Sean buick 76
New member
Amazing thread! I stumbled onto this forum due to Paul Muller, he has been a huge help to me as well with Buick’s. Amazing projects, super cool! I will check out your rocket stove website! Keep the dream alive!
Henry Yunicks Red Hot Vapor Engine Re-Creation
- Thread starter DeltaV
- Start date
I remember reading the original interview with Smokey about that hot vapor engine. I was intrigued that he could double the hp by just heating up fuel...
....then he said the engine also had a "checkvalve" in the form of turbocharger putting out 12lbs of boost, ans it became pretty obvious the boost was what doubled the hp. (Glancing through the hot rod article, I didnt even see them mention the boost level. But I remember it was very clearly printed as 12lbs in the older interview)
Smokey was known to BS people. Has anyone actually verified the Hot Vapor Fiero got 51mpg? Because Im already calling bullshit when Im being told the 12psi of turbo boost is just a "intake checkvalve keeping the fuel vapors from escaping the engine".
....then he said the engine also had a "checkvalve" in the form of turbocharger putting out 12lbs of boost, ans it became pretty obvious the boost was what doubled the hp. (Glancing through the hot rod article, I didnt even see them mention the boost level. But I remember it was very clearly printed as 12lbs in the older interview)
Smokey was known to BS people. Has anyone actually verified the Hot Vapor Fiero got 51mpg? Because Im already calling bullshit when Im being told the 12psi of turbo boost is just a "intake checkvalve keeping the fuel vapors from escaping the engine".
Last edited:
He also said the air/fuel mixture is heated to over 450 degrees which is about 910 degrees absolute.
Let's say that the ambient outside temp is 75 degrees. That will be 535 degrees absolute.
910 divided by 535 is 1.7
A pressure ratio of 1.7 at sea level is 10.3 psi.
This means that it takes at least 10.3 psi of boost to compress a 450 degree air/fuel charge so it has the same density at sea level without boost at 75 degrees.
So the 12 lbs of boost is needed to restore the hot air density back to ambient air density with no real gain in power due to air compression (boost).
The turbocharger was truly a check valve allowing the intake air to be heated without losing density.
When the fuel is vaporized completely and run as lean as needed combined with almost no thermal energy loss from a radiator cooling system and recovered energy from the exhaust by way of the turbocharger, I would expect very high gas mileage.
Last edited:
It didnt have very much higher mpg than a normal stock iron-duke Fiero, if any. According to 4cyl Fiero owners in online forums, they get 30-50mpg stock. Hearing "51 mpg" is only an insanely high number to people that have been around mostly V8s (which is how many of us were raised in America before the mid 1990s), but its a normal mpg number for anyone that has been around Ford Festiva/Aspires, Geo Metros, old Corollas, old Hondas, etc. I believe Smokey played into this lack of knowledge because how many V8 guys know what a stock 4cyl Fiero mpg is? I will ask rhetorically, how many mpg did most of you guys reading this assume it got stock?
(Btw, I've seen several of these cars listed above run normally with clogged radiators, missing waterpump impellers, missing radiator hoses, etc. They really dont need much cooling system to begin with. So whatever the "fuel cooling" thing that Smokey reported is also taking advantage of many hot-rodders lack of firsthand experience with these small engines in light cars of the 1980s and 1990s)
I found in 1 of the articles that someone had driven that Fiero (I can post the name if you want me to find his name) & said he only got 40mpg with the car (well, with the setup, since it was installed into another Fiero). He went on to defend that the car got only 40mpg because he was flooring it around so much, but from first-hand experience of driving several small engines in light cars, I'm curious how much mpg was really lost by flooring it. Most of those small cars I listed will get over 30mpg while flooring it all around town.
Either way, Smokey said a lot of things. Most of it was pure bullshit & deception that he was known to spew. I'm not listening to the physics that he wants people to believe is happening. He was known to point to facts as a means of getting peoples attention away from what he was hiding. For instance, when the original interviewer pointed out the turbo (i found it was actually pushing 15psi; which to me is the most obvious reason the engine hp doubled) & Smokey got mad & screamed "its not a turbocharger! Its a homogenizer!". Your numbers might be right about the physics, but Im feeling that there are more complicated things at play here.
