Re: Gasoline grade BTUs per gallon?

Pooh Bear <rabbitsfriendsandrelations@xxxxxxxxxxx> wrote in
news:4477601A.B1ECBE3@xxxxxxxxxxx:



"K. Jones" wrote:

Bill, would it be more accurate to say an engines can "*be built*
with slightly greater efficiency by utilizing a higher effective
compression ratio"?

That's a diesel ! They have much higher compression ratios than
gasoline engines and are therefore more efficent.


The higher compression ratio is only one part of the efficiency advantage
of a diesel engine, the other part is the fact that a diesel has no
throttle, it has no appreciable "vacuum" acting on the pistons when moving
down on the intake stroke that a normal gasoline engine has, to make a more
accurate comparison it needs to be evaluated against a Miller cycle engine
(Google Mazda Millenium or Miller cycle for more info).


Saab's new bio-power gasoline engines that run on E85 are more
efficient on ethanol by turbocharging at a higher boost pressure than
on gas that utilises the higher octane of ethanol ( a bit similar to
having a higher compression ratio too ).



I think it was also Saab that came up with a variable compression engine
that, when lightly loaded ,raised compression ratio on the fly instead of
or in addition to advancing spark timing. Very promising from an efficiency
angle but the bearing that allows the pivot to operate the compression
ratio change may be it's Achilles heel.The way it worked, if I remember
right, was the head and cylinders were attached together and they moved up
and down relative to the crank by pivoting closer and further from the
crankshaft/crankcase. The engineering challenge would seem to be the pivot
bearing longevity and the (rubber bellows?)moving seal from the
head/cylinder assy to the crankcase. Also it would be a complex ecu map to
balance compression ratio, turbo boost, spark timing and engine load (not
to mention octane of fuel)to get better efficiency and still run on what
passes for gasoline today. A diesel would be a lot less complex , and think
of your local gas station or chain repair shop trying to diagnose and
repair this technology on your dime when out of warranty AARGH!
Guaranteed headache.
As good as Saab engineers are I would only consider this technology for
myself if Honda had a heavy hand in development and manufacture, I was gun
shy of the Honda Civic HX engine technology also.
Scott
.

Relevant Pages

  • Re: Ineresting new engine design
    ... The Scuderi Split-Cycle Engine changes the heart of the conventional engine ... combination of one compression cylinder and one power cylinder. ... the environment as well as the efficiency of the engine. ... With Rv the compression ratio and gamma the ratio of specific ...
    (uk.transport)
  • Re: Thanks for Patent help.
    ... >>As previously noted, NASA, DARPA, and DOE are satisfied that, though his ... > Sounds like this engine might be valuable for its high power to weight ... > efficiency you mentioned. ... > the ratio of mechanical output to heat input, ...
    (misc.rural)
  • Re: Tired of bumping along to Oshkosh?
    ... modern turbine engines may achieve compression ... >the compression ratio of piston engines due to the differences between ... >compression ratio in a piston engine has nothing to do with how you would ...
    (rec.aviation.homebuilt)
  • Re: Digital Tools Help Users Save Energy, Study Finds
    ... Blah, blah, blah... ... compression 1960's V-8" that implies any of the absolutely bizarre things ... sort of comment on compression ratios and engine efficiency. ... I point out that you don't know $h!t about A so therefore your internal combustion engine analogy obviously questionable. ...
    (comp.home.automation)
  • Re: Old car, new engine. Spanking...
    ... Hes probably got most of the extra power purely from daft compression ... IRL our Greek will get close to nothing on raising the compression ratio ... engine which in the escort Mk2 will be a blast to drive but it hasn't ...
    (uk.rec.cars.modifications)