40 mpg Prius vs 50 mpg European Diesel cars

Every time he drives by, they start thinking about lunch.

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Reply to
DH
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Burning 500 million barrels of it a day would certainly stink the place up.

Reply to
Bill

Mmm... onion rings and fish!

Mike

Reply to
Michael Pardee

"I think you are wrong. Both diesel and petrol engines are built to the same tolerances and, though engine management for diesels is even more sophisticated than petrol, the impact on cost is negligible."

Horse... well, feathers.

Why "think" when you can "know"? Google is your friend. Here, let's look at example parts costs:

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Mahle Piston Set - .50mm Volkswagen Jetta GLI Piston Set: List price, $311.03, "our price" $259.19

Mahle Piston Set - .50mm Turbo Volkswagen Jetta Diesel Piston Set: List price, $504.68, "our price" $420.56

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Volkswagen Golf III GL 4 Cyl Cylinder Head Gasket, Reinz: Your Price $21.43

Volkswagen Jetta Diesel Cylinder Head Gasket, Reinz: Your Price $29.92

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These are typical, and reflect significant design, construction, material and, yes, tolerance differences (especially in the fuel injection system, where pressures can exceed 2000 psi even in indirect-injection configurations). If you'd ever seen even an economy automotive diesel engine stripped down, you'd have an appreciation for this. And, worldwide, diesel engines are very popular; your conjecture about relative volumes is incorrect, though certainly they hold in the U.S.

If you'd look instead of "thinking", you'd find nuggets such as "The cylinder head for the [VW] turbo diesel uses a different gasket [vs. the gas model] and is cast from a special stronger alloy. Different materials are also used for the turbo diesel cylinder head's valves, valve seats, and combustion pre-chambers."

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and "Although theforged-steel connecting rods are similar to those used in thespark-ignition engines, the pistons are of far more robust dimensionsand are totally different in design, since they must be capable ofattaining very high compression pressures and withstanding the loads ofcompression ignition. As on other Volkswagen engines, full-floatingpiston pins are secured by circlips. The connecting rods for the turbodiesel engine have greater piston pin clearances, however, and thepiston skirts are notched for clearance with the piston-cooling oiljets."
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and "Dieselengines and high performance gasoline engines feature an oil coolerattached to the filter housing through which engine coolant circulatesto help moderate oil temperature."
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You are correct, however, regarding the lubricity of diesel fuel and the whole-life lower cost of diesel engines, at least mechanically (although as I've noted from my experience, the rest of the car can be just as crappy and have just as short a life as a gasoline model!). Much depends, of course, on the relative costs of fuel. That varies, even in a given location. In the '70s diesel fuel was usually considerably cheaper than gasoline in the U.S. Today it generally isn't. In Europe today, the relative prices of the two fuels depends mostly on regional tax policies, since taxes are a much larger component of fuel costs there than in the U.S. (where they're still very high compared to, say, oil company profits per gallon).

And you neglect the fact that in conventional (non-hybrid) installations, diesel engines need all the stuff a Prius doesn't: alternator, power steering pump, belts and followers, clutch or torque converter, transmission, shifter and linkage, and so on-- all of which needs maintenance, the occasional repair, and periodic replacement of significant components. By comparison, the hybrids need their little planetary-gear power-split gizmo, two electric motors, and a battery.

Reply to
Scott

The following link sheds considerable light on relative cost of production of petrol and diesel. The striking thing is that, for an given type of crude (and, I suppose, any given refinery) there is an optimum ratio of the volume of output between the two fuels. Changing this affects costs directly and, also, indirectly by increasing pollutant problems which have to be addressed at increased cost.

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Reply to
Ken

Is it really an either/or proposition? I always had the impression that petrol and diesel fuel came from different fractions in the catalytic cracking process. Is that not the case?

Geoff

Reply to
Geoff Miller

You win this point - that is the case if you talk about the natural raw products in the simple stages of refining.

Now if they want to spend a bunch of energy cracking the heavier hydrocarbons that would make diesel into lighter ones for gasoline, or the opposite by combining the light ones to get more diesel out of that barrel of crude, they can. But while it adjusts their output, it also adds a bit of cost.

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Reply to
Bruce L. Bergman

There was much discussion in this thread about a diesel hybrid

It turns out that GM of all people is way ahead in devloping hybrid diesel - in buses. the following links tell the story - diesel, hybrid, regenerative braking - the lot! 60% gain in economy.

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I owe it to an Australian electronics magazine - Silicon Chip - which is running an article in its June issue on this GM - Allison project which is not pie in the sky - the vehicles are operating in various parts of the US.

Reply to
Ken

Except you wouldnt do that for the sake of your engine would you, poor thing accelerating hard when cold!

Agreed, modern common rails are amazing little creations. Mind you I manage to average 45 from a carb'd petrol engined small car that is 17 years old so you'd have hoped they could have got a little more out by now :)

J
Reply to
Coyoteboy

When cold the Prius engine speed doesn't change noticeably on even fairly strong acceleration, like we do going up the hill from our house - that is done by the electrics. The engine continues to do its warm-up process at about 1200-1500 rpm. Of course, you wouldn't want to take any present day car right onto the freeway when cold, that would stress the engine. In a serial hybrid (not available in production today) it wouldn't matter at all.

Mike

Reply to
Michael Pardee

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