It's a classic example of a "snake oil salesman": a guy dazzles a crowd with his overly complicated mod that allows the car to get stock mpg, and doubles its hp (with 15psi of turbo boost). Amazing. But not really.
If it was me, I would just search thr internets to find a guy with a turbo 4cyl Fiero & just ask what his mpg is before designing and building this crap. Would save a lot of time & aggrevation if it doesnt work out.
Last edited:
Well let's see.
The stock HP for that year 151 cu in. engine was just under 90.
The report was that the modified engine made 250 HP which is 1.65 hp per cu in. instead of the advertised 1.8.
That is also 2.77 times the stock HP.
As I previously posted it takes 10.3 psi of boost to bring the engine back to 90 hp when the intake charge is 450 degrees.
Any boost over that is contributing to the increase in power over stock. It would take an additional 1.77 atmospheres or 26 lbs of boost to make 250 hp.
Adding the 10.3 would be a total of 36.3 lbs of boost.
So if the actual boost was only as high as 15 psi instead of 36.3, the additional 4.7 lbs of boost over 10.3 would have made about 125 hp. The only place left to account for the large amount of power over 125hp must come from increasing the efficiency of the engine.
Kinda hard to fake 36.3 psi of boost.
I suspect the person you knew that drove one of the cars was experiencing a lot more than 125 hp.
I agree that the gas mileage was marginally better than the stock engine but most of the hype was about having huge power gains while maintaining exceptional gas mileage.
The big problem with Smokey's engine is it only works correctly when it is hot in fact as it warms up there is a zone where the engine will experience detonation if the tune up is off just a little.
That doesn't work for short commutes or short runs to the local store.
However, putting Smokey's character aside, there is some good data to be gleaned from the project.
What amazes me is that some of these older low tech engines got as good if not better gas mileage as the late model electronically controlled engines.
Anyway, the investigation here has become about circumventing a lot the problems and restrictions by operating an engine in the detonation mode.
Enter the Bourke engine.
Yes it comes with its own set of problems to be solved but that is part of the fun.
Last edited:
Bronctopia
Well-known member
My daughter had an iron duke manual fiero.
With the engine in the trunk, and the radiator at the opposite end of the car, there was a gallon or more of coolant just in the hoses. That radiator barely even got warm unless it was high summer with spirited mountain driving.
The car was also very light and low. As I remember it usually got around 40mpg on mixed rural/city driving.
With the engine in the trunk, and the radiator at the opposite end of the car, there was a gallon or more of coolant just in the hoses. That radiator barely even got warm unless it was high summer with spirited mountain driving.
The car was also very light and low. As I remember it usually got around 40mpg on mixed rural/city driving.
I dont want you to think Im attacking you. I've studied this engine years ago & am purposely playing the devils advocate while hoping someone actually shows me this engine is possible.
However, what your saying that its about huge power gains while "maintaining" exceptional mpg is not how this thread started. And an 18mpg from 4.9 is nowhere close to levels that would be considered exceptional....this is why Im playing Devils advocate, because every time this hot vapor tech is brought up, people assume it tripled the mpg somehow. It didnt. Nor did it make the engine run cooler. However, I'm open to the possibilty that it may have been an interviewer's fault for everyones focus on the mpg, while the actual intention of the build was somwthing else.
I respect Smokey and his creative engineering (in other areas). But I bring his character into the equation when HE IS THE ONLY WITNESS that his car got 51mpg & made 250hp.
Afaik, Tony Allers (the guy that owns Smokeys engine) is the only other person to drive it & he could only verify that it got 40mpg. Which is normal for a stock naturally-aspirated 4cyl Fiero. But how much should we have expected it to drop with a turbo?
I'm reading your math. But show me the evidence that this car actually made 250hp & goes 0-60 in 5 seconds. The only thing I found is that Tony Allerd said Smokeys engine "smokes the tires at 60mph". Impressive, but the car was also on tractor tires & its possible he said "tire" & the interviewer heard "tires". Maybe someone can find this guy on Facebook and ask him about his car. But either way, I would want to see an actual dyno sheet. Or even a guy that said he held the stopwatch to clock the 0-60.
Tony Petersen (that worked at GM with the Fiero) put a 235hp into a Fiero at GM & it went 0-60 in 4.9..so why did Smokeys 250hp only do it in 5.9? From what Im seeing on the Fieros forums, it appears you dont need 250 hp to run 0-60 in less tha 6 seconds.
