Why no diesel Prius?

[roflwaffle]

Originally Posted by Christ

Thanks for the link to the paper. Saved that one.

Unfortunately, the maps shown in that paper reference an increase in emissions when road speed and load are increased steadily, which should be obvious.

What I'm referring to is steady state RPM with varying loads. In other words, when you're cruising, and you start going up a hill, then going down the other side.

Sure they do. Look at the map for NO. At 1500rpm and 2bar, NO is at 100+ppm. Hold speed the same and increase the load to 5bar, NO emissions increase to 200ppm. Emissions increase w/ both engine load and engine speed.

Originally Posted by Christ

If you're not using all the available power, you're pretty much wasting fuel. You can tell if you're properly loading your diesel engine by checking EGT's though. You should be in the ~600* range for best efficiency in most cases, IIRC.

That's not necessarily true. Generally, as long as an engine is above half load it operates pretty efficiently, however at maximum load efficiency tends to drop slightly compared to at high, but not maximum, load.

Originally Posted by Christ

The thing about diesels is that it's hard to control load without metering airflow, so it would be very difficult to test for emissions properly. When you floor it in a diesel, it starts injecting fuel based on a pre-set pump that was supposedly tuned.

All diesels do a great job at governing fuel, and load, not airflow. Even very old designs only use an intake throttle to generate vacuum, which the IP uses to govern fuel and load. The full load screw allows the operator to increase or decrease the amount of full load fuel injected depending on oxygen content, which depends on pressure and humidity mostly.

[cRiPpLe_rOoStEr]

There's at least one company lurking to offer a Prius Diesel conversion, while retaining the HSD system.
http://dieseltoys.com/pricing-2/toyo...s/prius-diesel

BTW, to manage the automatic shut-off into a Diesel doesn't seem to be so hard. Ceramic glowplugs can lead to a more efficient pre-heating, and among others are already available in the Mazda SkyActiv-D engine which is usually available with the start-stop system, composite-material valve covers and oil sumps (just like the ones used in the Detroit Diesel Series 60) retain more heat into the engine, and there are also hybrid heavy-duty vehicles such as trucks and buses in Europe, and even in Brazil, which feature a driveline layout quite similar to the Prius...

[GreenHornet]

This is a very old thread Cripple Rooster :-)

Despite this thread being ancient I took some time reading through it. There were some good arguments which these very same arguments have been going on for years.

Diesels and gas engines are not an apples to apples comparison and this is where the problem comes in. They are too completely different animals down to the fuel they burn.

The EPA shuns the diesel here in the states due to its Nox emissions because the diesel engine is categorized in the same classification as gas engines.

Do diesels have the ability to minimize NOx? absolutely people in this thread have all ready pointed out some ways. The good thing about diesels are they are built like tanks compared to gas engines. They are built to take a beating and last. This opens the door to use additives such as water/methanol injection systems which reduce NOx considerably. The reason they reduce NOx is because they allow the diesel engine to heat up more than it would otherwise and the result is a more complete fuel burn of the diesel. They have been doing this for years and one person in this thread pointed out simply using water to clean up the diesel particulate which is also true. What happens is you get the steam cleaning effect when you add water which also aids combustion to a lesser degree btw. There are plenty of companies out there offering this technology for diesel engines just Google diesel water methanol injection and you will get plenty of options.

So we can clearly clean up the diesel engine particulate there really should not be much debate here so what about cost, size, and efficiency.

Cost is a little higher due to the beefier construction of most diesels. This also translates into more weight usually. The efficiency is greater with diesels this really is no arguing point this is just a plain fact. Diesel fuel has more energy than gas pure and simple gas engines are becoming more efficient as technology continues to evolve and here in the states the price of diesel is more to try and make up the energy difference and again suppress the diesel!

There are many reasons we do not see diesel hybrids here in the states many of the points have all ready been touched on in this thread. One important consideration and was kind of touched on was the loading issue. One can not simply decrease the weight of a vehicle and get better fuel economy because what happens is you create a worse loading situation than you had previously. Engines like to work in there most efficient range. Take it out of this range and you get greatly reduced fuel economy it is this simple.

