The Mission of our site is to provide information on collecting cars to make you a more informed and happier collector. It is important for a car collector to enjoy their muscle cars, sports cars, hot rods or rat rods in a way that makes them happy, We will bring you the stories behind the owners and the cars. The stories about how the collector cars were acquired, about the breakdowns, about the special trips and especially about the people encountered along the way.

Smokey Yunick’s Hot Vapor Fiero; 51 mpg and 0-60 in less than 6 Seconds! See and hear it run in our exclusive VIDEO!

Smokey Yunick Fiero

Smokey Yunick Fiero

Updated 1-17-2011

(Note: We have recently added some additional publications from Popular Mechanics and others at the bottom of this page.)

This is a one of a kind Feature Car that will never stand out in a parking lot. The difference is under the hood and in its history. It is a Smokey Yunick Research and Development Hot Vapor Fiero. Smokey spent decades working on the Hot Vapor Engine. It has been tested by many, including Hot Rod Magazine; it has been called a fake; it has been said that it doesn’t exist and it has been called the solution to all of our high gas prices. You can do your own research on the Internet and in books and reach your own conclusions. (To read more about Smokey Yunick on our site Click Here.)

Hot Rod Magazine has done at least two articles on this car and both can be found reproduced hear at the bottom of this page. The most recent was in the September 2010 publication.

Since this original web site post was published the Smokey Yunick Fiero has relocated to the Don Garlits Drag Racing and Car Museum in Ocala Florida. If you are in the area stop in and see it for yourself.

Smokey Yunick Fiero

This life size photo of Smokey Yunick watches over Tony as he works his own mechanical magic.

Smokey Yunick Fiero

This is car owner Tony Allers tweaking on the Fiero.

I am not a mechanic or a genius. Smokey Yunick, in my mind, was both. It is a fact that he held many US Patents and gave NASCAR fits with his interpretation of the rules. He is a Legend in Motor Sports and we need a few more like him today. He invented “thinking outside the box” and being successful. He had no formal education past the 10th grade but taught many a college grad a thing or two about engines and aerodynamics and other things.

Smokey Yunick Fiero

The Smokey Yunick Hot Vapor Engine, running R&D prototype in a Fiero. (air cleaner removed)

I urge you to do your own research on Smokey if you are not familiar with him. I never met him but Tony Allers, the man who owns this Fiero was a friend, acquaintance and customer of Smokey’s.

After spending a few hours with Tony Allers I know they won’t be the last. Like Smokey, he is a very interesting individual and his garage is a small shrine or museum to Smokey. Having been an acquaintance of Smokey’s family he not only owns the experimental Fiero but also some of the fixtures and old stock from Smokey’s Best Damn Garage in Town as well as a few motors and other artifacts. (Click Here to Check Out Tony, His Garage and New Projects)

Smokey Yunick Fiero

A Plain Jane but remarkable little Fiero.

Smokey Yunick Fiero

Only modifications to the interior are the additional gauges.

The car is uneventful in its appearance. It’s an early Fiero and white. You would walk by it in any parking lot or car show and not give it a second note. It is very clean with a terrific paint job and some strange tires but nothing to make you stop. Even with the engine bay exposed you know something is different, maybe a turbo, but nothing spectacular. Start it up and it sounds like a strong little four banger. As they say the proof is in the details and Tony Allers has the details.

Smokey Yunick Fiero

Watch out Corvettes, this Fiero has the Smokey Yunick touch.

There is way too much to this story to tell in even this extended coverage but I will try to give you an accurate overview as reported by Hot Rod in June of 1984 by C. J. Baker.

Smokey Yunick Fiero

This is the Homogenizer.

Smokey Yunick Fiero

This is what the Fiero’s engine looked like when Allers got it.

If you would like to read more about Smokey Check this out:

As most of us believe making the fuel cold increases density and improves performance. Cooler air and cooler fuel means more air and more fuel into the combustion chamber; bigger bang. That’s why our cars run so well in the spring and fall with that cool crisp air. Smokey went a different direction. He believed that the quality of the mixture was more important than the quantity. Most engines of the day burnt only 25% of the fuel and wasted 75%.