You have math & science to back up your stance. But I really just want to see 1 person that has succeeded in replicating this engine. (Or find 1 person that was at the dyno or holding the stop watch for the 0-60.) There are guys on the EcoModder forum that have the scientific know-how & resources to make things like this setup work, yet none succeeded.
I don't feel that you have been attacking me and I have no problem with you playing the Devil's advocate.
What I have been, is waiting for you to ask the better question.
I went through the calculations to show you where the big discrepancy is.
If I was going to play the Devil's advocate the question would be: Why does the engine have a 277% efficiency over the stock engine at WOT for power that suddenly drops off to 10% at best at partial throttle for gas mileage?
At WOT the Adiabatic efficiency for the stock engine would have to be raised from 30% to 83%.
Unless the exhaust gas was relatively cold exiting the turbine and there was no radiator at all you would be losing more than 17%
This looks more like a ported and cammed engine with the addition hot air apparatus.
One of the articles stated "Smokey's original motors had trick rings, forged pistons, and Carrillo rods,"
There was no mention of head improvements or cam change but that doesn't make it so.
The last 300 six I put together had a ported big valve head and a 232 .050" duration cam set up for 300 hp.
It breaks the tires loose in second gear at 1200 rpm and makes power to 5500 rpm.
It got just over 17 MPG on a trip from Spokane WA to Bouse ID in a 1977 2wd truck @ 70 mph and 2400 rpm.
If I added a Smokey hot vapor system including the "homogenizer" it would indeed get better gas mileage and a lot more power.
Could I then contribute the power gain over a stock 1980 300 to just the hot vapor system?
This may not be what is going on in Smokeys hot vapor engine but would explain some of the results that borderline "Far fetched".
It is unfortunate in a way this thread's title leads one to believe that DeltaV is actually recreating Smokey's hot vapor engine.
This entire thread is an exploration of possible ways to create a true high efficiency internal combustion engine where ideas have been tossed back and forth with none of them relating to the Smokey's engine.
The first post quickly steers the discussion away from the hot air engines shortcomings and none of the following 100+ post have anything to do with Smokey's engine.
For instance, in Smokey's engine the hot air is used to vaporize gasoline while recycling the hot air's thermal energy back into the engine.
In DeltaV's engine the heat and a catalyst is used to break down long chained hydrocarbon liquid fuels (Deisel, Kerosene, Gasoline, Ethanol, Methanol) into short chain Methane, Ethane, Propane and Butane to be used as a complete burn fuel.
The engine is no longer limited to one or two fuels or the fuels octane rating.
Smokey's engine uses a carburetor throttle plate to control engine power.
DeltaV's engine eliminates a throttle plate and associated pumping losses which is the first step in higher efficiency.
We moved to an engine design that doesn't require a spark ignition that will operate under very lean mixtures so the engine can be controlled solely by fuel volume without the use of a throttle plate.
I'm not going to summarize all 100+ posts any further. You can read them yourself. I think you get the picture.
There is nothing in all the post's that resembles Smokey's hot air engine.
Smokeys hot vapor engine was a great effort at the time and supplied some very good data.
At the time of the oil embargo any increase in fuel mileage was a big deal and I feel that Smokey played into that.
What also is not mentioned is that most suburbanites or city folk often times make trips that barely allow the engine to come up to operating temperature meaning the car would travel most of the distance without the hot vapor advantage.
You will see in the later posts of this thread that this engine is not a hot vapor design and will not have this problem
Last edited:
Just to better understand the "Hot Vapor" engine, The goal is to recover as much heat as possible produced by the fuel to increase the engines efficiency by making it work instead of wasting it.
Heat is taken from the coolant to preheat the mixture before the Homogenizer.
The Homogenizer compressor is heated by exhaust gas to vaporize and homogenize the mixture before entering the exhaust heated intake manifold where the mixture is raised to its final temp of 230 degrees C.
From Smokey:
"The purpose of the homogenizer is to fully atomized the fuel air mixture to an extreme fine vapor. Otherwise it would be impossible to further heat up the mixture. When the mixture has passed the homogenizer wheel it is more heated. Partly because of the friction and partly because the homogenizer is incapsulated in the exhaust system. The mixture is now 140° C.
