Not too long ago the car makers where competing with each other on performance—mainly measured by horsepower and acceleration. Fuel economy did not have high attention in the benchmarks for premium cars. This has changed recently and fuel economy is suddenly a major trait that every OEM has on its list.
This trend was not only driven by environmental regulations of various governments but the fuel price itself. Also consumer behaviors have changed a lot and our society is undergoing a paradigm change with regards to our transportation concepts and mobility behavior.
These days more and more new car customers are looking at the datasheets and specifications for fuel consumption and emissions. The prestige and image of many cars are now largely driven by its benchmark fuel efficiency and emission values rather the pure horsepower backed driving performance and acceleration. So this changing consumer behavior and the strong government involvement via rules, regulations and incentives for environmentally friendly cars leads the automotive market towards a new generation of cars to satisfy this trend of “green transportation”. And that’s the main reason why hybrid-electric Vehicles (HEVs) are showing up in every fleet and product line of the major car manufacturers.
What we often forget, especially here in the U.S., is that fuel efficiency and low emissions are not only achieved via revolutionary game-changing technologies like the emission-free electric powertrain of a hybrid vehicle. Looking at the fuel efficiency of currently available or shortly announced HEVs, you would be surprised that this fuel efficiency can be pretty closely matched by a modern diesel engine using state-of-the-art direct fuel injection systems and an electronically controlled and well optimized motor control unit. The big difference comes with the price "bump up" for the technology that the buyer pays.
A diesel engine typically adds only moderat cost compared to a comparable gasoline engine (in the range of approximately $1-2,000). The price adder of HEVs vs their traditional standard combustion engine version is normally at least 2-3 times as high. The reason for this is that hybrid-electric vehicles need to incorporate a complete electric powertrain plus all the energy management and storage systems, a high voltage battery, and plenty of electric systems like inverter, converter, and charger applications into the vehicle architecture.
Therefore the additional electronic content in a HEV is much higher than the little electronics in the motor control unit plus some diagnostic and monitoring sensors which are needed to build a very efficient direct fuel injection system for a modern diesel aggregate in a much more cost effective way.
Checking the numbers
Let’s look at the table below, which shows the average highway fuel consumption in miles/gallon of HEVs vs diesel. There is not much difference between similar sized and powered diesel and HEV cars. The emission values of those cars are also in a comparable range. Only the pure city consumption of the HEVs seems to be superior since the HEV-engine typically shuts down (so called start-stop mode) every time the car is stopped in a traffic jam or at red lights. But adding relatively low cost start-stop functionality to a regular diesel engine (so called micro-hybrid) would push the diesel city mileage likely into the same range as the one advertised for gasoline-HEVs.
Looking at these numbers the diesel solutions could offer quite some threat to the penetration of HEVs. In countries in Europe where diesel is a well established engine type and the consumer acceptance is at least as high for gasoline powered aggregates we see already a very strong market penetration of diesel while HEVs seem to sell much harder compared to U.S. or Japan, for example.
The www.fueleconomy.gov is certainly the best website that I've seen for making apples to apples comparisons to all types of cars. I think Chevy has the right idea with the Volt (and similarly, the plug in hybrids). That way we can take advantage of cheaper electricity, regenerative braking and still have the convenience of gas (or diesel). Until we can effectively use hydrogen as a storage medium or we make some signficant electrical storage breakthroughs, gas is required for the American culture.
Addressing the big car hybrid comment, if MOMS are insisting on using SUVs to take their one or two kids to school, why not use 30-50% less gas by having a hybrid. The price today is overly inflated because most add signicant other amenities along with the hybrid features.
First off, I welcome everything being done to improve diesel efficiency, especially in the urban driving. However, I note that GM killed their belt-assisted, auto-stop cars in May. One reason being the lack of usable, regenerative braking that saves vehicle kinetic energy instead of just heating the brakes. But it is also important to understand user efficiency versus EPA lab test results.
If you go to www.fueleconomy.gov, you'll find not only the vehicle specifications but actual owner reported milage:
MPG(vehicles) - Model
38.4(004) - VOLKSWAGEN Golf2L, 4cyl
40.6(002) - AUDI A3, 4cyl, 2.0L
--.-(000) - AUDI Q7, 3.0L
49.2(104) - TOYOTA PRIUS, 4 cyl, 1.8L
49.5(015) - HONDA Insight, 4 cyl, 1.3L
28.3(002) - LEXUS RD 450h AWD, 6cyl, 3.5L
23.6(003) - TOYOTA Highlander, 6cyl, 3.3L
The low numbers of diesel owner reports is consistent with the USA diesel skepticism. But the reason we bring up user mileage is the hypothesis of "equivalent highway mileage" between a diesel and hybrid falls apart in practice when the car is in the driveway and the kids have to get to school. So ask someone making that claim, "What is your urban car?"
In reality, very few can afford separate highway car and urban cars but must mix both urban and highway traffic. That is OK with hybrid owners who believe diesel ownership, like chastity, is its own reward . . . and punishment at the pump.
Bob Wilson, Huntsville AL
About big cars being hybrid: that's a move that I really do not understand. Yes, the fleet average has to be the main driving force, and the wide margin on price. I really don't see the point of making a Lexus LS hybrid. It's an "autobahn" car, it doesn't need hybrid. Fortunately, small hybrids are finally arriving: Honda Jazz/Fit and Toyota Corolla.