Smokey Yunick Fiero

Hot Vapor Engine with air cleaner removed.

Smokey’s premise was, heat the fuel too 400-440 degrees and you could vaporize the gas more efficiently and obtain more power from less fuel. He designed a new cam; a homogenizer (exhaust driven turbine) to mix the air and fuel and a new intake manifold that is totally wrapped by exhaust gas ducting (to heat the mixture). The system is more complicated than my brief description but you can see in the diagram how it works. I have also included excerpts from the Hot Rod Magazine article as follows.


The following are excerpts from the Hot Rod Article to further explain the technical details of Smokey’s Hot Vapor Engine.

“…consider the Pontiac Fiero shown here. Equipped with Smokey’s “expander-cycle” exhaust and induction system, and requiring only a cam change inside the production 151-cubic-inch (2.5 liter) Iron Duke 4-cylinder, the car now gets more than 50 miles to the gallon, develops 250 hp and 230 ft.-lbs. of torque, runs more smoothly than any 4-cylinder you’ve ever experienced, starts and idles smoothly and cleanly, has no computer controls, passes federal emissions standards, an oh yes, it’ll accelerate from 0-60 mph in as little as 6 seconds flat! Here’s how it works.”

“Some parts of gasoline vaporize very easily at low temperatures to help get a cold engine started. Other parts have a much higher boiling point to prevent the fuel from vaporizing in the fuel lines enroute to the engine. What this all comes down to is that in today’s typical engines, only part of the fuel entering the combustion chambers is in a combustible state. To fully vaporize pump gasoline, and to keep it vaporized for complete combustion, the incoming air/fuel mixture needs to be elevated to between 400-440 degrees F.”

“First, all the hot water existing the engine is channeled through a heat exchanger directly under the carburetor (or throttle body injection, TBI, unit).”  (Next the mixture flows through what looks like a small turbocharger, but this is not a turbocharged engine. The turbocharger-like device is actually a homogenizer and the second-stage vapor generator. In the homogenizer an exhaust-driven turbine drives what appears to be a rotary compressor totally wrapped with exhaust gas ducting. The homogenizer serves to mix the incoming air and fuel into one uniform, homogenous mixture with the surrounding exhaust gases further elevate the mixture temperature to about 285 degrees F. From there the mixture flows through an intake manifold that is totally wrapped by exhaust gas ducting, elevating the mixture temperature to the desired 400-440 degrees F in this third, final stage. The fuel is now fully vaporized and distributed uniformly in a truly homogenous mixture that will burn cleanly and evenly in the combustion chambers without detonation or severe pressure spikes in the cylinders.”

“…all traditional internal combustion engines are dealing with non-homogenous, incompletely vaporized mixtures today. It is also true that the heating of the incoming mixture reduces its density and causes it to expand. On a normally-aspirated engine, such expansion would just push right back out through the carburetor, but on Smokey’s system the expansion is trapped in the induction system because the small turbocharger (homogenizer) serves as a one-way check valve. Consequently, with the expansion contained, the induction system becomes pressurized, providing high mixture density and artificially aspirating the engine.”

“There is a lot of physics and chemistry involved, and a few of the details contained in the various patents on this design have been intentionally withheld by the Smoke,…”

A copy of the entire article is also provided below if you are interested and your eyes can withstand the poor quality of the copy.

According to Hot Rod (their tests, not Smokey’s) the Fiero 151 cubic-inch 4 cylinder engine now produces 250 hp and 230 ft.-lbs of torque. They report it gets more than 50 mpg and will do 0-60 in less than 6 seconds with no emissions.

Smokey Yunick Fiero

Here is a 300HP three cylinder Hot Vapor Engine, prototype built from a V6.

The technology was tested on 3 cylinder engines to 454 V8s with equal success. The calculations are 1.8 hp per cubic inch of displacement. Your 302 would produce 630 hp; a 350 equals 720 hp and that big 454 would kick out 817 hp! All this and it has a mild idle and is completely street able.

Tony hopes to build a new version for his big block Avalanche by the first of the year and get 25 mpg or better towing his show car! Now that will be sweet! Go to his page to see more.

