100 MPG

[Pinhead]

Went from 15 mpg hiway to 16.5. Sandwiched a piece of screen door between two carb to manifold spacers and got 18 mpg.

How did you do that without getting a vacume leak ?

well, i tried it in my truck, so i'll answer you. you just sandwich the screen between two gaskets and torque her down like you should.
but let me warn you, its not a perfect system! in my truck, the first tank it brought me from 14 to 15mpg, and it slowly declined from there. after about 5 tanks of gas, the screen started to get clogged up to the point where i couldnt run over half throttle. a good spray of carb cleaner cleaned that up for the next two tanks, then i needed it again. last night, i only had about a 30 mile range before it clogged up, so i'll take it off after this class. anyway, i think the problem i have is that my screen is aluminum. aluminum corrodes, leaving a black residue, which is more than enough to clog its holes. while i havent had it off yet, i think thats whats happening-it makes sense to me.
so my plan is to find a screen made of brass or something that wont corrode, and it should do better.
anybody else tried it?

Actually, the aluminum when heated can actually catalytically crack the fuel. The black/brown "sludge" that you're getting on the aluminum is actually the heavier additives that are in the gasoline.

I've been looking for stainless screen for quite a while.

To take this a step further, do this experiment. If you've got your screen, spray some WD-40 through it (using the nozzle). You'll see that the liquid breaks up slightly. Now, take the screen and while spraying the WD-40, tilt the screen slowly. There will be a point (determined by the fineness of the screen) that the liquid will seem to disappear and will be atomized extremely well. If you can incorporate that into your carb screens, you'll get huge jumps in performance and efficiency.

Running high compression increases thermal efficiency in two ways. 1) the air/fuel is squished together tightly so it can react faster; and 2) the higher CR also makes the expansion ratio higher, meaning the expanding air has more time to push on the piston.

The problem with running extremely hot fuel is detonation. This can be avoided, however, with an extremely efficient combustion chamber design. One with a lot of swirl and turbulence in the chamber before the air/fuel is ignited. This further increases the burn speed and allows for less ignition advance, further decreasing detonation tendencies.

If you're truly interested in increasing the efficiency of your engine (gas mileage and power) go to MPG Research and read some of the discussions about PowreLynz (which create a Variable Boundry Layer in the intake port for higher turbulence and aide in fuel vaporization), PowreRingz (which further the idea onto the back of the intake valve), PowreValvz (which give you Infinitely Variable Valve Timing for more torque "under the curve"), Singh Grooves (which increase turbulence in the chamber for more thorough fuel burning and less detonation), and Edging (which further decreases/eliminates detonation and increases torque/horsepower). There are many more mods that will increase FE, but these are my favorites. They address the cause of detonation/ping, and allow you to get a LOT more horsepower by running much higher compression; the side-effect being higher fuel efficiency.

There are quite a few over there working on fuel heaters, many of which are having various degrees of success. Most are using coolant to bring the fuel temps up to ~200°F.

 

[Pinhead]

Matrix Fuel Heater at MPG Research.

 

[Patrick66]

Get a scooter
i think its the only way to get 100 mpg without going to the extreme and investing more than youll ever save. my 50cc 2 stroke air cooled scooter gets More than 100 mpg and it goes 45 mph. that is where the governors set at.
i havent done research on this and alot of you know way more than i do, but i dont think the energy contained in a gallon of gas you pump from the shell station down the street is enough to move a 3000lb object 100 miles at any speed usable for even just drivin around town, definately not for any performance(and i assume that most you are on this forum because you want performance). tuning can give you some good mpg though but, i think probably about 50-55mpg is the max for 200ci carbed engine.

get a scooter if you want 100+ mpg.

 

[XFlow_Fairlane]

I say heat it while pressurized to keep everything in liquid form. this way metering of it will be easier. once sprayed from an injector the lights will vaporize adn the heavys will come out in a fine mist (think like one of those air/water blasters)

this would require an ECU with mapping for fuel temp vs VE so as the density of the liquid fuel changes it can be metered accordingly. you would only need a simple temp sensor mounted on your fuel rail for this. it would require a dead head system after the fuel is heated so that hot fuel is not returned to the tank. this can be as simple as heating it after the regulator into a dead headed rail.

this would be pretty simple with a little work with the megasquirt coding I would think. use a GM all brass temp sensor in a fuel rail, insulate the rail al ittle bit. after fuel leaves for the "fuel rail spur" pass it through a heat exchanger on the manifold with the sending unit sending back temp info (this might not even be needed though. while the motor is cold it will just dump denser "rich" fuel charge into the motor until the coolant temps come up) as long as your heat exchanger is well oversized to give a constant fuel temp even under high flow rates you can prob eliminate the fuel temp sensor from it all.

detonation will be an issue with a well vaporized mix that is hot (like say under compression stroke you might get some rouge ignition)

 

[mikeyo]

If still searching for a fluid to use for a heat transfer media Dow Therm C would be a good choice if you can get your hands on it.
On some of the heating systems I service the Dow Therm C transfers thermal energy at 375 C (643 F) normal operating temperature.
Just a thought.

