The Mystery of Mr Yunick

Mystery is a funny old thing; life is generally richer for it but when it comes to engineering, a mystery is like having worms, it constantly gnaws away in a really irritating way. So, dear reader, I am going to give you worms.
As you may know, a traditional car engine struggles to turn 30% of the fuel’s energy into useful power, although bigger engines are better in this respect and the largest piston engines can reach up to 50% efficiency.
There have been many attempts to make a better engine, but not content with these options, a legendary NASCAR mechanic and top racer Henry ‘Smokey’ Yunick started thinking about the main losses – coolant and exhaust heat – and how that energy could be re-routed back into producing useful power. And as he was a very practical kind of chap, having also invented a silent tyre, extended tip spark plugs and reverse flow cooling, he not only devised a theory but set about building some working engines, based on bog-standard road cars.
After building a number of amazing engines, one of which was used regularly by his daughter as a daily driver (see correction below!) , he also set about patenting the system all over the world. Once he had the relevant protection for his idea he was going to show the world.
Unfortunately, and rather frustratingly for the world in general, he then died. His company and family are still pursuing world wide patents on the various clever bits that make it work and are reluctant to let anyone else play with his creations.

(Please see the fantastic reply from his daughter below for corrections!)

His patent applications make interesting reading, and generate as many questions as answers. What he describes is a way of recovering almost half of the waste heat from a standard car engine, some of his conversions are claimed to double the car’s acceleration and its mpg at the same time. His daughters VW Golf is said to produce 150bhp (up from 110 as standard) and average over 60 mpg (up from 30mpg).
One of the problems with using petrol in an engine is that it tends to form clumps of molecules which can only burn on the surface, leading to un-burnt fuel and partially burnt fuel being thrown away down the exhaust pipe, these are the hydrocarbons (HC) you see on the mot test results.
Interestingly Smokey’s design uses carburettors, the heat is used to evaporate the fuel giving a more homogeneous mixture which burns more completely. This is a technique used even today by the car industry on injection systems, at part load fuel is injected onto the back of a closed intake valve to use the heat.
Heat is the key to Smokey’s design – in simple terms it first uses the coolant to heat the air fuel mixture to 90ºC at which point the fuel is almost entirely gaseous. It then uses the exhaust, which completely surrounds the intake, to increases the charge temperature to 230ºC. At this point the mixture has expanded quite a bit so a turbo or ‘Homogeniser’ as they call it (not a turbo in the traditional sense because it further heats and mixes the fuel with air) blows down the manifold to stop the mixture escaping back up the intake. The heat will have increased the charge pressure quite considerably, thus turning more heat energy into pressure energy that the engine can convert into torque. And the turbo, sorry – homogeniser, will have boosted things a bit further too, but of course the density will be quite low unless the turbo is running very high boost, and there is no intercooler to waste heat energy. With very high intake pressure it is also possible to re-design intake cam duration to get more cylinder filling, although it is not clear if this is part of his design.
Now the piston compresses the mixture which heats it up further to 820ºC. Now normally this would have detonated and blown the engine to bits, petrol mixture goes bang at about 350ºC, so clearly Mr Yunick was doing something very clever here and the info he had released may be deliberately misleading to buy him time whilst he got the patents, but what ever he did there it is his main secret and you will no doubt be very disappointed to hear that I have absolutely no idea how he does this. Clearly the nicely mixed charge is not really at 820ºC if combustion is going to start with a spark in the conventional manner, although enough energy has been put into it to reach this temperature. If combustion starts in a diesel type compression ignition then the whole charge will go bang at once, rather than a diesel’s controlled gradual burn, and blow the piston. Something must control the combustion?
Could it be water injection? Water mist would reduce the mixture temperature and itself expand in the fierce heat and generate more pressure and thus power. But that’s just a guess on my part and no mention of any other substance exists on the patents.
On the cars he converted there is a very small radiator and no fan, allegedly coolant volume is very small too, helping warm up time. These cars have been driven by a number of journalists and the performance and fuel economy have been verified, so in that respect the design has been ‘shown’ to work.
The only clue comes from some of the mechanics that worked for him who have alleged that the engines were very prone to pinking and melted pistons, but to be fair so do many ordinary mass production engines when they are in their prototype stage.
It’s a strange situation, undoubtedly Smokey was a great mechanic and built some of the best race cars in the world, so he was no amateur and knew what he was doing. Some people have wondered if it was an elaborate hoax to poke fun at the establishment, but why would you fund world wide patents for a hoax and what about the cars’ performance? And why are his ‘prototypes’ still in use? Why won’t the family let anyone else take the engines apart? So many questions.
It’s interesting to note that these revolutionary high efficiency engines are still only using 60-70% of the fuel’s energy, so it’s not in the league of infeasible perpetual motion machines, the energy balance makes sense. It’s just the combustion control that makes no sense and is without any explanation. These ‘Hot Vapour’ engines, if they turn out to be real, have amazing abilities and could herald a new era for piston engines. Just imagine a 600bhp V8 that does 60 mpg. It’s a beautiful idea.