Smokey Yunick Fiero

Some of the Moroso parts with Smokey Patents.

Remember I said the Fiero had a strange set of tires? Well, Smokey was an expert on all things car. He designed what he liked to call the “Bald Eagle” tire for Good Year. It is a slick with groves in it to make it work on the street in everyday conditions. It also has a special compound to reduce deterioration from ultra-violet light rays. There were only 100 of these experimental tires ever produced and 4 are on this Fiero and 2 are in Tony’s storage bay just because something might happens to one of the others.

Smokey Yunick Fiero

Look closely on the side wall of the tire and you will see and X in the serial number for experimental and “Not For Sale” stamped on the side.


What do I think? I think the Hot Vapor Engine is real.

Why didn’t GM, Chrysler, Ford or Toyota build it? Big business makes decisions by committee and doesn’t like to take chances; it moves slow.

Why doesn’t Edelbrock, Year One or Jack Rousch or some other independent jump in and make crate motors or conversion kits? I would love to give one of these a try. If I could double the horsepower and mileage on my muscle car I would be on it in a heart beat. Can you imagine over 700 Horse Power and 30 MPG or better from your 350 powered Corvette or Camaro?

Maybe it is just another urban legend but how do you explain the results of all the tests conducted by independent testers? Just maybe the reason GM, Ford and Chrysler are doing so poorly in today’s market place is because of poor decisions they have made in the past, maybe not pursuing the Hot Vapor Engine was one of those poor decisions.

If you would like to do some more research on your own you might want to begin the Smokey Yunick site at: or if you want to know what someone else thinks, take a look at what Banks Power | Cool Air Equals Power has to say about Smokey’s invention.

Smokey Yunick Fiero

The SY4 is only found on this car; it stands for Smokey Yunick 4 Cylinder.

Now for the video!

The following is a copy of the original Smokey Yunick Hot Vapor Engine article in Hot Rod Magazine article that appeared in the June 1984 publication.





The following is a copy of the second Smokey Yunick Hot Vapor Engine Article that was published by Hot Rod Magazine in September of 2010.


This is a copy of one of the Patents for the Hot Vapor Engine.


We would like to thank Tom Beeman for suppling these articles.

If you have trouble reading these try clicking on the image and then clicking on it again; it should increase in size and be easier to read.


Comments (89)

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  1. Daniel Soliz says:

    It’s time. Smokey was right and soon eveybody will know. I have the dodge 2.2 engine Smokey built and some extra parts.all I can say at this time is wow! It was a life long dream to see all those engines. Gm 1.8, 2.5 and the chrysler 2.2 he also built a ford tempo engine. Ok now to drain the oil and pull the pan. My plans are to clean up the engine,repair some of the exhaust tubes and run it. Thinking of running it on a dyno and then buying a car to put it in. I will keep you updated. Daniel

  2. […] Re: Turbo Iron Duke? Call Smokey Yunick, he did it in a Fiero….. With a Carb, imagine what you could do with SFI? […]

  3. Steve says:

    One question has been bothering me for some time: If the idea is complete atomization of the fuel, then why don’t natural gas-powered vehicle have more power? I know natural gas has less energy content than gasoline, but the air/fuel mixture is perfectly atomized with CNG. Why the huge difference between that approach and Smokey’s??

    And why won’t some car MFR adopt this technique with gasoline back to $4+ per gallon? Are there safety issues?

  4. Al Bore says:

    I wrote most of this back in 2009 and updated this for your questions. you may find some answers here.

