Oil & Fuel General diesel question

[irvingj]

John_bud-- thanks for being gracious. Yes, gas engines also can have long strokes-- the David Brown designs of the 50s & 60s come to mind. The guy designed tractor engines, but also the twin OHC 6-cylinders used in Aston-Martins (hence, the "DB6, DB7," etc.). The '52 XK120 Jag I grew up with was similar; gobs of torque at low rpm. I was mainly referring to the lower exhaust temps (and greater mechanical efficiency as a result) diesels enjoy...

Redneck- I'm not up on all the changes in diesels over the past 20 yrs or so, but I do know there's a WORLD of difference between the '82 Peugeot 504D wagon I had for a while and the '05 TDI Jetta wagon I now have- that little VW will chirp (or smoke) the tires in all 5 gears if it's pushed hard-- and a Jetta TDI set new world records for the Pike's Peak hillclimb recently. (Seems I read somewhere that "Peugeot" was French for "slow"...)

It's sad to see that most any other industrialized country has such a higher percentage of diesels than we do here-- in Europe, even model airplane engines are about 50% diesel. I'm just waiting for a breakthrough in waste biomass diesel production-- a lot of progress has been made so far.... John_bud-- as you can see, I invented verbosity! With apologies, Walt

 

[john_bud]

J

It's sad to see that most any other industrialized country has such a higher percentage of diesels than we do here-- in Europe, even model airplane engines are about 50% diesel. I'm just waiting for a breakthrough in waste biomass diesel production-- a lot of progress has been made so far.... John_bud-- as you can see, I invented verbosity! With apologies, Walt

I agree completely that the "powers that be" in our government as well as the pressure groups have tied the hands of both the auto companies as well as consumers. Looking at it from a different angle, the "greenies" are always pointing to the EU as the end all be all of eco friendliness. Yet, the EU has MUCH much MUCH looser exhaust emissions laws than we do and they thus use much less fuel than we do per mile traveled. They also paradoxically, have both the ultra high end 250mph and the 100 mpg 800 pound machines. Neither of which they are allowed to sell here due to our idiots ---er --- politicians. In fact, we can't even sell many more diesels as the refineries have been optimized to produce gasoline at the expense of diesel. Now they are short of diesel, but have too much gas.


I don't know if you have invented it, but I am trying to improve it with the addition of tautologous adders to the verbosity.

jb

 

[Reg]

They ALL have computers (-:

Some are analogue and are implemented as relatively simple linkages, but they're still computer control systems.

Gas engines (carburetor) are regulated by an air restriction (hence the name throttle).
The amount of air flow determines the amount of fuel that is vaporized into the air stream - more air + more fuel = more power {Greatly simplified}

Diesel engines (generally) are regulated by controlling how much fuel the injection pump sends to the cylinders, the air stream is "fixed' or wide open. Diesels have been "fuel injected" for a very long time now, although I think the first engines ran on coal dust and I don't know how that was delivered to the cylinder(s).

Turbo and superchargers increase the mass of air by compressing it, allowing more fuel to be burned at the same air/fuel "mix" ratio.

 

[john_bud]

They ALL have computers (-:

Some are analogue and are implemented as relatively simple linkages, but they're still computer control systems.
.

Are you saying that the flyball governor is a computer of the analog flavor?

Never thought about it in that light, it may stretch the bounds of "computer" a bit.

 

[SnowRidge]

Are you saying that the flyball governor is a computer of the analog flavor?

Never thought about it in that light, it may stretch the bounds of "computer" a bit.

A bit?

 

[Mickey_Fx]

Boy, lots of comments. Some with repeat info, others clarifying an answer from a question, etc.

One thing not mentioned so far is combustion chamber design in diesel engines. Close 3 decades ago when I was reading up on diesel engine design, there were at that time 5 combustion chamber types, each with their own operating characteristics. Some designs permit high speed (close to gas engine speeds) operation, others that permit low compression ratio's not much higher than was common 20-30 yrs ago in gas engines. I seem to recall the Perkins in my MF was something like 15:1 and 10:1 wasn't that rare in some gas engines. Some designs require glow plugs for starting on a cool engine and other don't. Again, my perkins didn't have glow plugs.

Combustion chamber design plays a big part in how a diesel engine operates/performs. As has been stated several times, in a gas engine speed is controlled by the amount of air entering the engine. With diesels you control fuel.

Personally think the biggest problem here in the States when it comes to diesel engines is owner resistance. With self-serve refueling being the norm, owners don't want the stinky-oily mess to get on their hand and into the car.

 

[Redneck in training]

Europe has more rational measure of polution cars produce. They measure pulution per kilometer/mile driven. US automakers lobbied government to base polution by percentage of polutants in the exhaust. Otherwise the European standard would punish large vehicles unles they were super superclean. The result is that diesels produced in Europe (by all US automakers among others) couldn't be inported until recently because they couldn't comply with US clean air standard even though they poluted much less per mile driven relative to large cars. I rent a lot of cars all over the world. When I go to Europe I always ask for diesel. Few weeks ago I rented Ford Fiesta diesel. It did about 50 mpg at normal driving.

 

[SnowRidge]

Personally think the biggest problem here in the States when it comes to diesel engines is owner resistance. With self-serve refueling being the norm, owners don't want the stinky-oily mess to get on their hand and into the car.

Right now it is the up to $1.00 a gallon price premium for diesel fuel.

The lowest differential I have seen locally is $0.60. Most stations seem to be charging $0.90 more for the stinky-oily stuff. With the average station charging just over $1.50 for regular, it definitely costs more to operate a diesel vehicle than a gasser, even factoring in the diesel's higher mileage.

 

[irvingj]

Oh, I don't know.... When diesel was up to almost $5/gal, I started tracking cost per mile for fuel-- I wanted to know if it was more economical to drive my wife's Toyta Matrix, since gasoline was so much less than diesel at the time.

Cost per mile for fuel came very close in the 2 cars, but even at the worst, the TDI was just a bit cheaper. My highest cost per mile (fuel only) for the Jetta was 11.28 cents, when diesel was $4.859/gallon. That was in July, and I must have done a lot of short-trip driving, as fuel consumption was a poor 41.15mpg on that tank. Back then, it was far cheaper to run my Yamaha Virago 750 using premium-- mileage was the same or better, but even high-test was much less than diesel.

Today I filled up the Jetta; cost was $2.799/gallon; mileage was again only 41.11 (more typical for cold weather), but fuel cost is now back down to 6.8 cents per mile. Wife's Matrix is currently getting about 24.5mpg; cost on her most recent fill-up was 8.6 cents per mile.

Although it was really hard to part with after 30 years, I'm glad I no longer have my '72 Blazer to feed!

 

[SnowRidge]

You are comparing two different vehicles. I'm talking about the buyer looking at diesel versus a gas version of the same vehicle. Most everyone in my area drives pickups, so that is what I am most familiar with. Diesel pickup sales have collapsed almost completely, even worse than gasoline powered pickups.

If you have to have a new truck with a big engine for towing, for example, it currently makes more economic sense to buy a big gasser than it does to buy a diesel. I don't think that trend is going to change, although I sure wish it would, since I already have the diesel.