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RobertISaar
02-19-2013, 04:01 AM
hopefully, this ends up as a very long thread, filled with good information, or at least theories that have merit...

so, what is thermal efficiency(specifically, the thermal efficiency of an otto cycle engine, since by a large margin those dominate the US market)?

it's how much of the energy contained in the fuel is actually used to power the engine, rather than getting "lost" as exhaust or cooling. it's commonly quoted that roughly 1/3 of the energy contained in gasoline is actually used in a useful way(driving the piston down its bore, which turns the crank, which powers the transmission, which turns the axle, which turns the wheels, with each step losing efficiency along the way), the other 2/3 is lost to the exhaust system and to the cooling system.

now, 33% isn't that great... you could be making 3 times the torque or achieving 3 times the fuel efficiency, depending on how far your foot is in the throttle, obviously.



so, now that we know what we're working up against, what can be done to convert the energy lost in the cooling system and exhaust system and use it to drive the engine?



friction = bad, no exceptions. friction takes useful energy to make more heat, which ends up in the cooling system.

heat IS energy. pressure IS energy. anything that can be done to keep those two things inside the combustion chamber and not the surrounding metal will keep energy out of the cooling system. when the spent air/fuel charge comes out through the exhaust port is another place for it to sink into the surrounding metal. the exhaust manifolds and downpipe as well. you could actually help cold-start emissions quite a bit if you kept all of the heat coming out of the engine intact until it hits the catalytic converter.



other suggestions???

one way of extracting energy from the exhaust is obviously a turbocharger, though with increased airflow/airmass caused by boosting, don't expect to see any MPG benefit. if you're looking for more power, it's a great way to go about it, since at least the energy left in the exhaust will be doing something.

there was some brief discussion before about coating internal parts with substances that would reject heat... seems like a good place to cut cooling system losses.

it seems like the cooling system is the low-hanging fruit... extracting work out of the exhaust(besides a turbo) seems to be difficult. using the exhaust to heat up the coolant to normal operating temps faster is actually getting used on some common cars now(prius is one IIRC).

neat fact: a hotter engine absorbs less usable energy into the cooling system due to the temperature differences. a 1500*F flame hitting a 70*F piece of metal gets more of it's heat sapped away than the same flame hitting a 210*F piece of metal. this is why some rather "radical" engines(NASCAR) run really hot thermostats/coolant temps.

another neat fact: aluminum conducts heat a LOT better than iron... thus, an aluminum head will transfer more heat out of the combustion chamber than an iron-head engine of the same design would. because of this "feature", you'll generally run more advance since the engine will be less likely to detonate/pre-ignite. one way to help minimize heat loss regardless of head material would be to minimize surface area.





MOAR THOUGHTS!?!???

EagleMark
02-19-2013, 04:15 AM
I think Smokey Yuinick knew this in early 80s, or at least did something with the knowledge. Went against all we are taght about cool air and fuel.

http://www.legendarycollectorcars.com/featured-vehicles/other-feature-cars/smokey-yunicks-hot-vapor-fiero-51-mpg-and-0-60-in-less-than-6-seconds-see-and-hear-it-run-in-our-exclusive-video/

1project2many
02-19-2013, 07:36 AM
Good start. This subject is very near and dear to me and I've got plenty of years learning, reading, and trying different approaches to improving engine efficiency and in turn, thermal efficiency.

The cooling system is a necessary component and will continue to be so as long as we keep introducing 2/3 more fuel into the chamber than we need to move our cars. What we need to do is find a way to reduce the necessary fuel to that amount necessary to move the vehicle. One of the reasons the mixture must be so rich is because of the amount of inert gas in the combustion chamber. Nearly 79% of what we injest in the engine won't add power and actually inhibits combustion. In order to get enough fuel molecules next to the available oxygen molecules we simply dump too much fuel into the cylinder. The reaction starts and continues until almost all O2 is consumed and the unused fuel is ejected as unburned hydrocarbons to be treated in the converter. Altering the balance of nitrogen and oxygen to favor O2 means less fuel can be used without combustion failing, and less gas needs to be pumped to produce the same power output. The first attempt that I'm aware of was around the beginning of the 20th century using special membranes to separate O2 and N2. The fact that we rarely hear of this suggests the results were less than favorable but the idea is still correct.

EagleMark
02-19-2013, 08:24 AM
May be the same issue rarely talked about in the Yunik fiero, even aircraft grade oil had a hard time dealing with heat. Standard car oil did not last at all! That was early 80s, was synthetic around then?

gregs78cam
02-19-2013, 08:24 AM
I have a read quite a lot about the work that Smokey did, and I think he had the right idea, heat up the air/fuel mixture (more heat stays in the engine) and mix it very well to get the most efficient combustion possible. I have been wanting to try my hand at making it work, just don't have time or money required. As far as coating engine components, if I had known about it when I was building my 383 I would have done it. I think it would go very well with making Smokey's ideas work.