    Al Bore says:
    August 7, 2009 at 7:43 pm

    Smokey was the master of common sense and looking at what others WONT SEE! Smokey has seen about every kind of fuel delivery system there is and he simply and elegantly used his gift of observation to whip the problems that he overcame. This system does not depend on ATOMIZATION! But instead employs VAPORIZATION, bypassing the change of a Liquid into tiny unevenly sized fuel droplets(Atomizatation) By Vaporization of the air fuel blend Smokeys Hot Vapor Engine is an adaptation of the system used on PROPANE Fuel engines where the unvaporized liquid propane is vaporized with the engines hot cooling system . Smokey increased the Thermal Efficency of the Gasoline engine by utilizing the wasted heat from the exaust and coolant to EXPAND, Vaporize and Homoginize the air fuel Mixture. the articles that I have read show that the increased heat utilization allowed a radiator of a much smaller area than original.
    This is what keeps the hot Vapor from auto igniting: The turbo also pressurizes the mixture thereby increasing the temp of autoignition and preventing it from backing out of the intake as the engine reaches operating temperture .
    An article in Pop Mechanics in the eighties also showed photos not seen elsewhere of some trick heads that Smokey crafted with extremely angled Intake valves to promote some kind of wild swirl action in the Combustion Chamber possibly leading to NO Pre-ignition. also the lack of worries about pre-ignition allowed the compression ratio to be raised considerably and resulted in great increases in HP and Torque per cubic inch.
    The Big Car Co.s have spent billions to curcumvent other inventors patents and thats why Smokeys patents have not been used because his patents are unable to be defeated or copied around his patents to be utilized.
    after all, the last thing that Big Oil and Car co’s want is a car that does not wear out as fast, is less complicated and uses less fuel products.
    Smokey did not wait for the Detroit crew to make it happen.
    HE DID !!!!

  5. Gene Climer says:

    That is the secret. If you knew that answer, you’d understand what Smokey did. It has to do with the composition of gasoline. You need to know the parts that make up gasoline and what they do when you heat them up enough to atomize them. Trust me, CNG does not behave the same as these various constituent parts of gasoline as you heat it up. Therein lies the secret mystery that Smokey would not talk about. Gene

  6. Al Bore says:

    Remember this system does not work on “Atomization” but is rather a heated fuel “Vaporizer” and air/fuel vapor “Homogenization” delivery system thereby mixing all of the different constituents of the gasoline compound blend thoroughly.
    I may be wrong about the positive manifold pressure being the reason for no pre-ignition.
    After reading the hot rod article above again, it became obvious that the answer is that the complete vaporization and homogenization of all fuel present is what stops the knock which is caused by uneven fuel conditions in the combustion chamber leading to chaotic flame propagation or “Knock”.
    The details about the reliability issues were interesting and understandable what with the junk late 1970’s low buck engine that smokey was using and adapting to his apparatus. I am sorry that crane was not able to pull all the problems together to offer some kind of kit to the public.
    the engine management principles detailed in the 2010 Hot Rod article above will make this concept come to pass but only if skin flint Detroit does not have to pay license fees to use them. I hope I am wrong.
    I also hope that the Yunick family is still somehow able to capitalize on Ralph and Smokey’s efforts.
    My background is one of having grown up in and around my Fathers Propane gas business in the Tampa Florida area where all of the company vehicles were propane fueled and conversions were sold and made to customers equipment. that provided me an early knowledge of heated fuel vaporization techniques and the advantages of that system over Atomization as in non heated systems like carburetors and fuel injection.
    an example is that the engine lubricants never got dirty or diluted with condensed unburned fuel caused from ring blow by.

  7. Gene Climer says:

    Yes, when I said atomization, I meant vaporization. Sorry about my slang terms I am slinging around here. The turbo does not do the boosting, it does the homoginizing. It also acts as like a one way check valve to hold the pressure (Boost) generated by the expanding constituents of gasoline. This is where the pressure increase in the intake comes from, which is the work being done by the thermal efficiency increase. The waste exhaust heat performs work on the intake, and the cooling effect of gthe vaporization (Like and AC system) cools off the exhaust. It is not just about thermal efficiency, though the thermal heat/cool exchange is critical, it is the sum of all these things simultaneously. What do you buy to increase the octane of gas? Toluene. Toluene is already there in the gasoline and it expands at a different temperature than the other parts. You have to look at the chemical process going on here to see the whole masterful puzzle that he solved. Toluene is the key. Gene

  8. Steve says:

    Surely patent rights cannot be an impediment any longer. Those patents would long since have expired. And the Chinese would steal the idea regardless.

    So why won’t anyone build this?

  9. Al Bore says:

    Ralph Johnson is still around with some of what smokey knew in his head.
    Does Ralph participate in these forums?

