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Sunday, September 11, 2005

Diesel Cars in the US

I regularly hear and read claims that there is some industry conspiracy against bringing diesel cars to the US, or that Americans won't buy diesels because of the bad taste left behind by the terrible diesel products of the late 70's.

Both claims are, to use an old fashioned word, bunk. Here is a short explanation of why I think diesels are not being introduced yet.

The most significant engineering problem with using diesel engines in light duty vehicles, at this point, is the EPA and the California Air Resource Board (CARB). The EPA has mandated that light duty vehicles meet very stringent emissions standards, called Tier II. Because of their inherently high NOX emissions, diesels can not (cheaply) meet these emissions standards. Diesels can be made to meet these standards with a few tricks. CARB's rules are even more stringent than EPA's--diesel passenger cars have not been certified for sale in California since 2003.

First, clean diesel fuel is necessary, with low sulfur levels, so that catalysts can be used to change the NOX into N2 and O2. Without low-sulfur diesel, the catalysts get "poisoned" by the sulfur in the fuel, and can not do their job. Cleaner diesel fuel should start showing up at the pumps in 2006.

An alternative to using a precious metals based catalyst for NOX controls is to use urea injection, where the chemical is injected in the hot exhaust stream. GM is proposing to use this system for its pickup trucks, but EPA has not approved it yet, as the system would require the driver to keep a urea tank filled.

The other major diesel emissions issue is particulate emissions, or soot. The current solution is to capture the particulates in a particulate trap oxidation catalyst at lower temperatures, and burn the particulate at high temperatures.

As to the noisiness and hard-to-start legend of diesel passenger cars, the myth would be dispelled the moment that modern diesel engine cars from Europe would be demonstrated here. American's aren't stupid, and we don't have a very long memory (not necessarily a good thing). The real consumer objection to diesel performance is that they are low horsepower, high torque engines. Diesel engines don't like to spin fast (peak power might be at 4000RPM, dropping dramatically at higher speeds). In order to get performance closer to a gasoline engine, diesel engines need to be turbocharged (like the VW TDI), and also may need an intercooler.

Diesel engines, because of their higher internal pressures, and high torque output, need to have much stronger internals then a corresponding gasoline engine. A diesel engine may have a compression ratio of 20:1, compared to a gasoline compression ratio of 10:1. A diesel engine will tend to be heavier than a comparable gas engine.

The problem with diesel engines for light duty passenger vehicles boils down to basically one thing: cost. To have a diesel engine that meets EPA and CARB requirements, you need to have a complicated and expensive dual catalyst or urea injection + catalyst system. You need to have a turbocharger and intercooler. You need a much stronger engine block, crank, pistons, connecting rods, valves, and head. You may wind up with an engine that costs several thousand dollars more than a comparable gasoline engine. At which point, the added cost of the powertrain outweighs the short term fuel savings (like HEVs), and the average consumer has no great incentive to buy a diesel powered car.

If the "value equation" isn't right, there is no way that automakers are going to invest heavily in passenger car diesels.


John B said...

A quick question and thanks in advance for an answer - is the VW Golf/Jetta or Passat TDi presently being sold in the U.S.?

BTW - in Canada, the price differential between a base engine Jetta and the TDi option is $1,675 (cdn) - about $1,400 U.S. Those were VW numbers from early 2005 (may have changed since)

John B said...

Here is a quote regarding VW diesels in Canada:

"About half VW's Golf and Jetta sales this year are diesels - 70 per cent for the larger Passat - despite price premiums ranging from $1,500 to $2,000 over gas-engined versions."

The Auto Prophet said...

I believe that the VW TDI vehicles are not for sale in California and "Green" states (which follow California emissions rules), so only about 2/3rds of US consumers could buy one.

If VW doesn't find a way to meet Tier II emissions, these products will be not be availble in any US state.

C.J. said...

I remember diesel fuel was quite a bit cheaper than gasoline at one time. Could "cleaner" diesel fuel be part of the reason for the price hike?

dzlsabe said...

AP-they(your bosses)need to let you drive your euro divisions cars and give you some ULSD. Then you'd
know what i know.

ps-see trollhattan

The Angry Engineer said...

AP, nearly 1 million heavy-duty light-truck buyers each year attempt to prove you wrong, and that's despite the inflated price for diesel engines in that market due to tight supply. GM, for example, sells every Duramax they can, despite its $5500 price. Does that engine cost $5500 more than a gas engine? I think not.

