100 MPG

[mikeyo]

That's like saying "if it were possible the manufacturers would be doing it." They spend millions on R&D, too. Tell every cylinder head porter and engine builder that the millions in R&D over at Ford makes our engines perfect and therefore un-improvable, and that they haven't actually been seeing increases in horsepower...

I told myself that this post was over my head but I can answer this one.
Go down and see what your local, qualified, engine machine shop will charge you to do a proper port and polish. Now, with no other changes how much power and/or mileage is this worth? Now do you think the bean counters at Ford or GM will allow the extra cost of production on models that they make many thousands of? The high end performance models likely have little room for improvement in the area of practical and effective design mods. And for the buyer of a new Taurus, you think he wants to spend an extra grand for the car because he found out it has a 3 angle valve job? 99% of new car buyers don't know what a valve is.
The engine design guys for the big three are likely some of the hardest core performance guys around. They can't build $30K engines for $25K cars.

 

[Lazy JW]

Any of you guys actually measured EGT, CHT and power with different fuel mixtures?

I have and I'm bloody confused after reading most of the posts.

Are you going to share?

 

[XPC66]

You guys are starting to get onto the right track in my oipinion. Sure you can see a theoretical drop in adiabatic flame temperature at over unity equivalence ratios because of higher residual mass fractions, but of concern is how the flame speed varies with the ratios.

For the exercise the flame temp is around the 2000°k mark within normal AFR engine ranges. At stoich the flame speed is what..750mm/sec while leaning out will be around 500mm/sec and halve that again if there's 20% gas recirc. Because the flame speed is slower at lean the flame front is slower and thus dwells resulting in lower and later peak pressures. The slow travel results in detonation. The continued burning upto blowdown means the EGT elevates, taking out the valves in the process. CHT drops because of the reduced reduced heat gain (e.g. loss to the exhaust ).

Sure the flame front(s) gets a kick along with the swirl and turbulance introduced by higher compression, quench pads and the like, but that 10, 25 or 34 m/s can snuff rapid propogation if there isn't enough contiguous fuel in it's path, resulting in even hotter EGT as it burns further into the exhaust cycle.

 

[Anonymous]

...resulting in even hotter EGT as it burns further into the exhaust cycle.

Here we have why lean burn creates heat in an inefficient engine.
With excess O2 combustion temperatures are lower but so is burn
speed. When the flame continues into the exhaust stroke engine
temperature rises.

 

[Patrick66]

this makes my head hurt

 

[XPC66]

Ok put simply; if you have a 4" diameter birthday cake with 10 candles and you fan it, chances are you'll snuff them all. Put 100 candles on the cake and fan it and you'll find far more candles stay alight, with the extinguished ones likely to be reignited by the other flames. The enthalpy of the individual candles is the same, but they aggregate to much more heat.

 

[Lazy JW]

....
For the exercise the flame temp is around the 2000°k mark within normal AFR engine ranges. At stoich the flame speed is what..750mm/sec while leaning out will be around 500mm/sec and halve that again if there's 20% gas recirc. Because the flame speed is slower at lean the flame front is slower and thus dwells resulting in lower and later peak pressures. The slow travel results in detonation. The continued burning upto blowdown means the EGT elevates, taking out the valves in the process. CHT drops because of the reduced reduced heat gain (e.g. loss to the exhaust )....

So less fuel = more heat. I like that Reckon how can I explain to Mama that if she puts less wood in the cook stove that her muffins will bake faster? Plus I won't have to cut as much firewood! I'll probably end up having hot tongue and cold shoulder for supper

But seriously, what if we leaned this out at say, 975 rpm? Seems like flame speed wouldn't be as critical then. With adequate burn time I would think that less fuel=less heat just like in Mama's cook stove.
Joe

 

[XPC66]

You're twisting the content to suit your stove. But seeing as you want to go that way, your mumma's stove flue has a choke to coarse regulate the exhaust flow and thus the fuel/air mixture doesn't it? If you loaded the firebox up with kindling and kept the choke at miniumum opening what happens? If, instead, you put a small amount of kindling in, open the choke fully and get the bellows onto the flame, what happens? How hot does the stove top get, how hot is it in the firebox, how hot is the flue? Of course with an engine you have a time contraint of a 180° stroke.

