Compression at which gasoline will ignite

I know deisel engines use compression to ingite the fuel, I am wondering how much compression would it take to do the same with nomral gasoline?

its the heat that ignites the fuel, compressing the air fule mixture heats it up rapidly and sometimes ignites it too early. there are so many variables to consider when talking about pre-ignition of fuel. so you could probably just look up the flash point of gasoline and get a good idea of how hot it has to be to ignite in the chamber.

Google is a wonderful thing...

its the heat that ignites the fuel, compressing the air fule mixture heats it up rapidly and sometimes ignites it too early. there are so many variables to consider when talking about pre-ignition of fuel. so you could probably just look up the flash point of gasoline and get a good idea of how hot it has to be to ignite in the chamber.

Google is a wonderful thing...

Well as mentioned in this post: http://www.automotiveforums.com/vbulletin/showthread.php?t=512043

I want to vaporize the fuel before it hits the intake minfold. Now talking to my auto teacher, he says that especially in the summer you may have it ignite way before you want it to because the gas molecules can only expand so far before they ignite.

the reason that it's worse in the summer is because the summer air is hotter. an increase in pressure will change the temperature, when you compress something it gets hotter. vaporizing the fuel will give you a more consistent, quicker, and better burn but probably won't do anything for knocking.

the reason that it's worse in the summer is because the summer air is hotter. an increase in pressure will change the temperature, when you compress something it gets hotter. vaporizing the fuel will give you a more consistent, quicker, and better burn but probably won't do anything for knocking.

What do you mean for the knocking? This is essentially the same concept as natural gas except there's an added step. Yeah I know the summer air is hotter but I'm actually wondering how much of a difference it would make.

it makes a big difference if you're running on the edge of knocking when it's cold outside. knocking is when the fuel burns before it is supposed to, it sounds like a knock in your engine, it's bad, kinda like taking a sledge hammer the the top of your engine.

Vaporizing the fuel helps fuel economy because it burns more completely, this gives you more power with the fuel you have so you don't need as much to do the same ammount of work. injectors already do this to a point, they have a high pressure pump pushing the fuel through a small nozzle, this makes the fuel into a mist. other things help like ethanol, it helps the fuel vaporize, and apparently acetone (paint thinner).

As for your original question, look on howstuffworks.com for how diesels work, this will give you an idea of the differences between a gasoline engine and a diesel engine. trying to apply a principle from a diesel to a gasoline is usually impossible without completely redesining the engine.

It has nothing to do with compression. Its heat in minus heat out. Compression adds heat, but to say what compression is the starting point doesn't take into account the millions of other variables involved.

I'll check that stuff out and mess around and try to build a pre-vaporization unit.

I'll check that stuff out and mess around and try to build a pre-vaporization unit.

Cody

An after market for the Ford Model T was a vaporizer carb.

Here is a web site that you might be able to find some info about it: http://www.mtfca.com/



FYI

Dan

yeah compression prolly aint the only factor. My carbed 350 used to diesel a lot when i would shut it off until i fixed the timing. I know that engine couldnt have had more than 8:1 compression, its an emissions-era 350 for God's sake lol

yeah compression prolly aint the only factor. My carbed 350 used to diesel a lot when i would shut it off until i fixed the timing. I know that engine couldnt have had more than 8:1 compression, its an emissions-era 350 for God's sake lol

When a gasoline engine diesels it isn't caused by compression it is caused by a hot spot in the cylinder(carbon deposit). If your idle is too high or maybe if timing is bad when you turn off the key the engine still turns drawing in fuel because carbs do that, and the hot spot in the cylinder ignites it.

FYI A diesel only compresses air(direct injection) When the piston moves up on the compression stroke, there is only air in the cylinder. Just before top dead center, fuel is injected into the compressed air and ignites.

As for this fuel vaporization, Cody, is your vehicle fuel injected?

Cody

An after market for the Ford Model T was a vaporizer carb.

Here is a web site that you might be able to find some info about it: http://www.mtfca.com/



FYI

Dan


Well if you think about it, when fuel air mix comes out of a carb it is just that, fuel air mix, the fuel is still very much a liquid and it is just sloshed around with some air as it heads down the intake runners to the cylinder. This is why the insides of cylinder heads(ports) are often rough to create a turbulance to mix this mixture better. So on a model T, I guess that anything that will mix this a little better would be a considerable upgrade.

