Better fuel efficiency through vapor carburators?

[lamar]

I'm sure everybody has heard all the stories about high mileage carburators and the oil companies etc. But why has this problem not been solved? Approximately two thirds of the fuel we burn in our cars goes out the tail pipe. I've read that someone has used catalytic cracking to breakdown the fuel into a more user friendly vapor and got incredible mileage. Naturally I'm a bit of a sceptic but I'd like to hear what people have to say about the idea.

 

[Cliff_J]

The fuel delivery and combustion process aren't the issue so much as the design of the ICE itself.

The design of the diesel ICE offers better efficiency with its higher compression ratio to create higher average cylinder pressures and slower burning fuel to allow longer periods of high cylinder pressure, but still loses plenty of BTUs out the tailpipe and into the cooling system.

I think its a lost cause to search for better efficiency with the fuel itself like trying to gain aerodynamic efficiency by changing the type of carpet used on the floor of the car. But hey, I enjoy paying $$$ at the pump - NOT!

A high-output and cheap to manufacture fuel cell would double our efficiency instantly even from the existing fuel sources, and allow further flexibility into others. That's the answer, IMHO anyways.

Cliff

 

[Michael D. Sewell]

1.) ALL of the fuel I burn in my car goes out the tailpipe.
2.) Almost all of the fuel I put in my tank gets burned.
3.) I can prove it.
4.) So can you.

 

[faust9]

Originally posted by lamar
I'm sure everybody has heard all the stories about high mileage carburators and the oil companies etc. But why has this problem not been solved? Approximately two thirds of the fuel we burn in our cars goes out the tail pipe. I've read that someone has used catalytic cracking to breakdown the fuel into a more user friendly vapor and got incredible mileage. Naturally I'm a bit of a sceptic but I'd like to hear what people have to say about the idea.

This sounds like a "hoakey" explanation of EGR. EGR shows a minimal improvements in milage but it doesn't do it by altering the exhaust gasses into some magical vapor. Moreover, combustion is an oxidation process--how much energy would be required to reverse that process? Answer: A significant amount (more than required for the original reaction). Where is this extra energy coming from?

High milage carbs are around and fairly easy to manufacture. The problems associated with these are power and emissions.

 

[Michael D. Sewell]

All around the globe are thousands of racing teams who spend every waking moment thinking about how to get an extra horsepower out of an engine, and how to get a tenth of a mile per gallon more on their fuel mileage. At the same time, there are tens of thousands of mechanical engineers working for automobile manufacturers(maybe the most competitive industry in the world) who would dearly love to get any possible edge on the competition. A lot of people would have you believe that it has never dawned on any of these engineers to improve the efficiency of their products. What do you think these engineers do all day?

 

[russ_watters]

Originally posted by Michael D. Sewell
All around the globe are thousands of racing teams who spend every waking moment thinking about how to get an extra horsepower out of an engine, and how to get a tenth of a mile per gallon more on their fuel mileage. At the same time, there are tens of thousands of mechanical engineers working for automobile manufacturers(maybe the most competitive industry in the world) who would dearly love to get any possible edge on the competition. A lot of people would have you believe that it has never dawned on any of these engineers to improve the efficiency of their products. What do you think these engineers do all day?

Well put.

Lamar, there are certain fundamental restrictions on the efficiency of internal combustion engines. It is extrordinarily difficult to get an otto cycle engine above about 35% and the efficiency is directly related to compression ratio as you can see from THE EFFECIENCY EQUATIONS. Compression ratio is why the diesel cycle (similar to, but not exactly the same as the otto cycle) is a fair amount more efficient than the otto cycle.

One thing not talked much about though is tighter computer control over the combustion process. Its really not that expensive and though it only adds a few percent to the efficiency, it reduces the nastier emissions by a considerable amount.

 

[Ivan Seeking]

Since higher compression ratio's also produce more NOX's, two different environmental concerns come into conflict with each other here - efficiency and NOX pollution. I assume that we are forced to seek the middle ground on this point.

Does anyone know how efficiently the fuel is atomized in modern fuel injection systems as compared to the theoretical ideal, and to what degree does this impact the final fuel efficiency?

My preferred solution: Go Hydrogen.
https://www.physicsforums.com/showthread.php?s=&threadid=4127

 

[Cliff_J]

The lean burning of H2 in an IC engine with a high compression ratio (to give us high efficiency) will still result in the production of NOx. Given that H2 used on an existing ICE will suffer a 15% decrease in power output, it won't be until the technology of direct injection makes it way from the lab to a production line that we'll see a 15% increase in power output compared to a gasoline engine. Not bad, lots of promise once the compromise over higher efficiency of fuel spent/NOx produced is optimized.

Also, there are researchers working on devices to reduce NOX emissions by 90% or better via a fuel powered chemical scrubber. They are retrofitting this device to existing ICE engines like on a bus to cut down on its output, same could easily be applied to an H2 vehicle espcially since the size could be much smaller. I don't remember the details, but it was on a science channel show like 'TechKnowledge' or one like it.

I've also read of a place that uses a metal hydride as the storage mechanism for H2, offering a greater density per volume than even liquid H2. It is low pressure and should the container become ruptured its not flammable even if in direct contact with a flame. It suffers from high cost and is can be easily destroyed by exposure to components in regular air. Some place was using in a Corvette they retrofitted to run on H2. I'll see if I can dig up some links.

Cliff

 

[Cliff_J]

Here's a couple relevant to what I posted:
http://www.eere.energy.gov/hydrogenandfuelcells/fuelcells/pdfs/fcm03r0.pdf
http://www.unitednuclear.com/h2.htm

Also, why no support for E85 and biodiesel as interim fuels that can readily replace fossil fuels and utilize the same infrastructure? They definitely would be accepted with open arms from our shrinking agriculture industry, reduce our dependence on foreign oil, and require no expensive fuel cells or public education about the safety of H2. Instant green IMHO.

Cliff

 

[Ivan Seeking]

Great links! Thanks.