 

[mikeyo]

Hmmm....if you put a really big load of wood in the stove, opened the flue, and put the bellows to it, wouldn't it get hotter than a little wood and the rest the same???

 

[Lazy JW]

.... How hot does the stove top get, how hot is it in the firebox, how hot is the flue? Of course with an engine you have a time contraint of a 180° stroke.

That depends on if I brought in green jackpine wood or dry tamarack

Anyway, my 1941 John Deere tractor tops out at 975 rpm. Does this significantly alter the flame speed influence of a lean mixture? How about my White Ox pulling a 20,000lb load at 2500 rpm?

I suspect that a great deal of knowledge is directed at high-horsepower, high rpm useage and somewhat less is aimed at improving BSFC at lower speeds. I'm just trying to get a better understanding of the world from the viewpoint of my needs.
Joe

 

[XPC66]

Hmmm....if you put a really big load of wood in the stove, opened the flue, and put the bellows to it, wouldn't it get hotter than a little wood and the rest the same???

Well if you put loads of wood in the limitation would be getting enough smoke out to get the air in. Sure you will get more heat to boil that big arse pot of water on the stove top, but is the firebox temperature any different with a small amount of kindling burning steadily compared to a large amount of kindling with insufficient oxygen for a complete burn?

 

[XPC66]

.... How hot does the stove top get, how hot is it in the firebox, how hot is the flue? Of course with an engine you have a time contraint of a 180° stroke.

That depends on if I brought in green jackpine wood or dry tamarack

Anyway, my 1941 John Deere tractor tops out at 975 rpm. Does this significantly alter the flame speed influence of a lean mixture? How about my White Ox pulling a 20,000lb load at 2500 rpm?

I suspect that a great deal of knowledge is directed at high-horsepower, high rpm useage and somewhat less is aimed at improving BSFC at lower speeds. I'm just trying to get a better understanding of the world from the viewpoint of my needs.
Joe

Presumably with such a low revving engine the valve overlap is minor, short duration and spark close to TDC? If you run lean you'll probably need to advance the spark some tangible degrees, which may cause a few headaches with detonation.

With zip overlap you aren't going to get any benefit from blow through that might otherwise provide some relief to the exhaust valves.

It's widely known in the aircraft industry that the loss of cooling from the latent heat of vapourisation (largely residual mass fractions) because of a lean condition results in elevated cylinder and exhaust temperatures, which promotes oil buring at the rings and det. The exhaust valves carry 33% of the heat of combustion and rely in part on the cooling from the fuel. Double whamming them with increased gas temp and lower cooling is just asking for trouble.

 

[Lazy JW]

...Presumably with such a low revving engine the valve overlap is minor, short duration and spark close to TDC? If you run lean you'll probably need to advance the spark some tangible degrees, which may cause a few headaches with detonation.

With zip overlap you aren't going to get any benefit from blow through that might otherwise provide some relief to the exhaust valves...

Good guess! On the Johnny Popper the exhaust closes at TDC and the intake doesn't start moving until 10º ATDC. There is actually 10º with BOTH valves closed, I observed this some 20 years ago when I rebuilt the engine but only recently found those numbers in an old manual. Ignition timing is specified right at TDC as well. I presume this is due to the slow speeds and the intent is to get peak pressures at the best crank angle.

BTW, compression is a whopping 4.75:1
Joe.

 

[Anonymous]

Dont know if this has been posted on this forum before but it is an interesting concept but a big departure from current technology. 6 Cycle engine?


http://www.autoweek.com/apps/pbcs.dll/a ... WEEKSISSUE

 

[Anonymous]

Wow, I thought Crower had died some time ago. The bio neglected to mention that he had one of the best racing fuel injections of the old days. The man hardly ever did his thinking inside the box; no suprise he came up with this.