  10. Gene Climer says:

    Ralph does not waste his time chatting up wanna-bee garage mechanics about Hot Vapor Engines. Ralph tends to avoid such people like the plague. First, he has to think you have something between your ears. Then you have to pass some test of which I have not made is past yet. Of course, I am not sure I have made it past the first test.
    If I lived near Ralph, it would sure be an honor and a priveledge to work under him and with him and to learn some small percentage of what he knows.
    Gene Climer


  11. Doug O says:

    Has Ralph or anyone else experimented with these yet?
    Plasa ignition modules?

    Cheapest horsepower you can buy IMO. Yes I drag raced and learned from spending what power you can get at what price, this is it.

    Please do check this out.

    I have posted here before, this box when turned on brings your rpms up 50-125 with the flip of the switch(draws less than 3 amps on).

    Over 30 percent increases in fuel mileage,power,almost NO emissions or none at all(depends on engines condition pre install). Pretty amazing stuff;)


  12. Doug O says:

    Wanted to add that I’m making special spark plugs, modifying some now that will enable spark plugs to last longer due to the plasma’s endothermic heating.

    6-8k is the normal lifespan of a Modified Champion solid core plug. And with the fuel savings it’s still worth changing them out and paying the labor if your vehicles plugs arent over an hour to change.

    The average is a third in fuel savings.

    I am working on several designs that throw plasma into the cylinder using Lorentz force.

    Thank you for the inspiration, I don’t think I never woulda known who Smokey was unless I found this site awhile back.

    It’s one of the reasons why Im starting this business. Everyone deserves this and cheap.
    Big oil HAS TO GO DOWN.

  13. olmon says:

    One of the problems with running a motor in those temperature ranges is valve life. Back in the 50s there was a carb that would give fantastic fuel economy on any vehicle. It worked using heat to vaporize the fuel and it DID work, however, valve life (from what I have heard) was in the 5/6k range. I know that there are materials now that can withstand the heat and still function, but those materials aren’t cheap. I rather suspect that is part of the reason for this not going into production.

  14. Al Bore says:

    Most US engines until the elimination of lead additives did not have removable hardened valve seats and until the car makers started using better materials in their cylinder heads did this problem exist.
    There used to be in Sunoco 260 leaded gas at the time advertised as the highest Octane pump gas you could buy, 6 Grams of tetra-ethyl lead in every gallon, so after a while you had pumped quite a few pounds of lead thru your motor and out into the air, Chlorine and Bromine were added also to the leaded gas to act as “scavengers” to keep the crankcase cleaner but they mixed with water vapor and became acids that dissolved away the exhaust system. have any of you ever seen a swimming pool cleaner guys truck bead? that’s why that lead poison was banned from gasoline.
    The lead acted as a shock absorber between the valve and the seat to prevent early head failure on those old lead burning junk motors.
    Cheap gasoline motors converted to Natural and Propane gas fueled motors sometimes experienced exhaust valve recessing where the valve would pound itself further and further into the head material. the seats were just cut into the the cast iron of the head.
    Back in the 60’s I used only Amoco super premium “White Gas” Unleaded gasoline in my cars and after 195,000 miles my 69 Opel Cadette Rallye 1.9 litre motor was still running great with no loss of performance. and it still had all of it original exhaust system intact.
    Some motors then were just plain cheap junk and some were much better. I did not have any exotics to find out.

  15. mike says:

    Do we need to see these engines on the Big 3 showroom floors before we turn Smokey’s innovation into reality? Have we become that adapted to group thinking? There have been many products and innovations that never made it to the market place because of the threat these innovations pose to the ‘Powers That Be’, (read oil companies and car companies). The Fish carburetor, Tucker car are two right off the top of my head. Smokey’s technology will never make it into new cars if folks working in their shops don’t lead the way and Build them first! Lets shame the car companies into using this technology. Smokey did R&D work for GM and he was not even able to get GM to use his design. We’ll likely see this technology incorporated by some hungry car manufacturer in China or India before GM gets their head out of their asses. We are living in a world facing Global Climate Change. Decreasing supplies of oil and other natural resources are causing wars and conflicts and much pain and suffering to people around the world. Right now we’re witnessing an unprecedented Nuclear Meltdown in Japan. If the time is not now for thinking outside the box, than we surely are doomed for our short sighted thinking and fodder for extinction. Tinkerers and shade tree engineers lets bring this technology Smokey Yunick, Charles Pogue and others have developed and let it see the light of day in the 21st century.