If Cody could do something to increase this turbulance as the fuel air travels toward the cylinder maybe it would help, but REMEMBER not too many people can out engineer the factory not even the aftermarket.

As for this fuel vaporization, Cody, is your vehicle fuel injected?

Yes it is but I'll porbably experiement on a cheap, disposable engine. I made a thread there: http://www.devhardware.com/forums/showthread.php?p=501878#post501878 here about it and one at AF here: http://www.automotiveforums.com/vbulletin/showthread.php?t=512043

BTW, I'm not out engineering anybody. This technology has been around for a century, it's just been covered up by the oil industry.

http://www.get113to138mpg.com/FivsGenIV.htm
This has to be the cheesiest website I have ever seen. I hope no one has sent him any money. Don't get me wrong, I'm all for better gas mileage but this is a crock of shit. All car manufacturers have to comply with CAFE. Corporate Average Fuel Economy. So if there is some great way to get one hundred miles to the gallon, they would have done it. You don't see the government or oil companies stealing any hybrid cars.

Good gosh. I wasn't going to say anything until now. There is no oil company conspiracy. The Pogue carburetor and its vaporization carb cousins are hoaxes. Just because it has a patent and someone said they drove a car 200 miles on one gallon of gas doesn't mean anything other than an ill-concieved publicity stunt to draw attention to a business.

The patent office was used as advertisement for years... still is. I can patent a new hair growth formula, but that doesn't mean it works.

Do a search for "pogue myth" and you'll turn up all you need. It has even been discussed at length here, but had you done a search you would have known that. Its a myth. The reason no one uses it is because it doesn't work, not because the oil companies squelched it.

Please do some more research before continuing talking about vaporization carbs. It will save us a very long argument.

http://www.mikebrownsolutions.com/fish3.htm
http://www.newmediaexplorer.org/sepp/2003/06/07/original_blueprints_for_200_mpg_carburetor_found_i n_england.htm

As you read up, you'll even see that there are huge discrepancies in the facts. Some reports place Pogue in a retirement home in his hometown of Winnipeg, Canada, where he had created the carb in 1935, while others place him in England creating the carb in 1890 before the carburetor itself was even invented. Some reports come from people who have visited Pogue in his retirement home last year, while others report that he died in 1975.

[QUOTE=curtis73]Good gosh. I wasn't going to say anything until now. There is no oil company conspiracy. The Pogue carburetor and its vaporization carb cousins are hoaxes. Just because it has a patent and someone said they drove a car 200 miles on one gallon of gas doesn't mean anything other than an ill-concieved publicity stunt to draw attention to a business.

Uhh...I think I just said that.

So how come this technology is used in airplanes to keep the fuel from freezing?

As a single engine pilot and mechanic, I can answer that one. They don't. They use carb heat to prevent freezing, but it has nothing to do with those vaporizer carb designs. Airplane carbs don't have the advantage of underhood heat to prevent icing, nor do they have hot intake manifolds. They also venture into altitudes where the ambient air is often 30 below. Carb heat is simply sourcing intake air from behind the cylinders where its warmer. It is intended to be used at high altitudes, or where humidity and barometric pressure dictate. Its no different than a manual version of a preheater shield on the manifold of an 80s car with the vacuum assisted thermac door.

It has nothing to do with the vaporization of the fuel, its designed to prevent the carb from freezing into one big snowball causing a dangerous condition where you can't alter throttle position. That would be bad. :)

Trust me, at 6000 feet in the winter where the ambient air is 10 below, the best intake air temperature you can muster with the carb heat wide open is about 100 degrees at a very slow cruise; no more than a Qjet in a buick in the summer. The older (1973) Piper Archer II that I fly I won't even take up if ambient temps are below about -10; primarily because the cabin heat sucks, but also because if I want to cruise above 100kts, I can't get enough carb heat to safely prevent freezing.

In answer to your question, they are not there to prevent fuel from freezing, or to extend fuel consumption, they are there to prevent the EXTERIOR of the carb from turning into a snowball.

Uhh...I think I just said that.

You did. I just couldn't keep my mouth shut :grinno:

You did. I just couldn't keep my mouth shut :grinno:


works for me

Well the ideal fuel for a car is propane and not gas. You can also run a car off of natural gas. This is the same concept, turning thje liquid fuel into vapor. I asked my auto teacher who's been teaching 30 years and he said it's possible and the thing I'd have to worry about the most of pre-ignition.

