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What would the perfect Range Extending Engine look like with current technology? It has been said that the current 1.4L engine used in the Volt is not the perfect type of engine for this type of vehicle. So I started to do some research. The current 1.4L engine produces around 65KW (wiki says that it does this at around 5600rpm) but can also do 75KW at 6000 rpm. According to some other forum contributers they stated that when driving on a steep incline for an extended period of time that the engine does not have enough power to keep the battery at a constant level of charge and in fact the battery will start to drop below the floor buffer if ran long enough. They performed these tests to see if the engine could keep up on the steep incline, so please no "They should have been in Mountain Mode" comments.

In doing a quick google search I found that Lotus has or is developing a purpose built range extending engine to perhaps be sold to OEM's. It is a 3 cylinder that can produce 35KW, or there is a supercharged version that will produce 50KW.

Last summer, word broke out that the 2014 Volt would drop the current 1.4L for a 2.0L turbo engine. Lots of people were complaining that this was too big of an engine for the Volt. So again which is the proper way to go. The lotus engine produce less KW's, than the current 1.4L, but it said to be a purpose built range extending engine. But then if you don't know your terrain or forgot to put the vehicle into Mountain Mode you could potentially drop your battery to the point that you would have to pull over. Where as the 2.0L Turbo is said to be too big of an engine, yet I believe it would produce enough KW to keep the battery at a constant state of charge when driving up steep inclines for extended periods of time. Plus if in the future the ELR is to use the same engine again as the volt then it would be able to provide more performance that is expected out of such a vehicle.

So, is the goal of perfect range extender to be as fuel efficient as possible or is it to powerful enough to provide enough KW's under all scenarios? What do you think?
 

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I am not an engineer and could not say about all the specs. and which engine would be the best. That being said I have always been interested in the ECE external combustion engine or the Stirling Engine. It is supposed to be quieter than an ICE and more efficient. But I could not say for sure if there would be any negatives to this type of engine as a generator in the Volt. My limited understanding of the Engine is that it does not provide enough low end power to get a vehicle going. Something that would be provided for by the batteries in the Volt. Check this out- http://www.stirlingengine.com/faq/#3
 

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You asked the right questionS. No one good answer. I'd argue a TDI, but that runs costs up. The other alternative is the Tesla. trade the ICE for battery capacity and uber car performance.
 

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All you need is an engine with enough power to run the generator, currently about 85 HP. You can do this with any size engine you want, but the goal is do it using the least amount of fuel. However, one consideration I would add is how much noise and vibration does it generate. If it were up to me, I'd love to see an inline six with enough displacement to provide enough power to run the generator at max output at a low RPM. Yes I know more internal friction, and higher cost but one thing I really miss from my 3-series BMW was the smooth inline six, it felt like a turbine.
 

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Many topics on this before.

I wouldn't want anything with a turbo on it. The Volt is already too complicated compared to other cars. I wouldn't want to add any more failure points. Especially knowing that turbos are inherently unreliable.

I'd be really interested in a turbine engine.

I'm also interested in the little motorcycle engine that BMW will be using in the new i3.
 

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To me the ideal generator for an EREV is one that puts out just a bit more power than needed to drive the vehicle on level ground fully loaded at 80 mph. Anything more than that is overkill. Any less and you can't run indefinitely on the highway. Mountain mode should take care of the higher demand situations provided it get's activated at the proper time.
 

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To me the ideal generator for an EREV is one that puts out just a bit more power than needed to drive the vehicle on level ground fully loaded at 80 mph. Anything more than that is overkill. Any less and you can't run indefinitely on the highway. Mountain mode should take care of the higher demand situations provided it get's activated at the proper time.
Agreed. And the Volt range extender is more powerfull than that as it can handle 100mph on flat ground with no issues. In order for the Volt's range extender to not keep up you need to either be racing the car hard or climbing some decent sized mountains. And GM even has that covered with mountian mode.

The Volt doesn't need a more powerfull range extender. It needs one optimized for the duty cycle with the best BSFC to meet the overall average power demands of the user (with a reasonable margin).

For me the power output of the current 1.4L is more than acceptable. But in the future I think GM could design an engine better optimized for the application.
 

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TDI would be the best compromise on paper, but the complexity it would add is asking for trouble.

I like the serial-parallel design in the Mitsubishi Outlander. My perfect EREV ICE would serve not only as a highly efficient range extender but also as an on-demand high output power booster. Like a Clark Kent Atkinson that can switch to a Superman Otto. Nah, that wouldn't be adding complexity at all...

OK Chevy got it right. the current 4 banger is the ideal compromise for now.
 

