DIESELOLOGY 1.1

Mr_Shiftright

This forum is for talking about that odd duck in American passenger cars and light trucks, the diesel engine.

This is a place to ask, link, or teach all about diesels, from history to tech stuff to maintenance.

I say "odd duck" because, unlike most of the rest of the world, we in America regulate diesels to rather heavy duty static machinery, busses, trucks, and marine engines, with the occasional use in a 3/4 ton pickup. America currently makes no diesel passenger cars.

I'll start with one subject in dieselology in the next post

Mr_Shiftright

Since we Americans are not used to dealing with diesels very much in our passenger cars, SUVs, etc., we tend to have some misconceptions, or perhaps more accurately, we hold some generalizations which are sometimes true and sometimes not true.

SUCH AS: Are these true or false?

1. Diesel engines are built stronger than gas engines, so they last way longer

host's opinion: "it depends". Yes, diesel engines are indeed built stronger, but compared to modern gas engines, their longevity in a normal passenger car is not astronomically better. As a rough ballpark, let's say around 150K for a gas engine and around 225K for a diesel. Of course, a few will blow up at 50K and a few will make it to 300K.

2. Maintenance on a diesel engine is simpler so maintenance costs are less

host's opinion: Not really. The maintenance is simpler BUT MORE FREQUENT. And when repairs are necessary, a diesel engine generally costs more to repair.

3. Diesels have more power than gas engines of the same size

host's opinion: Generally not, but they do pull a lot better at very low rpm, and with a turbo, their power is almost equivalent except at very high rpm.

4. Diesels are more economical pound for pound than gas engines

host's opinion: Quite true.

5. Diesels pollute more than gas engines

host's opinion: Depends entirely on the type of pollutant. With some emissions, diesels are better than a gas engine, with others, worse.

6. Diesels are better off-roaders

host's opinion: Not always, especially in the case of the hazard of hydro-locking. If a gas engine takes some water in the intake, it might be able to handle it, but if a diesel takes in water from fording a stream, etc., it will be devastated (due to much higher compression ratios than a gas engine).

7. Diesels generate less heat.

(host's opinion: that's true in terms of exhaust temp, so it would be safer in the bush).

Any comments, ideas, counter-opinions on this or other subjects in dieselology?

shipo

Diesel awareness in the USA might actually be driven by a combination of injection technology from (mostly) European manufacturers, European Diesel fuel formulations (lower sulfur) and from a fairly unlikely source, the General Aviation community.

Given that the availability of tetra-ethyl lead (TEL) (which is used in the fuel (100LL) burned by most small aircraft), is seriously limited now, and promises to become virtually unavailable within 5 to 8 years, and alternative must be found. Currently, there are at least six small aviation Diesel engines in various stages of development around the world.

From my perspective, there are two extremely promising configurations of Aero-Diesels, either one of which I would be proud to fly behind, and both of which have technologies that could easily be adapted for automotive usages.

The First is the Zoche line of Aero-Diesels, which are air-cooled, and designed around a two stroke radial configuration, the three versions they intend to market are:

V2 / 81.3 cid / 121 pound / 70 HP version
R4 / 162.6 cid / 185 pound / 150 HP version (two V2s butted together on one crank throw)
R8 / 325.3 cid / 271 pound / 300 HP version (two R4s sharing a crank with two throws with cylinders offset by 45 degrees)

The other engine that I am very optimistic about is the Teledyne Continental Motors (TCM) GAP Diesel, which is a water-cooled, two stroke, H4, of unknown displacement (probably about 300 cid), weighing in at “Under 300 pounds” and putting out around 200 horsepower.

In the case of all four engines, they rely on a turbo-charger for scavenging of the cylinders during normal operation, and in the case of the Zoche engines, low RPM scavenging is accomplished through the use of a mechanical super-charger, while the TCM engine is probably going to use an electrical booster to drive the turbine in the turbo-charger until the engine is developing sufficient heat to drive the turbine itself.