On what principle do you determine that propane is the ideal fuel for a car? Just because a hydrocarbon exists as a gas at room temperature doesn't make it any better. The word Carburate means to turn a liquid into a gas. A carburetor uses pressure and heat to turn gasoline into a liquid. When metering liquid propane into atmospheric pressure, you are using.... heat and pressure. The ONLY difference is the temperature at which they evaporate.

A carburetor doesn't just put little droplets of gasoline in the air, it evaporates it. Surrounding heat, venturi, and the screaming hot walls of the intake and head port make sure that almost all of it is entirely evaporated by the time it reaches the chamber. Its not perfect; there are still a few droplets, but its not like just squirting gas from a spray bottle.

That very principle is demonstrated in the fact that Propane (although it has slightly fewer BTUs than gasoline) makes less power than an identical gasoline engine. Propane only has 86% the BTUs as gasoline, and takes much more to be stoichiometric. So, all that extra fuel you're using to make less power doesn't seem to make sense except environmentally.

And don't get me started on the "ideal" fuel. There is no such thing. Each one has their own set of benefits and trade offs. But everyone here who wishes to keep their status as a member agrees with me... Diesel is the best fuel :) Just kidding.

Seriously, you keep quoting your teacher. We're all very knowledgeable folks here. He's given you a basis, but its partly his opinion. Open up your mind a bit to the possibilty that we know what we're talking about, too.

Seriously, you keep quoting your teacher. We're all very knowledgeable folks here. He's given you a basis, but its partly his opinion. Open up your mind a bit to the possibilty that we know what we're talking about, too.

Yes I understand you guys know what you are talking about and that's a main reason I joined here. I just could see this working. I don't know why. I know fuel is vaporized essentially when it hits the intake manifold. What I'm thinking is if the fuel is vaporized beforehand that heat that was supposed to vaporize the fuel could be used to expand the gas molecules a bit more (and my reasoning behind no real loss in power). I also reasoned that there are already engines that run on "dry" gas. They seem to work fine. That got me to thinking if gas were in a gas state before it could work and use less gas overall.

I'm not going to attempt making this thing until the semster is over and I have a good firm base on mechanics. Also I bought a chemistry and physics book (I work at a public library and these books were surplus and cheap :D).

About the whole oil conspiracy thing I think there's some of it going on. Come one Exxon just posted record profits for any corporation. What would be worse than something that would reduce the use of their product and cause profit loss? They knew that fuel saving devices were a threat to theri industry just as the robber barrons knew competition was a threat to their business. Don't think the oil industry is so innocent of everything. I heard the found of google is making a documentary about the oil industry.

if i understand what you're trying to say, you want to get the fuel into a gaseous state before it enters the cylender. i don't understand this thing you were saying about no lost energy, there's very little energy lost in pumping the fuel, the only energy lost is to the alternator.

the boiling point of octane is 125 degrees celsius so you might have to preheat the gasoline to 150 degrees. the problem that comes with this is that you'll have some very high pressure gas trying to force its way out of the injectors and it'll be hard to controll the ammount that flows. another thing is that in the event of a colision the car could very easily burst into flames. if you can control the gas and control the flow, then you might have some improvements in fuel efficiency and power, becuase there will be more surface area and the gas will react faster.

I think your biggest problem will be getting the gasoline into a controlled gaseous state. after that it'll be getting the right fuel/air mixture.

BTW curtis, you weren't kidding, the diesel engine is the best engine that's widely available today. you know the reasons, most of which you probably told me at some point or another.

I think your biggest problem will be getting the gasoline into a controlled gaseous state. after that it'll be getting the right fuel/air mixture.


And that's why my teacher said it would have to worry about pre-ignition and getting it too hot especially in the summer than it would have to be. Plus I'd be able to generate this heat from the exhaust manifold. I mean 30% of the gas in there is used for turning the crank the other 70% is lost to heat in the combustion process. You can "recycle" that heat. Most likely I'll probably try this on a small engine first before I get to something that will cost a lot of money if I blow it up.

The evaporation of gasoline in the intake and carb forces evaporation adiabatically which cools down the mixture considerably. Adding heat first means that you have hot fuel vapor without the benefit of that adiabatic cooling and detonation and power loss may be more of a destructive roadblock instead of just something to watch for. The downsides seem to outweigh the benefits currently.

The best way (with current technology) to recover heat is with a turbo, but there again without the detonation-reduction of the cooling evaporation, it might be a reliability issue.