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I think an engine that could just get the car over 80 mph would be a mistake, simply because it would limit its appeal. Some potential buyers would not want a car with a top speed of 80 mph. The speed limit on some highways in the US is 75 mph, and I have no doubt that many will want to drive over 80, even if I never will.

As far as I'm concerned effeciency is the only thing that is important, since the engine plays no part in getting the car going from a stop except to generate the electricity for it when the battery is low. It only engages with the wheels at higher speeds with low load. Honda has done good work with their Vortec engine and variable valve timing, and that is the route GM may need to take, unless they have other ways to squeeze more power out of less fuel.

A gas turbine sounds intriguing, and this seems like a good application, since turbines don't do well at slower speeds, they are supposed to be very efficient, and presumably they wouldn't vibrate as much as a piston engine? I would be interested in a quieter engine that vibrates less, but, once again, efficiency is priority number one for me.
 

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I think the engine should be the minimum size required to supply enough power to climb a reasonable grade at highway speed. 65mph is acceptable. (what's a typical grade out west in the 'big' hills?) The smallest engine possible will provide the best economy. Since the 1.4 can't quite do it, maybe a 1.6 or 2.0 is right, but I would also try to stay naturally aspirated. No turbo or supercharger to make things more complicated.

Also, an engine designed more specifically to work as a generator may produce more power at the same RPMs. If our 1.4 was truly an 'off the shelf' version just re-tuned for optimized charging, maybe there are some mechanical design differences that would allow a 1.4 specifically designed for charging to be able to keep up.
 

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I think the current engine allows the Volt to go to its top rated speed on a flat (30 kW to go 65 MPH on a slight uphill). I'm sure Walter knows, I think he's run the numbers, so perhaps he'll jump in and help out.
 

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I guess the present engine is OK for a one size fits all power plant. But how many other cars are so equipped? I find the present engine to be completely inadequate. The power it produces for the fuel it consumes and it's horsepower to weight ratio is pretty sad. And for the ELR it is even more inadequate because more will be expected.

A smaller version of the 2014 Cruze Turbo diesel would do a far better job of; driving MGA and thus potentially get 0-60 times in the 6s with enhanced passing capabilities, keep up in mountain mode driving at 80+mph up mountain grades from more that 5 miles or so before PPR sets in and up mileage into the mid or high 40s in any mode.

Not that this should necessarily be the default but certainly an option.

And, a turbo diesel is a simpler power plant than any twin overhead cam high compression spark engine.
 

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A smaller version of the 2014 Cruze Turbo diesel would do a far better job of; driving MGA and thus potentially get 0-60 times in the 6s with enhanced passing capabilities, keep up in mountain mode driving at 80+mph up mountain grades from more that 5 miles or so before PPR sets in and up mileage into the mid or high 40s in any mode.
A turbo would require a different motor and probably major changes to the drivetrain. Ditto for the diesel. And both would be more complex and expensive. I also don't see why a 2.0L engine would get better mileage than a 1.4L.

I think I've read where the genset based on the 1.4L on the ELR will deliver 62 kW. That should be enough for all driving other than on the track. Because the 0-60 times are mostly due to restrictions on the battery, changing the engine won't change these times, absent a complete reworking of the powertrain.
 

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I think they should use one of the little itty bitty turbines that JETMAN uses oh his jet pack!
 

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You are correct 80 MPH may be a bit low. I was adding +5 to 75 and forgot about areas with even higher speed limits. I just find the current 100 mph a bit high.

I also find it interesting that some people on the thread want more engine power and some want less.
 

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Just my opinion, but I think the future volt engine as well as many other GM products will be the new HCCI format currently in development
 

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I guess the present engine is OK for a one size fits all power plant. But how many other cars are so equipped? I find the present engine to be completely inadequate. The power it produces for the fuel it consumes and it's horsepower to weight ratio is pretty sad. And for the ELR it is even more inadequate because more will be expected.

A smaller version of the 2014 Cruze Turbo diesel would do a far better job of; driving MGA and thus potentially get 0-60 times in the 6s with enhanced passing capabilities, keep up in mountain mode driving at 80+mph up mountain grades from more that 5 miles or so before PPR sets in and up mileage into the mid or high 40s in any mode.

Not that this should necessarily be the default but certainly an option.

And, a turbo diesel is a simpler power plant than any twin overhead cam high compression spark engine.
No, no, and no. :) The Volt's engine is actually very efficient for a traditional ICE engine, and it is sized very well for the application. The best of breed current Prius engine gets about 8% more power for the same amount of fuel in the best load range. Best of breed small turbo diesels, using fuel with 10% more energy, get almost 20% more power for the weight of fuel in the best load range - with far heavier engines.

