The Truth About Diesels

the truth about diesels

No wonder the Germans are so gung-ho on sending their diesels across the pond. Europe’s two-decade long diesel-keg party has been crashed by a new generation of super-efficient, clean and cheaper gasoline engines. A royal diesel-overproduction hang-over is inevitable. The Germans’ morning-after solution: send the stinky leftovers to enthusiastic Yanks waiting with open arms, who’ve conveniently forgotten their killer hangover from the last US diesel orgy.

In 1892, an experimental ammonia engine literally blew up in engineer Rudolph Diesel's face. Laid-up in a hospital bed, he pored over Nicolaus Otto’s pioneering work on the internal combustion engine. Diesel identified its weakness.

Diesel tumbled to the fact that the Otto engine’s efficiency was intrinsically compromised by the fact that it mixed fuel with air prior to compression. Too much compression resulted in uncontrolled pre-detonation. Diesel’s solution: inject fuel separately from the air to allow super-high compression and eliminating the need for a throttle (reducing pumping losses). Diesel's engine was roughly 30% more efficient than Otto's.

In 1989, VW/Audi ushered in the modern direct-injection (TDI) diesel. The group's oil burning powerplant set a high-water mark in the diesel’s long development. With Europe’s high fuel costs, the more expensive (yet efficient) diesel engine could now pay for itself quite easily. The calculation triggered Europe's diesel-boom, resulting in a 50 percent market share vs. gasoline-engined propulsion.

But Europeans have been paying a price (other than at the pumps): particulate emissions (Particulate Matter, or “PM”) and NOx pollution. Many European cities have serious particulate and diesel odor problems. Several European cities impose restrictions on diesels during PM alerts.

The new generation of “clean(er)” diesels that meet the US Tier2 bin5 standards cut PM emissions substantially, but not completely. Already, there are warnings that PM from “clean” diesels still poses a significant health risk.

The diesels coming our way carry several other penalties, especially versus the gas hybrid. The complicated and expensive NOx catalysts and urea injection schemes (“BlueTec”) cut efficiency by five percent. Meanwhile, the next Prius is projected to be 15 to 20 percent more efficient. And Toyota is bringing down hybrid production costs.

The diesel vs. hybrid mileage/cost gap widens… further. And the “clean” diesel’s just-barely compliant emissions still can’t touch the gas-hybrid’s practically breathable exhaust.

Then there's the elephant in the room: global warming. Clearly, the political winds are blowing against CO2. Diesel fuel has higher carbon content, resulting in 17 percent more CO2 per gallon of fuel burned than gasoline. With the diesel’s efficiency superiority down to 25 percent, a “clean” diesel emits only 13 percent less CO2 than yesterday’s gas engine. And that small gap is… wait… gone.

While the diesel’s efficiency peaked in 1989, and lost 5 percent to PM cleansing, gas engine development is on a roll. Engineers are systematically tackling all the inherent deficiencies that Diesel identified in his hospital bed. (No wonder Rudolf was considered paranoid; maybe he suspected that eventually the Otto engine would catch up.)

A farrago of new gas-engine technologies has converged, which Europeans have been quick to embrace. VW’s 1.4-liter 170hp TSI gas engine is a perfect example of the trend. The TSI starts off with the help of a supercharger (no turbo-lag), and then switches to turbocharging (no parasitic losses). With diesel-like torque and direct injection, it’s the best of both worlds.

A CO2 output comparison with two other similar-output VW engines is telling. Their 170 horse 1.4-liter TSI produces 174g/kms of CO2. Their 150hp 2.5-liter five cylinder engine (US Rabbit only) emits 240g/km. And their 170hp 2.0-liter TDI diesel (not US compliant) produces 160g/km.

American Rabbit drivers are paying a whopping 38 percent efficiency penalty compared to the Euro-Golf TSI, as well as giving up gobs of torque and twenty horsepower. If VW’s 170hp TDI were “cleansed” to T2b5 standards, its CO2 output would be no better then the gasoline TSI.

And that’s just the jumping-off point. Start-stop technology, full valve control, and stratified direct-injection offer anywhere from 10 to 25 percent further improvement potential. Combine these goodies with mild-hybrid assist/regeneration, and the diesel party’s kaput. No wonder the Germans are all hard at work on mild-hybrid technology. It’s their best shot to keep up with Toyota’s CO2 meister, the Prius (102g/km).

