup- mostly about energy recovery.

On long highway drive, hybrids are no better. In stop and go traffic- that's where they gain a benefit. For most of the tests I've run, the CO2 used to accelerate the car during an emissions test (a short time) is the same as the CO2 used to keep it at a steady speed (most of the time). The more transients, the worse the fuel economy. So if you can recover the energy that is wasted going into the brakes- or at least some of it, you can use it on the next acceleration.

Idling is a very small portion of fuel, as is the decel. But non zero for sure.

As for a volt style set up, the theory there is that you can run the engine in a much smaller window, where the engine is more efficient, therefore gaining a little more efficieny. In theory. As a side note- if one was going to go fully down this path, I would not choose an Otto cycle set up- it's main benefit is that it's quite flexible, and is good at delivering a very wide range of output. There are better cycles if the duty cycle is more limited.

A friend, who is a electric car fan, was loaned a new Volt for a couple of days. he gave a rather detailed report on another site. there is a lot of room for argument.

I actually did account for regen. Is it really that large of a payback?

I also specifically did not talk about plug-in type hybrids (like the Volt) That is another ball of wax.

As far as the decel and idling goes... I was under the impression that a newer car under deceleration does not inject fuel. (Why would it?)

A lot of newer ICE powered cars also have a stop start feature.

I am gaining knowledge here, but I am not convinced yet....

In reply to alfadriver:

Better cycles like the atkinson cycle (right?). Or whatever the name of a gas turbine cycle is (Brayton? Can't remember from over a decade ago!).

Rob R.

Alfadriver pretty much hit it. Hybrids are great in city conditions because the ICE seldom if ever runs. Its a double advantage since it stops the two biggest problems of regular cars at once. (Tail pipe emmisions & increased fuel consumption ). When it comes to highway travel the hybrids are no better, and possibly a bit worse than comparable conventional cars.

I used to get a good chuckle when I would see a prius passing my sprinter van at 80+ mph, since it was quite likely that my fully loaded work truck was consuming less fuel.

I've been seeing a lot of Tesla S models recently, I don't laugh at them, I envy them.

I envy the Tesla also!

Totally different vehicle there.

As is the Volt.

Rob R.

wvumtnbkr wrote: As far as the decel and idling goes... I was under the impression that a newer car under deceleration does not inject fuel. (Why would it?)

A manual under significant engine braking will cut fuel. An auto will drop into the highest possible gear and basically idle (it'll downshift as it hits idle revs in each gear).

mtn wrote: Simple answer: They aren't burning [as much] fossil fuels and emitting toxins and particles into the air that are wrecking havoc on the worlds climate. So, no, they are not more efficient in terms of energy consumption, but more eco-friendly.

where do the ULEV vehicles fall in here ?

in the past weren't there some cars (notably Honda and probably others) that claimed that there cars exhaust gasses were cleaner than the air they were taking in ... sounds like marketing hyperbole to me, but knowing how dirty the air is LA used to be ...

wbjones wrote: in the past weren't there some cars (notably Honda and probably others) that claimed that there cars exhaust gasses were cleaner than the air they were taking in ... sounds like marketing hyperbole to me, but knowing how dirty the air is LA used to be ...

No it's actually true in a lot of heavily polluted cities. You wouldn't want to breathe it but the exhaust would contain less pollutants.

ULEV just means Ultra Low Emission Vehicle (there are different grades like LEV, PZEV and ZEV, etc)...not necessarily efficient (in fact emissions control equipment decreases efficiency slightly).

Obviously it would have to be an EV to get the ZEV (Zero emissions) rating and a hybrid to get the PZEV (Partial Zero Emissions) rating, but a LEV or ULEV is usually a regular ICE car with low emissions.