Again, if anyone is interested in this - Hydrogen powered cars, and a Hydrogen Economy in general - please see the link that I provided.

https://www.physicsforums.com/showthread.php?s=&threadid=4127

There are many other good links contained within the thread. I feel that H2 cars, and H2 production generally are some of the most important emerging technologies. As for options like biodiesel, in principle I support anything that could help reduce our need for oil, but I also feel that we need a coordinated effort to get hydrogen off the ground...so to speak. In this sense I prefer to see a focused effort for H2. As for E85, there seems to be a lot of problems with cars that run this stuff. At the least I have heard such talk from technical people. I'm not sure of any specifics. I know that home produced ethanol for farms has or had [at least] really taken off. In the long run though, I worry about the implicit wisdom of putting food in competition with energy.

 

[Freddie]

To: Lamar
Why has the problem not been solved? Goood question! Answer: (A) You pay for all the unburned fuel going out the tailpipe. (B)This represents positive cash flow for refiners and petroleum companies. (C) They get very upset at people who want to increase fuel efficiencies by factors of 2, 3. 5, etc. (D) What happens to good hearted people who want to cut BIG OILs cash flow by factors of 2, 3, 5, etc? In the 1920s a lot of work was done to improve gasoline mileage. For some strange reason, it is very difficult to locate records of this work. On the Internet, "This page is not available" comes up many times. I wonder why? Nevertheless, there is a lot of valuable information on the internet. It will just never be implemented in the United States. Think perhaps China, Russia, India, etc. Good luck.
Freddie

 

[megashawn]

Ok, hopefully no one will beat me up.

I had heard that buy running your fuel through a copper tube, and wrapping this tube around the heater core water line will heat the fuel, causing it to expand, thereby burning it more effiecently. I don't know the technical reasons why.

Anyhow, something similar to this is used with propane conversions, where they use hot water from the cooling system to expand the propane before it is fed to the engine.

 

[Freddie]

Megashawn: No one will beat you up. But, if there was a whiff of publicity re large capital investment to commercialize, Poof - you would vanish!
If you have droplets of fuel, the droplets cannot vaporize and burn in the short time available in the cylinder. So maybe a little of the outer layer of the droplet vaporizes and burns and the rest goes out the exhaust to heat your catalytic converter. Vaporizing fuel was the basis for many improvements. Your reference to propane vaporization is astute.
The big jump in fuel economy is the introduction of water vapor into the cylinder to:
1. Lower peak temperatures thereby reducing heat losses.
2. Extending the time during which cylinder pressure is relatively high. This is significant because high pressure early in the cycle does very little while moderate pressure when the crank is at 90 degrees does a lot.Vizualize a sine curve.
I read a reference which stuck with me but I cannot relocate, but the reference was to an Oldsmobile 88 idling at 80 rpm. Typical "normal" idle speeds are about 500 rpm and up. My personal belief was that this was an example of water vapor introduction.
There are many references on the Internet which can be found, also many books available giving more details on specifics. Try "unusual engines" on Google and be prepared to give up several hours, days, weeks, depending on your interests
Good luck
Freddie

 

[megashawn]

I've heard of water injection, is this what your talking about? That is one of the greatest developments for engines in sometime.

I've also understood, perhaps incorrectly, that a turbo system increases the efficency by reintroducing unburnt fuel back into the system.

 

[ShawnD]

I've also understood, perhaps incorrectly, that a turbo system increases the efficency by reintroducing unburnt fuel back into the system.

Turbo is when more air is forced into the cylinder to give higher compression.

 

[russ_watters]

To: Lamar
Why has the problem not been solved? Goood question! Answer: (A) You pay for all the unburned fuel going out the tailpipe. (B)This represents positive cash flow for refiners and petroleum companies. (C) They get very upset at people who want to increase fuel efficiencies by factors of 2, 3. 5, etc. (D) What happens to good hearted people who want to cut BIG OILs cash flow by factors of 2, 3, 5, etc? In the 1920s a lot of work was done to improve gasoline mileage. For some strange reason, it is very difficult to locate records of this work. On the Internet, "This page is not available" comes up many times. I wonder why? Nevertheless, there is a lot of valuable information on the internet. It will just never be implemented in the United States. Think perhaps China, Russia, India, etc. Good luck.
Freddie

Please keep this nonsense out of the engineering forum. Do you have any idea how many engineers there are in the world? How easy do you really think it would be to keep such technology off the internet? A halfway competent physicist can build an H-bomb (the CIA did a test to find that out). How much harder do you think it is to make a new carburetor? The idea that there is some secret technology out there that is being suppressed is absurd.

Have a look at the efficiency equations I posted. They don't leave a whole lot of room for 100mpg cars.

I had heard that buy running your fuel through a copper tube, and wrapping this tube around the heater core water line will heat the fuel, causing it to expand, thereby burning it more effiecently. I don't know the technical reasons why.

Yes. Pre-heating reduces the activation energy needed inside the cylinder. You can also recover heat from exhaust gas for the same purpose. But here's the catch: it takes energy to pump the gas through the extra piping and extra money to build the engine and the benefit is maybe an extra percent or two of efficiency.

I've also understood, perhaps incorrectly, that a turbo system increases the efficency by reintroducing unburnt fuel back into the system.

A turbocharger and supercharger both increase the airflow to the engine - turbocharger by using exhaust gas to spin a turbine (losing some energy in the process), and a supercharger by using the drive or cam shaft to run the blower (using some energy in the process). In practice, neither result in higher efficiency, just higher peak power output.

Also, water injection isn't nearly as exciting as its made out to be. It can give a few percent more power or a few percent more efficiency. It doesn't overcome the laws of thermodynamics.

The fact of the matter is that 100mpg is possible with existing technology, but it'll never happen because people don't want it. They want horsepower, air conditioning, power windows, and space. Those things and fuel economy are mutually exclusive. An in-line two seater that looked like a glider fuselage could easily achieve 100mpg (they were sold in the '60s as a matter of fact) - but no one would ever buy it.

 

[Cliff_J]

A turbo or supercharger increases volumetric efficiency - the ability to get air/fuel mixture into the combustion chamber. More mixture, more power. It doesn't change the efficiency of the system in terms of the energy input/output ratio but instead just the amount you can input/output.

Where is this increase in efficiency from water injection coming from? My understanding is using water as a means of controlling detonation (heat control) which means any gains are the result of some other factor (like high compression ratios) and not from the water injection itself. A better formulated fuel could be used in the same engine with the same result without any water in that case, its just the water allows the usage of a lower grade fuel.