Next step is the inlet system which is totally incapsulated in the exhaust system. Here the mixture gets heated up to 230° C! Now things start to happen.
Here it expands like hell Smokey explains, exactly as we want to. Of course. Here the homogenizer has a further role: to be a back valve, to hold back the pressure which comes from the expanded fuel mixture. Without this back valve the top will be thrown to Orlando... well.. Besides the homogenizer presses with 0.45 kg. When the mixture reaches the combustion chamber more than 25% of the energy "is ready to go" (230° C). And with full compression, before ignition, the mixture has reached the extreme 820° C. After this comes the spark.
You see says Smokey, what forces the piston down is not the heat, it is the pressure..."
Smokey was unwilling to discuss why his hot vapor engine was able to run at such high temps without detonation.
"
Heat is taken from the coolant to preheat the mixture before the Homogenizer.
The Homogenizer compressor is heated by exhaust gas to vaporize and homogenize the mixture before entering the exhaust heated intake manifold where the mixture is raised to its final temp of 230 degrees C.
From Smokey:
"The purpose of the homogenizer is to fully atomized the fuel air mixture to an extreme fine vapor. Otherwise it would be impossible to further heat up the mixture. When the mixture has passed the homogenizer wheel it is more heated. Partly because of the friction and partly because the homogenizer is incapsulated in the exhaust system. The mixture is now 140° C.
Next step is the inlet system which is totally incapsulated in the exhaust system. Here the mixture gets heated up to 230° C! Now things start to happen.
Here it expands like hell Smokey explains, exactly as we want to. Of course. Here the homogenizer has a further role: to be a back valve, to hold back the pressure which comes from the expanded fuel mixture. Without this back valve the top will be thrown to Orlando... well.. Besides the homogenizer presses with 0.45 kg. When the mixture reaches the combustion chamber more than 25% of the energy "is ready to go" (230° C). And with full compression, before ignition, the mixture has reached the extreme 820° C. After this comes the spark.
You see says Smokey, what forces the piston down is not the heat, it is the pressure..."
Smokey was unwilling to discuss why his hot vapor engine was able to run at such high temps without detonation.
"
Last edited:
From numerous stories I've read about Smokey, I'm feeling this is hitting the nail on the head. He was a genius, not only in racing, but also in taking advantage of situations in general.
Either way, for the sake of passing on information for anyone that is interested in this engine, this guy has at least 4 videos on his youtube channel:
Playlist of the Hot Vapor engine being disassembled. He has 5 or so videos in thr playlist on this engine.
For those that are interested in this engine, these videos will probably be very valuable, since he covers specs of the engine as he tears it down.
For those that are interested in this engine, these videos will probably be very valuable, since he covers specs of the engine as he tears it down.
Last edited:
Bronctopia
Well-known member
Smokey's hot air iron Duke has always left me puzzled.
If we assume the fuel is spherical (and by that I mean Octane), the heat of vaporization is about 34kJ/mol (at 400K or 127C).
Comparing that to the heat of combustion of Octane, at aprox 5430kJ/mol, we can see that you can fit at most 0.63% of the combustion energy into vaporizing the fuel.
I'm all for a 0.63% increase in efficiency, or even 4 times that if it were the case that all of the energy to vaporize came from the crankshaft in a normal ICE, but even then we are talking only 2.5% potential efficiency increase from fully vaporizing fuel.
If we assume the fuel is spherical (and by that I mean Octane), the heat of vaporization is about 34kJ/mol (at 400K or 127C).
Comparing that to the heat of combustion of Octane, at aprox 5430kJ/mol, we can see that you can fit at most 0.63% of the combustion energy into vaporizing the fuel.
I'm all for a 0.63% increase in efficiency, or even 4 times that if it were the case that all of the energy to vaporize came from the crankshaft in a normal ICE, but even then we are talking only 2.5% potential efficiency increase from fully vaporizing fuel.
Bronctopia
Well-known member
Trying to move some of a heat engine’s waste heat back into the cycle (variously called a regenerator or economizer) works in some cycles, but the 4 stroke Otto cycle has the problem that trying to increase the temperature (and pressure) of the intake charge before the compression stroke will cause the engine to put more work into the compression stroke.