I also don't think that the diesel powerband is a problem for most drivers. How many people, on a regular basis, go past 4000 RPM? I'm guessing that the percentage of those that do is in the low single digits.

I don't think that diesels are for everyone, but I think they provide a great way to save fuel at minimal environmental cost.

The Auto Prophet said...

Diesels make perfect sense for large pickup trucks, which need to haul heavy trailers. In that case, the fuel economy and efficiency gains of diesel make good sense.

My post was focusing on passenger cars.

John B said...

Several years ago I test drove a VW Golf TDi - about 20 km. mostly on highway within Toronto. I had a very favourable impression - not drag race material but plenty of power (torque I expect) for everyday driving and passing at any highway speed. No need for a 5 speed manual - whatever speed you are doing just put your foot down and it accelerated. It was very quiet when moving and comfortable at 120 km/hr. At 120 it still accelerated nicely - I may have taken it up to 130 or 140 km/hr. The only diesel noise I could hear occured at a red light when I rolled the window down. I would certainly consider one next time - assuming VW reliability is OK.

Rick said...

Diesel cars make great sense. My family owned one for almost two decades. One of the important factors behind diesel cars is the fact that they LAST LONGER than gasoline engines. Much longer. It is not uncommon to see a diesel car with 200k miles on it. Over the life of the vehicle this more than makes up for the extra expenditure for the diesel engine. The fuel savings are just as good if not better than a hybrid, and a diesel will last years longer. The same arguments used for trucks can be used for cars as well.

The Auto Prophet said...


Of course, you are correct--if you keep a diesel car or HEV long enough, it will more than pay for itself.

However, the average American car owner keeps his car about 8 years. If you assume that the average owner drives 15k miles a year, the average mileage that people keep cars for is only 120,000 miles. And if that is the average, that means that about half of car owners trade their car in before 120K miles.

sh said...

Speaking of:

Biofuels may be hazardous to your car’s health
Experts warn of worn-out gaskets, long-term damage to vehicle engines

But despite the obvious benefits of alternative fuels, car experts caution that there are some hidden drawbacks. A quick switch to E85 or biodiesel, if it is done without enough research and preparation, can cause more harm than good, these experts say. Specifically, an older car may suffer from worn-out gaskets, or lasting damage to a gasoline tank or a vehicle’s overall fuel system.

“It all comes down to lubrication, corrosiveness and viscosity,” said Stanley P. Miller of the Alternate Fuel Project Center. “You can get problems if you haven’t replaced parts of your vehicle that are not compatible with the new fuel you’re putting in your car.”

Anonymous said...

DCX just introduced a CRD Chrysler 300 at the Frankfurt Auto Show. It seems as though these engines offer value to those who do keep their cars up to 100,000 miles. (I do). Personally, I think that the minivan could benefit from a diesel engine. Just think, if DCX offered this new hight tech (Mercedes) 3.0L CRD in the Town & Country and Dodge Caravan, it would offer the torque that American drivers like and improve the fuel economy at the same time.

I for one would consider it.

Eric H said...

Excellent analysis. I know that there are places that specialize in selling used diesels (primarily TDi) for the California market. People should be aware that several states have enacted whatever-CARB-says-is-good-enough-for-us laws, so what happens in CA goes beyond their borders.

Biofuels aren't a problem for the plastic parts in newer cars (since 98 or so, I think), though the biofuels could loosen some of the dino-sludge and clog the car's fuel filter.

For more info, I highly recommend Fred's TDI club and the forums therein.

Anonymous said...

As for the weight issue, Honda sells a 2.2L turbodiesel in Europe (available in the Euro Accord, e.g. Acura TSX sold here) that has an alumin(i)um engine block instead of the traditional iron block, and is therefore much lighter. From what I've seen, it's as good as a BMW or Audi diesel (the engines it's been compared against). Whether it's as durable as an old-school iron block diesel engine remains to be seen, but it goes to show that it's at least feasible.

FWIW, I would totally buy a 330d if it were offered here in the states. I rented an old body style Opel Astra with a 1.6L turbodiesel last summer that had so much torque that, despite being overloaded with six people, I could not stall it, even at 600rpm. It might as well have had a one-speed transmission.

substitute said...

The Passat and Golf/Beetle TDIs are indeed for sale in California, and I see a lot of them on the road around here.

substitute said...

on the other hand, i'm an idiot and those are all at least two years old.

mike said...