  16. James says:

    This all reminds me of my step dad’s tinkering with alcohol vapor fed into a re-calibrated propane conversion kit for a 6cyl Ford Econoline. He had the exhaust vaporizing alcohol but never got the expansion of the vapor managed – the van got t-boned and the project stalled.

    The van got 80 mph on a cruise at static speeds but once there was a demand more fuel, raw alcohol ran right through the vaporizer and flooded the engine.

    All you back yard engineers need to be locked in the same room for while.

  17. Brian says:

    Most people miss one of the primary reasons the “Hot Vapor Engine” get the milage it does. It is the exact same reason a diesel engine gets better mileage then a conventional spark ignition engine, but not the only reason. While most focus on the thermal effency of combustion, which the H.V.E. is considerably better at, the other aspect is missed (not by Smokey). And the aspect is that the vacuum in the intake is reduced or eliminated.
    When a conventional (read not diesel) is driven at crusing speed the engine generates a fair amount of vacum that is constently leaked to the atmostphere thru the throttle plates. This vacuum is not free, but must be created by the pistons sucking the air out of the intake. It is wasted by just filling it in thru the throttle. In the H.V.E. most of the vacuum is eliminated by heating the air in the intake and expanding it, in fact the air is expanded so much Smokey wisely put a check valve on the intake to hold it in. (see page 28 of the Hot air engine report) And this of course is the turbo. As he states the Turbo is small because it does not have to do much but keep the air from going back out after it is heated.

  18. […] Insane gas mileage!!! Ol' Smokey's Hot Vapor Iron Duke got 51 MPG.. From just reading the link, and accompanying articles, you can gain some insight. There is an […]

  19. Fastjeff says:

    Smokey explained his “trick” that prevents detonation in HVC engines in his book. He said that gasoline–any gasoline–has a wide range of octane numbers for its various constituents: about 30 octant numbers. (In other words, ‘these’ molecules right here are 80 octane, where those over there are 103.) The concept he used was to RAPIDLY vaporize the gas BEFORE the lower octane constituents could cause trouble–it’s all there in his book.


  20. brad says:

    i dont buy it. i love fieros but i wanna see the dyno numbers. that and this is a turboed motor theres no way it cannot be, the one big difference is that instead of pushing air thru the carb its pulling it thru. and turboed dukes are not unheard of rare but not nonexsistant. this basicly utilizes a warm air intake on an equvilant tbi engine today. only theres no computer to regulate fuel consuption and this does it by vaporizing it before its sucked into the engine whereas a tbi would read the airflow and inject accordingly. also to add 4.9 v8;s from the cadillacs have thier fuel injected ontop of the valves thus accomplishing the same thing more effectivly and they get around 30 mpg with nice torqe and hp. and to add even further the 4 cyl fieros were already rated at 40mpg by gm which i do find a little high for the time but not out of the question so 10 mpg gain isnt that impressive and would easly be obtianed by a cam, tire and cold air intake change. as for the claimed horsepower i say agian show me dyno sheets or a video would be more convincing and ill buy it but untill then im thinking this is a little out there.

  21. Gene Climer says:

    Brad, if you looked at the invention disclosure, you’d see the turbo. So, no problem there. The idea of this motor is not to get more HP, although he did that. The idea was to make it more efficient. In doing that, he made both more HP and used less fuel. Less energy in and more usable HP and you have it in a nutshell. The engine is a closer approximation to an Adiabatic engine then the typical TBI, EFI or DI gasoline engine. A closed loop wideband EFI system could be retofitted and bring Smoky’s engine into the 21st century. That and a couple more innovations I have in mind ought to make it almost bullet proof to boot. Gene

  22. brad says:

    ahh ya well i know it shows a turbo but its refered to as a homoginizer so im assuming that it was meant to not boost at all but i believe that it would be to what extent i dont know though. interesting way to build a motor none the less and over doubling the output at that.