The benefit of the Zoche engines are that they are fairly small and light for the amount of power they generate, however, given that they are “Radials”, either new aircraft will have to be designed to accommodate the engines, or some fairly substantial cowling modifications will have to be made to retrofit either the R4 or the R8 to an existing design.

The TCM offering, on the other hand, while being a little heavier than the significantly more powerful R8 Zoche engine, has a form-factor that fits in existing cowlings, and it operates at a lower RPM (2300 vs. 2700), which keeps noise down dramatically because the tip speeds of the propeller blades can be kept sub-sonic.

Now for the good part, even though Diesel fuel weighs about a sixth more than AvGas, Diesel contains more power per pound of fuel than said AvGas, allowing airplanes to carry less weight (in the form of fuel) for any given amount of flight duration, AND it costs way less than half the price of AvGas per gallon in every part of the world EXCEPT here in the USA.

Best Regards,
Shipo

alcan

I keep seeing this mental picture of an 8V71 Detroit in a Cessna. LOL

shipo

He, he. Gives a whole new meaning to a "Flying Bus". ;-)

Best Regards,
Shipo

Mr_Shiftright

It's interesting that the diesel engine has been around almost as long as the petrol engine but really hasn't undergone the same level of sophisticated development until recently, as you noted.

Did you know that Rudolf Diesel originally intended his engine to run on palm oil?

haspelbein

...and his famous last name. I wonder if he every realized that his last name would ever reach this kind of visibility.

I didn't know that it was in fact palm oil. But I did know that the diesel engine was designed to burn a variety of fuels.

On a side note, I find it fascinating how the development of direct fuel injection is also very much tied to the diesel engine, and still the reason why Bosch still has such a high market share for fuel injection and engine control systems.

Okay, I'll take the bait and comment on the list. I think we have a couple of chicken-and-the-egg issues here:

1. Diesel engines are built stronger than gas engines, so they last way longer

They don't last longer by design, but are often used in vehicles for utilitarian purposes (trucks, taxi cabs, etc.), which are more rugged by design and therefore tend to last longer.

2. Maintenance on a diesel engine is simpler so maintenance costs are less

I agree on the simple and frequent maintenance. But do the repairs cost more because they are not as popular as gas engines, and fewer technicians work on them ?

3. Diesels have more power than gas engines of the same size

No, but have low-rpm torque. Turbos are nice, but still lag behind the gas engines. Even with the turbo, diesels get better gas mileage.

4. Diesels are more economical pound for pound than gas engines

Absolutely. I'm waiting for the diesel-hybrid.

5. Diesels pollute more than gas engines

Depends on the pollutant. Particles and NOx tend to be higher than gas. I've seen very good particle filter solutions on busses and trucks, but so far not cars. The particles also drastically limit the use of catalytic converters.

6. Diesels are better off-roaders

Put a snorkel on the air intake, and I'll take the low-end torque any time.

7. Diesels generate less heat.

The host asked about heat then talked about temperature. Diesels are more efficient engines, and will therefore emit less heat overall.
The temperatures in the combustion chamber is higher, but I'm not positive about the exhaust.

shipo

Once again, referring to light aircraft, the makers of Aero-Diesels are telling the GA community that they will not need a "Turbo Inlet Temperature" ([non-permissible content removed]) gauge as the exhaust temperatures are something like 400 degrees lower on the Aero-Diesels when compared to blown AvGas engines.

Best Regards,
Shipo

Mr_Shiftright

Yes I have heard also that diesel exhaust temperatures on cars at least are around 200 degrees less minimum. Not sure of all the reasons why, but it seems to be true.

Rudolf Diesel apparently committed suicide by jumping off a ferry but his death remains quite a mystery.

8u6hfd

Normal operating temperature on my TDI is 190 degrees Fahrenheit.

But if you let it idle for a while, the operating temperature drops a bit.

haspelbein

Apparent is the operative term, as he just disappeared from the ship. The only indication that it was in fact a suicide, was a cross marking the date of his disappearance in his diary.

Nevertheless, his engine design is impressive. In particular, I find the range of diesel engines amazing: You can have diesel motorbikes , as well as engines in ocean liners with something like a 9-foot stroke.