RobertISaar
02-19-2013, 08:25 AM
i've always wondered what the overwhelming amount of nitrogen did to the burn rate / completeness...

if we moved up to 100% oxygen.... would that also significantly alter the stoich ratio for a given fuel? it seems like it would have to.



i've also heard of the various theories and how the "adibiatic" fiero worked.... or didn't work. the big issue is that the engine ran so hot that it required a very expensive oil that didn't last very long. it also had absolutely horrible drivability until it was fully warmed up. but, the idea of using the exhaust to heat up..... well, everything, it's interesting.

gregs78cam
02-19-2013, 09:29 AM
Now that you bring up oil, I read an article, and subsequently contacted the company to see if they would be producing anything for automotive applications, they said no.

http://www.coatesengine.com/csrv-system.html

Short story, spherical rotary valves, no oil in top of head, much better flow, higher compression, much less friction, higher revving, more power, better economy. Only for Harleys, and commercial generators.......as of like 8 years ago or so.

Think something like this, direct injected, and turbos.

Turbos bring up another question I have. Can a turbo be sized appropriately, and tuned to actually make boost while at a steady state of output. I mean say for instance start with a 2.0L (really I am thinking something around 600cc-1.0L) engine, setup and tune the combination to make 3-5 psi while cruising. Not much but enough to offset the pumping losses, and use the exhaust velocity to do something useful.

bentrod
02-19-2013, 01:21 PM
Man I remember being younger and reading that hotrod article like 10 times. When it came out I believed with in 2 years, that was the future of cars, all cars.

But what happened? For all the lame excuses that could come up, from auto manufacturer's laziness to oil company conspiracies, you'd think SOMEONE, SOMEWHERE would after 20+ years figure out how to mass produce an engine like the one he made.

There is clearly money to be made on making an engine with the stats he provided. Yet no one, not even greedy mega multimillionaires (who could hire Smokey and a team of 10 engineers) could figure out how to mass produce it and make conventional engines as a thing of the past?

Was it too good to be true? Was hotrod lying to us? Why don't we see more of these cars around now? What went wrong?

Maybe it's getting older that makes more skeptical but something tells me we are missing the whole story about that 230hp iron duke.

RobertISaar
02-19-2013, 07:47 PM
Turbos bring up another question I have. Can a turbo be sized appropriately, and tuned to actually make boost while at a steady state of output. I mean say for instance start with a 2.0L (really I am thinking something around 600cc-1.0L) engine, setup and tune the combination to make 3-5 psi while cruising. Not much but enough to offset the pumping losses, and use the exhaust velocity to do something useful.

what kind of cruise RPM would be desired? around 2,500(with a 2L)? because i can definitely see turbine housings small enough for that to be a reality.

gregs78cam
02-19-2013, 09:37 PM
yea, 2000-2500 rpm, 4K-5K with a <1L. Turbos are great at making better than 100%VE at WOT, why not at cruise?

Playtoy_18
02-19-2013, 10:22 PM
I am interested and am playing with the ideas of thermal efficiency as well a small bit.
One big issue I see is with all the energy conversions taking place.
From chemical to heat to mechanical etc..
The heat is a necessary evil,as the expansion of the chemical combustion reaction is what transfers to mechanical energy.
I am trying to make those conversion processes more efficient in order to coax more efficient power.
One thing i've been playing with is the use of specialized coatings.
Coating the piston and chamber will help retain heat where it can be used in the cylinder instead of wasting it into the cooling system.
At the same time however,the fuel delivery must also take a new turn.
One big issue with fuel is atomization,fuel will only be consumed in the combustion process from the surface of a droplet of fuel as I have been taught.
So to actually use less fuel,the fuel must be almost completely vaporized or else the rest of the droplet goes right out the exhaust.
Direct injection helps accomplish this,as the ecoboost from Ford has shown.
Offhand I think the v6 twin turbo in the f150's is running about 12psi,10:1cr and over 350hp from a 3.5.
I want to say the sho or one of them is actually running higher boost and cr as well.
I believe it is from some of the benefits of such higher pressures/better atomizatin as well as the excellent effects of controlling cylinder temps.

I'm trying to negate alot of the parasitic effects of the mechanical parts as well using dry film and ceramic coatings as well as thermal transfer and barrier coatings.
Coming up on some actual engine testing,and i'm anxious to see if it is going anywhere.
I have both of smokey books and honestly alot of where my ideas come from,I admire the hell out of him.
Interesting topic,subscribed.

RobertISaar
02-19-2013, 11:08 PM
fuel vaporization is a big issue... one reason why i would hesitate to coat the intake valves with anything that would prevent it from heating up. if anything, let that run hotter, the fuel charge spends some significant time sitting on it.

it would be neat if there were some type of coating(catalyst?) that could be applied to the backside of the valve that either reduced the temperature necessary for gasoline to vaporize, or otherwise would help it along.

Playtoy_18
02-19-2013, 11:12 PM
http://www.techlinecoatings.com/articles/Coating_a_Valve_Article.htm

I used the same product on the inside of a carb manifold,he had to rejet down two sizes and play with the plug gap when tuning it afterwards.
Offhand I would say in general it definately helps keep the fuel in the airflow and off the walls.

*sorry,that covers the front and not so much back of valve.
The dry film product creates a "boundary level turblulence" that promotes flow as well as keeping the fuel suspended and off the port walls.

