When DaimlerChrysler unveiled the Citadel concept car at last year's Detroit Auto Show, it was the first demonstration of its patented "through-the-road" (TTR) hybrid powertrain. This system featured two complete powertrains with no mechanical link between them (a gasoline engine powers one set of wheels, an electric drive system moves the others; an engine-control computer coordinates both). Novel it was; understood it was not. Criticism of this idea—some of it coming from certain German engineers—centered upon the redundancy and consequent weight penalties of having two drive systems. Besides, shouldn't hybrids be little economy cars that get 70 mpg, rather than big, fast vehicles like the Citadel?
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| The Dodge Durango TTR hybrid concept, a Texan-sized hybrid based on the Citadel concept car. Perhaps they'll call it the "Alamo" if and when it comes to market. |
Tom Moore, vice president of Liberty and Technical Affairs Engineering and Technology at DaimlerChrysler, would disagree. First of all, Moore is from Texas, where everything is big. Secondly, Moore is responsible for putting the TTR idea into DCX's newest concept vehicle, a hybrid Dodge Durango. Its rear wheels are driven by platform-mate Dakota's 3.9-liter, 175-hp V-6 through a standard 2wd driveshaft. Front wheels are powered by an 88.5-hp Siemens 3-phase AC induction motor that recharges its batteries through regenerative braking. This results in a "full-time" on-demand four-wheel-drive system that gives the hybrid Durango better acceleration performance than a regular Durango equipped with the largest available engine, a 5.9-liter V-8. However, Moore has more reasons for championing this big hybrid than just being a Texan or liking fast trucks. After all, why should compact cars be the only market segment to benefit from hybrid powerplants?
Big Savings
The most obvious reason for this kind of hybrid powertrain is to increase fuel economy, thereby also lowering emissions. The hybrid Durango gets 18.6 mpg. Not staggering, but a 20% increase compared to the 5.9-liter's dismal 15.5 mpg. What's more impressive is looking at the fuel savings from Moore's Texan viewpoint. The hybrid Durango will produce an overall 0.01075 gallons per mile savings. Compare this to a conventional passenger car getting 27 mpg, in which a 20% increase in
fuel economy would only yield a savings of 0.00617 gallons per mile. In the 865-mile drive across Texas on I-10, for instance, the Durango SUV would save 9.3 gallons of gas. The hypothetical hybrid passenger car would save only 5.3 gallons on this drive.
The other issue here is that SUVs are selling like hotcakes. If this hybrid Durango SUV is brought to market, Moore says, DaimlerChrysler can sell 50,000 to 100,000 of them. And they could do this without a lot of capital investment, since the new hybrid would use standard production parts for everything save the electric powertrain. Furthermore, these production numbers would go a long way toward developing the component volume needed to produce a profitable mass-market 70-mpg compact hybrid, according to Moore. So the big question is, "Will this hybrid SUV ever come to market?"
Like anything, there are pros and cons. On the positive side, the electric drive system is packaged to fit in approximately the same space that was previously occupied by the transfer case and front differential. This means that the hybrid Durango doesn't compromise ground clearance, nor should there be any nightmarish assembly problems, according to Moore.
The batteries are mounted under the cargo area where the spare tire would have been; the hybrid makes use of run-flat tire technology rather than having a spare. The batteries themselves do pose a challenge, as traditional lead-acid batteries would not last more than six months under this type of demand. Lithium-ion batteries for hybrid vehicle applications are in development by Saft (Cockeysville, MD) and, according to Moore, would be available as early as 2003.
As for weight issues, the smaller V-6 in the hybrid allows for the downsizing of numerous other parts (radiator, catalytic converter, driveshaft, etc.). A production version of the hybrid Durango would therefore weigh the same as a 4wd V-8 Durango.
Big Brother
The downside of the hybrid powertrain is that it costs more. DCX is quoting a $3,000 price differential between a regular Durango and the proposed hybrid Durango, at the retail level. What this means for manufactured cost is anyone's guess; however, DCX officials have repeatedly affirmed that they have no intention of bringing any product to market that does not produce a profit. Given the oft-repeated (but rarely proven) "truth" that the American consumer will not pay
for environmental friendliness, that would just about sink the hybrid Durango's chances of making it into production. Unless, of course, DCX can get Uncle Sam to pick up the difference in the form of tax credits. Moore has his hopes pegged on a tax-credit bill (HR 2380, Energy Efficient Technology Tax Act) that would give consumers this $3,000.
Sound too good to be true? Perhaps, but even without the tax credit, there might be another way to get a hybrid Durango into production. While Moore may only be joking when he talks about mating the electric drive system to the big 5.9-liter V-8, the Texas paradigm tells us that if there's one thing that Americans are willing to pay for, it's performance.
