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#11
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"Don Stauffer" > wrote in message ... Only solutions- hard- are to greatly > increase the operating temp of engine, and make long stroke, slow > turning engines, which are big and heavy, and while a bit more fuel > efficient, raise the horsepower-needed requirement (self-defeating, of > course). Increasing the efficiency of fuel burned is of course the goal. I did some calculations recently taking the thermal equivalent of mechanical horsepower, and relating it to heat content of gasoline per unit time. (I know that theory and practice here diverge a bit, but for a given horsepower generation there is a direct relationship to fuel burned per unit time) One horsepower is 0.7547 kiloJoules per second. Heat energy to be derived from gasoline is about 50 kiloJoules per gram. If you drive 70 miles in one hour, and use 1 gram per second, that is 3600 grams, or approximately one US gallon (hence 70 miles per gallon). Backing everything up, this would have generated 67 thermal horsepower at 100% conversion efficiency. All things considered, to attain 25-30 mpg on some of todays cars is a pretty decent feat, considering the above ultimate limitations. |
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#12
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Doug Warner wrote: > "Daniel J. Stern" > wrote: > > > >You should've been over on rec.autos.makers.chrysler early last week. Some > >ignorant dip**** calling himself "Whoever" was arguing that restricted air > >filters don't reduce fuel economy. He dug himself a hole most of the way > >to China, making all kinds of hilarious claims regarding having formerly > >designed EFI system, talking about how the O2 sensor controls the fuel > >injectors' pulsewidth during open-loop operation, etc. > > I read you original "discussions" and then did some more research. > Neither the TPM or the MAF have full control over fuel flow. > Although, per this > article:http://www.asashop.org/autoinc/jan97/techtotech.htm > the TPS has less influence than the MAF.. > I suspect this may vary between systems.. Agreed, except what is a TPM? I describe sensor importance this way: MAF is the big dog, TPS input is very important, coolant temp very important though not a quick response input like the previous two, and the O2 sensor(s) provide feedback so the ECM can determine which output values to dictate by use of a programmed data table. Toyota MDT in MO |
#13
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> writes:
>"Steve W." > wrote in message ... > It produces hydrogen rich >> bubbles before being introduced into the engine draft" I have to agree >> with PM when they ask anyone to explain how it works. >Hundred percent agree. Many scam artists in a lot of fields use enough >scientific buzzwords to >impress and amaze the uneducated. There ought to be a law... That people be educated? |
#14
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"Ryan Underwood" > wrote in message ... > > writes: > > >Hundred percent agree. Many scam artists in a lot of fields use enough > >scientific buzzwords to > >impress and amaze the uneducated. There ought to be a law... > > That people be educated? Maybe that is reaching a little far, Ryan ;>). |
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#16
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On Tue, 20 Sep 2005 08:50:45 -0500, Don Stauffer wrote:
> wrote: [snip> > Indeed. Present auto engines considerably exceed the efficiency my old > thermodynamics prof said was the maximum a car engine would ever reach. Huh? I mean... was he talking about the maximum theoretical thermodynamic efficiency, or about how far up to that maximum the efficiency in his opinion would be able to go? shakiro [snip> |
#17
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"shakiro" > wrote in message ... > On Tue, 20 Sep 2005 08:50:45 -0500, Don Stauffer wrote: > > > wrote: > > [snip> > > > Indeed. Present auto engines considerably exceed the efficiency my old > > thermodynamics prof said was the maximum a car engine would ever reach. > > Huh? I mean... was he talking about the maximum theoretical thermodynamic > efficiency, or about how far up to that maximum the efficiency in his > opinion would be able to go? > > shakiro > > [snip> |
#18
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"shakiro" > wrote in message ... > On Tue, 20 Sep 2005 08:50:45 -0500, Don Stauffer wrote: > > > wrote: > > [snip> > > > Indeed. Present auto engines considerably exceed the efficiency my old > > thermodynamics prof said was the maximum a car engine would ever reach. > > Huh? I mean... was he talking about the maximum theoretical thermodynamic > efficiency, or about how far up to that maximum the efficiency in his > opinion would be able to go? > > shakiro I am interested also. You may all remember that some 40-50 years ago, engineers calculated that a 'car' would never be able to exceed 140 mph in the quarter mile. So much for that. I remember professors talking in terms of 25-35% efficiency for an IC engine, I believe. As I mentioned in my original post, 'theory and practice tend to diverge'. Thermal efficiency (or thermodynamic efficiency) is probably still not so very great, but has probably improved since those days. Transmissions, engines, etc combine to give reasonable speed and acceleration (with minimized losses) without usually coming anywhere close to the published maximum horsepower specifications (which are often bogus to begin with). I think this is the most significant factor behind the good mileage we get now. Smoky Yunick worked on adiabatic engines as a consultant during his 'retirement' and made considerable headway. We are closer to being able to build such high temperature engines today than ever before. Lubricants can be made that will hold up near 200C, and metallurgy/ceramics can run in that range and much higher easily enough. To go significantly higher, organic lubricants may not be able to hold the mark....at least, not yet. Eutectic fluids might do it now. Interesting possibilities, anyway. |
#19
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shakiro wrote:
> On Tue, 20 Sep 2005 08:50:45 -0500, Don Stauffer wrote: > > wrote: > > > [snip> > > >>Indeed. Present auto engines considerably exceed the efficiency my old >>thermodynamics prof said was the maximum a car engine would ever reach. > > > Huh? I mean... was he talking about the maximum theoretical thermodynamic > efficiency, or about how far up to that maximum the efficiency in his > opinion would be able to go? > > shakiro > > [snip> The later. He felt we had perfected it. This was before higher octane fuels, higher temp thermostats, and the improved oils and sealed, pressurized systems that allowed the later. |
#20
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