40 mpg Prius vs 50 mpg European Diesel cars

Modern diesels have electronic fuel injection. Here are some good descriptions of what causes diesel clatter:

That's an interesting link, although about all I can say is the subject of clatter is still controversial. It sure sounds like the combustion profile is important.

Mike

I wouldn't describe the subject of the source of diesel clatter as controversial. IMO, "uninformed" is a more accurate description, especially in the U.S. where diesels are not common in passenger car applications.

Basically, diesel "clatter" is the same sound you get when a gasoline engine is knocking. Add different tolerances and you get more noise at idle.

One of the problems in the USA is that our diesel fuel has a lot of sulfur, which makes for stinky polluting exhauts gases. If and when we can get low sulfur diesel fuel, the situation could then improve.

Morton

Overall mileage. I actually get better mileage on the freeway than I do on surface streets; that's because my surface street driving usually has a stop sign every half mile or mile, with speed limits of 40 to 50 MPH, and usually for fairly short distances, so the engine doesn't get to warm up. When I'm in downtown traffic with speeds of 25-35 MPH, I often get in the upper sixties after the first five to ten minutes of driving.

The two people I personally know of who get in the sixties live in West Virginia and in Hawaii.

Because the US uses a dirty blend of diesel fuel. That is scheduled to change in a year or 2 with a mandate for clean diesel fuel.

Ultra-low-sulfur (

Yes, I see the poor b*st*rds made hardly any money this year.

Hybrids work at the other end of the driving spectrum. The only advantage they offer on the open road (where diesels shine) is the ability to reduce engine size while maintaining passing performance, but in town they reduce the amount of time a gas or diesel engine is run in the lowest efficiency ranges. Hybridizing with a turbo diesel power plant is a very attractive idea - each covering the weaknesses of the other. There is no reason a TD hybrid 5 passenger sedan couldn't offer more than 100 mpg in town and 80 mpg on the freeway, at least at 65 mph. Mainly it takes advances in the power electronics.

Mike

I think the biggest drawback to a hybrid diesel is cost. Both the diesel powerplant and hybrid power plant cost more than a conventional gasoline (etrol) engine so a diesel hybrid would have a double cost disadvantage to overcome.

Don't forget the 'energy recovery' aspect of using the 'reduction of momentum' (braking action) to help recharge the batteries instead of throwing it away as waste heat.

Mind you I don't know how important this is in the big picture but it must be considerable because of the added complication of the system that's required to implement it...vice the simple alternative. Anyone know?...

My impression is that the energy recovery part of it is almost a freebie. The main job of the electric bits is to let the petrol engine run at a steady and most-efficient speed. The e/motor is a way of handling the zero-to-low road speed range where a petrol engine would struggle, unless backed by conventional gearbox and clutch. It also "fills in" when there are energy demand peaks.

Once you have the e/motor, you can add a planetary gear: together these simplify continuously variable transmission (IOW, a gearbox substitute) and fine dynamic regulation of p/engine load.

The e/generator lets the e/motor be powered (indirectly) from the petrol tank, so visits to power sockets are not needed. Also, it enables sugar-on-it features like regenerative braking.

Other bits (battery, ECUs &c) make the main units work together.

That's why one must think in terms of whole systems. (AIUI, NB.)

Still dont see it, my friend has a commonrail TD and gets 45 doing city driving, which is still above a hybrid?

Would be harder than with a petrol - re-starting a diesel requires far more cranking torque, so you'd need more powerful motors and its likely to cause a jerk, unlike a petrol car that can smoothly be 'bumped' as its low compression.

Dont worry, you are getting to pay the extra 5 cents per gallon that the new hydrotreators are costing. The refiners pay those costs right along to the consumer.

Lynn

"my friend has a commonrail TD and gets 45 doing city driving"

interesting, what make model car is that?

Drivel indeed, starting with the 40 mpg Prius bullshit.

I get better mileage than that with my Prius, burn less expensive fuel, and my exhaust emissions are cleaner. What's your point?

Trains and heavy trucks are using diesel engines. What does that tell us?