100 MPG

[XFlow_Fairlane]

well actually heat does go up as you are doing work on it. the bigg thing to worry about is heat loss into the cylinder walls and head. this is where smooth chambers help (less surface area) and coatings help.

100mpg is not feasible in a speed going car (IE anything other that a wind tunnel designed body and faster than 70mph)

the power needed to simpley overcome the drag of the body and rolling resistance is gonna take more full than when you can get out of the full needed for 100mpg. basicly there is no way to retro fit an existing car.....but a car fully designed to operate at X rpm and with a slick body could do it. there are some motorcycle guys that build a full aero bubble for a small dicplacement bike with tall gearing that can get around 150-200 I think but they are pushing ALOT less air.

 

[Anonymous]

actually, i am trying to debate something.

the original post says "The compression stroke creates heat which causes more fuel to vaporize"

this is not true- compressing air makes it shed heat, not create it. and compressing vapor causes it to return to liquid.

saying that more fuel will vaporize because of the increased heat is like picking yourself up by the beltloops.

i'm not trying to be a dick, i just thought LazyJW was funnin' with me, so i was giving a little bit back to him.

gas law states PV=nRT

there's no heat factor there. just temperature.

 

[Anonymous]

The weather is unseasonably warm here in Houston.

 

[Anonymous]

ok turbo_fairlane_200,

Your best guess here, what's the max mpg I'm going to get. This experiment is going in a BRICK (1951 truck).

 

[Anonymous]

this is not true- compressing air makes it shed heat, not create it.

WHERE do you get THAT from???????

 

[XFlow_Fairlane]

this is not true- compressing air makes it shed heat, not create it.

WHERE do you get THAT from???????

no crap....are you gonna make me dig out my thermo book and list some equations?


I think with that truck and it set up for any decent power (ie capable of driving at safe speeds in traffic) you would prob be lucky with 20mpg. there is no way a brick like that will break 30mpg and be able to accelerate safely (without a turbo) this past summer I was driving witha fairly lean jetting in a 5200 (stock pinto jetting) with the T5 3.50 gears and TAILGATING semi trailers and I could only get 27 (was driving at 60-65)

unless you chop that top and drop it on th eground it will be tough to get some decent milage.

 

[80broncoman]

this is not true- compressing air makes it shed heat, not create it.

If that is true then there has been alot of money wasted on intercoolers and aftercoolers. In fact why are we trying to limit boost pressure? Throw those wastgates away!!

 

[Anonymous]

If that is true then there has been alot of money wasted on intercoolers

No lie...and I DARE you to grab the tube after my turbo compressor discharge after a run!!!! :fume:

 

[Lazy JW]

actually, i am trying to debate something.

the original post says "The compression stroke creates heat which causes more fuel to vaporize"

this is not true- compressing air makes it shed heat, not create it. and compressing vapor causes it to return to liquid.

saying that more fuel will vaporize because of the increased heat is like picking yourself up by the beltloops.

i'm not trying to be a dick, i just thought LazyJW was funnin' with me, so i was giving a little bit back to him.

gas law states PV=nRT

there's no heat factor there. just temperature.

Reckon in my ignorance I must be confusing heat and temperature, but to my uneducated mind they do seem to be related,at least first cousins maybe

When this old hillbilly was a young lad my Dad didn't own an air compressor so when we had one of our frequent flat tires he would patch it and then hand me the tire pump. (it is possible to inflate a tubeless tire with a hand pump). I learned early on not to touch the bottom of the tire pump Reckon maybe it didn't "increase heat", so that heat must have "moved" by osmosis from the sweat of my brow to the tire pump? :roll:

My 1941 John Deere Model "A" tractor (another one of those hillbilly gadgets") has a HEATED intake manifold to increase the vaporization of the fuel (at least that's what it says in the sales brochure). This tractor was designed to burn stove oil with spark ignition. I challenge anyone to get an engine to run on that stuff without adding some extra heat for vaporization.

It is true that raising the pressure also raises the boiling, or vaporization point. But if you add enough heat it can still get there.

Joe

 

[Anonymous]

the compression stroke doesn't increase heat....

Huh? Reckon how does a diesel engine ignite the fuel sprayed into the cylinder then?

If you are intersted in capturing some of that waste heat going out the tailpipe, do a search on compound aircraft engines. They used turbos that were mechanically geared to feed power back to the main piston engine. Very complex and expensive, but it worked. They were superseded by those pesky turbine engines though.
Joe

This needs clarification. Heat and temperature are two completely different things. Temperature is self explanatory. Heat on the other hand is very often misunderstood. Heat is the transfer of energy which causes temperature changes and the amount temperature will change with a given amount of heat transfer is different for different materials.