 

[dieselmaster]

i see this thread has kind of died off from the original subject of 100 mpg vehicle. In todays fuel crisis if you want to call it that i would beleive more intrest could be stirred again. Biggest thing against fuel economy is drag on the vehicle. Most of you guys i assume are running pre 80's vehicles which lets face it are far from the shape of a rain drop, most aerodynamic design for wind resistance. That and rolling resistance to the road making to large aspects to cover when gaining fuel mileage. In the old hot rod article on classic inlines they increased tire pressure to 50 psi i think, less rubber on the road to roll more. But to the beef of it, that hunk of iron that is suppose to propel us down the road is what most people want to improve upon. Set the inline to run like a diesel, lots of heat due to incredible compression to ignite the fuel, very efficeint, but our blocks would blow apart. However high heat in the chamber burns th emost fuel thus utilizes more of the fuel that is sucked in. More heat means we must disipate it faster, bigger rad, more fans, bigger water pump for more flow, evens experiment with a/c refrigerant as a cooling product in some way, (cold air intake utilizing an evaporator, not my idea ford made that first.) I heard some guy in the sixties figured out how to vaporize, not atomize, the fuel to make the particles as small as possible. In a diesel we atomize the fuel with extremely small orfice holes in the injectors and high fuel psi. The smaller the fuel droplet the easier it is to burn it up due to less surface area. Vaporizing is the way to go. A little bit of water in with th emix to help keep the heat down a little and to carry condensed oxgen into the cylinder, more power from cheap water, not a lot keep in mind. less engine power loss from internal coatings on pistons, rods, cranks etc. complete fuel distribution from items like the new aluminum intake from classic inlines, great product to quit wasting fuel. Our cars now, i own a 68 falcon with a 200, can feasable get 50 mpg with most of the things i mentioned, getting past that will require the engineering. I've read alot of the threads, well a number of them, a lot of guys hear have a heck of brain in their skull that i'm sure these items coudl be tested and addressed.

 

[Patrick66]

just thought i'd throw this in.

95 mpg civic:
http://ecomodder.com/forum/showthread.php/aerocivic-how-drop-your-cd-0-34-0-a-290.html

Approximate mileage on a flat road at 85F, 95mpg at 30 to 65mph, 85mpg at 70mph, 65mpg at 80mph, 50mpg at 90mph.

 

[Anonymous]

Well, craftsmanship is not his long suit! And I'm skeptical about the guy and his claims. The front wheel skirts (with inside rollers spinning madly) fit so close to the tires that he must have about a 200' turn radius. Has he ever really had the car on the road?

Like a lot of guys who haven't read anything about aerodynamics, he thinks that anything vaguely teardrop-shaped is going to be very slippery. Actually, the long tail of the ideal (for a given cross-section and velocity) tear-drop can be truncated considerably before drag increases significantly, especially at ordinary driving speeds. Eliminating the kicked-up "spoiler" on the trailing edge of the Civic top would account for much of the improvement he attributes to the tear-drop tail.

The full fender skirts, assuming you can steer the car, are a big drag reducer. A full belly-pan, which he seems not to have tried, would also be good (oops, now I see he does have a belly-pan). His idea of diverting over the car any air not needed for cooling is good. Careful control of airflow through the engine bay also could help.

Look at the photos again. The guy does such crappy bodywork (yes, I understand it's just a test-of-concept) that the parasitic drag of the rough edges hanging out must subtract considerably from whatever reduction he has made to profile drag. Reducing parasitic drag is why the car companies went to the trouble of flush-mounting the glass and eliminating rain gutters.


Check out this VW prototype: http://blog.wired.com/cars/2008/07/laugh-at-high-g.html

 

[shortbox07]

im no engineer or thermodynamics guru but this thread is very good "food for thought" excellent input on everyones part

 

[Ronn]

100 miles a gallon? Heat? Temp? Efficiency? MY personal theory is to just go look at the TESLA ROADSTER.

If there was a way for us gasoline guys to get that kind of performance, we would have it by now. No conspiracy there. My thinking is that why would the government or auto mans hide something when there is so much more money to be made to manufacter and distribute it as a customer upgrade or a standard option to every known automobile being produced?

There will ALWays be the need for fossil fuels and no amount of automobile effeciency will put a dent on that.

Imagine..400+ miles without a drop of gasoline! and 258 HP! Yes you heard it right, The Tesla Roadster does this, with electric. Now imagine a small 2 cylinder engine installed running on hydrogen, solely for the purpose of running a generator to charge the system on the fly! we could see 1000 miles before having to stop for...hydrogen and a snack! lol

Hey I'm with yall on this, just thought this a good way to stir the pot with some new ingrediants.

TESLA