[desmo9]

The question is how many people would opt for a V6 diesel in a pickup or SUV when it'd likely be a $2-3K premium? 30mpg is a stretch in a full-size pickup, 23 is more like it. At a 3mpg increase it would take over 100,000 miles to break even on the premium paid. Furthermore, the general (light-use) market still has cold feet about diesels. Where are diesels finding success? In Europe, where gasoline is so expensive, the payback on the diesel premium is much shorter. In the U.S., heavy-duty pickup buyers value the extra low-end torque of diesels. Any gain in efficiency is a bonus. I'd love to see something like a Colorado offered with the rumble and grunt of a diesel, and I'd be one to spend extra money on it... but I'm not sure the overall market reception would make it a good case.

 

[desmo9]

Weight of a truck has almost no bearing on highway mpg, where the low-20s figure comes into play. Aerodynamics, rolling resistance, and gearing are about it. The frontal area and drag coefficient of a half-ton is not much different than a 3/4 or 1-ton, so I still don't see a 40% gain. Energy/gallon of diesel, going by memory here, is about 10-15% greater than for gasoline. So everything else being equal, if a 1 ton can achieve 20mpg, I don't know how a half-ton could do much better than low-mid 20s'. Maybe 25 for a 2WD. V6 thermal efficiency would not be too much better than a V8, so not a huge gain there. Would have to run the numbers.

I'd concur, though, that if you could eke out 8-10 extra mpg on a light-duty truck, there would be a good case for doing it.. with the expectation that people would pay for it.

 

[desmo9]

I meant it the way you said it... diesel has greater energy/volume than gasoline. Sorry if my wording was unclear.

I'm not sure about the "working hard" thing, because the torque needed to push the vehicle down the road at a given speed is the same. I suppose you're saying that a diesel can operate at a lower point on the BSFC curve on-highway, which may be true.

One factor I did leave out, though, which adds another couple mpg in diesels favor, is efficiency. If memory serves, there is another few percentage point gain in efficiency (how much fuel energy is coverted into "go" energy), due mainly to higher compression ratio. Add this to the 15%-ish gain in energy per gallon.

It does seem like a smaller diesel in a half ton would be marketable, if for nothing else the torque spread and to Peterbilt soundtrack. But are these guys willing to pay $3-4 grand for it? The gas V8s are no slouch.

 

[desmo9]

Originally posted by 87GN&98VET+Apr 20 2004, 04:51 PM--></div><table border='0' align='center' width='95%' cellpadding='3' cellspacing='1'><tr><td>QUOTE (87GN&98VET @ Apr 20 2004, 04:51 PM)</td></tr><tr><td id='QUOTE'> <!--QuoteBegin-desmo9@Feb 27 2004, 12:54 PM
Weight of a truck has almost no bearing on highway mpg, where the low-20s figure comes into play. Aerodynamics, rolling resistance, and gearing are about it.

You're kidding right? I hope so because weight has a HUGE effect on gas milage. What do you think effects rolling resistance (besides tires)?

Diesels cost more because the cylinder pressure is so much higher that premium materials / components are required. What I don't get is that if the OEs put as much $$ into developing SI engines such as 42 volt systems, electric water pumps, steering pumps, AC compressor, etc, pneumatically controlled valves, regenerative braking, the list goes on - the economy might be as good or better than diesels. Gain efficiency by increasing volumetric efficiency through turbocharging and reduce pumping loses. [/b][/quote]
No, no kidding. Weight has a negligible effect on rolling resistance, especially negligible compared to wind resistance. Weight impacts city mileage figures, but as long as you're fairly steady on the throttle and keep appropriate pressure in the tires, weight has very little impact on the highway figures. If you don't believe me, throw 1500 pounds in the bed of a pickup, pump up the tires a bit, and hit the highway.

 

[desmo9]

Originally posted by airbalancer@Mar 20 2004, 12:58 PM
Why should there be a premium for a diesel? Why are paying an extra $1000.00 for 5.3 l over 4.8l ?
I think they put a premium on because lemmings like we are will pay it. :chef:

The $1K premium on a 5.3 over a 4.8 is indeed a fleecing by the marketing division, but the diesels do cost alot more to build. From their substantial lower ends to their injector technology, more content is involved. But like the premium of the 5.3, the $5K Duramax premium is rather inflated. But charge what people will pay, right?