Oh, and if you're talking about getting 100mpg the same way the grassroots approach is to building electric cars where every compromise is optimized for efficiency, I'll pass. I've been in a couple fender benders, I wouldn't want to be the guy with no legs having a Zinardi bar named after me. Build a hybrid motorcycle instead, at least it'd be fun.

Cliff

 

[Freddie]

ShawnD:
You are right re the turbo. It put more air into the cylinder, which = more oxygen, which can burn more fuel to give more power. I don't see any effect on efficiency.
Re water vapor, which does affect efficiency, you also get reduced NOx as a side benefit of reduced peak temperatures.
Megashawn: You are referring to a specific technique to vaporize the fuel (copper tube). Numerous techniques have been used. The reason it works is that liquid fuel cannot access enough Oxygen to burn properly. In vapor form it can and does burn readily. The droplets of liquid fuel are the nasty critters you want to get rid of (unless you are an oil company).
Freddie

 

[Arctic Fox]

I thought about designing something that would create large amounts of ozone to feed into the intake. This, along with changing over from gasoline to *propane. Being as my vehicle is already fuel injected, I don’t see any other choice for me.

*That’s a spicy meatball!* :D

 

[Freddie]

My apologies to all. I just discovered that I do not have permission to access this page. And I don't know the routines that I need to get authorized. So thanks to all who participated in what I thought was a worthwhile discussion. Just goes to show ya.
Freddie

 

[russ_watters]

My apologies to all. I just discovered that I do not have permission to access this page. And I don't know the routines that I need to get authorized. So thanks to all who participated in what I thought was a worthwhile discussion. Just goes to show ya.
Freddie

Sounds like you accidentally hit the "edit" button instead of the "quote" button.

 

[Freddie]

Greetings to all:
I have found a really neat website for anybody interested in Internal Combustion engines and related Thermodynamics. Go to http://kahuna.sdsu.edu/testcenter/testhome/indexclosedcycles.html
HOWEVER: This presents an Introduction to some important concepts and thus leaves out some other concepts. I would like to see your comments and if more than 1 or 2 people are interested, I have some comments which may or may not be interesting.
Freddie

 

[Freddie]

better fuel efficiency thru vapor carburetion

The website reference got mangled in copying. The one I was trying to reference was:

http://kahuna.sdsu.edu/testcenter/testhome/indexclosedcycles.html
insert: /testhome/indexclosed cycles.html

This is for an Internal Combustion spark ignition engine.
With reference to all the racing car drivers trying to improve efficiency, etc., water injection kits are readily available on many web sites and have been for many years. There is no secret. Regarding the efficiency equations, I don't see the reference to the effect of steam. I must have misread the equations because steam properties have been well understood since the mid-1800s or earlier. Of course there are those who believe that steam engines never really existed, and water vapor has no effect in creating motive power. I know at least one of you who will not drive his car in the rain because water vapor (or droplets) in the airstream will wreck his engine. Hey, it's OK with me. I somehow got the impression that Physics Forum was a friendly exchange of information. It is really depressing to be sadly disillusioned. But for some of you younger guys out there, Steam Engines really existed.
Freddie

 

[Cliff_J]

Freddie, my engine has 10.5:1 compression. That puts the temp of the intake charge after compression over 500F even assuming 80% volumetric efficiency. After this, the charge is ignited.

The work needed to compress the mixture and heat it (causing the water to form steam) will not be recovered during the power stroke.

Any water will be steam well before the fuel ignites - it will happen to absorb some of the heat in that process from its latent heat during transition so the charge will be cooler when ignited and less prone to detonation. Since there is a lower chance of detonation, you can run a higher compression ratio and this will give you higher efficiency. Its an indirect effect, not a direct one.

No one said there is no steam, its just it is not a factor since its factored into the system before the combustion occurs.

Cliff

 

[russ_watters]

That's a pretty good looking site. No, it doesn't say anything in the efficiency equation about steam because in the specific engine they are showing, steam isn't injected. If you add steam, you need to also use the equations for an open steam cycle. But its even more complicated than that: since the energy required to turn the water into steam comes from the combustion, some of the energy added by the water injection is energy taken away from the regular otto cycle.

FYI, steam engines are only slightly more efficient than gas engines - and their bulk more than outweighs the benefit for a car. To really get a thermodynamic efficiency boost, we need to start using Brayton cycle engines...

And you're right that this stuff isn't a secret. Feel free to use the info available on the net to get yourself a water injection system. Let us know how it works...

 

[Freddie]

The work needed to compress the mixture and heat it (causing the water to form steam) will not be recovered during the power stroke.

The work needed to compress the mixture and heat it will not be recovered duting the power stroke

Looks to me like you are violating the 2nd law. How can you tell when it does not apply?

 

[russ_watters]

Looks to me like you are violating the 2nd law. How can you tell when it does not apply?

No, freddie - the work required to turn the water into steam is now part of the steam. It can be reclaimed only by turning the steam back into water - and in this case it is lost when the steam is sent out through the tailpipe of the car. This is called an open cycle.

I encourage you to start learning thermodynamics. The Carnot cycle is the place to start. HERE is an overview presentation of a college level Thermo 1 course.

 

[Freddie]

Russ:
"Some of the energy added by the water injection is energy taken away from the regular Otto cycle" Exactly right. But the mechanical energy involved is trivial. The tradeoff is that you are taking energy from a high temperature source (initial combustion) and using it to create steam which carries a much lower, but useable pressure out to where the crank angle provides reasonable torque. I don't see anyone talking about the fact that the crank provides a sinusoidal output for a constant input.This seems to be either totally ignored or buried somewhere or considered too obvious to mention. You know that you can have detonation, with very high temperatures and pressures and very little contribution to torque output because of the crank position.
Nest item: "It can only be reclaimed by turning the steam back into water". No, Russ, the purpose of an engine is to turn heat and pressure into work. This happens as the piston moves down and the steam pressure decreases in accordance with the appropriate curves. If the stroke is long enough, you may get condensation. In general, you will be exausting steam at a much lower temperature and pressure because the work was extracted from it. As it leaves the cylinder, it may certainly condense to water.

 

[GOD__AM]

Yes. Pre-heating reduces the activation energy needed inside the cylinder. You can also recover heat from exhaust gas for the same purpose. But here's the catch: it takes energy to pump the gas through the extra piping and extra money to build the engine and the benefit is maybe an extra percent or two of efficiency.