In order to get better fuel economy You have to reduce not only the weight of the car but the size of the diesel to try and be effective. This creates another problem normally and that is acceleration. If you decrease the engine size to much it will take you a year just to accelerate to 50mph! How many cars here in the states weigh less than 2,000lbs? There are not to many and this makes it impractical to simply put diesels in them the weight would be to great and acceleration would suffer greatly. You would have to put in a bigger diesel to have acceptable acceleration which would decrease fuel economy. You can deliberately under power and overload a diesel engine which will increase mpg most of the time but acceleration will no doubt suffer. So it is a trade off you will experience if you decide to perform an engine swap or conversion. The best way to do it is to design from the ground up which takes time, knowledge, and experience.

This is the main issue but one in which can be overcome by hybridizing the diesel with electrics. This can also be overcome by decreasing the weight of everything and improving aerodynamics. Just because you decrease weight of the vehicle does not mean you have to sacrifice safety like most here in the states think. The car manufactures here have there hands tied with much red tape especially as it pertains to safety standards. They take the simplest route and build a larger vehicle to appease the safety gods and it works for the most part. The big car guys have to continually compromise for safety and is a big reason we are stuck at the 45-50mpg area currently.

Here in the states most people want a bigger vehicle with 5 seats or more even though the majority of the time they only use 2 or less seats. This is due to the fact most people can not have or afford more than 1 vehicle. So they buy a vehicle to accommodate all potential passenger situations. It makes sense but is highly inefficient. As fuel prices continue to rise and they will there is no doubt people will start to be more willing to downsize and become more practical. We have been playing this game for years and years. The same arguments and the same tradeoffs have been debated for many years. The difference today vs 60 or 70 years ago is advanced technology. We now have batteries that are more powerful and lighter. We have advanced our electrics to a point where hybrids are practical and can make an impact. The ICE is more efficient now and can also play a big part.

So if this is the case why did we see cars 50years ago or more get similar fuel economy? The reason is they had to pay better attention to weight and aerodynamics. They did not have all the safety standards we do today. There was no insurance back then, if you crashed well you screwed up and had to pay for it! We now have an entire industry built around the statistical fact people will crash and they prey on this fact.

There are just so many reasons why we don't see diesel hybrids its a real shame because diesel and electric is a great marriage properly done. I have come to the conclusion many years ago that if you want it done right or done at all you have to do it yourself :-)

So that is why I am building my own diesel hybrid..

GreenHornet..

[cRiPpLe_rOoStEr]

If I would ever own a Prius, I still believe I'd try a Diesel conversion anyway.

[Arragonis]

A Prius - which rattles like b@ggery, combined with a rattly diesel engine.

Genius, why hasn't this been done before

[cRiPpLe_rOoStEr]

Originally Posted by Arragonis

A Prius - which rattles like b@ggery, combined with a rattly diesel engine.

Genius, why hasn't this been done before

Many times, Prius fans and dieselheads have a mutual hatred. That probably explains why nobody done this before.

[Arragonis]

I know, I used to be on the Diesel side.

Assuming we are talking a Turbo Diesel I wonder how the turbo would like being spooled up and then shut off quite so often as the Prius engine goes on and off. Wonder if the new VW hybrid engine thingy has some extra oil circulation to protect the motor.

[Cobb]

4 years and only 1 company is offering the conversion with an est 60-70 mpg.

The prius 3 I drove got 65mpg without too much trouble. I could squeeze 70 by changing my driving style. It would take even longer to break even from the conversion costs.

Originally Posted by cRiPpLe_rOoStEr

There's at least one company lurking to offer a Prius Diesel conversion, while retaining the HSD system.
Prius Diesel...

[Arragonis]

When the Prius engine breaks I can advantages is a smaller engine, maybe with a turbo and an oil circulation system for the turbo - ecoboost style maybe ?

I'm substantially unimpressed with the Prius 1.8 motor in terms of efficiency, but the drivetrain as a whole is pretty good.

[euromodder]

Originally Posted by cRiPpLe_rOoStEr

If I would ever own a Prius, I still believe I'd try a Diesel conversion anyway.

Such conversion would be pretty foolish.

It'd never be as smooth as the original.

It'd not return the investment - once you're already in Prius MPG territory, you're also in low-return-on-investment territory. It uses so little, that it's hard to get any gains.

It'd pollute more, by putting out more harmful pollutants - NOx and PM.


I can only tell diesels are NOT the solution, however attractive they may seem to US drivers.
You guys only see the inflated MPG numbers.
On this end of the Atlantic, we get to see and live the problems with these so-called clean & green diesels - but they are neither


Europe is already starting to move away from diesels - even despite the largely CO2 based tax-politics.
Don't duplicate our mistakes.