 

[The Plankster Prankster]

If still searching for a fluid to use for a heat transfer media Dow Therm C would be a good choice if you can get your hands on it.
On some of the heating systems I service the Dow Therm C transfers thermal energy at 375 C (643 F) normal operating temperature.
Just a thought.

in a project i had which never got off the ground, we found a solder whose melting point was 212F and used that for our heat transer liquid. you dont have to worry about it boiling off

 

[Anonymous]

Ok. Ok.Ok.

Long time lurker, new member, First post.

Try this Web site:

http://www.mpgresearch.com

Pretty good site. Good information on this. Answers a few of these questions.

Vizard wrote a great article on this (If you don't know Vizard, then you need to spend some time with his work. One of THE old-school gurus):


http://www.gofastnews.com/board/engine-technology/74-100-mpg-carb-does-exist.html

 

[Pinhead]

It's not the thermal conductivity of water that makes it advantageous as a cooling medium... It's the specific heat that makes it work so well. It is able to absorb a LOT of energy before the water's temperature rises. Very few substances have a higher specific heat, and the ones that do are pretty exotic.

 

[xctasy]

I get quite tired of people dredging up information which isn't valiaded on an engine dyno. You guys can find a way of mathematically reducing heat loss, and improving mechanical efficiency.

Dimensional analysis by a second year unviersity student could put this post to rest, but I'll humour you with the diagram above.



Okay, lets set 10 ground rules. Shove this 'mystery magic mile motor' into
1) a 2800 pound car (all up, including passangers and fuel for 100 miles),
2) at 75 mph,
3) with a 20 sq foot frontal area
4) and a nice 0.18 drag factor, for an over all drag of 3.6 on the bottom axis. A Fox mustang or Ford Probe with a Probe IV body.

5) Acceleration has to be 0 to 60 mph in less than 13 seconds, quarter mile in less than 18, with four 100 pound passengers.

6)You can use modulated displacement to shut down cylinders if you like, you'll need to....

7. Use an optimized engine with ideal gearing ( assume constantly variable transmission)


[Already, its possible to get 70 miles per gallon at 75 mph if its on a flat road].

8 ) Drive train loss is 26.5%,

9) rolling resistance about 3 hp. Weight is stated there not becasue its relevent, just because I don't want someone arguing out of the box again.

10) the 100 miles per gallon has to be achieavble for 100 miles, with four 100 pound people, and the road has a 0% grade, but the car must be able to start out doing 75 mph for 100 miles

So, how are you guys gonna improve the BSFC to less than 0.045, and how low will the BSFC have to be to get 100 mpg at 75mph?.

 

[Lazy JW]

....
So, how are you guys gonna improve the BSFC to less than 0.045, and how low will the BSFC have to be to get 100 mpg at 75mph?.

Thank you, Deano
My old Allis-Chalmers Model C tractor built in 1950 delivered BSFC right at .50 lbs/hp-hr when tested in Nebraska back in the day using updraft carburetion and 6:1 compression ratio.
Joe

 

[Lazy JW]

Ok. Ok.Ok.

Long time lurker, new member, First post.

Try this Web site:

http://www.mpgresearch.com

Pretty good site. Good information on this. Answers a few of these questions.

Vizard wrote a great article on this (If you don't know Vizard, then you need to spend some time with his work. One of THE old-school gurus):


http://www.gofastnews.com/board/engine-technology/74-100-mpg-carb-does-exist.html

I've been lurking at the mpg site for a while now since Pinhead gave us the link. Interesting.

Been trying to learn what I can about the groove theory. Lots of anecdotal evidence but relatively little hard data.

Engines without significant quench pad are mostly out of luck it seems.

David Vizard was quoted as saying that the grooves are a band-aid that can help old-style, lousy heads.

Larry Widmer was quoted as saying he had tried grooves and found them to be helpful only at lower rpm, like less than 3k

Apparently one 383 was dynoed before and after grooves and it lost power at high speeds but gained torque below 3k


Anyone seeing a pattern here? Our Ford Sixes seem to fall nicely into this category. Gonna have to ponderize on this a bit more
Joe

 

[Anonymous]

...