Never the less this pre-heating of the fuel is used widely on snow mobiles.

 

[russ_watters]

Never the less this pre-heating of the fuel is used widely on snow mobiles.

I didn't know that, but it makes good sense.

 

[Freddie]

I stumbled across a website that shows combustion pressure curves for normal operation, knocking, and water injection. There is also some detailed text under the graphs. With 1644 hits, I guess a lot of people are interested. For the graphs, go to
http://www.aquamist.co.uk/dc/technic/technic.html
Also, thanks for the info on snowmobiles. Will check it out.
Freddie

 

[Cliff_J]

Freddie, the first line says it all:

Figure above shows cylinder pressure versus crank angle traces of cycles of different operating conditions

Your argument seemed to be that water injection by itself offered improvements in efficiency. While on that, there's an underlying belief in the thread that there is some 'secret' to outstanding efficiency that lies on the fringe that is held back from the general community.

This seems silly, the application of water injection is used for specific purposes like the Harrier jump jet or by the participants in tractor/truck pulling events or drag racing.

If the water injection has any benefit it is that it allows the other parameters (like ignition timing or compression ratio) to be modified to give the overall system a small boost that would have occurred had those parameters been optimized as such without the addition of the water.

Cliff

 

[russ_watters]

Freddie, that page shows cylinder position vs pressure and states that the area under the graph indicates torque. Just by eyeballing it, how much more area do you think there is under the graph of the water injected test than the standard? Even assuming fuel flow is constant across the graphs (it isn't), how much efficiency gain do you see indicated by that graph?

Cliff, Freddie has noted that this technique was used in WWII aircraft - it would seem the conspiracy is just in keeping the technology out of production cars. But if there really were that much benefit, you'd think after-market kits would be a big seller...

 

[Cliff_J]

Found the other thread this morning and this little snippet.

The MAJOR problem with using water injection in a car is that the engine runs so cool that your heater has no heat source. You need to install a gasoline car heater, like the old VW bug used to use. But some people live in warm climates and would not consider this a problem.

If true, why not work out a licencing deal with the McLaren-Mercedes Formula 1 team to assist them with the overheating problems they faced earlier this year? Plus now they'd have substantially more horsepower. Any competitve motorsports team would welcome such an advantage with the millions of dollars on the line. And the millions spent on hybrid technology, fuel reformation, et cetera could be eliminated if true with potential billions in profits for a company bringing such a product to market. The expression TINSTAAFL doesn't even begin to address how incorrect your assumptions are about the benefits of water, please re-read the responses you've received and reconsider the role any water would play.

BTW Russ, the Lancer Evo and Subaru WRX Sti both come with a water spray from the factory. Its only used when a button on the dash is pushed to spray on the outside of the air-to-air intercooler to help lower the compressed air temp more. So water spray has been included in a production car but not as a combustion enhancing product and most definitely not as an overall efficiency improvement. The more popular aftermarket item on high-boost turbocharged gasoline applications appears to be alcohol, and with its low stochiometric ratio it'd be easy to use just enough to cause the overall system to run rich and help cool things like the exhaust valve. But for a drag race of 8 seconds who cares if the system efficiency has dropped if the power output has increased?

Cliff

 

[Freddie]

Hello! HELLO! WHERE IS EVERYBODY? Are Russ and Cliff and me the only ones interested enough to post on this thread? I waited a long time, hoping someone else would speak up. But no one did.
OK.RE McLaren Mercedes Formula 1 team: When you are pushing the limits of a technology, one of the common results is overheating. This team is highly knowledgeable on water injection and everything else related to racing technology.
Next: This thread and related thread started out with a casual remark re "water injection". The recommended mix is 50% ethanol, 50% water. This is what users commonly mean when they talk about water injection. There are also other mixes which are outside the scope of this thread. I don't know what the Air Force used, but it had to have a lot of alcohol to avoid freezing.
When this thread started out, the question related to higher mileage and someone jumped in with all kinds of info on racing technology. I didn't know that racers were interested in high mileage. I always thought they were interested in high power and fuel economy be damned. Just shows how iggerant I am about things that I am completely iggerant on. Also, I am getting tired of posts from Humanities majors and Education (ugghh) majors. Where are the technical people? This is supposed to be an Engineering Forum.
How the heck do we get so many clicks on this topic and NO COMMENTS except two or three of us?
Freddie

 

[Cliff_J]

Depending on the type of racer, fuel economy is very important. For drag racing, its of little concern as the track is a fraction of a mile. For any kind of endurance race, now it plays into how much fuel is needed on-board (typically limited by regulations) plus how long it will take to make a pit stop (since fuel delivery is usually the longest item) and so on. Racing officials have put rules into place to give the teams with the best economy an advantage.

So racing is about best compromise in terms of use maximum extraction of fuel's energy potential. Its THE area of development with billions of dollars dedicated to that cause. Just like how general aviation benefits from ever increasing military aircraft development, the general automobile consumer benefits from racing.

Freddie, you didn't answer me about my question regarding the validity of the idea of steam playing any part in the process of 'increasing efficiency' after I brought up the idea that the combustion chamber temperature exceeds the boiling point of water and creates the super-heated steam well before the point of combustion, that the steam creation on the compression stroke could only HURT the efficiency since there is not a process that can extract that energy back out of the steam by general laws of conservation.

Also, by adding alcohol you're adding another combustible. So while the MPG might go up because it ignores all the inputs (2 fuels instead of one) the overall system efficiency has likely gone down.

The SAE holds a high-mileage competition where high-school and college level teams build competition cars as engineering projects. The high-school level teams routinely get MPG in the 400s and up and the college level teams get over 1000 MPG running highly optimized cars. This has been going on for a while now, nothing new...

Science is about more than fancy equations, its about understanding how to correctly analyze data and combine it with your understanding of how that data works. Looking at any facet of the current automobile we could address areas that could lead to further enhancements in efficiency, no doubt. But that water injection as discovered in the 1920s as some sort of revolutionary idea that has been completely missed by the entire engineering society? An idea that far outside the range of common sense deserves scrutiny in its scientific mechanisms and properties that allow it to work and some anecdotal evidence doesn't provide information in this regard.