Mr_Shiftright

And even a diesel racecar at the Indy 500! It did pretty well, too, until the air cleaner got clogged somehow. It wasn't the fastest, but it was STEADY and surprised everyone.

haspelbein

I'm not familiar with the story behind the diesel racecar at the Indy 500. Do you maybe have any links ?

Reminds me of behind stuck behind a diesel BMW 7 series in Europe on a curvy country road. There was no way to get around it, as it simply outperformed the V6 Opel Omega (same platform as Saturn L series, Cadillac Catera). I only caught up with it when the road went through towns.

Mr_Shiftright

Here's a link to an Amazon book review. A search on "Google" search engine also will give you results: Search "Cummins Diesel Indy 500"

http://www.amazon.com/exec/obidos/ISBN%3D0917308042/ref%3Dnosim/cruiseincomA/104-6161796-7482357

alcan

Didn't a diesel powered 50 foot catamaran set the new offshore powerboat speed record last year? Seems to me it was in the 150 MPH + range.

0patience

Cummins has a 600hp/1800ft lb torque motor they are working on. This engine is an in-line 6 and is totally computer controlled. Fuel, cam timing, valve lift and duration is all controlled by the computer. It also weighs 70% of what a conventional heavy truck engine weighs.
In the last 5 years, diesels have made major jumps in power and torque ratios. Not the same old mass pullers with little jump they used to be.

ezshift5

.........my '82 Pickup Truck (265,500 miles) has been turning in 42-48 MPG since purch used in '85.
Maint. IS expensive when done by the factory(DLR)
Wish a new(small diesel pickup) model was offered

Mr_Shiftright

I had one of those pickups for a while. Really economical little truck but the engine is very rough and very slow. But you're right, a small diesel pickup with more power and more refinement would be a nice vehicle.

tboner1965

...turned in some respectable times. I was shagging cones in the middle of the course.

I think he was the only vehicle to need 3rd gear today 8^)

TB

krzyss

Airplane engines to be diesel ?
Nihil novi sub sole.
Germans and Russians had diesel plane engines in 30s. German Ju 86 had Jumo diesels but I will check the internet for it.

Krzys

PS VW 1.9 TDI 130 hp (Europe)
VW 1.8 T (150-225 hp) (All the world)
But diesel beats gas in milage (can you spell TORQUE).

Links:
http://www.zoche.de/lighter.htm

8u6hfd

VW 1.9 TDI, 150 bhp!!!! (from VW Driver Magazine, March 02, 0-60 in 7.0 seconds!!!)

Damn the US for only having Diesel No.2

haspelbein

Only the JU 86 with the Jumo 205 C engines. The two-stroke diesel engines were very toublesome and there were several efforts to replace them with gas engines. I don't know about the Russian plane...

krzyss

with diesels.

http://www.csd.uwo.ca/~pettypi/elevon/gustin_military/db/sov/PE8PETLY.html

haspelbein

The JU 86's engines are said to have been a constant source of trouble. Do you know how the Pe 8 fared in comparison ?

krzyss

that because Soviets and Germans exchanged ideas (20s-30s) it might be that Pe-8 (aka TB-7) had Junkers designed but russian build/modified engines. It seems that final models had gasoline engines so it probably was not big succes.

Try google.com.

Krzys

Mr_Shiftright

Clessie Cummins put a diesel engine in a Packard way back in the 30s. The first American diesel car you might say. Drove it cross country or part way as a demonstration. I imagine early diesel cars were pretty rough. I've driven early Mercedes diesels and they were pretty brutal, although not as bad as a London Taxi from the 50s (Perkins I believe).

haspelbein

Any news on the diesel-hybrids ? I remember the announcements for the Ford Prodigy and GM's counterpart, promising fuel economy of around 80 mpg. But I haven't heard much (or seen on the web) since those announcements came out.

mullins87

But I think a diesel hybrid makes more sense than a gasser any day. With the hybrid, you won't have any of the performance complaints that you now have with a conventional diesel powered vehicle.

rest_stop

Why can't a gasoline be made to operate the same way a diesel engine does? There wouldn't be a need for high octane gas or a spark plug for that matter to run a gas engine. Anyone knows why?