The lack of rare earth seem really a big problem, along with the peak of many other resources, oil in the first place (but copper too seems precious). My opinion is that there is no "one-size-fits-all" solution. Several options look promising: for the mum that goes daily from home to school and backwards, a pure electrical car may be enough. For a truck that crosses the continent two times a month, we'll have to stick to diesel, maybe turbo-compounded with several intercooling stages. If I had to buy today a large van, I'd get it diesel, for sure, but for a city-car, I'd prefer a hybrid one. BTW Let's see how the new Peugeot diesel-hybrid fares. Many of the solutions, however, are outside the mere automotive technology: for example, kids can just simply walk to school or use public transportation, trucks can be loaded on electrical trains etc, but these issues are a bit OT :-)
Well that is what PSA in france is going to do later. Use a diesel + electric to recuperate the brake energy. At present the HEVs is mainly used by major auto oems to get the fleet averge CO2 emission into the legally prescribed level. Read well, the fleet average. So you start by cleaning up your prestigious models that people want to buy because it confirms the status they want to display... Why would you buy a gas guzzling large car or SUV? Its just Human to do so! It is beatifull, mighty, rich in its expression of your status and an expression of your wealth and social position. Look at the LX400H series hybrid SUVs - drive a large heavy car and yet have a CO2 performance of a middle size car.
Hello Markogts, of course you have good points here. My reaction.
1. Emissions other than CO2. Sure the diesel engine running on diesel fuel has an issue reaching Euro 5. Fine soot particles and NOx emission are traditional problems of (not yet warm running) diesels. However, the R&D is now turning to running diesel combustion process with petrol like fuels or also very well possible running it on methane. This relieves the catalytic converter from having to deal with the soot. The CNG way is high potential with "big gas" replacing "big oil".
2. Energy efficiency. The average petrol engine otto cycle efficiency is under 22% mechanical output. This is why Toyota went to the Atkinson cycle which reaches nearly 31 % at its sweet spot. Combine this with electric traction to extend the rpm-torque range et voila overall 25% performance is feasible. Add brake energy recuperation and you gain another 10%.
3. A major hurdle in upscaling HEVs is the scarcity of technology metals, in particular the heavy rare earth additions needed to get high coercitive field strength at automotive temp of the rotors (typ 150 -180 deg C peak). The lack of in particular dysprosium is strangling the future motor production volume. Batteries may be a major problem today but there are at least alternatives such as the bipolar lead acid (weighing 50% more than same size same power same power density yttrium doped lithium iron phosphor oxide)
Based on this I think that HEVs and complete EVs will evolve much slower than we would like to. In 2020 potential volumes run in the 10 million vehicles/year. So, remains for us as ordinary consumers the other 55+ million cars/year... the smelly old petrols and diesels. Whats your opinion?
The article has three major mistakes.
First, the advantage of HEV is well beyond the start-stop in urban traffic. I won't go in details, but that sentence is simply misleading.
Second, I doubt that the cost of a modern diesel engine is so much lower than a HEV powertrain. When you make comparisons with Europe, please bear in mind a simple fact: Europe lags USA and Japan on emission limits by 10 years. A modern diesel "Euro 4" can be readily sold in Europe (up to this December) but the same car would never pass the EPA rules. Europe has always had a very permissive policy on diesel emissions, that's why these cars are so common here. But when you want to compare apples to apples, then you have to consider the price of SCR and urea injection: the car becomes an expensive chemical laboratory.
Three: about the reliability. In the recent 10 years, the biggest part of problems came from the diesel powered cars (please check with ADAC statistics if you don't believe me). It is true that basically the diesel engine should be more sturdy and massive, but the "add-ons" have proven very unreliable: turbine stators stuck, particulate filters clog (especially on short travels), debimeters get dirty, electronics goes crazy (I think the Ford Focus 1.8 tdci was maybe the first case of problem solved only by a firmware update).
I don't want to bash the diesel, it DOES have some advantages, especially for the typical American way of driving, just bear in mind these issues when comparing solutions.
PS for a pure serial hybrid, a diesel, constant RPM, downsized engine would be the best solution, IMHO.
As a customer, I can understand the comparison between HEV and diesel cars. As an engineer, I don't. Diesel cars are competing with gasoline or fuel cells. They are a way to store energy. HEV are not storing energy, but are providing a way to transform chemical energy into mechanical motion. They are competing with the standard mechanical powertrain.
What about an HEV powered by a diesel engine?
Hi guys and girls (if any...). The higher carnot efficiency of diesels is obvious. Europe is typical diesel country about 1/3rd of all ordinary cars is a diesel here. Why? because of fuel efficiency. Only the taxation of these diesel cars holds us back otherwise they would be the majority. We drive two VW diesels, a polo 1.8 sdi doing 20 km/l if driven in a sporting manner but well behaved 24 km/l if you hold back on the paddles. Not slow at all. Second is a two-metric-tonne T5 transporter van. Big thing. Drives 13 km on a liter of diesel. Thats a lot of cargo bay + 5 person seats (double cab version) and yet using less than the average SUV. And it does not drive like an old truck, no it is actually like a nice car. Silent, reasonably fast, has airco, cruise control etc. No big deal. This how we keep our holidays affordable...
Best regards Henk Mol
Nice article.. I recently moved from a Gasoline car to a Diesel..and never once regretted. It's pheomenal torque, performance and low emission will put a gasoline to shame. And contrary to popular belief you do get quality fuel in India- and India' commercial tansports run on diesel.. The only reason diesel cars sell less in India than gaoline is due to the premium you pay for Diesel. And given that US does not have such issues, Diesel could make a killing if the mindset could change.
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