Freddie, I think the idea is that Russ and I believe that you are close to actually understanding the issue at hand better once you re-examine your assumptions.

And assuming something works everywhere and has benefits to all circumstances because it was used in a specific application doesn't seem very well engineered to me. You haven't even provided the ratios in terms of lbs/hr for the 'water' to the fuel and air flow rates in lbs/hr and the suppossed increase in efficiency as a result. Without a scientific test, all we have is a guess.

Cliff

 

[Freddie]

Freddie, you didn't answer me about my question regarding the validity of the idea of steam playing any part in the process of 'increasing efficiency' after I brought up the idea that the combustion chamber temperature exceeds the boiling point of water and creates the super-heated steam well before the point of combustion, that the steam creation on the compression stroke could only HURT the efficiency since there is not a process that can extract that energy back out of the steam by general laws of conservation.

Very good observation - that the generation of steam occurs early in the cycle. And yes, it does take energy to do it. After combustion, this same steam, gets heated some more which raises its pressure. But it does not just disappear. The pressure is carried farther out in the cycle and the energy is delivered back as work on the piston. The only energy that gets wasted is the heat of the exhaust gases.
I only claimed that alcohol-water injection has been used to increase mileage. I didn't say it was a universal remedy for everything. The Air Force used it successfully on fighter planes during WWII. People who are into racing are paying $1000 and up for commercial alcohol-water injection kits. This is outside of my budget so I have not bought one.
I am still having trouble with using this site, using quotes, etc. so I need to limit my remarks. Re the racing use of water - alcohol injection, the website reference is www.rallycars.com/Cars/waterinjection.htm[/URL] and if this site doesn't mangle it, like it did the previous one, this will work.
Freddie

 

[russ_watters]

The SAE holds a high-mileage competition where high-school and college level teams build competition cars as engineering projects. The high-school level teams routinely get MPG in the 400s and up and the college level teams get over 1000 MPG running highly optimized cars. This has been going on for a while now, nothing new...

Any links to that? I've never heard of it.

 

[faust9]

I only claimed that alcohol-water injection has been used to increase mileage. I didn't say it was a universal remedy for everything. The Air Force used it successfully on fighter planes during WWII. People who are into racing are paying $1000 and up for commercial alcohol-water injection kits. This is outside of my budget so I have not bought one.

I disagree with this. I race quite a bit. I have a 94 Mustang with a welll build 302, a 79 T/A with a 455, and a 91 R6 which puts a little over 125Hp to the ground--tough to do on a 600cc Bike. Water injection has limited use in racing today for amny reasons one of which, the biggest in my opinion, is the introduction of cheap CNC machined Al heads. These heads allow a builder to make a 1000+ Hp running a turbo or blower without having to rely on water injection to lower the peak combustion temps.

Iron headed engines can benefit from this OLD idea, but I haven't seen it used since the mid 80's outside of Rally car classes because of the limitations of the class itself. http://www.rallycars.com/Cars/WaterInjection.html

Water injection does not produce more Hp. Any time you lower peak combustion temps you lower peak combustion pressure (the thing that that eventually does the work) which lowers the total power output of the engine. You've mentioned adding alcohol mixtures into the frey; however, these mixtures produce LESS power than a pure gasoline mixture. You are essentially displacing a fuel that releases more energy per volume with a lesser fuel.

Water injection should not be used in automobile racing to improve performance because that's not what it was designed for. Water injection is a tool to save the builder $10,000+ because it limits detonation. WWII aircraft usage many be different because of lower O2 levers and what not. Automobile applications don't suffer from that problem though.

Take a clue from builders--water injection doesn't improve power. If it did every dragster, 1/4 mile racer, race bike, or any other race vehicle would be using it. You can produce more Hp running Al heads and an electronic ignition with a knock sensor(carb'ed or FI) than by running water.

If you want to improve fuel effeciency go for it. It's actually easy to do. I have a T/A that I can milk 25-30MPG out of if I wanted to. I've done it. I've done it using a Q-Jet. Did I get the power levels I wanted? No. Where my NOx emissions through the roof? Yes. Fuel effeciency is easy ti come by by iteslf; however when you toss in emissions and power requirements then you're playing with a whole different deck of cards. Water injection will lower emissions but at the same time it will not increase power.

I't boils down to the fact that water injection and pump gas will have a detremental effect. Water/alcohol mixture on a turbo 4 and pump gas will increase the octane rating of the fuel allowing more aggressive timing curves but running a higher octane gasoline fuel to begin with will yield even more power.

NASA did a study of Water injection for aircraft use--not increase power but to lower NOx emissions. http://gltrs.grc.nasa.gov/cgi-bin/GLTRS/browse.pl?2004/CR-2004-212957.html

 

[Cliff_J]

Russ, best link I could come up with quickly but I've read a few other sites about it before and a friend in college built one at his high school in the early 90s so I'm sure there's more info out there. With theirs they took many liberties including using the B&S bottom end but with a 125cc Honda 4V head from a motorcycle. They started with a fuel injector from Artic Cat but it was tough to get good atomization with the low duty-cycle and low fuel pressure they used for their RPMs. They used bicycle sprockets, chains, and tires at over 100psi to minimize rolling resistance, aerodynamic shape that had no room for operator and make them sweat like mad, etc. They shaved the head too to maximize the CR and so on which caused them to need to overcome plenty of other obstacles as well. But in the end it still mustered like 250MPG at nearly 20MPH which was faster than the other teams. Of course, this is how I'm remembering a story told to me that I've never verfied.

http://www.sae.org/students/supermw.htm

Cliff

 

[Cliff_J]

faust - you left out one area where alcohol injection is handy and that's for the turbo applications with extremely high boost. Forgetting the absurd ECR calculations intended for the calculus-challenged, a slow burning fuel that complements the longer pressure curve that boost generally adds (so the peak pressure increases say 20% but the BMEP increases 30% type thing) we get more of the curve closer to the 90 deg past TDC point where we can maximize torque. Especially if the rod/stroke ratio isn't great and we can take more advantage of pressure at a point of less side-loading. Oh the compromises...