Another theoretical advantage of hybrids is that because they have the electric motor to assist with acceleration they can get away with a smaller gasoline engine than a comparable non-hybrid car, so you can use a 60hp electric with a 60hp gas engine and get comparable acceleration to a 120hp normal car, but when you're cruising down the highway only using 40hp, the hybrid's 60hp engine is more efficient than the normal's 120hp engine. Most hybrids, however, don't really take advantage of this and just add the electric motor onto the smallest available gas engine already in the lineup and just tune that for max efficiency, so you get a small gain, but not as much as you could have.

HappyAndy wrote: I used to get a good chuckle when I would see a prius passing my sprinter van at 80+ mph, since it was quite likely that my fully loaded work truck was consuming less fuel.

Yeah, I don't think that's true. At steady state highway speeds the main thing that affects gas mileage is aerodynamics. The engine size also matters as a bigger engine will be shedding more heat. The aero of a Prius is massively better than the aero of a Sprinter. Drag does vary as a cube of velocity so the difference between 80mph and 90mph is pretty pronounced, but it's still not likely to offset a Sprinter's higher cd and frontal area and bigger engine.

Hybrids do not get worse gas mileage on the freeway than their standard counterparts. The hybrids almost always get better gas mileage than their standard ones due to having the smaller ICE engine.

Civic: 25 city/39 hwy
Civic Hybrid: 40 city/43 hwy

Toyota Yaris: 29 City / 35 hwy
Prius: 51 City / 48 hwy

(I believe the Yaris and the Prius share a platform, though the Prius has some modifications to the platform.)

wvumtnbkr wrote: A lot of newer ICE powered cars also have a stop start feature.

That's where I was going to go.....I know the VW lupo does/did this. What other examples do you know of?

There's also the issue of variable displacement/cylinder shut-off engines. Didn't caddy build one like that?

JoeyM wrote: That's where I was going to go.....I know the VW lupo does/did this. What other examples do you know of?

Recent VW Scirocco Bluemotion.

Some new American cars are bringing back cylinder deactivation but it's a tricky technology. New engines cycle which cylinders they deactivate rapidly because sustained deactivation greatly accelerates wear on the cylinder.

1 - Regenerative braking. Normally you use the brakes to convert kinetic energy into heat, sound, and light.

2 - Engine can be shut off at stops, rather than idling.

3 - ICE engines have a range where they operate most efficiently. Low RPM and high load (standing start) is definitely not it. Electric motors provide instant torque from a standstill. The ICE is at its peak efficiency cruising at relatively constant rates, which is where electric motors are least useful. The two power systems compensate for the weakness of the other allowing you to have a smaller ICE and lighter battery packs.

In reply to Beer Baron:

1. True
2. ICE vehicles can do this too.
3. True (except the smaller battery part)

Where does the weight factor in to all of this?

Rob R.

Regenerative brakes? So you never have to replace the brake pads?!

JoeyM wrote:

wvumtnbkr wrote: A lot of newer ICE powered cars also have a stop start feature.

That's where I was going to go.....I know the VW lupo does/did this. What other examples do you know of? There's also the issue of variable displacement/cylinder shut-off engines. Didn't caddy build one like that?

Yep. A lot of full-size trucks do it too. Which explains the 20+mpg highway rating on some.

wvumtnbkr wrote: In reply to Beer Baron: 1. True 2. ICE vehicles can do this too. 3. True (except the smaller battery part) Where does the weight factor in to all of this?

Mass means inertia, which means greater force required to accelerate. Weight means greater downward force which means slight increase in rolling resistance (which is still less parasitic than wind resistance). Accelerating mass from a standstill is what is going to suck up the most energy.

Curb weight on a Prius is about 3,150 lbs. Not the fattest pig out there. For comparison, the Nissan Leaf weighs 3,350, despite being dimensionally smaller. I'm guessing the Leaf has a larger batter pack because that is the only way it can provide range.

EastCoastMojo wrote: Regenerative brakes? So you never have to replace the brake pads?!

Some landspeeders use magnetic brakes. They turn forward momentum into a magnetic field and there are no wearable parts. Power is proportional to speed though so the closer you get to stopping the less stopping power you have...but they turn useless well above street-legal speeds.