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Doctorate in Mechanical Engineering, entreprenuer
Interests: diesel and gasoline engines, cars, aircraft, railroads, electric drives
Recent Activity
I think that it is a beautifully designed car and it is probably really pleasant to drive but I still think that the price differential over the Chevy Volt is way too much. Maybe, I could justify a $10,000 price differential but the differential is apparently more like $30,000 (2016 ELR price and 2015 Volt price?).
This car looks really nice and the coefficient of drag of 0.26 is impressive but it will not get 60 mpg. With the diesel, it might get a real 45 mpg and with the 3 liter turbo-charged gasoline, it might get high 20's with careful driving. The numbers that come out of the European and Japanese driving cycles are very much inflated.
The Malibu is a larger vehicle than the Volt which more the size of the Chevrolet Cruze. Anyway, I am glad that GM is bringing out a reasonable strong hybrid onto the market. With the Volt, the Bolt (which needs a better name in my opinion) and the Hybrid Malibu, GM will have a reasonable electric lineup to build on.
Probably the only practical way to make hydrogen without generating CO2 is high temperature electrolysis using nuclear power and even then it is questionable. We will never have enough "renewable" electric power to waste on electrolysis. The power density is just not there. A good estimate for average electric capacity is 1 w/m2 for wind energy and about 25 w/m2 for solar photovoltaic for a reasonable sunny location. I did a calculation for the land area just to supply the current electric requirements for the US using 1.5 Mw wind turbines with the recommended spacing and ended up with twice the area of Wyoming.
Carnegie Mellon drove an automated car from Pittsburgh to San Diego(?) sometime before the DARPA Grand Challenges. So it was at least 12 years ago. They probably needed to take over for fueling and stopping but I believe all of the actual highway driving was done fully automated. Also, they did not announce their intentions to do this before hand.
If I understand this correctly, you could lower the smog level or at least the ozone level just by driving thru polluted air.
With a 50 mile range, the GM Volt looks like the clear winner among the PHEV vehicles announced today -- the Hyundai Sonata with 22 miles, the Mercedes-Benz C 350 PLUG-IN HYBRID with 19 miles, and the Volkswagen Cross Coupe GTE with 20 miles. For a point of reference, I live in the wide open west (Salt Lake City area) with a daily commute of 44 miles on the rare days that I only drive from home to work.
D You are probably confusing vehicles (maybe with the Plug-in Prius which has a limited electric power output). The current Volt has always run in full electric mode as long as the battery has sufficient charge and has a listed top speed of 100 mph with the notation in parentheses -- Test Track so it may be computer limited to 85 or so. Anyway, it has 149 hp in electric mode. With the battery depleted, it still mostly runs electrically with the ICE driving a generator. At higher speeds, the ICE clutches in to drive the wheels to optimize fuel efficiency.
Peterww GM has lots of dynomometers and exhaustively tests all of the engines. What the estimated torque figure means is that they have not finalized all of their ignition and fuel mapping. With computer controlled ignition and injectors, there are many possible parameters to set to optimize emissions, power, response, and economy. One of the more amazing videos of GM engine testing is on the following video which show a fully gimballed dynomometer running a race simulation on a Corvette engine with the engine tipping for cornering, acceleration, and braking loads.
I really doubt that there patents are worth much other than the goodwill that Toyota hopes to gain. All of the car companies have been working on this for a long time and probably have more patents than they know what to do with. Fuel cells have been worked on since 1838 (177 years)! Talk about a technology that has taken a long time to become commercially available. In 1959, Allis Chambers (remember them?) introduced a fuel cell tractor.
Maybe they have decided that the best use of their fuel cell patents is good publicity.
Out of curiosity, I wonder how much the CO2 is increased when you burn peat to make electricity.
This is not exactly new. The Chevrolet (GM) Corvette has had transverse glass leaf spring for both the front and rear for quite a while -- 15+ years?
Lad, Most 2-stroke diesels are relatively clean running while most 2-stroke gasoline engines are quite dirty. 2-stroke engines require a positive manifold pressure to work. The small 2-stroke gasoline engines use the back side of the piston to pump the fuel-air mixture into the combustion chamber and therefore need to have oil in the mixture as the bearings, etc are exposed to the fuel-air mixture. 2-stroke diesels have superchargers and/or turbochargers to supply the positive manifold pressure and the fuel is directly injected into the combustion chamber in a normal diesel manner. It is possible to build a clean burning 2-stroke gasoline engine but it requires a super-charger, direction injection and probably either poppet exhaust valves or opposed pistons. Most 2-stroke diesels either use poppet exhaust valves or opposed pistons and are referred to as uniflow scavenged engines. Most 2-stroke gasoline engines are loop-scavenged.
I am guessing that it is a student project. It looks like something that my students would build and needs some packaging and professional design work. However, if the cost is comparable to a pure battery vehicle, it is probably a good thing but you do not typically need as much range in this type of vehicle.