I often thought about a hypersonic method of evaporation. You've probably seen the foggy fountains in stores. They have a little hypersonic speaker that adds enough energy to the water to evaporate it instead of heat. Its the same technology used in cool-mist humidifiers. I wonder if that might be adapted to gasoline technology. You wouldn't have the advantage of adiabatic cooling, but at least you wouldn't be adding temperature to the mix either.

Of course you all realise that Direct injectin Gasoline engines make all of this redundant?

The evaporation of gasoline in the intake and carb forces evaporation adiabatically which cools down the mixture considerably. Adding heat first means that you have hot fuel vapor without the benefit of that adiabatic cooling and detonation and power loss may be more of a destructive roadblock instead of just something to watch for. The downsides seem to outweigh the benefits currently.


From what I read it's better to have a warm mixture because it ignites better.

A warmer mixture ignites better, but detonation is when it ignites too well. The mixture that exists in a plain old carbureted engine is pretty good, and the spark energy is definitely enough. Getting it to burn doesn't seem to be the problem. Keeping it from burning on its own (detonation) is. I don't think its limiting factor in efficiency is the temperature of the incoming mix.

In fact, much more power (at the expense of greater HC emissions) can be found by cooling down the intake mixture. It can be pretty cool and still vaporize the intake charge effectively. Cooler, denser air means more molecules of oxygen per volume, which means we can add more fuel. Some guys ice down their intakes between races, use special ice canisters with coils for the fuel lines, and go to great lengths to source air from outside the engine compartment. Of course, that is just for power, not MPG. It stands to reason that the denser air racers crave supports more fuel being ingested, and therefore less MPG.

On the other end of the spectrum, the auto manufacturers in the 80s went to great lengths to source hot air from under the hood. This made less dense intake charges which supported stoichiometric mixtures with less fuel. The downside is higher NOx emissions, but EGR counteracts that pretty nicely.

I think the key here would be to find a way (since the spark energy does more than enough to ignite the mixture) to completely vaporize the gasoline without heating it. Then you would have the benefits of both the cool charge and the complete burn.

Do an internet search for HFI. I haven't been able to find it again, but a few years ago, an engine builder came up with a pretty good idea. He designed a passive direct injection fuel idea. He drilled a passage all the way through a head front to back, removed the intake valve seats, and drilled a small passage to intersect with that passage. Then he re-installed valve seats and drilled little fuel jets in them. He then pressurized that whole passage with fuel. When the valve was closed, the engine received no fuel. As the intake valve opened, it drew in air and fuel. Since the valve seat was hot (at temperature) the gas easily and instantly evaporated. His design had no throttle, instead he varied RPM with a variable lift system he designed. He had a 4.3L V6 chevy that was a running prototype.

I'll see if I can find any pages on it. If I do I'll post them here.

A warmer mixture ignites better, but detonation is when it ignites too well. The mixture that exists in a plain old carbureted engine is pretty good, and the spark energy is definitely enough. Getting it to burn doesn't seem to be the problem. Keeping it from burning on its own (detonation) is. I don't think its limiting factor in efficiency is the temperature of the incoming mix.


Yes I refered to this as "pre-ignition." I may have put the wrong term on it but that's what I meant. That is what I can see being my biggest obstacle.


In fact, much more power (at the expense of greater HC emissions) can be found by cooling down the intake mixture. It can be pretty cool and still vaporize the intake charge effectively. Cooler, denser air means more molecules of oxygen per volume, which means we can add more fuel. Some guys ice down their intakes between races, use special ice canisters with coils for the fuel lines, and go to great lengths to source air from outside the engine compartment. Of course, that is just for power, not MPG. It stands to reason that the denser air racers crave supports more fuel being ingested, and therefore less MPG.


I know it makes the fuel more "rich." This is one of the factors why when it's really cold outside (below 0) you see a big change in gas mileage. I want to make this system for fuel economy, not performance. This is for the everyday driving in which takes most of my gas at least.


I think the key here would be to find a way (since the spark energy does more than enough to ignite the mixture) to completely vaporize the gasoline without heating it. Then you would have the benefits of both the cool charge and the complete burn.

