http://blogs.cars.com/kickingtires/2...-isnt-sex.html

CNW Marketing has only one customer, the salesman on the display floor, and all of their nonsense comes from that pool of ignorance. But even CNW Marketing knows better than to put lipstick on that pig.

Don't get me wrong, diesel will play an important role once it is married to a hybrid drive. But as a standalone, power plant in a car, it can't compete with anything using a reasonably sized, hybrid drive system.

Vehicle performance is a function of total systems performance, not just the engine. Manual transmission equipped diesels can compete on the steady state, open highways but they are a dog in the city and most of us drive the city cycle day after day. But put a diesel with a serious hybrid system and suddenly we're looking at amazing performance and a solution to diesel short comings.

Bob Wilson

 

if a gasoline engine does better in the city than a diesel and a gasoline hybrid does better than a gasoline, why would you couple a diesel with a hybrid. I would argue that since the gasoline cars do better in the city there is no reason to go with a diesel hybrid for city driving.

I am all for the development of any advancement in technology or more buying options and would love to see some diesel hybrids, but strictly speaking if you cant match the performance task for task to a gas the diesel just doesn't offer an ecology argument. Even with USLD I am not sure you can get the emissions as low or millage as high as you could with the same configuration burning gasoline.

 

Hi,

The diesel can do better on the highway than ordinary gasoline vehicles because the inherent "lean burn" combustion. But ordinary diesel and gas vehicles share a common problem. They have energy losing overhead when not being called upon to generate significant motive power.

Every mechanical engine has a minimum amount of energy needed to keep turning at any given speed. But as the engine operates at higher power levels, the ratio of shaft energy to overhead energy goes higher and higher and within the limits of a heat engine cycle, the engine becomes efficient. What a good hybrid drive system does is keep the engine operating in this high efficiency, power range.

The hybrid drive system solves the universal problem of all idling or partial power, heat engines. It lets them go "OFF" and then brings them "ON" exactly when needed so they can quickly reach an efficient power range. It really is a beautiful dance.

Emissions are a different problem and if we continue to use heat engines for power, the Sterling has many desirable features.

Bob Wilson

 

twuelfing,

Think BIG electric motor (like the Prius uses, or even bigger), BIG capacity electric (hybrid) battery. Mate that to a "clean" diesel ICE.

In theory, you want to use "mostly" electric motor to propel the vehicle in the City.
In theory, you want to use "almost exclusively" the diesel motor to propel the vehicle on the Highway.
This would be similar to how the Prius works today, only more so (leaning on the electric propulsion in the City).
Part of the allure of the diesel is the efficiency it can bring on the highway.
I agree with you, though, in that the City MPG needs to be top-of-mind when designing ANY diesel-hybrid. Or else, it doesn't make much sense, as gasoline-hybrids do it pretty well already, and the gasoline ICE IS a better engine for the City.

 

I cant think like that as the current cars are not going in this direction. The prius is better then the honda, but neither have what would be needed to maximize a system as you describe, where the ICE is basically a generator to recharge the batteries.

 

No, diesel does better than gasoline in the city, without a doubt. How Stuff Works: Diesel Engine. Where a gasoline ICE has a set fuel-to-air ratio in order to burn, the diesel uses a variable amount of fuel and air, and a lot of air can still ignite the smallest traces of fuel in the compression engine. When idling, a diesel engine uses a minimal amount of fuel to keep turning over, and it's proportionally much less than a gasoline engine. When idling, a gasoline engine is at risk of overheating, whereas a diesel engine's temperature actually cools down! Another difference is that when coasting and with your foot off the accelerator, the gasoline engine continues to burn fuel while the diesel engine goes into over-run mode and uses zero fuel.

Diesel engines in passenger vehicles, which are de facto turbodiesels nowadays, sell themselves on the low fuel consumption. Buyers and sellers of a VW Jettta TDI know that they can go 600 miles on a tank. In fact, if it wasn't for the development of gasoline hybrid, then gasoline couldn't compete with diesel in this regard. Not in a hundred years. But diesel's Achilles heel for consumers has been its smelly emissions, its vibration & loud operation, and its lower horsepower. But they sell themselves to the consumer that knows that diesels have made great improvements over the last 10 years to deal with these issues. Europeans have led the demand for diesel engine alternatives because gasoline costs them two-to-three times as much as in North America.

I used to own a smart fortwo cdi, which is a 3 cylinder turbodiesel, and it was the second most fuel efficient vehicle, next to the Honda Insight. However, it wasn't the most efficient engine of its kind because it had to propel a vehicle that was as heavy as the Insight (ie. only half the weight of the average compact car).

Frankly, I'm glad that diesel passenger vehicles were a niche market prior to tougher new emission laws because despite their efficiency they still produce a copious amount of soot, particulates (asthma, anyone?), smoggy oxides of nitrogen, and more CO2, litre for litre. Biodiesel is hardly an option because it isn't widely available and no-one can agree on what standard to follow nor which blend will preserve the engine's integrity.

Gasoline hybrids beat diesel, but straight gasoline doesn't.

The argument in favour of diesel over gas-hybrid is that diesel is efficient at all speeds, without the "dead weight" of the battery pack on highways. But it's a specious claim, since not all hybrids are alike: Honda's latest IMA does use its battery power at high speeds, along with Variable Cylinder Management (VCM), allowing for moments of zero fuel consumption, assist, and regen.

 

The Toyota system use the "dead weight" battery on the highway for passing and handling hills. You'll notice in the attached graph that the battery contributes energy on the climb and recovers it on the down grade:


The only "dead weight" systems I'm aware of would be the belt assisted systems that to the best of my knowledge do not provide additional power during normal driving.

Bob Wilson