Last year, I test drove a Mercedes E320 CDI, that is the diesel version of the popular E320 sedan. wow!! you could barely tell it was a diesel, it actually out-accelerated the regular gasoline version and the only time you could tell it was a diesel was when you first started it or at stop lights with the windows down.

Jaosn said...

I drive a small Peugot 206, in the US I have a Honda Civic. I think that the two cars are comparible. I drive on the highway here at 140kph all the time without any problems. I also drive in the mountains without any problems. Noise from the motor is also not a problem. This car would suite all my city and highway driving needs if it was availible in the US.

Anonymous said...

American gasoline engines have always been, contrary to Japanese or European ones, a high-torque, low rpm units. So modern diesel makes perfect sense for an American consumer. It's power curve is very similar to that of old American V8s.

Anonymous said...

The question is not so much why don't we use diesel when europe does but why do they use it so much. Answer: taxes. In some countries in Europe diesel gets a HUGE tax benefit, so it's comporably cheaper. That attracts diesel cars. In countries in Europe where these tax savings are not as significant diesel is not such a huge part of the market.

That aside I looked recently for a diesel to replace my gas-thirsty nissan maxima and found that the cheapest new diesel in the US is about $22,800 for a baseline Jetta TDI, after dealer fees. I can buy a Mazda 3 or something similar for $15,100. It's going to take a long time to make up almost $8k in savings. I would LOVE to see toyota/honda bring over a diesel version of their econoboxes. I think they'd sell very well at the moment.

icerabbit said...

Don't think there are no emission standards in Europe. It's one of the hottest topics and companies pay themselves blue to comply with environmental rules & regulations. So maybe, in Europe they don't squeeze the last drop out of diesel emissions yet, because they've got more stringent rules elsewhere. While the US is heavy on car emissions, they don't do anything about curbing those from trucks, busses; nor the big industry. Consider diesel passenger cars the easy target; compared to fighting big industry.

Diesel fuel is taxed considerably less than unleaded fuel in the EU. Add longevity and better gas mileage and that's why in some countries half the cars are now diesels. Any size car can be purchased with a diesel engine. Cost is a little extra, but not prohibitive.

Horsepower, performance & speed arguments are bogus. They're fast enough compared to unleaded cars. You can't drive super-fast anywhere except the autobahn. Other places you're stuck in traffic or behind slower traffic. And, with current gas prices ... who doesn't want drive a little slower?

HoosierDaddy said...

Trucks and Busses are subject to emissions standards and have been for some time. In October 2002 NOx and Particulates had to be reduced, they step down again in 2007 and 2010. There has been significant costs associated with the new engines. Several thousand in purchase and lifecycle costs and a 3-10% reduction in fuel economy.
Diesels will become more practical when Ultra Low Sulphur Diesel becomes the nationwide standard in 06. Europe uses ULSD in their cars which makes emissions a lot simpler (Sulphur fouls catalysts in diesel engines much like lead did in gas engines). Without ULSD I don't think the OEMs could meet the 07 EPA standards. As it is most heavy trucks will have to be redesigned for the 07 engine due to the dramatically increased underhood heat from EGR (and in some cases multiple turbos). Not to mention a particulate matter filter/muffler the size of a 150 gallon fuel tank!
One option that is being considered instead of urea injection is an orboard reformer that would enrich diesel to burn the catalyst clean (Delphi supposedly will have a working product online on time). Urea is used in Heavy Trucks in Europe so it is more of a proven idea but it depends on the end user to work, so the EPA's reluctance is understandable.
The Jeep Liberty CRD is doing well and the heavy turbodiesel pickup market is profitable for the automakers, but I agree there aren't going to be a ton of new diesels on the market.
As for the price of diesel rising that is mostly due to surging demand for distillates in China. In California and other states where ULSD is required there is a premium built in, I think everywhere else is supposed to se a 7 cent or so price increase per gallon at the changeover. Of course as the available Crude supply switches more to Sour Crude with higher levels of Sulphur the cost will go up.

Soot Blowin' Otis said...

Their is no engineering problem. EPA and CARB are the PROBLEM.

Anonymous said...

My father bought an Escort Diesel in 1987. It got 68MPG on average. It was a Mitsubishi engine and ran very clean. I really think the car manufactors are behind in the times and are just idiots. Everytime I go to Europe, I cringe that I can not drive that Audi or BMW in the states.

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