8u6hfd

There are direct injection gasoline cars, offered by Toyota, Mazda & VW, not in the US though.

Gasoline engines, cannot run like a diesel engine, just because of thermodynamics, Different process cycles. But, given enough compression, it will pre-detonate (knocking), but this is eventually destroy the engine.

haspelbein

Just read an article about a new VW diesel prototype.

It has a magnesium spaceframe with with a carbonfiber body, and its looks somewhat remind me of the post-war Messerschmitt cars in Germany, simply because the seating position of the two passengers is similar. Here is a look at the interior .

The drag coefficient (cw) is at 0.159.

The average fuel consumption of this thing on the Autobahn is around 0.99 litres per 100 km, which equates to 237 mpg. The engine is a one cylinder 0.3L diesel. The top speed was around 70 mph.
While it is a prototype, it is fully street legal and is currently being road tested.

binarybabe

Hi,

I'm considering buying an '02 Golf with the TDI engine. (I'm afraid the gas prices are only going to get worse, what with the unpleasantness in the Middle East)

My last diesel was in a 79 Olds Cutlass Supreme and it was dirty and inefficient. I think I have DH talked into the VW TDI, but he wants information on maintenance.

What's expected and when? Is it stuff you can do yourself or need the dealer to do?

Thanks in advance,
Laurie

Mr_Shiftright

As a general rule, diesel maintenance is simple and less expensive BUT is done more often, so in that sense it's probably close to a wash in terms of maintenance expense, between gas and diesel.

Diesel fuel prices are generally pegged to regular gas prices in the US, unlike Europe where diesel fuel is considerably cheaper than gasoline (only $3.50 a gallon!)

Diesel engines generally last longer than gas engine but are more expensive to rebuild, so there again it's a wash.

Diesels are very economical vis a vis a gas car of equal weight and power and more thermally efficient and also usually smog exempt from most state smog laws (not that they are clean in all emissions, just the ones that are presently controlled)

In short, there is no compelling reason at present to buy a diesel car in America except for some small financial advantage at the fuel pump, IMO.

I drive a diesel (one of my cars). It is a larger Benz and really I could not drive such a big comfortable gasoline car for the present cost per mile I now have. Not many 4,000 lb cars get 26-30 miles per gallon at regular octane prices. My biggest expense is lots of oil, oil filters, fuel filters and air filters.

But with a smaller diesel car I'm not sure what the advantage really is.

Maybe TDI owners have a different read on this.

krzyss

Well, I am from Poland.
The country of (West) European prices and African income (excluding South Africa). Not to mention Scandinavian taxes ;-)
Diesels are very popular there, just like in the rest of the Europe.
Benefit of VW TDI in US is better milage than gasoline (almost hybrid territory). It does not make as big difference as in Europe where you get better mileage and diesel fuel is cheaper but one can get almost twice as far on full tank with quite good dynamics.

Krzys

PS Shifty - is your MB turbo or not ? Turbo diesels are much niecer than NA diesels.

PS2. Go to the dealer and ask for maintenance book for TDI. Ask for maintenance prices for TDI. Do your own computations.
You might get better response from www.vwvortex.com forum site.

haspelbein

Shifty, the 26 to 30 mpg for a 4000 lb. Benz is really not that impressive. I get the same with my E320 with a gasoline engine, and it weighs around 3600 lb.

I think the more interesting point is that you get this gas/diesel mileage from a car that was built 20 years ago.

Mr_Shiftright

Gee, I didn't realize the modern big Benzes were that economical. Is that just highway mileage? I regularly get about 25 mpg no matter what driving I do.

Mine is not a turbo and while I would like the power advantage, the Mercedes turbo diesels OF THE ERA are problematic and I want no part of them. There's that evil "trap box" device and of course, at this stage of old SDs lives, the turbos will be dying, at no small expense to repair. I've been through a few turbo rebuilds on Saabs and there is some work, the expense of shipping out the turbo for rebuild (NO WAY I'm going to a Benz dealer for THAT part) and often some stubborn studs to deal with.