  23. Gene Climer says:

    Yes, exactly. Of course the homoginizer is a turbo. It’s function is to act like a reed valve, a one way valve to keep the expanding intake charge from backfiring. It has to generate enough boost at low RPMs to offset the intake manifold pressure. It also acts more like an ordinary turbo when the intake charge is moving too fast for the thermal transfer to actually expand the intake charge. I really don’t think Smokey was a BS’r. When he said something, he meant it. When he did something, he did it. When he gave up on Nascar and especially on Indy to work on this motor, I have to think it was for a reason and not some kind of BS scam. You can dismiss it if you want.

  24. Mike Pelly says:

    The key words here are, adiabatic and homogeneous. Smokey (and Pogue) engines reuse exhaust heat to pre-heat the vaporized and homogenize the solution of incoming air and vaporized gasoline. Gasoline will not burn well unless it is surrounded with an adequate amount of oxygen. Hence the homogenization. Brilliant how Smokey devised a way of doing this task.
    Yes there is an optimal proportion of air/fuel mixture everyone knows and speaks of, When this mixture is homogeneously mixed as completely as Smokey managed to do, than such engines no longer require catalytic converters except on starting and warming up, Possibly also to tackle NOx, but not for hydrocarbons. If todays state of the art engines did actually burn this thoroughly and completely, we likely would not need to equip engines with catalytic converters, Cats only burn un-burnt fuel on a conventional gasoline SI engines. Adiabatic engines use this extra energy to increase MPGs.
    Think about how the only few similarities between the first cars over 100 years ago and new ones built today are. Both examples have round wheels and pistons and both vehicles introduce their gasoline as a liquid. Vaporized gasoline is an innovation that deserves the light of day.
    Smokey did R&D testing for GM so I’m sure they knew what he had and just chose to ignore it.

  25. Olmon says:

    Smokey’s work isn’t the only work in the area of increasing HP & MPG the is kept from the public. Back in the late 70s, Pratt & Whitney developed a twin rotor, turbo-charged & stratified charge, multi fuel motor, approx physical size comparable to a SBC, for the military that would, according to the R&D reports I read, produce 700HP on pump gas & 35MPG when installed in a 2Ton Military truck cruising @ 60MPH. I saw the R&D reports when I was working for a company that did exclusively prototype work back at that time, but have NEVER seen any reference to it online or anywhere else. (& I’ve looked) Can you imagine the performance & economy that would produce in a typical passenger vehicle??

  26. Eric says:

    Back in 1972 my father bought one of these, Pratt & Whitney army truck that ran really fast for the size of the truck. My brother & I installed it into an army jeep we had on the farm, the jeep would go over 100 mph. & was getting around 55 mpg.. We had a ball with this set up for over 6 years, then sold it to a guy with a logging truck. He said it was the best engine he had ever had in one of his trucks.

  27. bob reidel says:

    hi all the reason no one will ever see this on any veichle is simple …. the government will never allow it. there are hundreds of thousands of patents to increase the effeciency of engines. the loss of road use taxes would be tremendous. also the loss of revenue to the oil co,s. they have been in bed together from day one of the internal com. eng. henry ford & rockerfeller. 100 years of building wealth beyond comprehension. this will not change easily. regards bobbyr

  28. […] Smokey Yunick 50 Mpg, 0-60 6 sec. Fiero I had the pleasure of meeting with Smokey Yunick a number of years ago, in a casual 1 on 1 lunch. We talked about a lot of automtive things but mainly fuel efficiency and his then current work on a ceramic internal combustion engine. I bring this to this thread because the attached article, (if you read to the very end), gets to the same point as the Youtube blog about govt. stiffeling fuel efficiency because of loss of fuel taxes. Regardless of the opinions on Smokey's achievements, he was a proven hot rodder, and true back yard genius. Hope you enjoy the thought provoking article. Smokey Yunick’s Hot Vapor Fiero; 51 mpg and 0-60 in less than 6 Seconds! See and hear it run i… […]

  29. Jodie Big Eagle says:

    One of the reasons this engine wasn’t put into production was that it required exotic materials because of excess heat. I think that’s hogwash, however with the advent of ethanol production, why not use ethanol to fuel this engine? Ethanol burns cleaner and cooler than gasoline. It also evaporates at a lower temperature which would require less heating of the air fuel mixture. There are now many ethanol production facilities throughout the U.S. and more could/would be constructed if there were a viable type of automobile in production that burned ethanol exclusively.