Plus having a second fuel to absorb some of the heat of compression is handy if the intercooler isn't doing a good job, and lots of cheap fuel to run by the exhaust valve on the way out isn't a bad idea either. How else some of these guys are running 45psi boost is beyond me and I'm sure you've seen a engine grenade after it leaned out so shoving in some cheap insurance makes sense to protect the pocketbook.

But running 8sec quarters has nothing in the world to do with efficiency unless you need to get there in a hurry.

Cliff

P.S. And WWII was a time of frenzy, how else did it take so long for the P51D to arrive to escort the bombers? And arrive as some rushed airframe design with a limited-range low-power motor that almost doomed it until the airplane came on strong with the RR Merlin that could make the power and go the distance. As another example, I think I'd rather take any tire manufactured today instead of the synthetic tires during WWII. Have we beaten this horse long enough?

 

[racprops]

I have also been looking in how to get higher mileage.

I got this answer about using propane:

"Check this out:

http://www.welshtec.com/

A couple of board members use this kit with great results on their daily drivers. Basically 10 to 15 mpg depending on the driving conditions. I bought a kit and plan to install it on my 99 Regal GS when I have time. It basically puts small amounts of propane gas (does not spray liquid) into the manifold which creates a more complete combustion. It uses about 2.5 gallons on propane per 400 miles on the average passenger car and should take care of the need for high octane fuel."

I found this because they were talking about propane as a power booster in their TurboBuicks and how it was letting them run much more boost and get much more power, so what is good for racing can also help low speed power...

Seems that it can.

And the following questions lead me to seach for more answers and thus led me here:

"This has been such a learning adventure.

I had talk with a person that was saying that the modern injector is able to vaporize about 95 to 100% of the gas as it sprays the fuel into the engine, and that during compression some of this vapor gas will recondense!

If that is true than getting 100% of the gas converted to vapor will still cause pollution as some of it recondences and fails to burn and will still flow out the tail pipe.

So if true a hot/cold vapor carb system will do no good. Wish I were a combustion engineer. (Hope there is one here.)

I also read that gas back in the 30s was much more easly vaporized, true or not?

As for the report I read about how a computer would get in the way of a clean burn, I was told that this is true with Ford, as they are set to keep the catalytic converter burning to burn off gas, but that GM computers will run clean up to a set point that pollution starts to load up and then tip over and add fuel to fire the cat.

True of false??

I am also informed that the GM computers “learn” and to shock them with switching chips will only defeat this learning and cause it to switch back to its base defaults.

So if I switch out the chip I will lose the better settings for messed up ones of a performance chip, or worst if I try my “getting both worlds” of a stock chip and them a hot setting of a over riding controller the system will not return to it best settings until something like 45 starts??

I thought the computer had a set bunch of commands, that each is a programmed response to certain sensor readings, change a sensor reading and the computer will always respond with the very same response, every time, no change and no learning.

I have not heard of these things learning and fine-tuning themselves.

Any one knows for sure?

As in many things, I know enough to ask the questions but do not know the answers, these are such fine and specialized knowledge."

I am also building a add on system of a old Borg Warner 3 speed over
drive transmission behind the 700r4, so that I can down shift to 2nd
and have low gears for town driving that will rev the motor fast and
use less power moving out, and can still engage the 2nd over drive
for higher town speeds and on the high way upshift to third and then
even add in the 2nd overdrive for a double over drive. The motor with
a MAF controlled system and low 2000 torque cam should be able to
maintain speed as low as say 1200 rpm.(I think and hope)

And last:

Next is to find out how I can improve the Van’s wind resistance... Ground effects kit, with air dam and a rear wing?? Upsweep or downsweep like the rear window cleaner on old station wagons, to push the air back in behind the van to kill the vacuum?

To freddy, hope you still here and finds this interesting as I do.

I hope this is the right place to talk and learn.

Thanks.

Rich

 

[Cliff_J]

Rich, this is a good place to talk and learn but science and facts mean more than wives tales.

How could fuel condense during compression when the mixture will heat up according to the ideal gas law? It might cross the point where the vapor pressure is insufficient (haven't seen a phase diagram for gas) but the temps seem like they would be simply too high. The combustion is not 100% because of many factors including the shape of combustion chamber, mixture ratio, and time allotted to the burn. An engine could be run lean for a more complete combustion but that generally hikes up the NOx emissions from higher combustion temps. The EGR and catalytic converter make much more sense for the system to work properly and meet power and emission requirements.

The GM computers do have a set program but then can adjust to varying conditions and sensors when in closed loop. So if the MAF/IAT/MAP tell it to fire the injector for 5msec but the O2 tells it the mixture is rich it'll adjust the timing. For WOT conditions its straight from the stored injector maps until you get to the LS6 in the Z06 where it stays in closed loop. After 96 when OBD-II took hold the whole thing gets more complex when you have O2 sensors upstream and downstream of the cat. And when GM went to the metric LS1 V8 they have a different firing order to help clean up the intial startup emissions, the GenII 3.8 motors seem to have gotten more complex as well. Make sure you check for coolant around your EGR port in the plastic lower intake manifold, there's water passages around it and when the plastic melts it leaks...

As far as learning, the GM computers seem quite adept at it, especially once they stepped up the processing power to go SFI instead of batch fire. They can compensate for sensors getting old and even batches of gas - makes a ton of sense to keep the emissions as low as possible under an even greater set of conditions. Haven't been able to swap chips for years now...

A second transmission makes only mild sense, even manual cars show a roughly 18% power loss to the tires on the dyno and that 700R4 is already sapping plenty of power. If you can decrease the revs down the road it could help but you've added a lot of losses with that extra transmission so a gain might be tough to come by. Drive even a 3200lb Camaro around at only 1500rpm in 6th and it becomes apparent how difficult it would be to run much slower in RPM.

A rear wing designed to help minimize the turbulence of the air tranistioning from the top to the back could help, the rest would likely fall into very small improvements. Look at a new Corvette, a Lexus LS430, and a S-Class Mercedes-Benz. The first two have a Cd of .29 and the MB has a Cd of .27! Vastly different shapes, the last two have been carefully designed top and bottom to achieve such a low number. Oh and the Corvette has a larger engine and makes more power but gets better fuel economy at a lower price. So much for a rule-of-thumb!