What I think he meant was the compression stroke does not increase the amount of internal energy or enthalpy of the fuel/air mixture. The temperature of the fuel/air mixture does rise, but it's not because heat is being transferred to it,, it's because the fuel/air mixture is being compressed. Pressure and temperature are related for an ideal gas by the following equation: pv=nRT where (p) is pressure (v) is volume, is the molecular density of the material, (R) is the ideal gas constant, and (T) is the temperature.

Heat will ALWAYS transfer between two materials of different temperature in the direction FROM the higher temp material TO the lower temp material. So heat will transfer to the cylinder walls from the fuel/air mix, only when it's temperature is greater than that of the cylinder walls.

 

[Anonymous]

What I think he meant was the compression stroke does not increase the amount of internal energy or enthalpy of the fuel/air mixture.

that's exactly what i meant.

you're trying to maximize your return on energy input. temperature is just something that happens along the way.


yeah, NO CRAP. go ahead and dig out your thermo book. i've got one too, and mine's bigger than yours

 

[Anonymous]

Ok, lets look at this from another angle. Forget about mpg. Lets just look at the idea of vaporizing fuel. Can we, using a source of heat, vaporize the fuel completely, get it to the combustion chamber and compress it without it recondensing?

I don't think vaporizing is a problem. Or is it?

And we can heat the intake. In the combustion chamber, will the heat of compression be enough to keep the fuel from condensing at the higher pressure?

What is the maximun temperature thermostat that can be run? And why is that the maximun temp?

Cylinder wall temp, piston temp, cylinder head temp - at what temperatures do these run, generally?

 

[rbohm]

yeah, NO CRAP. go ahead and dig out your thermo book. i've got one too, and mine's bigger than yours

oh great, now we have someone with engineering book envy

 

[ASMART]

Here are some thoughts I have had on maximizing fuel economy. I haven't had the opportunity try them out but I am basing this on much reading and some common sense. Some may disagree and thatyis OK.

1. Run engine as warm as possible for 2 reasons
A. Warm engine will help vaporize fuel
B. The warmer the engine is the less heat will go in engine. Heat
expanding what is in the cylinder is what gives power.
2. Use a thermal barrier coating on the piston top, valves and head to
help prevent heat from being absorbed in the engine(coolant) and also
help prevent preignition. This will allow you to use less ignition
advance, more compression, etc. How much of difference in advance
or compression is a subject for testing .
3. Use long small tube headers to give you better efficiency in the lower
rpm ranges you will want to run in.
4. Use a short overlap cam. This will increase cylinder filling efficiency at
lower rpm range where you will want to be running for best fuel
economy. It also lowers the chance that air/fuel mixture will
be "sucked" out of the exhaust port.
5. Try a multispark ignition system. The leaner you go the more
important that is.
6. Use an electric Fan. That way the fan is only consuming energy if it is
needed.
7. Consider an electric water pump. Why spin the water pump when the
engine is cold?
8. Possibly warm the fuel. It would be interesting to see what temperature
is safe to warm fuel to. This could be done via exhaust or coolant heat.
9. If carburation is used, use a carb correctly sized for the engine. See
Holley's website for chart.
10. If using a carb, fine tune the accellerator pump and jetting.
11. Cruise control always get better milage than feet.

Thats all I can think of at this time. Let us know how your project goes.

 

[Anonymous]

yes, you can heat the fuel. Smokey Yunick had some kind of engine claiming to be Adiabatic, and preheating the fuel was part of that.

and there are plenty others, also.

 

[Lazy JW]

the compression stroke doesn't increase heat....

Huh? Reckon how does a diesel engine ignite the fuel sprayed into the cylinder then?

If you are intersted in capturing some of that waste heat going out the tailpipe, do a search on compound aircraft engines. They used turbos that were mechanically geared to feed power back to the main piston engine. Very complex and expensive, but it worked. They were superseded by those pesky turbine engines though.
Joe

This needs clarification. Heat and temperature are two completely different things. Temperature is self explanatory. Heat on the other hand is very often misunderstood. Heat is the transfer of energy which causes temperature changes and the amount temperature will change with a given amount of heat transfer is different for different materials.

What I think he meant was the compression stroke does not increase the amount of internal energy or enthalpy of the fuel/air mixture. The temperature of the fuel/air mixture does rise, but it's not because heat is being transferred to it,, it's because the fuel/air mixture is being compressed. Pressure and temperature are related for an ideal gas by the following equation: pv=nRT where (p) is pressure (v) is volume, is the molecular density of the material, (R) is the ideal gas constant, and (T) is the temperature.

Heat will ALWAYS transfer between two materials of different temperature in the direction FROM the higher temp material TO the lower temp material. So heat will transfer to the cylinder walls from the fuel/air mix, only when it's temperature is greater than that of the cylinder walls.