This only works when the engine is running and producing heat and even then you only get 1 KW from a engine that produces 450 KW (600 hp). A solid oxide fuel cell would probably be a better device as you would use it instead of running the engine when you only need electric power. Also, a modified turbo charger that includes a motor generator would generate more power using excess exhaust heat. But having said that, 1.5 million for some applied research may be a reasonable deal.
Davemart Theoretical efficiency is the efficiency you would get taking the ideal compression, ideal combustion, ideal expansion without any losses. Indicated efficiency is the efficiency that you would get taking the actual engine pressures so it would include compression, combustion, and expansion losses but would not include mechanical losses. What really matters is brake efficiency as this is the power measured with a dynamometer and compared with the theoretical power of the fuel consumed. However it is good to know something about theoretical efficiency and the indicated efficiency as that gives you some idea where your losses are occurring and what to strive for. You will not do better than Carnot efficiency but you can certainly get more than 45% as modern uniflow 2-stroke ship diesels get better than 50%. One of the potential problems with the proposed engine is that they say nothing about pollution controls. If they have high pressure, high temperature combustion which leads to higher efficiency, it also leads to high NOX generation. However, it may still be better than the 2-stroke SI engines running a mixture of gas and oil used for leaf blowers, etc. Those should be banned.
This is probably a very nice car and will get good mileage but as mahonj points out it will not get 57 mpg in the real world. The US (EPA), Europe, and Japan need to get together and have consistent mileage testing that is somehow close to what people could expect to get with normal driving. The US (EPA) ratings are probably much better than either the Japanese or European ratings but they have also had problems (and some deliberate cheating).
Roger Pham I am not sure what you are trying to say. GM designed the power train assuming that most of the driving would be electric only but that it would be fairly seamless when it was ICE was operating. Anyway, on engine design issues, engine RPM does not matter. What matters is mean piston speed. Interestingly, most engines run about the same mean piston speed whether they are large ship diesel running 88 RPM or small model airplane engines. Concerning turbochargers, GM certainly has experience with turbocharged engines as they have been building turbocharged engines for more than 75 years (Allison V-1710) and turbocharged cars for more than 50 years. (I had one of the first, a 1963 Corvair Spyder.) Their current 2 liter turbocharged direct injection engine is one of the more power dense engines available for a street vehicle with 136 hp/liter. However there is detonation limit to how much boost you run with a spark ignition engine. A turbocharger is basically a positive feedback device (more boost generates more exhaust which generates more boost, etc) so you can not run a turbocharger without someway to limit the boost otherwise something will blow up. Yes, GM could run a smaller turbocharged engine and they already have current turbocharged engines that would work but they probably decided the cost was not worth the gain as the engine does not run most of the time.
I should have put in a link for the Top Gear Prius vs BMW It is in the 2nd half of the 6 minute clip and the BMW was actually a 400 hp M3 with a 4 liter V8. They got 17 mpg with the 1.5 liter Prius and 19 mpg with the 4 liter BMW. One of the reasons that the Prius normally does so well on fuel economy is that it so under performing that there is little or no incentive to do anything but drive it slowly. The Volt has enough performance and drives well enough in normal driving that it is not an unpleasant car to drive.
Arnold. The Ackermann steering mechanism is a very useful approximation but it is an approximation and is only correct straight ahead and at one steer angle. It gets even more complicated when you consider individual slip angles for the different tires at different cornering loads. If you had individual servo driven wheel steering, you could do a much better job of having a correct solution for different steer angles and for different driving conditions. We build a agricultural harvester and I did the steering design. It has Ackermann steering but it is steer by wire and has 2 hydraulic cylinders but only one sensor. If we added a second sensor, removed the connecting tie rod, and added some more software, we could potentially have a better steering solution. However in our case, in probably will not make a lot of difference as the steering or Ackermann is optimized for the max steering angle. The machine is usually either going straight or making a minimum radius turn at the end of the field. At some point, I would still like to experiment with individual wheel steer. Individual wheel steer would probably make the most difference for high performance or racing vehicles.
I think that the ultimate solution is to have individual motors that can be driven at different torque levels. It would also be best to have individual steering drives so that the wheels can steer independently. The commonly used Ackermann steering mechanism ( ) is only correct straight ahead and at one radius.
I do not think that an Sonic based EV will compete with the Tesla Model S but it may help to push along EV market if they can keep the price reasonable. I also wish both GM and Tesla well in their EV endeavors and I would agree with Davemart that GM might do better by basing their new EV on a larger platform. However, I do wonder about the long term viability of Tesla. I know that this is heresy among some of the reader of Green Car Congress but currently Tesla's market cap (shares outstanding * share price) is about half that of GM which is not realistic and they are not currently making money so they are funding their continued development and production by selling stock. This is not unusual with startup companies but it can only gone on so long.
Henrik, I think that I can explain why the S60D and S85D out accelerate the S60 and S85. If you have sufficient power to induce wheel spin, you can launch faster with AWD. After the initial launch power when you no longer have enough power to spin the wheels, power to weight is more important.