The argument about 0-60 times shows you don't understand the Volt's current power train design - you'd need an engine with about 500 ft pounds of torque before connecting the engine in power split could result in the same acceleration the car has now in single motor EV/series below MG B's critical speed.

A modern turbo diesel is certainly not simpler than any twin overhead cam high compression spark engine. It is a twin overhead cam high compression engine itself - with turbocharger, intercooler, catalytic converter, and particulate filter (and/or SCR urea injection.)

Possibly more importantly, the fuel systems on all the ones that meet current US emissions are very particular about the lubrication properties of the fuel - and US diesel fuel isn't great, resulting in 1-2% of CR TDIs having the high pressure fuel pump explode and scatter metal filings throughout the fuel system. (I had an older rotary pump TDI for 6 years, and still lurk on the forums from time to time.

As for the OP's question... What do you expect from the range extender on an EREV? It seems the typical user is using it about 20% of the time - meaning on the one side that it is dead weight/wasted cost the other 80%, and on the other that bad performance and/or NVH should be avoided, since it is used for a meaningful fraction. Peak engine power isn't really a driver, since it isn't necessary for good performance. The engine will sit for long periods of time between uses, but needs to be reliable (there's a much better chance of being stranded away from home if it refuses to start than a traditional car.)

In a traditional hybrid, the focus has been purely on fuel economy - which is why they virtually all have Atkinson engines to get those last few percent of thermal energy out of the fuel. (Honda's first generation Insight had an awesome lean burn engine that got it into diesel efficiency levels on regular unleaded instead - and most efficient ad moderate rpms and power levels. Unfortunately, it won't meet modern NOx requirements.)

In an EREV, I think peak efficiency, while desirable, might reasonably be traded against size/weight, reliability, and NVH - a smaller/lighter engine would give you better performance in the EV modes the car is in most of the time, and one with low NVH would preserve the experience EV buyers love.

Given the above, I think you can make a strong argument that GM did choose the best engine for a first generation EREV with their short development period. The obvious evolution for better fuel economy would be a ~1.8-2.0 liter Atkinson engine, possibly with direct injection and even higher compression ratios. Whether that ultimately makes sense for the platform will have to be weighed - the extra weight/cost and possibly reliability (gasoline HPFPs don't have the best history, either,) with the impact to EV performance vs the additional efficiency in the less common extended range mode.

For the more out of the box crowd, I'd argue that the best near term choice for an EREV is a microjet. :) If you look at the development work for the concept C-X75, the Bladen microjets it had have a lot to recommend them. Much smaller/lighter than a traditional engine, and presumably far more reliable - only one moving part (the compressor/turbine/rotor) and no timing elements. Air bearings mean no lubricant to change, and as proposed it's entirely air cooled (you'd still have to have an electric fuel pump, but it doesn't have to be particularly high pressure.) So it's an engine with no maintenance that can sit forever (no EMM) and be ready to run when you need it. Turbines don't throttle well, but EREVs don't use throttle much anyway. You trade a small amount of ultimate efficiency in combustion and another small amount because it always runs in series. On the noise side, if always run at the same RPMs it should have a couple of predictable dominent frequencies - in which case it's easy to build resonators in the intake and exhaust to kill them. No vibration, obviously.

In the long run, if fuel cells become cost effective (and Hyundai just opened a plant to make automotive ones, so they clearly think they will be,) the EREV is the natural place for one. Silent and as efficient as oxidation is going to get, they deliver power electrically and don't throttle well - an EREV is pretty much the car you need to make it practical.
 

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I agree on fuel cells. An EREV is the perfect place for them. Businesses need a reason to build refueling stations, and car manufacturers need refueling stations to build the cars. With an EREV, you don't need to refuel as often, so fueling stations don't have to be quite so abundant.
The only problem is storage and boil-off, both problems have yet to be solved. Oh and production and distribution... But potentially a great source of power.
 

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The only problem is storage and boil-off, both problems have yet to be solved. Oh and production and distribution... But potentially a great source of power.
There are two main options I can see here. The first is hydrides (store the hydrogen chemically in solids that give off the hydrogen when heated electrically.) The second, which I think may be more practical/better is to store CNG in the car and reformulate to generate hydrogen on board.

I may be confused, but I still think the fuel cell EREV is at least ten years from the mass market, and more likely 20.
 

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Turbine generator is the best way to go, its powerful, extremely compact, only a single moving part in the main powerplant. It can also run off a multitude of fuels gasoline/NPG etc. It runs very smooth, not sure about noise though.
 
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