1project2many
02-20-2013, 01:07 AM
if we moved up to 100% oxygen.... would that also significantly alter the stoich ratio for a given fuel? it seems like it would have to.
Yes. The balanced ratio of oxygen to fuel is about 11:1. The end components are primarily CO2 and H20. But 100% oxygen carries it's own set of problems. Oxygen prefers to bond with other atoms such as Hydrogen and Carbon. Given the chance, O2 will quickly break apart to form bonds with these elements. In a warm engine with sharp edges and hot spots, increasing heat from compression is all the chance that O2 needs. Ignition can easily start well before the spark and with no inert gas to inhibit the reaction, fuel quickly burns. Additionally, free oxygen and excess heat can cause internal engine parts to burn or melt which rarely leads to long engine life.


Can a turbo be sized appropriately, and tuned to actually make boost while at a steady state of output.
Yes. That was a major part of Smokey's hot vapor engine.


fuel vaporization is a big issue... one reason why i would hesitate to coat the intake valves with anything that would prevent it from heating up.
But, and this is a big but, fuel that has changed phase and become a gas will expand and force much needed oxygen out of the engine. The turbocharger on the hot vapor engine played a dual role. First, it served as a giant mixer, a homogenizer, to turn fuel and air into a consistent mixture. Second, and more importantly, it kept the gaseous fuel from forcing oxygen back out of the engine.


So to actually use less fuel,the fuel must be almost completely vaporized or else the rest of the droplet goes right out the exhaust.
Direct injection helps accomplish this,as the ecoboost from Ford has shown.
What direct injection really accomplishes best is to move the vaporization phase away from the intake pathway and into the cylinder. Not only does this prevent O2 displacement but it allows the beginning and end of combustion to be better timed to specific positions of the piston and crankshaft.


it would be neat if there were some type of coating(catalyst?) that could be applied to the backside of the valve that either reduced the temperature necessary for gasoline to vaporize, or otherwise would help it along.
You've got the catalyst in your car already. Platinum and Palladium are excellent catalysts for combustion. We just need a binding agent that can be applied to engine parts and will withstand the heat of combustion. Anyone interested in mixing ground up cat ceramic with thermal barrier coatings?

Playtoy_18
02-20-2013, 01:49 AM
Don't the platinum and palladium have it's reactions after combustion though?
I thought we were talking about using the fuel more efficiently,after it's burned and needs a catlyst for emissions then the idea pertains more towards controlling emissions versus controlling combustion/fuel efficiency/vaporization etc..

1project2many
02-20-2013, 02:07 AM
They're typically used after combustion, yes. But that's not the only place they work. All the converter is doing is "burning" unused fuel... reacting oxygen with hydrocarbons and carbon monoxide. And really, if you think about it, what are hydrocarbons? They're just unburned fuel. The catalytic converter actually decreases the total fuel efficiency of our vehicle by making even more heat while burning the last of the fuel we didn't use in the engine. It's always seemed like such a huge waste to me. One way to save that heat, though. Put a turbo on the end of the cat. The exhaust can be thousands of degrees leaving the converter... why not use it? I actually think that's how some of the remote turbos are able to function so well. In the old days, pre converters, it seemed well proven that the turbo didn't work well that far away from an engine.

Fast355
02-25-2013, 08:15 AM
Easiest way to help thermal efficiency at part-throttle cruising is to heat the incoming air/fuel mixture. I saw 1-2 mpg increase by simply using a solenoid off my EBL ecm to operate the vacuum operated switching valve on the front of the air cleaner on my 83 G20 with the TBI swap. I saw IAT readings of 160-170*F cruising down the highway and MAT temps (open cage sensor in vacuum fitting) of 130-140*F. Unheated on a 100*F day, I saw 120-130*F IAT and 70-80*F MAT readings. Heating the intake air really helped me with being able to lean the engine out in lean cruise and keep it running smoothly.

RobertISaar
08-09-2013, 12:11 AM
had some thoughts lately that have me coming back to this thread.

some more thoughts on a current topic: catalyzing the fuel before it gets oxidized: won't fuel constantly being in contact with the catalyst cause the issue of the catalyst "melting down" like it does in the cat converter?

and new thought: EGR does a lot more than what i had previously thought... we all know it's original purpose is to reduce NoX emissions and while it's nice and all to have cleaner air, i'm more curious about the other benefits it can have, specifically on fuel economy, since burning less fuel means there are less potential polutants to deal with. sometimes it can hurt emissions, but i'm curious to see some interesting results.

but here is where some recently new thoughts came in: EGR is literally using the vacuum of the engine to draw exhaust gasses out of the exhaust, which lowers exhaust backpressure. obviously, the amount of pressure reduced will depend on a lot of factors, such as orifice size, manifold vacuum, exhaust backpressure and probably some other small factors.

but, applying a vacuum to the exhaust SHOULD actually help the VE of the engine, since now it has to work less to push the exhaust gasses out of the head. and of course, the gasses flowing into the intake should also reduce pumping/throttling losses since now there is a higher manifold pressure present.



actually accounting for all of this in the calibration? not a lot of masks seem to do that. they appear to do a pretty simplified calculation. i'm curious to see how the "linear" EGR valves effect all of this, compared to the older EVRV or 3 tower digital setups.