Last of all, a turbo does decrease engine life, there's no getting away from that.

haspelbein

The new Benzes have what they call a 'low-friction' engine. I'd like to know the details myself.

Basically, the gas mileage spread is very large, depending on your driving style. There is no way around the fact that these are heavy cars. In city traffic the gas mileage is around 20 mpg. Once the car is in motion, 30 mpg at around 70 mph are definitely possible. So I usually end up around 25+ mpg, as I'm constantly 'jamming' in and out of Silicon Valley.

I wanted to get my '96 E-Class as a diesel, but there were so very few available. It would be interesting to see their mpg in comparison.

Mr_Shiftright

What I love about diesels, or at least mine, is the RANGE I have. I have the optional long range tanks and so with one fill up on the highway I have gone from Utah to San Francisco and still had gas left over. I think with careful driving I could actually just about make it San Francisco to Denver on one tank of gas. It'd be close.

The big tanks are nice also if you pass a very cheap diesel truck stop and your tanks are down. I can save enough on a fillup for a decent dinner.

haspelbein

Yes, diesels do have a very nice range. Going from Utah to San Francisco is pretty impressive. Taking I-80 through Nevada, that state can seem endless.
I wonder if the upgrade of your fuel tanks was available because so many of those Mercedes with diesel engines were actually designed for cab duty.

I only took that trek through Utah to San Francisco once, with a 26-foot moving truck (diesel), pulling my car on a trailer. The mpg wasn't that great. I spent around $300 in diesel from Ohio to San Francisco. On the other hand, I pretty much moved all of my earthly belongings.

The biggest mistake I made was not filling up with diesel in Nevada. I had no clue what I-80 in the Tahoe region at midnight would be like. There are plenty of truck stops all throughout Nevada, misleading me to believe that it would be similar in California.

I finally found a tiny gas station that carried diesel (and was open) after the fuel gauge was on empty for a while, but trying to back out truck and trailer out of that gas station at 2 am was not fun at all.

Mr_Shiftright

Yep, you don't want to run out of fuel with a diesel. Very hard to get started again, and sometimes you need to bleed the fuel lines.

My tanks were an option I think, called "long range" fuel tanks or some such. At least that's what I heard, I've never researched it. All I know for sure is that you can put around 32 gallons of fuel in my car, which is not normal for a 300D according to the book.

haspelbein

Wow, now you only need dual fillers to take advantage of the dual pumps at the truck stop.

Mr_Shiftright

I rarely fill it up, that's a LOT of weight!

haspelbein

At roughly 7.33 lb/per gallon, and maybe 16 extra gallons, you're looking at 117 pounds of fuel. Depending on the weight of your passengers, you may have to kick out one in order to maintain the car's overall weight. It's a questions of priorities, I suppose.

Mr_Shiftright

Well, yes, but if I put in all 32 gallons plus rear passengers, that's over 500 lbs back there! A Mercedes 300D is a bull of a car, but not really a 1/4 ton pickup.

haspelbein

...how many diesel Benzes I've seen in Europe actually pulling a trailer. Prior to the advent of SUVs and minivans, in the absence of pickup trucks, a diesel Mercedes with a trailer hitch has been the next best thing for a long time.

Mr_Shiftright

Yes, but you're not putting all the weight on the rear springs in that case. My Benz gets too light in the nose with all that weight in the trunk. And the auxiliary tank is mounted pretty high up, level with the back seat, so the weight on turns is "high up".

8u6hfd

With my 02 Golf TDI (5-speed)

I usually get 54 mpg (granny shifting)
Hard driving, I got 50 mpg.

THe torque is great blasting up and down the mountains.

Stop & go traffic is a breeze, let go of the clutch, and it idles along at 6 mph.

And it's pretty quiet.

The expensive part is buying the oil (5w40 Delvac 1)

krzyss

imperial galons or US ones ?

Krzys

8u6hfd

US gallons

krzyss