Can we "pulse and glide faster?"

Hmmmm... I get some electric at 65 (I haven't tried faster yet), and I get 50+ MPG on the highways even with a new, 'tight' car. This is SOOOOOOO much better than anything else I've ever driven, have you driven better??? I certainly agree slower (the speed limit!) is better for MPG, but that sure isn't the car talking... And what's so bad about driving the speed limit anyway???

Confused,

 

Yes, like anyone, I certainly wouldn't mind even better MPG, but I'm not willing to make myself a impedance on the roadways to get even better MPG (read: wide variations in speed). I personally think 50 MPG is just fantastic on a 5-passenger 5-door (driving normally, using today's technology).

Until something real-world (driving normally) comes along that's better, I'm certainly thrilled with the gas economy of a motorcycle!

 

What you're asking about is being researched, with real Priuses, at U.C.-Davis and other places.

As these experiments sift down, we'll see, I'd guess, several "boosted-battery" configurations and/or EV-mode options emerge. Toyota may even adopt some proven modification other than its EV mode available in Europe.

The hybrid concept offers so many promising possibilities (as shown even by Toyota's other electric motor configurations, including one used on a van sold in Japan, and on a 'concept car' you can see on Toyota's website) that I think we're just at the beginning of hybrid development that will exceed all our present hopes.

Eventually the laws of physics (and gravity) will impose ceilings. But we're just on the floor now.

 

When driving at a speed that is fast enough for the gas motor to be at a good point on its efficiency curve, it is BETTER to run off the gas motor. There is a thermodynamic and conversion loss taking the energy stored in gasoline and converting it to mechanical motion of the engine crankshaft, and there is an additional conversion loss in going from there to stored electrical energy. The most efficient steady state is to run the ICE.

In addition, while the planetary gear lets the gas engine and electric motor balance out power at different loads, the gearing and the nature of torque versus speed for the electric motor means it can contribute less at high speeds.

Why then the hybrid? Because we don't always drive at steady state. You don't need nearly as much power to cruise as you do to accelerate; the combination of a smaller, lighter gas engine plus the electric motor boost provides the extra juice for acceleration. When the power you need to move the car is below what would put the gas engine into its range of optimum efficiency, you can drive the gas motor a bit harder and capture some if its energy into the batteries. When you hit the brakes you can recover some of your energy of motion into the batteries. You then have the batteries to help you accelerate, to power things like the air conditioning when the car is coasting so that the gas engine can turn off, and (since you have the energy there, why not?) to drive the car on the flat and level under certain conditions.

Consider the present-generation Honda Civic Hybrid versus the Prius. The HCH only charges the battery through rengenerative braking, and only uses the electric motor for an acceleration boost, yet it nearly matches the Prius in gas mileage. I chose the Prius both because it's roomier inside but also because it pulls out all the rabbits it can from the hat and I like that. However, the closeness of the HCH mileage performance illustrates how cruising on the electric motor is not the main contributer to improved gas mileage; a smaller, lighter gas engine and regenerative braking/electric acceleration boost provide much of the total benefit.

 

I agree with your reasoning.. And to comment on HCH efficiency.

Honda was brilliant with their 1.3L IDSI platfrom which uses a 2 valve per cylinder engine and not a 4 valve like Prius has. 2 valve engines are more efficient at lower RPM driving. (which is of course itself innately more efficient than high rpm driving which increases heat and friction losses) In a 2 valve engine, the "mixture motion" induced by the piston sucking air on the intake stroke is called "axial swirl" were the mixture swirls around the axis of the cylinder when its being drawn in. This is more efficient than the " tumble " that 4 valve engines produce. Of course the benefit of a 4 valve engine is higher rpm potential ( ie racing applications ) and therefor broader powerband.. which is not nessecary for a hybrid, or 90% of all other vehicles.

But automakers have been using " 4 valves per cylinder " as a marketing term and for increased power, NOT because it's a more efficient technology.

 

Blixt, you do realize this thread has been dead for over four years. In a situation like this, it probably makes more sense to start a new thread.

Tom

 

I agree with what you have written. However, I think it is only fair to add that VVT-i (and it's predecessor VVT) has done a great deal to achieve the benefits of a 2 valve cylinder while retaining the benefits of a 4 valve cylinder.

 

In essence, gbee42, I agree with your advice for Blixt ... but THEN "somebody's" gonna say "There's already a thread about this .... "

( snicker .... )

 

That would be me, first in line to beat your for starting a duplicate thread.

Tom