EagleMark
08-09-2013, 01:43 AM
Plus there is heat in the EGR entering intake cold charge, so how does that effect things?

RobertISaar
08-09-2013, 02:00 AM
well, as we've seen, heat helps the vaporization of fuel, which if significant enough, CAN hurt VE due to expanding fuel vapor pushing air back into the plenum rather than sitting in the runner. it will also likely contain SOME unburned fuel.

a hotter mass also experiences less friction when it moves since it is less dense(so less molecules to scrub up against port walls and even other air molecules).

i haven't thought too much about it, but i think some of the OBD1 stuff does have a correction to the intake runner temp due to EGR being active. how complex GM's code engineers got here, i have no idea.



it would be interesting if the equivalent of the carbon cannister used for evaporative emissions could somehow be used in the exhaust to capture any unburned fuel and have it get sucked up through the EGR system. i'm not sure how much raw fuel could be collected though. i would think one would want to position a device immediately before the catalytic converter since the exhaust stream will be the coolest there(and most dense) before the cat uses the unburned fuel and does it's job as a catalyst.

delcowizzid
08-09-2013, 04:34 AM
egr is meant to help by reducing pumping losses by lowering vacuam in the inlet ive played around a lot with egr and it doesnt really help at all for saving fuel mostly emissions.ive turboed a lot of non turbo cars and they get better MPG at cruise even without boost.the gain in torque at 100kpa is huge on turbo conversions but the whole cruise map is up in torque and you use less TPS to move the car at the same speed

Fast355
09-19-2013, 02:31 AM
egr is meant to help by reducing pumping losses by lowering vacuam in the inlet ive played around a lot with egr and it doesnt really help at all for saving fuel mostly emissions.ive turboed a lot of non turbo cars and they get better MPG at cruise even without boost.the gain in torque at 100kpa is huge on turbo conversions but the whole cruise map is up in torque and you use less TPS to move the car at the same speed


I have had luck getting MPG gains by tuning the EGR to come on at specific times. From the factory the EGR is open during heavy loads at part-throttle and minimal EGR at low load cruising speeds. This is exactly opposite of what you need for fuel economy but works well to control NOx.

34blazer
09-19-2013, 09:55 PM
I finally noticed MPG gains after removing the orifice washer on the gasket and turned up the DC 100%.

RobertISaar
09-19-2013, 10:10 PM
perhaps i'm not used to EGR systems other than the 2 and 3 tower digi setup, but orifice washer on/in the gasket? as in, an attempt to reduce EGR flow?



also, the puttmaster(92 ranger 2.3/5 speed) has had a check engine lamp on forever, just never saw it due to the instrument cluster being of a crap design(it's a copper foil sandwhiched between two sheets of plastic, i soldered everything on it rather than it relying on friction, now it all works correctly), pulled codes on it and got an EGR position code and an O2 lean code. an O2 code i was expecting based on behavior when ambient temps drop and the ECM wants to drop into closed loop but goes so lean as to cause significant misfiring until foot is on the floor or idling. the EGR position code combined with the O2.... may explain why fuel economy has been less than expected. 27MPG in the summer is about 4-5MPG lower than what i was expecting based on what i see with the other vehicles.

34blazer
09-21-2013, 03:55 AM
perhaps i'm not used to EGR systems other than the 2 and 3 tower digi setup, but orifice washer on/in the gasket? as in, an attempt to reduce EGR flow?


Im assuming that was the intention of the orifice in the gasket, this is on the Fiero BTW.

Now that im thinking about it, there is also an orifice gasket on my mustang(5.slow).

ericjon262
10-13-2013, 04:20 PM
we all know the fuel vapor is what's really powerful, so here's an idea, draw a vacuum on a fuel canister to lower the saturation temperature, and heat it up a bit, much like how a distilling unit would boil water, the trick will be getting the vaporized fuel delivered to the engine, because when you pressurize it, saturation temperature will raise, and you'll be back to a liquid. how about a carburetor? (please don't shoot me yet!) a venturi could easily deliver the vapor at a low pressure so that you don't have to worry about raising saturation pressure.

want to stick with fuel injection?

how about heating the pressurized fuel in the lines, where the pressure keeps the saturation temperature very high, that way when the fuel goes from the high pressure injector to the low pressure atmosphere, and saturation temperature drops, the fuel requires less latent heat to be absorbed from the atmosphere to flash to vapor.

the big thing though, will be to use exhaust heat to heat the fuel, much like an economizer in a steam plant. that way the heat is doing useful work, not just going off into atmosphere. the only real problem I see there, is the exhaust might be too hot to use for the heat source. if you used a turbo, the turbo compressor outlet would probably be a better heat source as it's not silly hot, and some of the heat is being used by the turbine blades to do useful work. but then you're also lowering air charge temps by effectively creating an air/fuel intercooler.

problems:

electronics don't like heat, how long will fuel injectors last with 250F fuel running through them? do we need to add a heat sink and liquid cooling to keep them happy?

the biggest problem I see is oil, most oil doesn't like being hot. roller bearings would reduce oil requirements, but add more complexity, and more points of failure.