Cliff

 

[hitssquad]

Drag coefficient vs drag-at-airspeed

Look at a new Corvette, a Lexus LS430, and a S-Class Mercedes-Benz. The first two have a Cd of .29 and the MB has a Cd of .27! Vastly different shapes, the last two have been carefully designed top and bottom to achieve such a low number.

Another way to get a low Cd is to design the car to be as large in frontal aspect as possible, even if this raises the drag-at-airspeed. Because of this, reducing the drag-at-airspeed can result in a higher ("worse") drag coefficient and increasing the drag-at-airspeed (as Lexus may have done with the LS430) can result in a lower ("better") drag coefficient.

Drag coefficients are useful specs to know about airplanes. This is because the drag coefficient is a ratio of drag-at-airspeed (something bad in an airplane) divided by airfoil area (something good in an airplane). The Cd number gives a concise estimate of how well the airplane's designers achieved the general goal of maximizing airfoil area while creating a minimal corresponding increase in drag-at-airspeed.

In regards to cars, drag coefficients are useful specs for marketing purposes. By simply engineering increased drag-at-airspeed by making the car larger, the drag coefficient correspondingly gets "better," and thus the car becomes more marketable (though this "better" Cd may catalyze worse freeway fuel mileage and premature drivetrain wear since more work might need to be done to push the car through the air; better Cd, since it generally corresponds to increased drag-at-speed, will also generally reduce maximum drag-limited speed, ceteris paribus).

Since Cd is actually

• drag D divided by the quantity: density r times half the velocity V squared times the reference area A.
  
  Cd = D / (A * .5 * r * V^2)

it seems that to come up with a useful drag rating for cars, one might simply take the above equation and delete the division by "reference area A". This would give us a drag number for a given car unencumbered by an otherwise accompanying frontal-area-handicap-factor. Drag specs computed this way, for comparing cars, would seem to be more useful than the traditional Cd (coefficient of drag).

 

[Cliff_J]

hitssquad - while I agree that the Cd may be influenced by the overall size of the car I would think it odd for the engineers of large luxury cars to make them arbitrarily larger to get a better number for marketing purposes. The current S-class is smaller than the model it replaces.

In addition, if we compare the straight drag force without respect to other factors a bus seems like a great waste of fuel with a large surface area, heavy-duty components, and overall large amount of mass. But factor in the number of passengers for a per person fuel usage...

So unless the "reference area" is not accurately based on an honest cross-section of a car the Cd still represents how carefully the aerodynamic drag was minimized with respect to the size of the auto. Sure my example of comparing large luxury sedans to a compact sports car has flaws but the point was about the efficiency of the design and not the raw drag produced.

Because if we assume a typical van with a shape approaching that of a large square box it has a large surface area and poor aerodynamic shape we could also assume a it to be a larger percentage of the total force necessary to move the vehicle down the road at speed. And the large mass will obviously hurt the acceleration and require a large amount of force there as well regardless of speed. So to engineer for better overall fuel economy with respect to cargo capacity we'd simply get a modern minivan.

Cliff

 

[racprops]

OK the compression pressure and heat keeps gas in a vapor state Correct?
Then a better vaporizing of gas may help the burn?

On the computer I was going with the older 87 one with the changeable chip and sadly batch firing, so it is better but not too smart, so is it a learning computer?

I am again told by local Fuel Injection tuners that the difference between a batch fires and FSI system is barely notable. And in my case, a 90s Chevy 350, not worth the cost to switch.

And again I was thinking I could run the stock chip for gas mileage and a performance add on computer system for power and higher performance. So if that will harm my mileage settings it may not be such a good idea, IE if the computer really learns and takes so long to retune its self?

As to the transmissions, I am concerned on internal drag, but an told that as automatics go, the 700r4 is one of the best in lower power usage, and I am considering using a lighter gear oil than the old 90W, more like the current performance transmission oils.

One of the extras I will be getting is a lower gear ratio with the use of second, this should give me a great city gearing, winding up the motor faster and using less power to get it moving in stop and go driving.

I am aware of the power drop in overdrive, and with two different overdrives I can use the best one for the best power range and both when I can, granted this will only be on flat ground, but as I live in AZ, and to get to the east I have to cross a lot of flat ground…

And I will running a Mileage computer so will “see” which gear will/is working best.

And I know it is a more complex system but I am willing to work with it. And lastly, truckers have run their front transmissions and with a second transmission called a “Browny” and two speed rear ends.

So gearing is very important to them, and yes I also know their power range is smaller, like 500 to 3000, but my new motor also is 800 to 4000 of real power making, so more gears are called for my setup.


I had been planning of a 403 Olds motor but when doing a little more research found out a Chevy 350 with a Tune Port Intake mades as much if not more torque that the Olds, and with the Max Air Flow sensor can run tighter and leaner at these planed lower RPMs than any other fuel deliver system, that a carb and Map system would be unable to operate correctly at these low RPM due to the low vacuum, which on these systems would cause more gas flow as they get a false reading.

And with the Chevy I am able to use a 9:1 ratio with a much better piston, a “D” shaped dish piston that gives a much better flame travel, so it will make a little more power than the old 8.1 Olds full disk and looser fitting pistons.

And with the van I can say positively a smaller motor seems a no go, I swapped an Olds 307 in place of a 350 and lost mileage and power big time.

Now the last question, which I cannot make out your answers, what will help the box get though the air best?

I am planning on an air dam under the bumper, and side panels which are called a ground effects kit, this is suppose to lower drag by keeping air out from under the van.

So I wonder which will work best: a spoiler, or a air foil on top and perhaps on the sides to push air back in behind the back to fill up that vacuum that is created behind the box?

I am not going to a mini van. Sorry need the room.


Thanks or all of your answers and help.

Rich

 

[Cliff_J]

Funny thing is the other day I was reading a site with details on an LS1 swap into a late-model S10. My dad has a 2001 with the 4.3L V6, barely eeks out low 20s for mileage. But the guys with LT1 or LS1 swaps are getting 26-29MPG which is about the same as the Camaro/Formula/Corvette. Go figure.

No, SFI isn't much of a gain. And the learning is short-term only, think like you have a low tire and you learn to steer funny for just a few miles until you find a service station to air it up. After you air it back up you go back to driving the way you had been.

