Engine Options

[FrankNvolt]

Seeing as we're stuck with some type of ICE why not offer some options.

I would suggest a small turbo Disel as the first option. And i would like to see the motor tuned to run at only one speed, it's max eff. point for generating electric power. Any excess should be dumped into the battery. You could really change the ICE MPG if you tune them for an exact power point!

Second would be small gas turbine, again tuned to single power point.

[emartin00]

The engine is in a way set to charge at a max efficiency point, or more precisely, a number of them. Originally it was designed to run constant RPM, but they thought people would find it disturbing when you slowed down and the engine was still revved up. They instead tuned it to run at an efficient point based on the power required for driving.

I would love to see some new engine options. A small 1.0-1.5L turbo would be great, or as you mentioned, a turbo diesel. I've thought about the turbine engine as well, but I'm not sure its the best option for a car based on the extreme heat output.

[Steverino]

Previous discussion about this point out that turbo's are not very beneficial for electric power generators. When was the last time you saw portable electric generator advertised as "turbo-charged"?

[jsmay311]

Previous discussion about this point out that turbo's are not very beneficial for electric power generators. When was the last time you saw portable electric generator advertised as "turbo-charged"?

I'm not an engine expert, so maybe someone who is can correct me if I'm wrong...

But isn't the idea here that a turbo-charged engine can allow for improved fuel economy because it allows you to use a smaller displacement engine while maintaining the necessary maximum power output with the help of the turbo?

I.e., under normal, low-to-medium power conditions, the smaller engine would provide improved fuel economy. But under heavy power demand (climbing a mountain, for example), the turbo could kick in to provide the extra necessary horsepower. (?)

This is how I understood the Ford EcoBoost approach, at least.

Also, why would the original Volt concept have used a 1.0L 3-cyl turbocharged engine if it wasn't well-suited to an EREV?

[FrankNvolt]

emartin00 "They instead tuned it to run at an efficient point based on the power required for driving.
"

I'm not sure that's the case actually, I happened to do this little trick on my Volt. The car was in park and in "Mountian Mode", so the ICE was active. then while at a standstill, and in Park position, i pressed the gas pedal, the engine actually did rev up! I was perplexed actually Maybe they were expecting me to do a Nuetural Drop start to beat a Prius off the starting line

Also, I've purchased large 200-400KW generators for backup power at my work, they do have turbo chargers on them (though not advertised, true) even one that runs on Natural Gas. Now that would be and EXCELLENT ICE option come to think of it

[saghost]

emartin00 "They instead tuned it to run at an efficient point based on the power required for driving.
"

I'm not sure that's the case actually, I happened to do this little trick on my Volt. The car was in park and in "Mountian Mode", so the ICE was active. then while at a standstill, and in Park position, i pressed the gas pedal, the engine actually did rev up! I was perplexed actually Maybe they were expecting me to do a Nuetural Drop start to beat a Prius off the starting line

Also, I've purchased large 200-400KW generators for backup power at my work, they do have turbo chargers on them (though not advertised, true) even one that runs on Natural Gas. Now that would be and EXCELLENT ICE option come to think of it

The original post was right. GM allowed you to speed the engine for familiarity, and in case you needed to speed charging for some reason. The gas pedal only does that when sitting stopped (though accelerating hard causes the engine to run faster too.)

For the larger case, you're thinking about one efficiency like it's the only thing to worry about. Running at a single speed means either a.) being limited in speed for long distance to the average power output, or b.) having too much power for most cruising cases - meaning you have to store that power and cycle the engine periodically.

The thing is, you lose ~20% of the power in the process of storing it and recovering it from the battery. By contrast, the difference between the 1400 rpm or 2700 rpm WOT bsfc and the best it can manage (which is at 1700 rpm,) is somewhere around 5%. So tell me, which one makes more sense and gets more economy? GM chose wisely. (When the car is using less power than the 1400 rpm WOT power output, the car adopts a different strategy that does involve cycling the engine.)

I'd love to see the gas turbine, but you have to trade the benefits (reduced pollution, multifuel nature, simpler operation, possibly cheaper if built en mass) against the drawbacks (lower efficiency, especially since it'd be pure series at all time, greater development efforts, public image of danger, noise levels [which might be solvable if it runs at a single RPM - it's amazing what tuned echo chambers can do.]) On the whole, I doubt I'll be seeing the gas turbine soon, as much fun as it'd be.

Diesel offers little benefit and several drawbacks (I had a TDI for 8 years and enjoyed it, but it isn't the right choice in the EREV paradigm, I think.) First, the engines are ~30% heavier for similar dispalcements and power levels (and require turbocharging.) Second, meeting US emissions with diesels is *hard* (US emissions are designed for gasoline cars - my Jetta actually had to be dirtier [generate CO, which diesel don't natively] to meet the NOx emissions target.) As a result, the emissions controls are expensive, and the cars are sensitive to fuel quality (current generation TDIs eat their high pressure fuel pumps and spit metal shards throughout the fuel system if there's a little water in the diesel - TDIclub is full of stories.) A DI Atkinson or HCCI engine can get similar economy without the cost or emissions issues. About the only benefits to diesel in this application are the long term stability of the fuel and for the eco crowd the burgeoning availability of bio-diesel.

Natural Gas is hard to store in adequate quantities, and not readily available everywhere - the exact opposite of what you want for an EREV engine.

[Steverino]

Here's the turbo discussion that I referred to http://gm-volt.com/forum/showthread....161#post169161

[FrankNvolt]

Now we're talking! That Capstone seems interesting. I think you would have to go with the 65KW unit 65Kw/746w = 87 Hp which is close to the ICE they are using, but weights in at what 300Lbs, I forget the ICE weight, still at least an possible option. Thanks John for the info

[blackr3]

I'd like to see more use of rotary engines. My other car is a Mazda RX8, which has a "tiny" 1.3 liter engine with 232hp. Rotaries are very compact, very light, mechanically simple, and so smooth that you'd barely notice it running. Plus, Mazda has them running on hydrogen.

[saghost]

Now we're talking! That Capstone seems interesting. I think you would have to go with the 65KW unit 65Kw/746w = 87 Hp which is close to the ICE they are using, but weights in at what 300Lbs, I forget the ICE weight, still at least an possible option. Thanks John for the info

Yup. So the turbine with its controller weigh 50% more, occupies four times the space (won't fit under the hood,) is sold for around $30k, and will reduce your fuel economy by 15-20% compared to the existing car (based on their 26-29% efficiency on the specsheet, assuming you figure out how to covert its 600V DC to the car's 360V without losing any of it or adding any weight.)
Sounds like exactly what we need...

Again, it's a cool idea, but the technology isn't quite there yet. I'll be interested to see if anything comes of Bladon's axial micro jet program.