Safety: will the hot fuel sit an the rail safely without problems when the engine is shut down?

pmkls1
10-13-2013, 05:16 PM
I just noticed this thread so I read through the posts to get caught up. I definitely have a lot to add, but I don't have the time right this minute. I just wanted to say that as soon as I have a minute (or more like an hour lol) to put together a response I'll add a little bit of info to the thread and address some of the ideas that I have seen some experimentation with.

RobertISaar
10-13-2013, 09:05 PM
i've seen the heated fuel idea work before on a carb.... the biggest issue i've seen with it is that due to the fuel being at such a wide range of temperatures, the density of the fuel changes enough to cause some interesting effects on the actual AFR.

at least with fuel injection, we could track fuel temp and get the fueling back in-line after some trial/error.

oil..... i don't think this would introduce that much more heat into the oil?

hot fuel that isn't moving would likely vaporize at the pressures a MPFI system runs at..... i imagine the simple solution behind that would be either a microcontroller that turns the fuel pump on and runs it for a few seconds at a time and repeats that a few times(either a set number of times or until fuel temp drops below x *F) or perhaps going really simple and setting up some 555 timers to just run it for a while after the ignition is off.

ericjon262
10-13-2013, 10:09 PM
i've seen the heated fuel idea work before on a carb.... the biggest issue i've seen with it is that due to the fuel being at such a wide range of temperatures, the density of the fuel changes enough to cause some interesting effects on the actual AFR.

at least with fuel injection, we could track fuel temp and get the fueling back in-line after some trial/error.

oil..... i don't think this would introduce that much more heat into the oil?

hot fuel that isn't moving would likely vaporize at the pressures a MPFI system runs at..... i imagine the simple solution behind that would be either a microcontroller that turns the fuel pump on and runs it for a few seconds at a time and repeats that a few times(either a set number of times or until fuel temp drops below x *F) or perhaps going really simple and setting up some 555 timers to just run it for a while after the ignition is off.

I was meaning that if the engine were running hot (to reduce heat losses) oil would take a beating.

IIRC, the Smokey Yunick Fiero didn't have a cooling system at all, just an oil cooler.

I see a small problem with the microcontroller idea, if you send the more or less superheated fuel back to the low pressure tank, it'll flash to vapor, you'd need to bring the temp back down to a more reasonable level before sending it back to the tank. A check valve could hold the pressure on the rail, but would the fuel start breaking down in the rail?

the thing I like best about the idea of doing an adiabatic engine fuel injected, is that you can make it idle until it's hot. whereas a carb you have way less control.

additional sensors I would think are necessary on top of the usual compliment:

fuel pressure sensor
fuel temperature sensor
fuel composition sensor
wide band a/f
MAT instead of IAT

egt probe may prove useful as well.

another "problem" gasoline is a mix of several different petroleum distillates, which will all vaporize at different temperatures and pressures, but this is easy enough to overcome by cranking the fuel pressure higher, thus raising the saturation temp of the lowest distillate higher then the fuel temp. which would improve total vaporization as a plus. Now for the next bit of science fun we would have to look at, what pressures will be necessary to prevent the vaporization at the higher temps?

then, there's the valves and valve seats, I see the heat being a bit of a bear on them, I'm sure there's some exotic material we could use.

damnit! you guys are making me want to start another project!

gregs78cam
10-13-2013, 11:17 PM
The easiest way is just like Smokey did heat the fuel and air in the intake tract, and heat it to a temp where all of the different distillates have vaporized, then mix the them REALLY well with a rotary vane type of compressor to also act as a check valve. And using TBI would still give a much more precise control as opposed to carb'ed, especially during warm-up.

ericjon262
10-18-2013, 06:32 AM
the vapor displacement concept Robertisaar mentioned had me thinking, how much air can be displaced by the expanding fuel? it makes me think TBI would probably be a better route, because then the fuel and air are drawn in together. more on this over the weekend. but for now, I need some sleep.

RobertISaar
10-18-2013, 06:52 AM
how about a 2" wide check valve? :laugh:

1project2many
10-18-2013, 02:44 PM
how much air can be displaced by the expanding fuel?
All of it. Ever wonder why an electric fuel pump, essentially an electric motor, placed into a tank full of fuel doesn't cause the tank to explode?


TBI would probably be a better route, because then the fuel and air are drawn in together.
Actually, more power is made when fuel vaporizes in the cylinder and air is drawn in cold. This is because both the fuel and air enter the cylinder at greater density than if they were heated first. The downside is it's harder to get complete combustion this way.

Pressurize the fuel / air mix then heat it to vaporizing temperatures and you'll get rapid and thorough combustion without loss of power or air.

ericjon262
10-18-2013, 06:54 PM
All of it. Ever wonder why an electric fuel pump, essentially an electric motor, placed into a tank full of fuel doesn't cause the tank to explode?


mixture is too rich. you can put a cig out in a gas tank if you want(please don't).