Well the L98 style TPI seemed to do well for mileage too, just not quite as good as the LT1 or the LS1 down the highway. Since the LT1 has been abandoned now with the LS1 stealing the glory the price has come down but not to the traditional SB prices. I'd at least hope you have centerbolts, I hated the leaks from the original design where some fool lost the spreader washers and overtorqued the covers... From what I've heard the SLP runners help a lot and are cheap at swap meets.

Oh, and for the 700R4 the lighter oil might be a problem depending on vintage, if it is a newer one with the better pump it might not be such a problem.

Spoilers prevent lift by spoiling the air flow, its how the stealth planes turn. This creates drag big-time. And while its a balancing act for a NASCAR guy with extra power to add some drag while getting more traction, you'd like to reduce drag instead.

So the turn-down style wing like you'd mentioned from station wagons could help. I say could because while it is potentially reducing the lower pressure area behind the van the turbulence there is going to be pretty big and the effectiveness might be kinda small. Its like some pickups where leaving the tailgate down does little besides get rock chips all over it.

An air dam helps trap the air and create a higher pressure. Good for forcing more air through the radiator, not so good for drag since you're creating more high/low pressure air to pull back on the vehicle.

I consider the ground effects on my TransAm as cosmetic. Once they're above a couple inches off the ground the effect is tiny. On a van, they make for nice steps.

Hey the box is the new style (again) with the Scion Xb and Honda Element being all trendy now. Both are small and lighweight but the Element is rated 24MPG while the Scion is 34MPG - obviously Toyota made some efforts to get that but the 100HP engine is likely a large part of it.

The engine might see the biggest gains. If you could go with aluminum Corvette heads and run 10.5:1 compression (each point worth 3-4% gain) and an appropriate cam and spark advance, you could likely help things out a lot. Not sure how much more than an L98 (which it sounds like you're piecing together) but for all that work, an LT1 swap sounds cheaper and just find one with a 95+ Optispark that's vented and you'd be set. Might be tricky to fit the accesories with f-body brackets (and corvette brackets were/are coveted by hot-rodders so very rare) but you'd have all the goodies then once you get the computer/wiring hooked up. My 96 TA with 90k on the odo got 28.5MPG on labor day weekend when I had to go 65MPH through Kentucky, better than the normal 26 when going around 80MPH - that's not too shabby!

An LS1 swap would rule, but too pricey so I won't bother. Regardless stepping up in the GM lineup over the years is a pretty easy trend to follow with increasing efficiency at affordable costs. And would probably have little trouble beating your old rocket block too.

Cliff

 

[hitssquad]

Tailgate up or down for improved aero flow

Its like some pickups where leaving the tailgate down does little besides get rock chips all over it.

Recent research has actually found increased drag with tailgates in the down position. Leaving the tailgate up reportedly creates a locked vortex flow which improves aerodynamic efficiency. Even better is to use a bed cover (AKA a "tonneau cover").

 

[racprops]

“Funny thing is the other day I was reading a site with details on an LS1 swap into a late-model S10. My dad has a 2001 with the 4.3L V6, barely eeks out low 20s for mileage. But the guys with LT1 or LS1 swaps are getting 26-29MPG which is about the same as the Camaro/Formula/Corvette. Go figure”

I think it is the power to weight thing, too small a motor and it works way too much and uses more gas than a big motor lazing about.

“An air dam helps trap the air and create a higher pressure. Good for forcing more air through the radiator, not so good for drag since you're creating more high/low pressure air to pull back on the vehicle.

I consider the ground effects on my TransAm as cosmetic. Once they're above a couple inches off the ground the effect is tiny. On a van, they make for nice steps.”

First if close enough to the ground I was under the idea that it pushes the air around to the sides and with rubber siding that I plan on getting as close as I can to the ground again to help keep that air out from under the van, I read that doing so lowers drag as there is less turbulence from all the junk under the van., and short of a full belly pan the best I can do.

As for the motor, it is out of a 90 Caddy, and a true 5.7 350 with the one piece rear seal and the center line valve covers and the early Torvek heads that are tuned for low RPM power.

It was bored .030 and is fitted with Keith Black pistons and the stock cam as every other cam rises the power band and is counter point to my projected power band and gearing.

On the Rear foils, I am thing a fairly sizeable one across the top and a couple of little ones on both sides, all to catch and fold in the air.

On the trans I will use standard Transmission fluid in the 700 r4 it was the old stick shift transmission that I was talking about using a lighter oil than the old 90 Weight gear lube.

Somewhere I read that they are again trying the 4/6/8 thing, where they cut out a few cylinders, for at cruse you really do not need all of the motor.

I always said that was a great idea, but sold in the wrong car, Caddy buyers are not the kind to worry about gas mileage, now put it into a Chevy and I bet it would sell.

Both seem to let the dead cylinders run as drag, it only they could really unload them like some A/C units do, by keeping the valves open so there is no compression and drag.

Rich

 

[Cliff_J]

Sounds like that engine should be fairly decent for the job, the truck versions just seem to never get decent mileage like the car versions do.

On the new 5.3L they are doing the 8/4 thing and are calling it displacement on demand (DOD). It involves a new throttle-by-wire and a chamber in the exhaust so when it transitions the throttle opens and the exhaust closes so you don't notice it. Inside the engine half of the lifters have an extra oil passage. In DOD mode a solenoid opens and pumps up the lifters to hold the valves open. Suppossed to gain 12-15% mileage. Only in trucks because GM doesn't have a V8 car aside from the Corvette and Grand Prix,er, uh, GTO (like a person can tell them apart on the street, and yes I'm bitter about the f-body being cancelled).

New Hemi in 300C/Magnum does DOD as well, but not the truck version of the Hemi. Both covered pretty well this summer in Popular Hot Rodding, might ask friends if they have old copies if you want to read up on it.

Mercedes recently setup the S600/SL600 models to do 12/6 cylinder and I have a friend whose dad purchased one and had many engine management problems with it. It was so bad he almost got a new car under lemon law policy!

So far it seems detroit has learned from the 80-82 caddy with the 8-6-4. But if you want to see how bad they can mess things up for their name then search on the "caddy that zigs" (remember the commercials?) the Catera. They're super cheap to pick up used because they are so bad.

As far as ground effects, I'd like to see some measurements. The air is always going to be coming in from the front and pushing even half of that air aside is going to require a lot of power.

hitssquad - interesting link!

Cliff