Battery for acceleration, Deisel Engine For Cruising?

[Angel And The Wolf]

According to this worksheet
Calculate HP For Speed
my 2010 Prius only needs 14 Horsepower to maintain 70 MPH on the flat. If I had a plug in rechargeable battery powerful enough to accelerate the car to cruising speed, (and help on the up hills), and let a small efficient diesel engine (say, a 16 HP Yanmar TS 190) [url=http://dieselparts.com.au/engines/ts190-yanmar/]
take over cruising duties, I wonder what Highway MPG I could expect.

[redpoint5]

Well, the math is easy.

What is the fuel consumption of the Yanmar to output 14 horsepower to the wheels?

Take your 70 miles driven in 1 hour, and divide by 1hr of 14 horsepower fuel consumption.

Lots of losses involved with converting genset power to electricity and then kinetic energy.

Conversions are:
chemical energy (diesel) > thermal > kinetic > electrical > *chemical energy (battery) > kinetic

*assumes output charges battery rather than directly used by motor

I'd like to see a vehicle with a 50 hp high efficiency engine that charges a relatively large battery which drives powerful motors. Perhaps a car could be made that does 0-60 in 4 seconds but gets 40 MPG on the freeway.

[Angel And The Wolf]

Originally Posted by redpoint5

Well, the math is easy.
Lots of losses involved with converting genset power to electricity and then kinetic energy.

I had assumed Diesel to transmission, not electric. The Prius ICE drives the planetary gear set directly. The Diesel engine would replace the Toyota four cylinder. The battery and motor turns the planetary gear set into a CVT by running the various elements at varying speeds, but that's not necessary.
, (when in ICE mode only.) Ordinary cars with planetary automatic transmissions use brake bands to give three speeds. There is no need to go through mechanical to electrical to battery to electrical motors to mechanical.

[oil pan 4]

Lots of losses, head winds, bumpy roads, hills, ect.
14hp, in laboratory conditions maybe.

[mort]

Originally Posted by Angel And The Wolf

I wonder what Highway MPG I could expect.

I looked at the Yanmar pdf. It says that the engine gets 162 g/hp hr
Assuming 14 hp that's 2268 g per hour = 5 pounds. Assuming 7.1 lb per gallon for diesel that's .7 gal or about 100 mpg. But the "netto" is 400 lbs for that engine. I don't think the Prius engine is even half that weight and can produce 140 hp, and has bsfc of 230 g/kw hr (Brake Specific Fuel Consumption (BSFC) Maps - EcoModder) which is 176 g/hp hr, about 10% worse than the Yanmar.
If a stock Prius gets 50 mpg at 70 mph (see http://ecomodder.com/forum/showthrea...tml#post204481)
I'd expect the Yanmar to get about 55 mpg.
Furthermore you will need a huge battery and electric motor to provide the power for acceleration and hill climbing. With that added weight...
-mort

[Angel And The Wolf]

Well, yes, this would need the PHEV batteries and motors. One correction: the prius ICE gets 98 hp @ 5,200 rpm. The electric motors provide the other 36 HP.

[Angel And The Wolf]

Originally Posted by oil pan 4

Lots of losses, head winds, bumpy roads, hills, ect.
14hp, in laboratory conditions maybe.

Yes, I said "On the flat". I also said "plug in rechargeable battery powerful enough to accelerate the car to cruising speed, (and help on the up hills)".
, and I would pad the HP by a few HP, not just use the 14 HP version.

I'm not even sure, in this day of "Premium gas priced" deisel, how much better MPG would be needed to offset the higher priced fuel.

Before we bought the prius, we looked at VW deisel Jettas. Glad we didn't fall for THAT!

[redpoint5]

I'd like to see something like the Gen 2 Volt but with a lower output engine and higher output motors and possibly bigger battery.

The engine and both motors are used to directly propel the vehicle during acceleration. The relatively underpowered engine could run near peak efficiency while cruising and recharge the battery for when extra oomph is needed for acceleration and hills.

Problem is, the system would be too complex for the general public because they would set the car to use all of the electric energy, and then rely on just the low output engine to pull up a steep mountain pass. Either that, or they would allow the engine to recharge the battery for short town trips that could have been done on 100% grid electricity.

[Ecky]

It wouldn't be as much better as you think, and probably much worse. Some thoughts:

An engine isn't most efficient at its maximum output. Here's a BSFC (efficiency) chart for my Honda:




Even though the engine can output 67HP, its efficiency is terrible there. It's actually most efficient producing ~17HP, or approximately one quarter of its max output. A 14HP diesel would probably most efficiently produce far less power.

On top of that, the efficiency of Honda's and Toyota's recent gas engines (particularly in their hybrids) is very close to that of the best diesels. Diesel fuel has a bit more energy per gallon, but it's also usually correspondingly more expensive. So in terms of cost per mile, it's basically a wash.

You already know this, but your car already uses an electric motor to aid in acceleration, and the transmission does its best to keep the gasoline engine in its most efficient range given the power output and capacity limitations of your battery and electric motors, and the acceleration you're asking of it. If you want to keep the engine from revving into less efficient ranges, simply accelerate more slowly. The Prius already does exactly what you're asking of it, and the engine is already close to the best out there, and is appropriately sized for the car - much smaller and fuel consumption might actually go up. Improvements over what you have will come from things like weight reductions, lower rolling resistance, improved aerodynamics, and having a larger battery which can be charged from the grid. And, FYI, there are plug-in conversions for your Prius:

https://parts.olathetoyota.com/blog/...-plug-in-prius




Be aware that electricity is not free. With low gas prices and high electricity prices, it's generally not that much more economical to drive on electricity. Sure, you're not burning gas, but you'll pay for it on your electric bill.

[Joggernot]

Is this BSFC in the Wiki? Brake Specific Fuel Consumption (BSFC) Maps - EcoModder