In an ideal case, all of that compression work could be recouped during the expansion stroke, but even in the ideal case it ends up being a wash as far as efficiency is concerned. Both the compression adiabat and the expansion adiabat move up the PV diagram in unison.
I would like for the Smokey motor to be true, but I haven’t seen enough trustworthy data to believe it. The sources I can find are all kinda full of vague mistakes like :
”Most engines of the day burnt only 25% of the fuel and wasted 75%.”
I assume this was just a non-technical reporter not getting the difference between thermodynamic efficiency and combustion efficiency.
In an ideal case, all of that compression work could be recouped during the expansion stroke, but even in the ideal case it ends up being a wash as far as efficiency is concerned. Both the compression adiabat and the expansion adiabat move up the PV diagram in unison.
I would like for the Smokey motor to be true, but I haven’t seen enough trustworthy data to believe it. The sources I can find are all kinda full of vague mistakes like :
”Most engines of the day burnt only 25% of the fuel and wasted 75%.”
I assume this was just a non-technical reporter not getting the difference between thermodynamic efficiency and combustion efficiency.
Some updates. I've been exceptionally busy with my wood stove business. We just got our EPA test data back with a 99.5% combustion efficiency and we are the third cleanest burning heater on the market, barely behind a catalytic stove (ours has no catalytic combustor) and a very expensive electronically controlled pellet stove (over 2X the price of our units). So I'm very happy with these results.
I also had to completely renovate an old factory my company just purchased so we can keep up with the rising demand for our heaters. I also had to hire 10 employee's. Picture below.
Regarding combustion, what I do know as a matter of fact is that pre-heating the incoming combustion air and fuel does indeed reduce emissions and increase burn efficiency. What I also strongly suspect is the latent heat absorbed by fuel vaporizing cools the cylinder during the compression and power stroke, which can rob power in certain mission profiles, and the energy required to chemically crack hydrocarbons also reduces peak temperatures and slows the burn rate down. What I am strongly convinced of is that isochoric heat addition is inherently more efficient than isobaric heat addition. The objective of this project, ultimately, is to create a fickett-jacobs cycle PDE for shaft horsepower. Adiabatic heat reclamation was not only used by Henry Yunick, but also a joint venture by Cummins and the US Army that pre-dates the work of Yunick by about a decade, and they achieved a 50% thermal efficiency out of their engines by using principles identical to Yunicks red hot vapor engine.
Hemming Article on Cummins engine
#1 Peer Reviewed Article from SAE about Cummins Engine
#2 SAE Peer Reviewed Article about Cummins Adiabatic Engine
Article from JSTOR about the same subject.
"The increase in fuel mileage at part throttle was partly because of very lean fuel mixture along with increase pressure in the intake manifold which eliminates the pumping losses normally seen at part throttle."
-This is actually a much bigger issue than most people realize, it only takes about 20 horsepower on average to keep a pickup truck cruising at highway speed. We cant run lean with conventional engines because knock/detonation. But with fickett-jacobs cycle engines, now we can run AFR's as high as 1000/1 without issue, so pumping losses are gone. No throttle plate needed. Now the engines HP output is determined by load, not RPM. From a high level perspective, reduced to as simple of a sentence as I can, by building an engine that embraces detonation into its cycle, we can run exceptionally high compression ratio's, lean burns, and basically break all the rules to create a more powerful more efficient engine thats whole is greater than the sum of its parts.
I also had to completely renovate an old factory my company just purchased so we can keep up with the rising demand for our heaters. I also had to hire 10 employee's. Picture below.
Regarding combustion, what I do know as a matter of fact is that pre-heating the incoming combustion air and fuel does indeed reduce emissions and increase burn efficiency. What I also strongly suspect is the latent heat absorbed by fuel vaporizing cools the cylinder during the compression and power stroke, which can rob power in certain mission profiles, and the energy required to chemically crack hydrocarbons also reduces peak temperatures and slows the burn rate down. What I am strongly convinced of is that isochoric heat addition is inherently more efficient than isobaric heat addition. The objective of this project, ultimately, is to create a fickett-jacobs cycle PDE for shaft horsepower. Adiabatic heat reclamation was not only used by Henry Yunick, but also a joint venture by Cummins and the US Army that pre-dates the work of Yunick by about a decade, and they achieved a 50% thermal efficiency out of their engines by using principles identical to Yunicks red hot vapor engine.