I think you missed my thought. I was more curious how much expansion would occur, and if it would be violent enough to starve the engine of air, remember, we aren't just hosing fuel down into the engine, we are precisely metering it in.



Actually, more power is made when fuel vaporizes in the cylinder and air is drawn in cold. This is because both the fuel and air enter the cylinder at greater density than if they were heated first. The downside is it's harder to get complete combustion this way.



this makes sense because the vapor expanding would help drive the piston down, almost like a supercharging effect, but I only really see this helping at lower RPM. keep in mind to, that we aren't talking 14.7:1 here, way leaner, way hotter, also, we aren't necessarily talking max power either, but instead efficiency. remember, heat is energy based on a difference in temperature, and only temperature, higher temperature difference, more heat, thus, more heat transfer. If everything is the same temperature, energy can't be lost to heat. cold A/F charge means more energy has to be put in to make it burn, lowering efficiency.



Pressurize the fuel / air mix then heat it to vaporizing temperatures and you'll get rapid and thorough combustion without loss of power or air.

basically, a draw through supercharger or turbocharger, this is similar to how smokey did it. he referred to the turbo as a "homogenizer"

EagleMark
10-18-2013, 08:11 PM
All of it. Ever wonder why an electric fuel pump, essentially an electric motor, placed into a tank full of fuel doesn't cause the tank to explode?
Gasoline in liquid form is not flammable. The fumes that come of it are when mixed with air.


mixture is too rich. you can put a cig out in a gas tank if you want(please don't).
High school auto shop our teacher had a little cabinet and placed a small can/cap of gasoline in there the night before. The next morning everyone was asked to be quite and no banging. We had a bet. He/teacher said gasoline is not flammable, we students knowing it is and most of us have caused many fires as well so we had proof disagreed. Loosers would be acid cleaning the floors in shop during lunch... This was going to be great watching him scrub floors!

So he lights a match with a arm length welding glove and other protection on, so we were also going to get to watch our teacher blow up! Cool bonus but we all liked him! He put the match out in the gasoline!

Cool! But we disagreed and said it must not be gasoline? He assured us it is gasoline and would prove it, he tapped the shelf a few times with his magic wrench and asked if we would like to smell? Dam, that's gas? So on a long stick he had a lit match and got it close and POOF, the fire we are all used to!

This was the beginning of our lessons of Air Fuel Ratios... he did buy pizza as we scrubbed floors during lunch!

RobertISaar
10-18-2013, 08:19 PM
i'd be curious to see what all methods cylinder pressure could be increased without increasing cylinder temperature(or even lowering it).... lower temps will automagically cause less heat losses, and higher pressure means more output.

ericjon262
10-19-2013, 12:00 AM
i'd be curious to see what all methods cylinder pressure could be increased without increasing cylinder temperature(or even lowering it).... lower temps will automagically cause less heat losses, and higher pressure means more output.


I'd like to hear the magic behind this, combustion is really hot.

RobertISaar
10-19-2013, 12:52 AM
well, current tech basically boils down to:

take a mixture of fuel and air and compress it(though external combustion is still around and doesn't compress the mix)
ignite it, creating pressure due to heating the air
get rid of it and repeat

now, the magic is all in step 2, since that is where the air and fuel start turning into something other than air or fuel. given the octane levels most people have to work with, what can be done to maximize the amount of pressure created by combustion, without causing detonation?

heat will obviously cause detonation, but it's a necessary evil, since heat(from the spark plug's arc) is what causes combustion. pressure alone doesn't cause detonation, but the heat created by pressurizing air/fuel can.

http://en.wikipedia.org/wiki/Atkinson_cycle

atkinson cycle engines seems to circumvent some of the negative work portions of the 4-stroke cycle. a higher static compression ratio offsets most/all/more(???) of the power lost due to the air charge getting taken out of the cylinder at the beginning of the upward stroke of the piston. without direct injection, it might take fuel with it? with a tighter chamber, a better chamber design in general would be useful.

this type of engine..... would probably sound a bit odd. i imagine any form of boost would be appreciated and would make the losses caused by being an atkinson design completely irrelevant or absolutely minimal since positive pressure in the manifold will keep air in the cylinder when boost is present.



i may or may not have gotten off-track from beginning to end.

RobertISaar
10-19-2013, 02:26 AM
some tech aspects.

http://pressroom.toyota.com/article_print.cfm?article_id=2722

there is probably a better link to be had, since this one tries to print, but it also doesn't load a whole bunch of other crap.


In the case of the Prius engine , the effective compression ratio is about 8:1, while the expansion ratio is about 13:1. As a result, it is 12% to 14% more efficient, in terms of power output per fuel consumed, than the non-Atkinson engine upon which it is based.

so, static compression is 13:1, while the engine only has to drive the load equivalent of 8:1 compression. 61.5% difference in compression ratios. from the way it is operated(pushing the air back through the intake rather than through the exhaust), pumping losses are also cut down as well. and the result is a ~13% improvement in BSFC. certainly something interesting to look into.....

RobertISaar
10-29-2013, 08:20 PM
had an interesting thought a couple of days ago, still seems to have some merit, so i'll throw it out there:

with sequential PFI: as soon as the intake valve closes, inject a calculated amount of fuel, wait, then inject the rest later.

thought process behind this requires a fair bit of math, but: for the first injection, inject only the amount of fuel that will vaporize by the time the rest of the fuel charge needs to be delivered. due to a smaller mass of fuel sitting on the back of the valve, the average temperature of the fuel mass should be noticably higher than a larger mass in the same situation.

this SHOULD result in a better percentage of the fuel being vaporized before being drawn into the cylinder. because of this, i imagine mixing will improve at least slightly, since fuel vapor is going to move and combine with oxygen a lot easier than a smaller number of larger droplets will.



if this actually does anything beneficial, or is even harmful, i don't know. seems like the kind of thing a manufacturer would patent if it worked well(or at all).

1project2many
10-29-2013, 10:12 PM
Robert, you don't want to maximize pressure in the chamber. You want to apply the most pressure where it does the most good. With the crank arm at or near TDC, pressure in the cylinder is nearly useless. When the crank arm is 90d ATDC, pressure in the cylinder does the most work. Ideally you'd create pressure quickly as the piston approaches 90 deg ATDC. But with cylinder volume increasing (at an increasing rate), this is tough to do. The best method would use a high octane, fast burning fuel and start ignition ATDC to allow maximum compression ratio while resisting detonation and eliminating negative work.

I'd love to see the timing curve on one of Smokey's hot vapor engines.

RobertISaar
10-29-2013, 10:25 PM
thinking about burn speed and octane, ignore gasoline's burn speed and let's say combustion happens instantly after being sparked. or at least, some yet unknown fuel is being used that has an instantaneous burn.

would octane rating matter if all of the fuel that was going to be needed for that cycle not get pumped in until the very last moment before ignition? there wouldn't be the opportunity for pre-ignition/detonation if no fuel was present. the flowrate of the injectors needed to do this type of event would have to be monsterous though.

i seem to remember this being very similar to how diesels can get away with very low octane ratings, when they inject, the fuel is instantly being consumed.

1project2many
10-29-2013, 11:52 PM
I'd say octane probably wouldn't matter in that case. But you still need resistance to pre-ignition as the chamber and the air within is hot.

I thought part of the attraction of gasoline direct injection is that fuel can be injected at or near the combustion event?

Diesel fuel is rated by cetane, which is a measure of how well it self ignites. Practically it's the opposite of octane.

Microwave ignition has been tried to get gasoline to ignite "everywhere, all at once." I'd have to dig around to find the expected decrease in time required for start to completion of reaction if this type of ignition would work.

FWIW, cetane improvers for diesel can be added to gas to encourage combustion. I do this frequently in my own cars. The results are obvious at the tailpipe and up to one ounce per gallon seems to work for most NA cars for an up to 10% increase in economy. But don't add too much as you'll get pinging.

EagleMark
10-30-2013, 12:54 AM
I thought part of the attraction of gasoline direct injection is that fuel can be injected at or near the combustion event?
Been awhile since I read up on it but yes, compression of air is easier without the fuel, then injection before ignition. Also eliminates possibility of detonation with more spark advace. But a second injection of fuel during the combustion event, no ignition needed extends the power stroke. Or FWIR it took less fuel in two injection events to make same power...

RobertISaar
10-30-2013, 01:20 AM
from what i understand with diesel, there is a very short delay after the injectors open and start flowing fuel before the fuel ignites. being compression ignition, they have a comparatively small window that they can start injecting in without risking there being enough heat in the cylinder to ignite the fuel. this window would be pretty centered around TDC with maybe some slight skewing towards the ATDC side. i would assume compression ratio dictates window size to a large degree. in a simplified and slightly inaccurate sense, the injectors inject fire. i have no idea how long combustion would still be taking place after the injector quits flowing fuel, probably dependant upon AFR? in any case, fuel that combusts(and gives pressure rise) after 90* ATDC would give diminishing returns, though would still give more output as long as there is still oxygen left in the cylinder to combust with.

that, from my limited understanding of diesel tech, is how diesels are so easily manipulated to increase output at the expense of fuel usage. it would seem you simply add more and more fuel until you end up with a rolling smokestack or quit gaining output. it actually seems easier on paper than managing a gasoline engine since you only really control when to start injecting and when to stop. with gas, it's when to start fuel, when to stop fuel, when to start charging the coil(s) and when to stop charging the coil(s).

if you were using a spark ignition, direct injection engine(note no mention of gasoline), you don't have to rely upon compression for the heat necessary to start fuel combustion. with a fast enough flame speed and an injector that was capable of flowing huge amounts of fuel in a very short amount of time, if the injection event started(and having a spark event VERY soon after injection begins) say at 75* ATDC and was completely done by 85*(and combustion stopped shortly after 90*), i don't think it would be of consequence if the fuel auto-ignited? this isn't really a good example due to completely ignoring engine speed, which is probably its downfall, along with unrealistic flame speed with conventional ignition systems, common fuels and the injector flowrate required.

microwave ignition, that seems like it would be....... electrically noisy. i'm sure that could be worked around at some cost, but otherwise interesting. i've seen mention of laser ignition for quite some time, but nobody actually implimenting it.

cetane as a gasoline additive, i can't say i've heard of doing that before(and am kind of curious to try out now). any known emissions issues, or is that actually an alternative use of it(ala "guaranteed to pass" among other products)?

gregs78cam
10-30-2013, 04:27 AM
The best method would use a high octane, fast burning fuel and start ignition ATDC to allow maximum compression ratio while resisting detonation and eliminating negative work.


What if you were to replace a small amount of the gasoline or with a another fuel (or simply add a small percent) that has an extremely fast burn rate, to help ignite more of the fuel in the camber faster. Has anyone on here ever done any conclusive testing of HHO? I have been reluctant to bring it up, since there are some pretty strong opinions on whether it does truly improve efficiency. I am hoping to someday have the time to datalog and analyze the true effects, and then possibly tune the fuel and spark curves to take advantage of the mixture.

RobertISaar
10-30-2013, 05:09 AM
everything i've read indicates a net loss of power. the amount of electricity required to create a given amount of HHO is never recovered by the output it creates(and then lost through belt friction and alternator efficiency).

however..... that math doesn't account for any effect the HHO might have on the air/gasoline mixture. i think that would have to be tested real-world to be disproven.

1project2many
10-30-2013, 03:30 PM
We do not have tailpipe emissions testing here. All emissions testing relies on OBDII monitoring and reporting. I have not found any long term negative effects from using cetane improver over the last 10 or so years. The recommendation to use Boric acid came from a chemist who once worked in the oil industry. Most easily obtainable forms of Boric acid are not soluble in gasoline. So I use a particular brand of cetane improver which contains such chemical.


from what i understand with diesel, there is a very short delay after the injectors open and start flowing fuel before the fuel ignites. being compression ignition, they have a comparatively small window that they can start injecting in without risking there being enough heat in the cylinder to ignite the fuel. this window would be pretty centered around TDC with maybe some slight skewing towards the ATDC side. i would assume compression ratio dictates window size to a large degree. in a simplified and slightly inaccurate sense, the injectors inject fire. i have no idea how long combustion would still be taking place after the injector quits flowing fuel, probably dependant upon AFR? in any case, fuel that combusts(and gives pressure rise) after 90* ATDC would give diminishing returns, though would still give more output as long as there is still oxygen left in the cylinder to combust with.

Diesels have come a long way and I'm not up to date with the latest tech but the old engines with a prechamber used timing curves that aren't that different from what we expect in a gasoline engine today. The diesel in my '82 mercedes has injection at idle set to begin around 24 deg BTDC and advances from there. The reason the mixtures have such a range is because of the way fuel and air are mixed. In the gas engine, a lean mix means fuel molecules are farther apart in the chamber. While you may initiate a reaction, you will not carry one across the chamber. In the diesel there's a high concentration of fuel in the area of the injector even if it's a very lean mixture. Honda was able to run very lean mixtures in a carbureted engine using a similar idea by using stratified charge. Look around for CVCC head design and theory.


if you were using a spark ignition, direct injection engine(note no mention of gasoline), you don't have to rely upon compression for the heat necessary to start fuel combustion. with a fast enough flame speed and an injector that was capable of flowing huge amounts of fuel in a very short amount of time, if the injection event started(and having a spark event VERY soon after injection begins) say at 75* ATDC and was completely done by 85*(and combustion stopped shortly after 90*), i don't think it would be of consequence if the fuel auto-ignited? this isn't really a good example due to completely ignoring engine speed, which is probably its downfall, along with unrealistic flame speed with conventional ignition systems, common fuels and the injector flowrate required.

Sure it would be of consequence. Look at some possibilities from unintended autoignition immediately upon injection. You'll have a highly concentrated charge with the outer portions in contact with O2 and the inner portions O2 starved. You'll alter the burn rate and peak pressure changing specific output and efficiency of the engine. You'll create excess carbon and other byproducts of incomplete combustion. And you might sustain damage to the injector if it's expected that combustion will happen away from the injector tip. If the system is designed to inject then combust, you'll have unexpected results. Maybe we could cause it to operate in diesel-like fashion instead?

I seem to remember reading about liquid propane injectors being developed that were intended to inject air and fuel at the same time. Maybe the idea was to use the air to add heat to the fuel and help with phase conversion. But mixing air and fuel during the combustion event imo is the best way to ensure a homogenized combustion environment. It also puts us closer to getting rapid combustion ATDC and can offset reduced cylinder pressure at TDC achieved when using other than Otto cycle. Another effect is there's less time for heat to conduct to the block and piston which means more energy can be used to drive the crank.

Oil burners today are rated from 85% to 100% efficiency. Steam is still an excellent medium for transferring heat energy. Maybe the days of external combustion aren't gone yet?

RobertISaar
11-18-2013, 05:45 PM
http://www.autoblog.com/2013/11/15/hyundai-twin-charged-gdci-engine-more-efficient-than-diesel/

now there is a spec sheet i've never expected to see.