  30. Doubting Thomas says:

    By now if this was doable some car manufacturer would have used it. Even if the US Gov’t conspired to kill it in the U.S. We have modern materials and manufacturing processes. If it was that great, and practical for mass production, it would have been done. The fact that it is not available is the best proof it is not practical.

  31. Bloshic says:

    The true reason for pre-ignition is the engines are designed to push inlet gas out with exhaust gas because fuel is to dense, to burn vapor properly the valve over lap must be reduced to at least 1 degree the vapor burns so well it ignites on the over lap and ignition timing should not be advanced, car engines are designed to waste fuel Why? psychos that own the oil own the banks that make the money. They don’t need money but they want the air we breath to be full of the exhaust product what ever they blend into it as chemical reaction take place when heat is added

  32. LPG says:

    Question to peolple who know more about this vaporizing technology… lets say, there is a system that runs on LPG gas propane, with injectors and a vaporizer… like this, liquid propane enters a vaporizer that is heated with water once the car is warmed up, then the liquid propane converts to gas and enters a rail, then to the injectors…. a piggy back CPU copies the cars gasoline injectors maps, and the car runs on LPG…
    Now, do you think this system can run gasoline in place of the LPG?… or is the LPG vaporizer is not hot enough to convert gasoline to vapor?… it would be nice to use a proven system to run vapor gasoline and reap all the savings.

  33. maxaccel says:

    the reason this engine never made it,was,
    it run so hot that a special aerospace oil was used in it that cost about 100$ a quart,,

    I suspect that inside of the combustion chambers and bores were also protected with Ceramic coatings,otherwise this engine would simply melt from its exesive heat,
    it probably wasnt very practical or cost effective to build for mass production,although with todays advanced technology it may be,,
    Since the patent is expired by now Im surprised no one has built this adiabatic vapor engine again,at least to prove it can work,,

  34. pascal lourde says:

    @ Steve. Natural, petroleum or propane gas has less calories that gasoline / petrol. It is not really fair to expect them to be any more efficient other than the fact that gas is cheaper as a fuel – and happens to be a byproduct of the fuel refining process. Generally engines running LPG are still no where near as advanced as ceramic engines by Isuzu or these examples of Henry Yunick engineering prowess.

  35. 200 MPG? you tell me says:

    […] Yunick developed his "Hot Vapor" engine years back, and the best he did was 51mpg – smokey Ynick, Hot Vaor Fiero, Best Damn Garage in town smokey Ynick, Hot Vaor Fiero, Best Damn Garag… . Those YouTube Magicians are playing games and making claims that won't stand up to actual […]

  36. […] Originally Posted by techinspector1 You are correct Brian, MANY have done it before, including some heavyweight names in the industry. Smokey Yunick comes to mind. The guy was a genius. Smokey Yunick hot vapor engine […]

  37. Coop says:

    There are people working on such things. I’ve not added a turbo on mine yet, and am already running on a single injector off of the cold vapors (LT-1, 355 ci). After re-reading this again from years ago, I’m seriously considering it now. If you would like to follow my progress you can subscribe to my youtube name sisqocracker and see my build diary for the car at I’ve had this page listed on my website, since I created it. He’s been a great inspiration (Smokey has) and for some people the only person whom once they heard that he had done it, believed what they had just witnessed themselves. For some seeing is believing and if I can get this thing to where I want it, maybe you can see it yourself as I will do a lap of America in it once I’m ready to go.

  38. R Wilson says:

    Working at a vw garage in the 70s we built a vapor engine using a bug engine and vaporizing the fuel in one of the heater boxes and routing it to the air cleaner/carb. Started it with the normal carb and then once heated up shut off fuel to the carb. Once the fuel was shut off the carb was used only as a throttle plate. Not very safe (it did catch fire once) but it ran quite well including a run on the highway.

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