Hemming Article on Cummins engine
#1 Peer Reviewed Article from SAE about Cummins Engine
#2 SAE Peer Reviewed Article about Cummins Adiabatic Engine
Article from JSTOR about the same subject.
"The increase in fuel mileage at part throttle was partly because of very lean fuel mixture along with increase pressure in the intake manifold which eliminates the pumping losses normally seen at part throttle."
-This is actually a much bigger issue than most people realize, it only takes about 20 horsepower on average to keep a pickup truck cruising at highway speed. We cant run lean with conventional engines because knock/detonation. But with fickett-jacobs cycle engines, now we can run AFR's as high as 1000/1 without issue, so pumping losses are gone. No throttle plate needed. Now the engines HP output is determined by load, not RPM. From a high level perspective, reduced to as simple of a sentence as I can, by building an engine that embraces detonation into its cycle, we can run exceptionally high compression ratio's, lean burns, and basically break all the rules to create a more powerful more efficient engine thats whole is greater than the sum of its parts.
Last edited:
"Smokey was unwilling to discuss why his hot vapor engine was able to run at such high temps without detonation."
-I have a hypothesis as to why. Completely vaporized short chained fuels posses a much higher octane rating, and homogenized fuel mixtures are much less susceptible to pre-ignition, colliding flamefronts, dead zones, etc. This may be why shorter chained hydrocarbons, though possessing a much greater percentage of hydrogen gas, tend to posses much higher octane ratings whilst having lower cetane ratings on average.
This whole thread has been interesting even for me to read back on. It really shows me how ignorant I was even just 4 years ago. I created this thread right after joining the Army, I was always fascinated by ICE's even when I was a teenager and have since read hundreds of books on the subject. I got on this forum wanting to gleam information from more experienced people than myself. At first I thought that reproducing the Yunick/Cummins adiabatic/vapor fuel system was a good start, but after reading so many more books on engine design I realized that all conventional otto cycle engines are built on a series of compromises and mutually exclusive barriers. We are all familiar with those compromises, one of the hundreds that comes to my mind is piston ring pack height and its relation to the wrist pin bore. With novel engine morphology's we can completely obviate connecting rods entirely, but I cant go into details on that. What I can say is that I rebuilt the original Bourke engine I purchased last year and its currently in a drone owned by a party I can not disclose and is being tested right now. Performance is absolutely phenomenal and leagues ahead of any other competing engine on the market, including liquidpiston and achates power.
The projects overall ovjective has changed a lot since the first post, like Paul Muller stated earlier. I now have 3 very good designs, 2 completely blueprinted, and I will begin making my first 49cc prototype this year if all goes well. I've had a lot of hiccups and unforeseen setbacks along the way (the most recent is a fried transformer on my lathe) as this has only been a side project for me whilst I've been trying to grow my rocket heater business. However, once I finish the prototypes I'll be launching a new company with 3 engine morphologys, two based on the Bourke (one of the two being a modernized air cooled naturally aspirated Bourke engine, the other being a double acting forced induction version) and the third morphology I cant discuss but I will say this, its uniflow scavenged, two strokes per cycle, compression/spark ignition hybrid, fickettp-jacobs cycle, opposed piston, completes four total strokes and two power strokes per revolution, only has 3 basic moving parts, there are no connecting rods or crankshafts, but it does have a power output shaft, the pistons never stop moving (even at top and bottom dead center) so it always remains in the hydrodynamic film regime of lubrication, combines the concepts of the rotary engine with the piston engine into one morphology, and possesses the lowest possible surface area for a given displacement regardless of scale. I conceived of the design during a DMT trip of all things. I am confident that this design is the paragon of engine technology, the only downside being that it would be impractical to scale for applications requiring displacements smaller than 1100 cc's. For small engines I still think a well done scotch yoke running on a roller bearing is hard to beat.
Last year I also met Aaron Murakami, Peter Lindemann, Eric Dollard, and many other people at the ESTC conference. Roger Richard, who was the original intended presenter, had some heart issues and graciously gave me the opportunity to present on his behalf. It was the highlight of 2021 for me, linked below is a 15 minute preview presentation. It was very fun and Aaron recently invited me to present again this year (though there likely wont be too many updates from last year).