You are right, of course. When I went to school, that was called the Second Law of Thermodynamics. Since I lack both a big thermo book and a big diploma I looked at the one really big book I do own, which is a dictionary. The word "heat" has 25 different meanings according to my Webster's Encyclopedic Unabridged Dictionary of the English Language. Definition #3 states "The degree of hotness, temperature". I am aware that in the rarified atmosphere in which engineers speak that this definition will be considered inaccurate but we mere mortals have to fumble along using the crude vernacular. It is unfortunate that this discussion has degenerated into petty sematics, because Mr. Cook has some legitimate questions that aren't getting answered. We should all look to the Reverend Robert Stirling for inspiration, he developed his heat engine out of concern for members of his congregation who had been severely injured in explosions of the crude cast iron steam engine boilers of the day. He and James Watt did their important develpmental work BEFORE the big thermo books were written. Memorizing lots of fancy formulas really doesn't impress me very much, but sincere efforts to find ways of making our precious natural resources last longer does. And if we don't, our great-grandchildren won't have the pleasure of ever driving a Ford Six.
Joe

 

[Anonymous]

yes, you can heat the fuel. Smokey Yunick had some kind of engine claiming to be Adiabatic, and preheating the fuel was part of that.

and there are plenty others, also.

NOTHING is truely adiabatic, i.e. no heat transfer. That is a direct violation of the second law of thermodynamics.

 

[Anonymous]

Here are some thoughts I have had on maximizing fuel economy. I haven't had the opportunity try them out but I am basing this on much reading and some common sense. Some may disagree and thatyis OK.

1. Run engine as warm as possible for 2 reasons
A. Warm engine will help vaporize fuel
B. The warmer the engine is the less heat will go in engine. Heat
expanding what is in the cylinder is what gives power.

Heating the fuel/air mixture will certainly vaporize the fuel much better. However, the hotter the air/fuel charge, the less compression it takes to reach auto-ignition temperature which necessitates lowering the compression to avoid preignition. The lower the compression, the lower the thermal efficiency.

I think the thermal efficiency could be restored if you ran the engine extremely lean. The extreme lean condition would help to prevent auto-ignition by 'thinning out' the fuel/air mixture. This would allow the compression to be raised again. It would also lower the combustion chamber temperatures such as to avoid detonation and meltdown of the piston.

Many would argue that running lean makes more NOx emissions because of the increased temperature of the burn. I have two arguements against this. First, I'm speaking of extremely lean. Extremely lean conditions do not cause the great rise in temperature that melts pistons because the burned fuel/air mix has to also heat all the excess air in the chamber which decreases the amount that the temperature will increase. Second, it takes 3 things to make NOx: temperature, pressure, and time. If you make the engine with fast-burn combustion chambers, the time part is alleviated.

Thermal efficiency is improved as the DIFFERENCE IN TEMPERATURE between the intake and power strokes is increased. Naturally, this is limited by how much you can compress the fuel/air mix without reaching auto-ignition temperatures. If the maximum temperature during the compression stroke cannot be increased, then the minimum temperature during the intake stroke must be dropped. This is the principal reason that we try so hard to lower the intake temperatures on our engines.

So we've got two factors we're trying to achieve, and they are directly conflicting with eachother:

1) We want to vaporize the air/fuel mix to take full advantage of the heating value of the fuel. This requires heating the fuel.

2) We want to increase the difference in temperature between the intake and power strokes, which is limited by the auto-ignition temperature of the fuel.

Now I'm not saying that there isn't a happy medium where the Hot-vapor concept may prove to be the more efficient method, but there are lots of things to consider. It would take some serious thermodynamic analysis to make this work I think.

 

[Anonymous]

Since I lack both a big thermo book and a big diploma I looked at the one really big book I do own, which is a dictionary. The word "heat" has 25 different meanings according to my Webster's Encyclopedic Unabridged Dictionary of the English Language. Definition #3 states "The degree of hotness, temperature". I am aware that in the rarified atmosphere in which engineers speak that this definition will be considered inaccurate but we mere mortals have to fumble along using the crude vernacular. It is unfortunate that this discussion has degenerated into petty sematics, because Mr. Cook has some legitimate questions that aren't getting answered.

Memorizing lots of fancy formulas really doesn't impress me very much, but sincere efforts to find ways of making our precious natural resources last longer does. And if we don't, our great-grandchildren won't have the pleasure of ever driving a Ford Six.
Joe

My intent was to help explain what is going on and to do so, you must clarify exactly what it is you're speaking of,, that's why I explained the difference,, not to boost my ego. It's all good and fine that fancy formulas don't impress you, but if anyone here does want a real solution to the 100mpg engine, we're going to have to get much more in depth in thermo than I have thus far.

 

[Silver Shadow]

Just to confuse the issue futher here's an article on hot and cold intake.
http://store.yahoo.com/basementgroupsto ... spres.html