About Ralph Hosier

I love exploring everything the world has to offer, the fabulous beauty and intricacies of nature, the stunning majesty and grandeur of the universe, and the fascinating range of chocolates available from the local sweety shop. I have led a charmed life, sure there has been extremes, but the highs far outweigh the lows. I get paid for arsing about in very fast cars, I get to write about them and amazingly get paid for this too. My days are usually filled by making prototype and concept cars for car companies, a dream job. I have lived many of my dreams, worked all over the world, raced cars built by my own hand (and hardly ever crashed really badly), seen things and done stuff. But nothing compares to the love of Diana and my son Peter, beyond my greatest hopes. I am a chartered engineer, a member of the Institute of the Motor Industry (IMI), and of the Institute of Engineering and Technology (IET) and I am a member of the Guild of Motoring Writers. A pleasing fact is that there are now more letters after my name than there are in it ;) R.Hosier B.Eng(Hons) C.Eng MIET MIMI MGoMW
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7 Responses to The Mystery of Mr Yunick

  1. trish says:

    Mr. Hosier-

    While I freely admit I am unable to argue the technical merits of Smokey’s Hot Vapor engine, as Smokey’s daughter I am fully qualified to clarify a few points you made in your blog posting.

    I have never driven a hot vapor car, I was not of driving age much of when Smokey was actively pursuing the technology.

    The design was patented in the USA only.

    Every major motor company and several branches of the US military looked at the engine and tested it to various extent.

    The family made the decision shortly after he died (2001) NOT to pursue the patents.

    Smokey donated a hot vapor engine to the Smithsonian Institution before his death. To my knowledge it has not been on display, nor has his iconic hat. A Smokey fan and gearhead named Tony Allers reconditioned a hot vapor, put it in a similar Fiero as Smokey was pictured on HotRod and has donated it to Don Garlits’ museum in Ocala FL. One of them is in the Brumos museum in Jacksonville FL, in the DeLorean Smokey once owned. I do have a couple of them, most notably in a RABBIT and there are another couple privately held.

    I don’t believe examining any one of the engines would be particularly valuable. When you patent an idea, you strike a balance of disclosing enough to gain the patent and not enough for someone else to copy your idea. As the engine has multiple designs involving differing numbers of cylinders, I believe someone would have to examine all of them in order to really begin to understand what Smokey was thinking.

    I have been asked about the technology many times. I believe there are a number of reasons it never sold. Smokey had attained quite a reputation for “cheating”. While he maintained he did not cheat, he simply read around the rules to find the grey areas and exploited them, (1) his reputation undoubtedly tarnished his credibility. (2) Smokey had little patience for politics of any type, and selling an idea like this involves a great deal of that. (3) It is counter-intuitive to everything assumed to be true about internal combustion- it’s a hard sell. (4) Metallurgy has improved a great deal; the cost of containing all that heat was prohibitive back then.