 

[Lazy JW]

...

Thanks for the stimulating input. I guess

 

[Anonymous]

O.k. guys. I only got through page two before I had to move onto other things. It seems that the discussion turned to fuel vaporization prior to entering the combustion chamber. My solution (if it has not already been suggested) is to use a fuel that is already in the vapor, or gaseous state. I.E. compressed natural gas, or propane. There is lots of stuff already running this and it may be a starting place.

 

[Anonymous]

...

Thanks for the stimulating input. I guess

I was responding to crashbox455's idiotic posts on page 1 and then I realized that they were from 2005.

 

[Pinhead]

...

Thanks for the stimulating input. I guess

I was responding to crashbox455's idiotic posts on page 1 and then I realized that they were from 2005.

Why? Technically he is right... Heat and temperature are two different thigns...

Heat: added or external energy that causes a rise in temperature, expansion, evaporation, or other physical change

Temperature: a measure of the warmth or coldness of an object or substance with reference to some standard value. The temperature of two systems is the same when the systems are in thermal equilibrium

Heat causes the temperature change. The reason they're not the same is because different substances can absorb different amounts of heat (joules) before their temperature (degrees) will change (specific heat, anyone?). In other words, dump a certain amount of heat into water, and dump that same amount of heat into metal, and tell me which substance's temperature rises more quickly. Water has a much higher "specific heat" than metal.

Also, there is another fallacy that is being spread on numerous forums, including this one. It's the old "lean mixtures burn hotter" argument. THIS IS NOT TRUE. Gasoline burns "hottest" (puts out the most thermal energy) at 14.7:1. The reason the engine runs hotter when it's running lean is because the air/fuel burns more slowly. There is more time for the thermal energy to be transfered into the engine. This is also why your horsepower drops so quickly when running lean (you don't take away X amount of chemical energy in your fuel for the same amount of energy loss at the crankshaft). This is because more energy is being lost into the engine instead of pushing down on the pistons.

Think of a compound bow vs a crossbow. If both of them have the same "pull weight" the compound bow will out shoot the crossbow every time. This is because the compound bow exerts all of its energy in the first few inches of the release, while the crossbow exerts its energy over a much broader range of motion.

In other words, make the air/fuel burn as quickly as possible as close to TDC as you can, to get all of the pressure within the first few degrees of the power stroke, and your engine will be much more efficient than a "slow burn" engine.

An engine that is overly rich will run cooler only because it takes some amount of energy to evaporate the cool liquid fuel before it will burn (but this not only makes it run cooler, it slows the burn). This is a complete waste of energy, though with most cylinder head designs is completely warranted to keep from burning exhaust valves, etc. This again is due to the "slow burn" nature of the cylinder heads, along with relatively low compression ratio (and thus expansion ratio).

Read up on Larry Widmer's engines, specifically the "soft head" design. He builds his engines without regard to compression ratio, except to keep components from smashing into each other. Most of them are in the neighborhood of 23:1 for pump gas and higher on race fuel. They consume a lot less air and fuel than their "normal" counterparts, HP for HP.

He was making engines which produced 1hp/cc back in the '80s, btw.

 

[StrangeRanger]

Heat is energy. So is work done.
The compression stroke compresses the fuel/air mixture in the cylinder which is work done to it. This adds energy in the form of heat causing the temperature od the fuel/air mixture to increase.

How exactly do you get a temperature increase without adding energy? Inquiring minds want to know...

It's too late and I'm way too tired to repeat Thermo 101

 

[Stubby]

1HP per CC, or 1HP per CU IN?

If I can get 250HP from a 250cc bike, I will have some fun. 8)

 

[StrangeRanger]

How about my 2300 HP Mazda6?

 

[Lazy JW]

...
Also, there is another fallacy that is being spread on numerous forums, including this one. It's the old "lean mixtures burn hotter" argument. THIS IS NOT TRUE. Gasoline burns "hottest" (puts out the most thermal energy) at 14.7:1....

A gentle correction: the savants on this forum have discussed this and agree with your statement. This mis-understanding does pop up regularly though.

One hp per cubic centimeter would be interesting. I wish I could afford to have Widmer build a 23:1 engine for the White Ox just to see what happens 8) 8) 8) Building a drag racer is one thing; building an engine that can live for 30 years, start at 40º below zero, idle around the hay field weighing 20,000 lbs, then pull that load down the highway at 60 mph in 100º temps on 87 octane while getting 10+ mpg is quite another.
Joe