Posted on 05/30/2007 6:47:18 AM PDT by PissAndVinegar
I didn’t say TDI diesels weren’t efficient. I said they can’t be as efficient while satisfying varying power demands as they would be if they were running at constant load driving a generator. A midsize sedan uses an average of less than 30hp over the entire driving cycle, but much more than that over short periods. A diesel or gasoline ICE that must be designed to meet the maximum load of 150+bhp is going to use more fuel than one designed for 30hp continuous load.
I also said the hybrids we have seen so far are “mild” hybrids that do not show anywhere near the potential of a series hybrid where the ICE is disconnected from the drivetrain. For a look at what is *possible*, look at what PML Flightlink produced. Is there a 650bhp diesel-only vehicle that can average 80mpg ? I’d love to hear about it.
Well stated.
Sure, go google “THERMAL EFFICIENCY” for diesel and gasoline.
Diesel contains more BTU per gallon than Gasoline, Diesel engines also operate at a higher temperature, a temperature that Gasoline Engines could not operate at, due to the higher compressions they convert more of the energy released to mechanical energy.
FWD cars are definitely cheaper to build - they can bolt the whole drivetrain, sometimes right down to the wheels and tires, together as a unit and then slip it up into the car in one step. Bolt on the engine mounts and connect a few hoses and wires and you’re off to the races.
I don’t know why the Japanese can’t bring us a decent RWD car that isn’t a Lexus or Infiniti. Honda does make one, the S2000, but I can’t even fit in it, and it’s too expensive.
That is what I thought.
Current Diesel engines for vehicles are ~40% and hope new improvements can raise that to ~45%.
Thermal Efficiency Improvement While Meeting
Emissions of 2007, 2010 and Beyond
www.eere.energy.gov/vehiclesandfuels/pdfs/deer_2005/session3/2005_deer_oladipo.pdf
Detroit Diesel Corporation
The most efficient diesel engine runs at about 50% efficiency, the most efficient gas about 38%.
The typical gasoline car engine is about 25%, and the typical diesel is about 40%. There are huge improvements in fuel efficiency with diesel over gasoline.
Will you please provide a source for your claim of 50% efficient diesel? Is this a “street legal” engine?
No, its not a car engine, its the most efficient diesel engine built... General production diesel cars are at about 40% efficiency.
http://people.bath.ac.uk/ccsshb/12cyl/
So this should have been written:
"There is a diesel engine capable of 50% but not available for vehicles."
Thanks for the clarification and information.
BTW, I was on the design and construction team using Wartsila diesels for power generation. Not this big, only 31,000 cubic inches and not from the Sulzer joint venture. My experience on that single job (not a very good sample set, I agree) was Wartsila was a lot better at making claims than delivering performance. But I do appreciate the information, thanks again.
Well, I’m not auditing their claims, just trying to point out that Diesel due to higher compressions and more BTU per gallon are generally more efficient.
I apologise if I wasn’t clear, the point was the MOST efficient gasoline engines only get to about 38% efficiency, while the most efficient diesels are around 50%.
In car engines generally its about 25% efficiency for gasoline and 40% for diesel, as I understand it.
Disclaimer: Opinions posted on Free Republic are those of the individual posters and do not necessarily represent the opinion of Free Republic or its management. All materials posted herein are protected by copyright law and the exemption for fair use of copyrighted works.