Do an internet search for HFI. I haven't been able to find it again, but a few years ago, an engine builder came up with a pretty good idea. He designed a passive direct injection fuel idea. He drilled a passage all the way through a head front to back, removed the intake valve seats, and drilled a small passage to intersect with that passage. Then he re-installed valve seats and drilled little fuel jets in them. He then pressurized that whole passage with fuel. When the valve was closed, the engine received no fuel. As the intake valve opened, it drew in air and fuel. Since the valve seat was hot (at temperature) the gas easily and instantly evaporated. His design had no throttle, instead he varied RPM with a variable lift system he designed. He had a 4.3L V6 chevy that was a running prototype.

I'll see if I can find any pages on it. If I do I'll post them here.

I'll definatly check that out. What's wrong with heating the gas? You can easily get the heat lost in combustion. I knwo it's also mechanically possible and I'll look into it.

I'll have to start with a small mechanical 4 stroke engine. This won't work with a 2 stroke because if you vaporize the gas before it hits the chambers then there's nothing to lube the rings and your pistons will seize up. Plus if something does got wrong it makes less of a mess with a small engine and is cheaper to fix.

Also another problem I'm going to be with fuel injection. I'll have to make sure I start with a carbeurted engine. No comptuers or anything emtering the fuel. I could see this getting very complicated with fuel injection.

Curtis now do you see where I'm coming from? Do you think this is possible now? I mean you mentioned about mechanically vaporizing the fuel.

Of course you all realise that Direct injectin Gasoline engines make all of this redundant?


wtf is a direct injection gasoline engine?

wtf is a direct injection gasoline engine?

Pretty much what it sounds like. Its an engine that injects the fuel directly into the chamber. Unlike diesel, it still uses a spark plug, but it moves the mass of fuel downstream. Benefits include an easier intake tune, more accurate metering (since you don't have to account for fuel sheeting on the intake walls) and for the same reason better economy.

Cody_e. You're on the right track, but just remember, heat in equals heat out. In this case the "heat in" comes as stored energy in the fuel. "Heat out" is in the form of force on the piston, sound, light, and hot exhaust. If you add more heat to the first side of the equation (by raising the temperature of the intake charge) you will increase how much comes out on the other side of the equation. In this case, like you've already identified, that heat will probably cause detonation.

To get fuel to evaporate you have to add energy. In the case of a carburetor, it uses mechanical means to force gas to evaporate and it sucks heat from its surroundings. In the case of HFI, you're using actual heat. In the case of those little vaporizers, you're using kinetic energy in the form of motion. I would think it would have the benefits of fully evaporating the gas without the drawbacks of heating it.

http://www.volcanicfuelinjection.com/index.html

There it is... Evidently HFI was already taken by the hydrogen fuel injection, so he changed it to reflect his last name, Volcin. Its VFI now.

Cody_e. You're on the right track, but just remember, heat in equals heat out. In this case the "heat in" comes as stored energy in the fuel. "Heat out" is in the form of force on the piston, sound, light, and hot exhaust. If you add more heat to the first side of the equation (by raising the temperature of the intake charge) you will increase how much comes out on the other side of the equation. In this case, like you've already identified, that heat will probably cause detonation.


But you also have to take into factor that you are "recycling" this heat. The heat given off in combustion will go back to vaporize the next batch of fuel. It would basically be a cycle of heat recycling.

True... so the only "extra" heat to deal with will be during combustion. That could be combatted with a little extra EGR or retarding timing. The EGR would pay off big time, but the retarded timing would reduce economy measurably. Maybe not as much as the complete vaporization would recover, but an interesting thing to ponder.

How would you work this with a cold engine? Preheater?

True... so the only "extra" heat to deal with will be during combustion. That could be combatted with a little extra EGR or retarding timing. The EGR would pay off big time, but the retarded timing would reduce economy measurably. Maybe not as much as the complete vaporization would recover, but an interesting thing to ponder.


Like I said I'm just a student so I don't know what EGR is. What is it?


How would you work this with a cold engine? Preheater?

That's another problem I thought of. Yes I would have to find some way to preheat it. Or maybe I'll have to experiment with it a bit and see if it's better off starting like a normal car would and running liquid through the thing and then as it heats up start vaporizing the thing. These are all little kinks I have to work out with this.

Like I said I'm just a student so I don't know what EGR is. What is it?

Exhaust Gas Recirculation. It recirculates exhaust back into the intake during low load situations like part throttle. Its primary function is to reduce NOx emissions by lowering the combustion temperatures. Properly functioning EGRs don't cost much power at all, but allow full ignition advance (which is one of the keys in MPG)