A study by the consulting firm AT Kearny confirms the diesel's demise. It predicts that only 25 percent of Europeans will find diesels an attractive economic proposition by 2020.

Have Rudolf Diesel’s paranoid nightmares come true? Not totally. Diesels are a welcome mix to the party for larger vehicles that spend a lot of time on the open road. Count on GM’s new 4.5-liter “baby” Duramax diesel to be more popular with the light-truck crowd than the gas hybrid option. But when it comes to smaller vehicles, the numbers just don’t add up.

Although Rudolf Diesel’s engine WAS intrinsically more efficient, it turns out that Otto’s engine is a lot more clever at learning new tricks.

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  • Fallout11 Fallout11 on Jul 18, 2007

    'No Escape From Diesel Exhaust' "Pollution levels measured inside cars, buses, and trains during commutes are many times greater than levels in the outdoor air at that same time. In some cases, the ultrafine particle levels are comparable to driving with a smoker." http://www.catf.us/projects/diesel/noescape/

  • Danwat1234 Danwat1234 on Jun 18, 2012

    The Prius C is a suprememly fuel efficient vehicle, getting 52MPG average US gallons in the real world (Fuelly.com) and more if you try. I don't think VW can compete with Toyota's Pri. The Prius C is only $18K for the base model and $20K for a level 2 or 3 Prius C. Cheaper than a TDI hybrid and as good of MPG without the complex emissions controls for diesels.

  • Master Baiter The D-bag elites like Al Gore demanding that we all switch to EVs are the type of people who don't actually drive. They get chauffeured around in black Yukon Denalis. Tesla does have a good charging network--maybe someday they will produce a car that doesn't suck.
  • MRF 95 T-Bird As a Challenger GT awd owner I lIke it’s heritage inspired styling a lot. There’s a lot of 66-67 as well as 68-70 Charger in there. It’s refreshing that it doesn’t look like a blob like Tesla, Volt/Bolt, Mach-e BMW I whatever etc. The fact that it’s a hatch makes it even better as a everyday driver thus eliminating the need for a CUV. If it’s well built and has a reliable track record I can see trading up to it in a few years.
  • Jbawden I thought sedans were dead? Coupes even more so. The core Charger/Challenger buyer is in it for the Hemi. To whom is this and the presumed EV Camaro marketed to? The ICE versions of these cars have a LOT of shortcomings, but rear drive, a V8, and a Tremec 6 speed made all that disappear. If you're forcing me into a 1,000hp appliance, then give me some visibility and practicality while your at it. And for the love of all things holy, please allow me to maintain a little dignity by leaving off the ridiculous space jam sound effects. What out of touch focus group think approved that? It's almost as embarrassing as the guy who signed off on the Pontiac Aztec.
  • Jalop1991 The simple fact is, America and Americans excel at building complex things (bridges, for example) but absolutely SUCK at maintaining them. We're too busy moving on to the next new shiny thing that a politician can get good airtime for. Fixing the bridge? Not sexy. Cutting the ribbon at a new EV charge site? Photo-op worthy. Demanding that the owner of said charging site be accountable and not let his site become the EV equivalent of a slum? Hard and not a newsworthy event.I have a PHEV and once tried some sort of public charging, just to see what happens. Failed miserably. We'd all be riding horses today if gas stations performed like EV charge stations do.
  • SCE to AUX Apps like PlugShare prove a few points:[list][*]Tesla's charging network is the best, almost always earning a 10/10.[/*][*]Dealer chargers are the worst, often blocked (ICE'd) or inaccessible behind a locked gate.[/*][*]Electrify America chargers aren't bad; my few experiences with them have been quite good. But they are also very new.[/*][*]Calling the help line is nearly useless.[/*][*]There are still charging gaps in high-travel flyover areas, which coincidentally have a lot of "Trump" flags waving in them.[/*][/list]As an EV driver and engineer, I don't understand how public chargers get so screwed up. They are simple devices. My home charger is 10 years old and has never missed a beat, but it only gets one cycle a day and lives indoors.
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