    All this said, I believe Smokey would welcome your debate around his technology as he strongly believed we needed to address our oil greedy ways. I just wanted to set some of your facts straight.


    • Freedomfalcon says:

      Ms. Trish,
      If I may presume to be so bold as to suggest. I politely disagree with the assertion you made about needing to examine all of your late father’s engines to get some idea of what he was thinking regarding his designs persuant to the Hot Vapor Engine.
      Smokey was headded off at the pass by the majors. It’s my opinion he uncovered a formula pertainent to all Otto cycles. A truly thorough inspection of his work in any of his working vapor efforts would most certainly reveal this formula of his.
      Carter Lee

  2. ralphhosier says:

    I am deeply honored that you have taken time to reply.
    Your father is still a huge inspiration to myself and a great many engineers to this day, anyone who has designed and built race cars knows exactly where he was coming from and has a deep respect for his brilliant rule interpretation, never cheating just optimizing!
    Many thanks

  3. Tony Allers says:

    I have driven the 4 cylinder Hot Vapor Fiero and it is truly incredible. Hot Rod Magazine did a feature article on the car in the Septem
    2010 issue. It has also been featured on Horsepower TV. The car provided instant acceleration at any speed and virtually zero
    emissions. I was able to get over 40mpg and could have done better if I was not addicted to performance. The car is on permanant
    display in the Don Garlits museum. I look for an announcement about this technology later this month from a major US corporation.
    Stay well and thanks for keeping Smokey’s technology in the public eye.

  4. punjehl crane says:

    ih i live in australia and have been very interested in smokeys hot vapor engines and have read everything i can find on them i have also done a small amount of mathematical modeling on the design the basic idea seems to be to recycle the waste heat in the coolant and exhaust gasses and use them to generate torque on the intake stroke i did some calculations on the mass and density of the charge temperatures and pressures he was running . some of the stuff about these engines i have read says that he used the stock compression for these motors. and ran AFRs of around 20 or 22 to 1. the hot vaporus charge removes the problems of charge stratification and peripheral quenching and wasted large droplets of fuel sticking to the bores and ending up un burned in the exhaust or engine oil . The density of the charge he was running from some calculations i did apears to be about the same as the cold NA charge the same engine would normaly drink ie charge at 2 bar absolute and 230 degrees c ends up being the same density as a cold naturaly aspirated charge with mist of fuel instead of vapor . the ideal gas law states that when compressed the temperature rises the math gives a pre ignition temp of around 800 degreesc but does not factor in the loss of heat in the cylinder, head and piston after this the charge temp is reduced and may not be hot enough to spontaneously ignite this in turn means the hot charge will expand and cool and push the piston on the intake stroke resulting in more torque not directly obtained from combustion and because of this heat loss the engine then uses less energy to compress the charge than was obtained from it this brings me to the piont of the valve duration. if this were to be modified to allow a shorter time for charge filling at much higher peak pressure the valve then shut at somewhere between 1/3 and 1/2 cylinder fill the gasses would them be allowed to expand and cool delivering torque on the intake stroke then the peak temp at point of ignition would be well below the 800 c ish temp sudjested by the ideal gas law . Im not sure if he messed with the cam duration but the possibilities look promising . one way on the other if the temperature is higher at the ignition point it means the temp and pressure will be higher during combustion from the same fuel burn resulting in more power from the same load of fuel or less fuel for the same power . i have done a half way experiment with this system with an old chrysler scorpion aka mitsubishi sigma which involved 1 coolant heat exchange after the carby after finding the car aws running too lean on the primary throat/jet due to loss of the stock egr that ran about 25% exhaust gas mix rate in the stock form indicating a rejetting to increase fueling by about 25% would be needed to correct the lean missing rough run on the primary circuit soinstead of rejetting i added the HX under the carby and this resulted in a small increase in fuel efficency and the complete abscence of indications of too lean burn because lifting the charge temp to thermostat temperature resulted in a lower air density and this corrected the mixture . the car runs much cooler in this configuration drives silky smooth but has lost a corresponding ammount of power. i suspect that smokey went through this same issue with his early experiments and thats why he added the turbo and exhaust HX to get back the lost power by bringing the charge density back up and add aditional efficency .some have speculated that this method of his is simmilar to the millar cycle used in some vvt and diesel engines but the miller cycle is wasteful as it achieves near adiabatic conditions by reducing the intake charge by leaving the intake valve open very late and letting some of the charge blow back in to the intake the reason for this instead of closing early is that below atmospheric pressure in teh cylinder leads to increased oil sucked by the rings and in turn dirtier emmissions like so many modern engines with egr and dpfs that have these parsitic things added that make them cleaner and drasticlay reduce the longevity of the engines. This means a smaller charge but also means increased pumping losses proper adiabatic cycling like in large ships engines is achieved by reduced filling of cylinders by closing the intake valve early to only allow partial cylinder filling so as to achieve atmospheric pressure at exhaust open this means large heavy engines that dont waste any energy in high exhaust pressures and noise production some of these diesels achieve close to 60% efficiency . but they are enormouse and heavy not what you want in a daily driver . i would like to build a copy of smokies system to satisfy my persoanl curiosity and get a more efficent car but at the moment i have neither the time or the money to persue the project due to university commitments but i plan a slight modification on his design for our vegi oil converted diesel tractor why do it to a diesel ? . because on teh whole teh system is simpler to implement on a diesel and althought there is no fuel vaporisation benifit except for higher precombustion temps i suspect all that extra torque from inceased intake pressures and teh boost to combustion temps will give a large power and efficency increase as well as more complete combustion . hope you find this interesting regards punjehl

