For SAE engineers...What do you think is the biggest obstacle to designing fuel-efficient, reliable engines?

Question

Too little cash for research? Japanese have good ideas locked up in their patents? What's your opinion.

Answer 1

For digitalquik playing an SAE engineer, he did a great job. I have a BS degree in Transportation Design and he hit the nail on the head.

Answer 2

The laws of conservation pretty much cap how much power we can expect out of a given amount of fuel in an air-fuel mixture inside an internal combustion engine.  Current engine technology such as variable valve timing are being used to wring every bit of power out of smaller displacement engines, and it's doubtful we can get any further.  I would expect to see this technology appear on even smaller displacement engines in the years to come; because all else being equal, a smaller displacement = less fuel consumption.  Up to a certain point; if the engine is too small, it will have to be overworked to maintain proper speed even with this technology, at which point a larger displacement engine that runs at lower RPM's will yield better fuel economy and longevity.  It's a balance.

The other factor that comes into play is aerodynamics.  Many modern cars have lost the sleek aerodynamic profile that became prominent in the 80's and into the 90's; presumably to make the cars more crash worthy, or possibly just because the market prefers a "Bigger," more pronounced front end.  If we can give a car a slipperier profile while maintaining its crashworthiness, the engine won't have to work as hard to maintain speed, and we could get away with using engines with smaller displacement.

Then there are the tires.  The market today wants handling, grip, and very short stopping distances.  This requires wider tires.  If people are willing to change their driving habits, we could substitute smaller, skinnier tires on our cars.  The result would be a much lower rolling resistance, meaning the engine wouldn't have to work as hard, resulting in the possibility of going with a smaller displacement engine.  I envision cars with tread widths of half of what we see today, with smaller diameters common which would allow for taller gearing.

Another factor is the engine load.  Accessories such as air conditioning take power from the engine.  If we removed many of the tasks currently performed by modern engines, they wouldn't have to work as hard, and we could get away with smaller displacement engines.  This means that air conditioning may no longer be a "Standard" option on future cars.

By the way, I'm not an SAE engineer, but I play one on TV.  ;)

Answer 3

Physics.

Light cars can be made to go over 100 MPG easily.  That would compromise safety.  So it is always compromise one thing for another.

Currently we only use about 1/3 of 1 percent to actually move the driver.  The rest goes into moving the car and heat exhaust.  So by making the car lighter it can easily go 100, 200 mpg.

Good Luck...

Answer 4

If the above answer were true, motorcycles would get over 100 mpg.