Businessweek: Ford Shows Why (Ford) Hybrids Aren't Nearly as Efficient as We Think

So the gen3 can shut off the engine at 80mph?

 

Gears are a marvelous invention.

 

You already know the answer and you also know why. That question is rather blatant "troll bait".

The real question is how will stirring the pot help? The goals remain the same regardless of automaker fallout.

 

It spins at about 1200rpm, with valve timing allowing a mere 2-2.5kw being drawn from the vehicle physics.

 

You just said in your comment a statement like you had not read past my first sentence. If you read it and understood, again, I don't understand your disagreement.

1) yes correct the aerodynamics have nothing to do with if a car turns off the ice at low load at high speeds. Aerodynamics though greatly influence how high the load is, lower loads for the same speed is efficiency. No disagreement with your statement, but it does not nullify mine, that the gen II and gen III prius liftback get great highway mileage because of aerodynamics.

2) Yes the electricity does flow in different ways on the highway to implement the eCVT. But that doesn't really do as much at highway loads as at lower speeds, and especially when accelerating or climbing. On the highway a six speed with proper shifts also does a good job. The HSD is different here, but not necessarily better.

3) I am not quite sure of what the difference in power carrier arrangement means. I thought changes to mg1 + universal gear lowered cost and weight, I didn't really read anything about efficiency.

 

Oh okay. So how come this morning when I shifted my Honda hybrid into 5th gear at 1500 rpm, it refused to let me accelerate to 80 miles/hour? (Hint: slow RPMs don't generate enough force.)

 

Accelerating to 80 mph is different than cruising at 80 mph. The power and torque requirements are different.

Have you never owned a bicycle with gears ?

 

No I've always owned a car. My 65 horsepower hybrid can't "cruise" at 80 in 5th gear either. The RPMs are too low & power not enough. (Do you understand the point I'm making? Small engines don't produce enough power to overcome wind resistance...... so they have to spin faster to compensate.)

 

How much power does the Insight require to cruise at 80 mph ? I know for the Prius, and the Insight will be less ...

You would have us believe that you have been driving a car since the age of ... 6 ? Even for you, your bullshitting is ridiculous. I am half tempted to believe that you have never ridden a geared bicycle. It would in part explain your amazing ignorance of the most basic mechanical concepts. E.g., a lower (bigger rear gear on a bicycle) does not produce more power than a higher gear.

 

Somebody's never heard of go-karts. I never had a proper bicycle. You talk about not understanding mechanical concepts & yet act as if my tiny 65hp hybrid engine should be able to cruise at 80 miles/hour and 1500 rpm ("just add more gears or a CVT"). Even the most basic understanding from driving a manual car reveals there's not enough Torque at that low rpm to overcome the wind resistance. I have to make the engine spin almost 3000.

 

You are imagining things. All I said was that a car uses gears to manipulate torque and rpm.

As for your specific question of the Insight running at 80 mph, I can tell you that the Prius has about a 290 Wh/mile energy requirement at that speed. The insight will likely be less, and certainly a manual car with appropriate gearing and the Insight's car body will be less.

For the Prius:
(290 Wh/mile)*(80 mph) = 23 kW energy losses to mechanical and air frictions

Power is related to the cross product of Torque and angular momentum
If Power is in watts
Angular momentum is in RPM, and
Torque in N*m, then

An ICE generating 23 kW spinning at 1500 rpm requires a torque of ~
ICE power in kW * 6

and more generally,
The required torque will be (ICE_power * 60,000) / (RPM*2*pi)

Addendum:
I just drove my Honda Fit to work. I cannot vouch for 0 wind speed or absolute level road, but the car at stable 60 mph was close to 60 mpg (amazing!) at about 2000 rpm, and about 2400 rpm for speeds between 65 and 70 mph. An Insight of course is much more aerodynamic than a Fit.

 

And the equivalent Prius gear for 5th is??? You are comparing a car with 5 fixed forward gears with a car with an infinite number.

I really want to believe you are just stupid and not trolling.

 

Troy - I have two points for you.
1. Buy a scangauge. (RPM)
2. Watch LeMans that was on two weeks ago. (1st place Audi Hybrid, 2nd place Audi Hybrid, 3rd place Toyota Hybrid).

My C can go 80 MPH at under 2,000 RPM.

 

Those are my only two options? I'm definitely not trolling. Perhaps I am stupid, because I don't see how a tiny 1.0 engine (Honda hydrid) can produce enough power to overcome 80 miles/hour wind resistance. One of my insights has a CVT but the CVT still spins the engine almost 3000 rpm. It cannot go lower than that, else the car would slow down (from lack of power).

The Prius C has a larger 1.5 liter engine. Perhaps it can spin 1900 rpm at 80 miles/hour for hundreds-of-miles, but I don't see how that's possible either. The C engine @ 1900 rpm doesn't produce the ~25 horsepower required to overcome 80 mph wind resistance. (Looking at a curve it appears the engine is only 18 hp.)

 

Well, it appears you have a sense of humor. Thank you for surprising me.

What curve are you looking at ? Link ?

Look at this SFC for the Prius G2 and G3 engines:



What power do you get when you use a torque of 80 N*m and 1800 rpm ? I wrote the equation for you a few posts earlier; you only have to plug in numbers and multiply and then divide for the answer ...

 

So?

The big 2.5L engine in my new 2014 Subaru also has to spin a bit over 3000 rpm at that highway speed. The same size engine in my previous Subaru had to spin at least 3600 rpm. And the little 1.6L engine in my partner's '80s-era Integra (considered very fuel efficient for a nonhybrid as recently as five years ago) has to spin over 4000 rpm at that speed.

Looking at a G3 BSFC chart, I think that at 2500 rpm, it is putting out about 32-34 horsepower. And watching the ScanGauge while returning home from a trip yesterday, that was about right.

At steady speed on level road, my little Prius engine always spins slower than my big Subaru engine. It takes an uphill slope of several percent before the Prius spins faster.

 

Is this math result correct ?

About 80 N*m Torque
Power (in kW) = 2.5 * pi * 2 * Torque / 60 = ~ 21 kW

 

When I actually wrote most of that reply over the weekend (posting from remote location failed, and I remained offline since), I was reading a different version of the chart, with a vertical axis marked in 20 N*m increments. It looked to me as producing 90 to 95 N*m, not the 80 you figured.

Looking at the chart you posted, I'll stick with that 90-something N*m. Blue line is Gen3, red is Gen2?

 

That was my guess too.

 

So the 1.8 engine makes about 28 horsepower @1900rpm. The 1.5 engine from the "C" is about 24 on that chart above. The 1.8 can overcome 80 miles/hour air resistance but I'm not convinced the C could, but obviously you know the car better than me.

Anway I'm trying to figure where we're in disagreement: Smaller engines produce less torque than bigger engines (given equal RPMs). The chart you posted shows that. (shrug) I'm starting to wish I had not come to the defense of the Businessweek author.

I should have just followed the crowd and said, "Yeah hybrids are perfection writ large, and any author who says otherwise should be fired." Like what the Tesla CEO did with the Top Gear host who said bad things about EVs. (Though Mr. Musk did eventually lose the lawsuit.)