  5. Freedomfalcon says:

    What if Smokey used only about one third of the intake timming(area under the curve)and relied upon the pressure in the intake manifold to move the piston down on the intake stroke? He said to use the engine like an expander. If so, then one has just gotten rid of the pumping losses consumed from the crankshaft in order to produce a vacuum asin any conventional Otto Cycle engine. What’s more is that rather than a thermodynamic drag of vacuum instead there is a benefit. This benefit is directly as a result of making work from waste heat creating a power cycle of the intake stroke even as it fills with a combustable mixture.

    Fuel quality- the Hydrogen part of Hydrocarbons has a very high flash point just over one thousand degrees F. Lean mixtures are hard to ignite after a point with a spark. Homogenous mixtures are also more resistant to detonation. But, they burn quickly. So, as the compression stroke nears top dead center crankshaft degrees it seems some compression alteration may need to be considered as the vaporous expanded mixture now gets compressed and therefore reheated. It seems detonation may be averted using the fuel vapor’s new octane and tailoring what dynamic compression there may be by using a bump on the heel of the cam to bleed this pressure back into the intake manifold(Briggs and Stratton’s did this). Yet, perhaps it may be necessary to deck the block or head to increase compression to match the vapor charge’s new resistance to detonation.
    It seems ignition timming may need to be relaxed to nearer TDC because of the flame speed of Oxygenated Hydrogen(part of the product of high heat, pissed off, bitch slapped air fuel mixture.) The molecules now perform like an air fuel b0mb with terrific flame front speeds which impart more of their energy much earlier in the powerstroke before twenty degrees of crank rotation.
    Less heat is the result of this type of reaction. The crappy lower ends of hydrocarbons that use to burn last inside a much larger cavity as the chamber grows past nintey degrees of crank rotation producing only heat with nearly no performance gain just aren’t there anymore and aren’t needed.
    All of this is theoretical on my part.
    Long live the Hot Vapor Engine, the memory of Smokey Yunick, and the mystery ge gave to all of the gearhead men chasing the understanding of pinwheels both of whom go round and round.

    • Ralph Hosier says:

      A lot of these ideas are actually used in many modern engines now. And the idea of using intake pressure to produce power on the intake stroke was extensively used on turbo F1 engines of the ’80s. Interesting stuff.

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