All in all, this is only the beginning of a lifelong journey for me. I'm going to have a lot of fun to share.
-I have a hypothesis as to why. Completely vaporized short chained fuels posses a much higher octane rating, and homogenized fuel mixtures are much less susceptible to pre-ignition, colliding flamefronts, dead zones, etc. This may be why shorter chained hydrocarbons, though possessing a much greater percentage of hydrogen gas, tend to posses much higher octane ratings whilst having lower cetane ratings on average.
This whole thread has been interesting even for me to read back on. It really shows me how ignorant I was even just 4 years ago. I created this thread right after joining the Army, I was always fascinated by ICE's even when I was a teenager and have since read hundreds of books on the subject. I got on this forum wanting to gleam information from more experienced people than myself. At first I thought that reproducing the Yunick/Cummins adiabatic/vapor fuel system was a good start, but after reading so many more books on engine design I realized that all conventional otto cycle engines are built on a series of compromises and mutually exclusive barriers. We are all familiar with those compromises, one of the hundreds that comes to my mind is piston ring pack height and its relation to the wrist pin bore. With novel engine morphology's we can completely obviate connecting rods entirely, but I cant go into details on that. What I can say is that I rebuilt the original Bourke engine I purchased last year and its currently in a drone owned by a party I can not disclose and is being tested right now. Performance is absolutely phenomenal and leagues ahead of any other competing engine on the market, including liquidpiston and achates power.
The projects overall ovjective has changed a lot since the first post, like Paul Muller stated earlier. I now have 3 very good designs, 2 completely blueprinted, and I will begin making my first 49cc prototype this year if all goes well. I've had a lot of hiccups and unforeseen setbacks along the way (the most recent is a fried transformer on my lathe) as this has only been a side project for me whilst I've been trying to grow my rocket heater business. However, once I finish the prototypes I'll be launching a new company with 3 engine morphologys, two based on the Bourke (one of the two being a modernized air cooled naturally aspirated Bourke engine, the other being a double acting forced induction version) and the third morphology I cant discuss but I will say this, its uniflow scavenged, two strokes per cycle, compression/spark ignition hybrid, fickettp-jacobs cycle, opposed piston, completes four total strokes and two power strokes per revolution, only has 3 basic moving parts, there are no connecting rods or crankshafts, but it does have a power output shaft, the pistons never stop moving (even at top and bottom dead center) so it always remains in the hydrodynamic film regime of lubrication, combines the concepts of the rotary engine with the piston engine into one morphology, and possesses the lowest possible surface area for a given displacement regardless of scale. I conceived of the design during a DMT trip of all things. I am confident that this design is the paragon of engine technology, the only downside being that it would be impractical to scale for applications requiring displacements smaller than 1100 cc's. For small engines I still think a well done scotch yoke running on a roller bearing is hard to beat.
Last year I also met Aaron Murakami, Peter Lindemann, Eric Dollard, and many other people at the ESTC conference. Roger Richard, who was the original intended presenter, had some heart issues and graciously gave me the opportunity to present on his behalf. It was the highlight of 2021 for me, linked below is a 15 minute preview presentation. It was very fun and Aaron recently invited me to present again this year (though there likely wont be too many updates from last year).
All in all, this is only the beginning of a lifelong journey for me. I'm going to have a lot of fun to share.
Thanks for sharing your most recent successes along with the ESTC conference video.
Great presentation.
I also appreciated some of your background information and plans for future projects.
I'm looking for your thoughts on the forced induction Bourke engine.
You shared the idea of using a supercharger as part of the induction system since both sides of the piston are being used for combustion.
Superchargers have parasitic losses and when added to a system, the total system efficiency decreases.
Some superchargers are more efficient than others but still have efficiency losses.
It's been some time so I'm hoping there is more baseline information to work with.
Is there enough thermal energy from the exhaust of the Bourke engine under very light loads to vaporize the fuel before entering the engine?
I realize there is less fuel to vaporize under light loads, but the intake air volume is still the same and the air temperature would drop from a heat exchanger as the engine load decreases.
Great presentation.
I also appreciated some of your background information and plans for future projects.
I'm looking for your thoughts on the forced induction Bourke engine.
You shared the idea of using a supercharger as part of the induction system since both sides of the piston are being used for combustion.
Superchargers have parasitic losses and when added to a system, the total system efficiency decreases.
Some superchargers are more efficient than others but still have efficiency losses.
It's been some time so I'm hoping there is more baseline information to work with.
Is there enough thermal energy from the exhaust of the Bourke engine under very light loads to vaporize the fuel before entering the engine?
I realize there is less fuel to vaporize under light loads, but the intake air volume is still the same and the air temperature would drop from a heat exchanger as the engine load decreases.
Last edited:
My train of thinking is to use a supercharger to push in just enough air to fill the cylinders, but at less than 1-2 PSI at most. This way the "supercharger" is working more like a scavenging pump, or external "intake" stroke so to speak. This allows for the greatest power to displacement ratio for 49cc engines, which are 50 state legal for motorcycles without a license. Some quick napkin math I did a while back shows that upwards of 40+ horsepower may be possible with such an arrangement. EGT's on the Bourke engine I rebuilt have seldom reached above 300 F, typically staying in the 220 to 250 F range under load. This is measured with a thermocouple placed immediately aft of the exhaust ports. My hypothesis here is that a TVS V180 supercharger will be approximal in efficiency/energy loss as that of the the exhaust and intake stroke of a 4 stroke otto cycle, and should still be leagues ahead of using the crankcase for scavenging as is the case in most small 2 strokes per cycle engines. That hypothesis could be wrong, please correct me if thats true.
Last edited:
1-2 psi of intake manifold pressure works on a 4 stroke engine but not on a two stroke engine.
On a 4 stroke engine the intake valve opens when the piston is near TDC and the cylinder volume is near its minimum.
As the intake cycle continues, the cylinder volume increases and the supercharger can maintain a low manifold pressure as it fills the increasing volume.
On a two stroke engine when the intake port opens the cylinder volume is near its maximum.
With only 1-2 psi of intake manifold pressure there will be very little cylinder fill since there is a zero net cylinder volume change during the intake port open duration.
A much higher pressure is needed to achieve cylinder fill with such a short intake duration
However, when you add a positive displacement supercharger to a two stroke engine, the intake manifold pressure does not stay constant.
Let's say the supercharger drive ratio is set up so the supercharger pumps the same volume as the engine volume in an effort to get 100% cylinder fill.
The TVS V180 has a three lobe rotor with a 90 degree twist so the airflow is not constant, but we will say it is constant to keep the rest of this analysis simple.
The intake manifold pressure would be at a constant zero if the engine airflow was constant, but it is not.
The graph below shows the intake port timing of both cylinders with a port height of 20% of the piston stroke.
The intake port is open for 74 degrees of crankshaft rotation and closed for 106 degrees.
During the 106 degrees the port is closed, the supercharger builds pressure in the intake manifold.
If during the closed port interval, the supercharger pumps the same volume as the intake manifold volume, the pressure will increase by one atmosphere or 14.7 psi at sea level. The pressure is released into the cylinder when the port opens.
Instead of a constant intake manifold pressure, there is a pressure increase followed by a pressure drop.
The peak manifold pressure is a function of supercharger flow in relation to intake manifold volume.
This is very similar to crankcase pumping using the piston and transfer ports where the pressure ratio is a function of crankcase volume when the piston is at TDC versus the volume at BDC.
The only difference is the supercharger is doing it externally with much higher parasitic losses.
Looking at the compressor map for the Eaton TVS V180 you will notice the highest efficiency zone is 72% with the majority of the map at 65%.
The supercharger would be operating from a zero pressure ratio at below 20% efficiency up to a higher pressure ratio at 65%.
Add the losses from the supercharger drive and you have significant parasitic losses outside of the engine which reduces the total systems efficiency.
The internal piston/crankcase pump does not have these losses and is far more efficient than an external pump.
The double combustion cylinder requires a piston with two crowns and a piston length the same as the stroke in order to cover both the intake and exhaust ports making the cylinder as long as three stroke lengths versus two stroke lengths for the single combustion chamber cylinder.
The double combustion cylinder engine has the addition of the supercharger.
Based on the above I believe a single combustion chamber, two cylinder engine with twice the displacement takes up less real estate than a supercharged, two cylinder, double chamber engine with the single chamber cylinder engine having a higher efficiency.
Last edited: