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Smokey's Adiabatic Engine

Smokey's Adiabatic Engine

Smokey's Adiabatic Engine

Somebody in another discussion thread made a mention of Smokey Yunick's adiabatic engine. I had never heard of it before, and did an internet search as well as retrieve the patent and dug up some old Popular Science magazines that discussed it.

For those of you not in the know, Smokey Yunick was a legendary race car mechanic and Popular Science correspondant. He died a couple of years ago. In March 1983 Popular Science carried a story about an engine he had developed that only had two cylinders and 78 cubic inches but developed 150 hp and got 60 mpg when installed in what looks like a Volkswagon Rabbit. He called it his "adiabatic engine." Supposedly all sorts of car companies were quite interested in the engine.

A followup story done in Popular Science in November of 2000 stated that the "engine came close to going into production with General Motors several years ago, but the deal hit a stalemate when patent owners couldn't agree on details." If you visit the patent office, you will find that the patent covering the engine (US 4862859) was allowed to expire in March 2002. (Web site for patent: http://patft.uspto.gov/netacgi/nph-Parser?Sect1=PTO1&Se...)

In reviewing the patent it appears that Smokey's engine used an "afterheater": coolant heat was used to vaporize gasoline, and exhaust heat was used to heat the air/fuel mixture coming from a turbocharger compressor to 440 deg F. In the cylinder the air/fuel mix reached a temperature of 1600 deg F before ignition -- all without detonation.

According to the Popular Science article, the reason for no detonation was "Smokey's Secret".

After reviewing some of the numbers provided in the Popular Science article and in Smokey's patent, I've been able to deduce the following about the engine;

1. The air/fuel ratio was something on the order of 22:1 to 27:1.

2. Peak combustion temperature was above 5000 degrees F.

3. Exhaust gas temperature (before the turbocharger) was about 2200 deg F.

4. Assuming no loss of cylinder heat to the cylinder walls (i.e., an actual adiabatic engine) the best possible efficiency was about 38%. If the engine used a Miller cycle modification, an efficiency of 48% would be possible (no mention was made of the Miller cycle)

My conclusions:

1. Smokey may have been able to get the engine to work, even though there was a high intake temperature, by using a very lean air/fuel mixture to prevent detonation.

2. There was no way that this engine was developing efficiencies of 50-60%.

3. It is doubtful that the engine, as described, would last long because of extremely high temperatures. With the claimed fuel flow and intake air temperature, the peak combustion temperature would be over 5000 deg F, as compared to perhaps 3500 deg F for a normal spark ignition engine.

4. I find it very hard to imagine that General Motors was ready to put the engine into production and didn't only because of patent royalty issues -- only to have the patent abandoned several years later.


Comments, anyone? Did anyone ever actually see this engine, or hear anything about it?

RE: Smokey's Adiabatic Engine

Here's some more on it.

The air fuel mixture is heated to 90 C by the coolant, then it goes through the turbo/atomiser, which heats it to 140C, then is heated further by the exhaust to 230C

Then it is compressed in the cylinder to 820C, at which point the spark fires.

Then it goes through the exhaust valve, heats the incoming mixture, and then into the expansion side of the turbo.

here are some claimed figures

Car/engine Fuel consumption 0-100 km/t
Plymouth Horizon, 4-cyl 23.51 mil/gal 14.5 sec.
Plymouth Horizon, Hot Vapor. 54.67 mil/gal 6.5 sec.
Pontiac Fiero, 4-cyl 21.97 mil/gal 14.2 sec.
Pontiac Fiero, Hot Vapor 51.10 mil/gal 5.9 sec.

My comments

(a) I'm a non believer, but it is an interesting mix of ideas

(b) As far as efficiency goes it would be better to drive the turbo direct from the exhaust and then use the exhaust from /that/ to heat the intake manifold. However that might compromise the temperature attained in the intake manifold

(c) other threads have covered the small increase in available energy you would get by pre-vapourising the fuel

(d) someone with some time on their hands could use these temperatures could probably figure out the pressure ratios in the turbine, and the likely thermodynamic cycle of the whole thing.

(e) crudely he is running diesel-like AFRs, so you'd expect diesel-like efficiencies.

(f) in order to develop 150 hp from 1278 cc he needs high rpm and/or high boost pressures. Lean mixtures burn slowly, so high rpm alone is not the answer

(g) The mpg figures imply something like 2.5 times the efficiency, admittedly off a fairly low base


Greg Locock

RE: Smokey's Adiabatic Engine

I remember that he allowed a car magazine driver to try one of these engines in a car.  Might have been "Car & Driver" mag.-can't remember.  But I do remember that the driver floored the throttle at low RPM, and it didn't detonate.

RE: Smokey's Adiabatic Engine

Oh, and another fact(oid) from the Rabbit article is that there was only 2 litres of coolant and no cooling fan.


Greg Locock

RE: Smokey's Adiabatic Engine


Ol' Smokey's engine achieved those performance numbers with the use of a special additive. Most racers are familiar with the additive. Anytime someone makes incredible claims about the performance of their engine, you can be sure they're using lots of the additive. The additive goes by the initials B.S.

There was one thing Smokey Yunick was famous for: cheating.

RE: Smokey's Adiabatic Engine

it does sound interesting, but last time i checked, steel melts at about half that temp (between 2300 and 2700 degrees F)  even if its only exposed to those temperatures for a moment, its still enough to damage the cylinder walls...

RE: Smokey's Adiabatic Engine



You really had me going for a moment there!!

And a note to Greg Locock: I have gone through the thermodynamic calculations, and they work out something like this. . . . .

The piston compression ratio can be determined from the differences in the temperature between the intake manifold and following compression. It's about a 10:1 compression ratio.

Assuming an adiabatic system with a 100% efficient piston compression and expansion and a frictionless drive train, the overall system efficiency is 55%.

Assuming a somewhat more realistic piston compression and expansion efficiency of 85% but still with a frictionless, adiabatic engine, the maximum efficiency drops to about 38%.

Once you factor in the losses from friction, exhaust gas piston blowby, and a non-adiabatic environment -- I don't think there's a snowball's chance in hell that the engine is achieving the advertised efficiency figures.

And, one last thing;

Tbuelna, do I have to cite you every time I use your description of the special miracle fuel additive??!!

RE: Smokey's Adiabatic Engine

Alum. alloys melt at much lower temps.~1,200 deg F., and *usually* they don't melt, so peak flame temp. doesn't mean didley.

RE: Smokey's Adiabatic Engine

Here's an fun experiment you can do.

Take a paper cup.

Fill it with water.

Place it on a bunsen burner or coleman propane camp stove.

It is possible to boil water in the paper cup, and the paper cup won't burn up -- even though the flames have engulfed the cup. Since water can't get above 212 deg F at atmospheric pressure, the water products the paper cup from damage from the flame.

NOTE THAT THIS DOESN'T WORK IF YOU USE A STYROFOAM CUP!! I tried it once to impress some people, and needless to say they were quite impressed.

But the same thing happens with cylinder temperatures. Temperatures much higher than the melting point of the cylinder wall metal can be tolerated, because the coolant protects the cylinder wall and the cylinder wall doesn't get close to the temperature of the gas in the cylinder.

RE: Smokey's Adiabatic Engine

Ok, im not afraid to admit it.  I tried the paper cup experiement.

Guess i need to read up on my heat transfer.

RE: Smokey's Adiabatic Engine

of course, if you had an "adiabatic" engine, you'd be closer to the styrofoam case than to the paper cup case...

RE: Smokey's Adiabatic Engine

Another thought: We know that the leaner it is, the slower it burns. Just how lean can it get before it pops,bangs, and just wont run.

Shaun TiedeULTRADYNE/LUNATI Arl,TX(stiede@ev1.net)

RE: Smokey's Adiabatic Engine

about 17:1 to 18:1, with pump gas and modern engine controls, if Honda can be considered experts in lean-burn automotive gasoline engines (new Civic, Insight are in that neighborhood)...

RE: Smokey's Adiabatic Engine

Right. That is why I too have trouble believing the Smokey thing. This spacific forum is therefore a waste of time.

Shaun TiedeULTRADYNE/LUNATI Arl,TX(stiede@ev1.net)

RE: Smokey's Adiabatic Engine


This particular discussion thread is useful in discussing why certain things did not work. Smokey's engine was touted in a international publication (Popular Science) as working wonders. Time has shown that the claims were a bunch of bunk.

But it is useful to look at the claims that were made and try to figure out just what they were doing and what did and didn't work.

As far as ignition with an air/fuel mixture; I agree that you do reach a point as you lean a mixture out where it will no longer ignite. But I also suspect that if you take the same mixture that won't ignite at room temperature and heat it, you will reach a point where it will ignite.

If, for instance, a 20:1 air/fuel mixture will not ignite at room temperature, will it ignite at 500 deg F? 1000 deg F? 5000 deg F?

For the same reason, I also suspect that leaning out an air/fuel mixture will prevent detonation -- or spontaneous ignition.

Hence the value of this discussion.

RE: Smokey's Adiabatic Engine

Agree, this discussion is worth it.  Obviously those who want to "change the channel" can do so, but I hope they don't.

I have very mixed feelings about this whole engine/concept.  Ol' Smokey was a very sharp guy-eg., his reverse-rotation Hudson flathead 6, which he did to help prevent unloading the inside front wheel.  He didn't even tell the drivers what he did.  Yet I remember some real goofs in his advice column in Pop. Sci.  I suspect he had someone writing that stuff.

I also have a problem with some of the stuff in the patent.  Even with slightly long rods for the stroke, I find it hard to believe that 13 deg. of rotation at TDC didn't move the piston 0.001".  Also, at least from a mech. POV, the last thing you want is max. cyl. pressure near TDC.  Much better to have it far later, when the piston/rod get some leverage on the crank.  It's easiest for the piston to turn the crank when the rod is at 90 deg. to a line between the rod and main journals, and this point is reached shortly before the piston is halfway down.

RE: Smokey's Adiabatic Engine

Long rods worked really well for him largely due to the horrible heads he had access to. By todays standards, his best is our junk. The long rod helped the head work the motor.


Shaun TiedeULTRADYNE/LUNATI Arl,TX(stiede@ev1.net)

RE: Smokey's Adiabatic Engine

Working with stratified charge engines has shown some interesting results:

The mid 70’s Honda and Mitsubishi pioneered the use of dual mixture engines.  One carburetor venturi provided a very lean air-fuel mixture, in the 22:1 range.  The other venturi provided a richer mixture, about 13:1.  The aggregate was about 17:1, since the smaller but richer venturi was about 11mm, while the leaner venturi was about 25mm.
The carburetors third venturi was approximately stoichiometric.  Depending on the load, the engine-out AF ratio would range from about 20:1 down to about stoich.

The engine ingested the lean mixture first, then the rich mixture.  The spark plug was located in the immediate path of the rich mixture, which then ignited the lean mixture.  This allowed the Honda CVCC and the Mitsubishi Micro-jet to achieve those fantastic emission and fuel economy numbers.

More modern attempts at running variable AF mixtures have been a little more difficult, primarily for catalyst control.  The cost and complexity of catalyst formulation for variable AF ratios increases drastically as opposed to one which operates at a tight AF ratio.


RE: Smokey's Adiabatic Engine

I was at his shop Feb. 1988 for the big auction he had. Was fortunate enough to be invited into the Holy of Holy's area where he did most of his R+D work. The engine in question was also a test bed for a number of ceramic engine components ( pistons ,valves and rings)along with ceramic coating of the same. The ceramic parts were made by a joint venture between Norton Co. and TRW. I think the high levels of NOx was the big reson GM shied away from it.As far as cheating you got to admire the guy for some of the stuff he tried and was successfull with.-----Phil

RE: Smokey's Adiabatic Engine

Adiabatic engine == high level of nitrous oxides.

Makes sense, since heat that is not absorbed by the cool cylinder walls will cause the combustion temperature to increase, which will also cause an increase in nitrous oxides.

I certainly understand the use of ceramic coatings in an adiabatic engine -- it provides a good insulation against heat loss.

You mentioned that the ceramic coating was used on rings. I can understand the use on pistons, valves and the cylinder wall. But rings? I wouldn't think that there was enough heat flux through piston rings for a ceramic coating to make much difference at all.

RE: Smokey's Adiabatic Engine

Piston rings are a significant path to conduct heat from the piston to the cylinder wall.  Reducing the conductivity of the rings would increase piston temperature.  Whether this is desired or practical is another question entirely.

RE: Smokey's Adiabatic Engine

Paper Cups!
You guys need to credit the right people here. Using tree bark to make a container to boil water in has a history going way back before the plastic cup. Native Americans, (among others) speak out!
(not sure if there is a particular bark to use, large leaves should do just as well.)
Sorry to intrude, I'll get back to just reading the thread since i have nothing useful to contribute.

RE: Smokey's Adiabatic Engine

I tried to find this BS product at the speed shop. They offered me was WA, apparently an alternative product:


I can only hope it's as effective.

Back on topic: If you use ceramic heads, valves and pistons, the rings become a major failure point, because there's no place for the heat to go. I read some research on this someplace, I'll see if I can dig it up.


RE: Smokey's Adiabatic Engine

The way I understand it was that the ceramic coatings, in particular on the exhaust valve, insulated it enough to lower the detonation threshold enabling a higher compression/expansion ratio. EGT was in the neighborhood of 900 deg F. at WOT. Ceramic coating the compression ring was an exercise to possibly eliminate the need for lubrication. Last I knew was the only thing that made it into regular production was the turbine blade of the turbo charger(homomgenizer). If memory serves me correctly this was picked up by Garrett.In the absence of varifiyable #'s I think in the end it was no better then a diesel.----Phil

RE: Smokey's Adiabatic Engine

In my humble opinion, (I have to say that for the lawyers benefit, don't I, ask Klick and Klack) most of what you read in popular science is bunk, isn't it?  Should be called popular science fiction.  This is my contribution to this thread.  I enjoyed the read very much.  Thanks to all who contributed.

RE: Smokey's Adiabatic Engine

Yep I have seen the hot cyclic engine of smokeys, seen it
run. It sounded a little like a lawnmower engine until ya
put the fuel to it then it sounded more like an airplane engine. He drove it back and forth accross the seabrease
bridge every day to and from work and accasionaly to a little cafe for a cup of soup. Smokey told me Gm had some
concernes as to heat sink he was confident that wasnt a problem but wasnt gonna tell them "a god damn thing untill
those pelicans get with the program" Later around 1991 0r
so I was down to see him and he had the engine out and ready
to take it apart  to see just how it endured. Later he called me about something and I asked him about the engine
All he said  Its damn well do able. This much I know about
about Smokey if he said it was so ya better bank on it. because it was so.

RE: Smokey's Adiabatic Engine

Looking back over Smokey's design and claims, it strikes me that it has some resemblence to a HCCI engine -- homogenous charge compression ignition engine.

First, a homogenous charge refers to mixing the fuel with the air quite throughly and heating it to promote vaporization -- prior to introducing it into the cylinder. What was Smokey's compressor -- a "homogenizer", and the fuel was preheated.

Second, the air/fuel ratio was quite lean -- at least for a spark ignition engine.

Perhaps I should start another thread on "Smokey's HCCI Engine"?

RE: Smokey's Adiabatic Engine

Thoughts of a Shade-Tree Mechanic, [another 5/25 Gemini],  re: Smokey Yunick's Adiabatic Expander Cycle ICE.
Everyone seems to be very positive that the thing just can't work. Their usual reasoning seems to be that it MUST detonate like a grenade because you're putting that A/F mixture in at a gazillion degrees F or C, or maybe K.
I seem to remember ol' Smokey stated he used a "Special" cam, and that the intake charge was at (X) degrees 'at' the valve.
I don't recall that he said it was at (X) degrees when it was in the cylinder.
I also recall something about a drop in temperature when a high pressure gas flows into a lower pressure region through an orifice.
Gee, what would happen to Smokey's pre-heated mix if he waited to open that intake valve very late, and then only opened it a wee bit?
Sounds almost like my previous statement, doesn't it?
The rest is tres' simple, recycle the heat instead of flushing it down the pipe, use high compression and long rods, and voila', HP with minimum fuel.
My only real question is: When will some enterprising investigative bloodhound trace the ownership of the Patent?
Who is at the top of that Food Chain? Are Big Oil and Big Government hand in hand? Did Smokey's Motor hit at the wrong time in History, right after the major auto makers had pulled the Computer Engine Control/You must have Fuel Injection for economy/Lean-Burn actually works SCAM?
Imagine the egg on the faces of those who perpetrated this Hog Wash, [especially at the next Stockholders Meeting], if a little ol' guy from Daytona invented a motor that REALLY was efficient!
But I ramble and digress, it's Hell getting old, but sure beats the alternative.


RE: Smokey's Adiabatic Engine

The patent was actually abandoned a year or two ago.

For a patent to stay in force 18 years it has to be renewed every few years, which basically means you have to send the patent office another couple hundred bucks.

Nobody sent in any money to renew Smokey's patent.

RE: Smokey's Adiabatic Engine

If you open the inlet valve real late and only slightly, the partial vacuum you creat will drop temps, but the increased compression ratio will only bring it back again.

Also, it will really kill power, which will need a larger engine to give enough power, which will kill economy, as it will be heavier, have a little more friction, and have more surface area to loose heat through.

The only benefit of preheating fuel is better evaporation, leading to more complete and possibly faster combustion.

Incomplete combustion is not a problem worth mentioning in a modern engine, but increased burn rate might allow later optimum ignition timeing, causing less pressure build up against the direction of rotation when near TDC, and more of the energy could be used for the power stroke, that is providing you actually got faster burning.


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RE: Smokey's Adiabatic Engine

I think Smokey's whole point was to reuse heat for power rather throwing it away in the exhaust and cooling system.  However, it seems to me that if you actually wanted to make USE of this waste heat, it would have to be put back into the engine during the power/combustion storke-not the intake stroke.

I know a lot of industrial turbine engines will reclaim waste heat, but they will add it AFTER compression, and before combustion and expansion.  There isn't much time or space between the compression and combustion cycles of a piston engine.

RE: Smokey's Adiabatic Engine

Sorry to be a little late posting but wanted folk to be aware that the Mitsi GDI engine has a mapped ECU and I understand, achieves a 40:1 AFR at idle dropping to 22:1 at cruise.  Not sure about WOT but assume AFR would reduce to close to stoichiometric for maximum power.

Presumably the very high injection pressure results in better atomisation of the fuel (= better kinetics) plus the ability to aim the charge in the direction of the s/plug, enables stable running even at these very high AFRs.  We own two vehicles (L4 and V6)with GDI engines and can vouch for their fuel efficiency.   

RE: Smokey's Adiabatic Engine

Actually guys it did work I drove Delorean with one in it in the 80's and Smokey's personal car,a Ford Fiesta,had one it in it for over 15 years.  The item that you are all missing is the fact the the fuel is vaporized.  When vaporized the surface area of the fuel is much greater thus making a faster not slower reaction, try it.  

Also the deal behind the big industry boys goes like this Smokey thought that to get the engine accepted by the big industry guys a try it would be good to give ,I believe 20%, of the engine rights to a past Ford/Chevy CEO named Knudsen, it turned out that no one really like him and he was a deal breaker in many cases.  The big industry guys also wanted Smokey to do all the work and not pay him what the thing was worth! Also Smokey finally bought out Knudsen's share of the motor and the motor was scheduled to go into the Delorean car, but we all know how that ended, this is in the Delorean history books!

For all of you guys who say Smokey was a cheat and fake then why did Hudson, Pontaic, Chevy, Ford, General Dynamics, Autolite, Unical, the list goes on and on hire Smokey as a consultant?  Ever here of a flow bench? A Dyno, Variable Power Steering, the list goes on and on, they are all Smokey inventions.  Oh ya, if you want to see a Smokey Hot Vapor engine run they got one that works at the University of Central Florida in the basement.  They dont advertise it but go see for yourself, room B119.

Ryan Bailey

RE: Smokey's Adiabatic Engine

Forgot to mention that Ferarri ran almost an identical engine setup in the 2001 Indy 500 and did very well.  

Also if you don't believe that the big industry guys would let the engine go do a BTU conversion on gasoline and hydrogen.  Think about this:  hydrogen in a gaseous form the container for 9/10's a gallon weighs 90 lbs, a cylinder, a container to hold twenty gallons weighs as much as some small cars!  Ok, take it in a liquid form, in the most expensive container you can get and cool it to say 350 degrees F below 0, that container still loses 1% a day.  The container in the moon lander lost 9% a day!  The shelf life of gasoline today is around 90 days, that is to get from the refinery to your gas tank, hydrogen would be the same, unless you somehow made it yourself from water, VERY EXPENSIVE!  So you guessed it you lose about 90% in the pipeline!  How many times you gonna have to fill up that Hydrogen powered car to go anywhere?  GM is wasting billions on this scheme just because of publicity.  It can't work unless you plan on paying 5 bucks for the what would be like a gallon.  This was all taken directly from Smokey's notes.

RE: Smokey's Adiabatic Engine

Oh ya, I am not a materials or thermo guy but Smokey told me that one of the most important things about his engine was that when you vaporized the gas it evened out the octane rating or made all the gas the same.  He said that in a gallon of gas the octane rating could vary by 20 points.  Just something I remembered.


RE: Smokey's Adiabatic Engine

Variable ratio power steering was developed and patented bt aebishop manufacturing in Sydney Asutralia.


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RE: Smokey's Adiabatic Engine

By the way, Metalguy. You commented on not wanting the ignition point at TDC. I beleive there is an engine under test where the piston is in two parts with the cwon separated from the main part by a spring so that at ignition the spring is compressed, storing energy that is released later in the cycle. I don't know who designed it or what's happened to it. Last heard it was being tested.

RE: Smokey's Adiabatic Engine

IMO and from a position of ignorance, three things killed Smokey's engine:

Smoke (or photochemical emissions) in the form of NOx because this forms in a certain time/temperature regime that would seem to have been present in this engine.

Durability.  See comments above.

Safety.  There would have been lots of HC vapour around and how is the latent heat from the engine when it is turned off, dissipated without creating more HC vapour?

Heating the fuel will definitely REDUCE theoretical efficiency if it is (erroneously?)assumed that complete combustion is achieved during the power stroke.  What is very interesting though, is that getting the fuel fully vaporised and right at flash point will reduce the ignition delay and make possible the more efficient extraction of the available energy within the milliseconds available while the pistion is descending.  It would seem that this is where the benefit mentioned above, comes from.

I trust that one of you clever folk will throw some efficiency numbers at the vaporised fuel Vs droplet fuel (incomplete?) combustion situation.  Me?  I'm going to sit on the sideline again...

RE: Smokey's Adiabatic Engine

Me again

SBBlue mentioned some efficiency figures and I totally agree that unless there was some type of combined cycle functionality we dont know about, Smokey's 50% claim is OTT.  

But I would think that a major factor still has to be ignition delay/rate of combustion and understand that they are not considered in theoretical efficiency calculations are they?

RE: Smokey's Adiabatic Engine

there was one other piece of the engine, besides the reduced heat loss increasing efficiancy his design with the homogeniser reduced pumping losses.
the engine had to run a special aircraft oil to withstand the tempatures acording to an article I read a while back.
I think that the secret to the whole thing was using a lot of egr as well, whatever the other piece was it was supposedly very simple and it had to be someting easy to hide like putting the egr stuff in the homogeniser unit.

RE: Smokey's Adiabatic Engine

I read the article about Smokey´s engine when it was published, just after graduation. I decided to perform some experimentation in my own car.

At the time, I had a VW Gol (parent of VW Fox to be export later to US by VW of Brazil) featuring the air-cooled boxer 1.3L engine (yes, the old beetle unit upgraded a little by Porsche engineering). My car was an alcohol version, featuring a 10.5:1 compression ratio, against 7.5:1 (if I´m not wrong) for the gasoline version, and a heated intake manifold (exhaust gases flowing around the intake pipes).

After some thought, I came to the conclusion that lean mixture were al least one of the secret for avoiding knock and improving efficiency. I decided to run the engine on gasoline, keeping the much higher compression ratio and the heating system. Air-fuel ratio and spark timing could be manually changed from driver´s position. Gasoline pump was connected to a plastic bottle in order to monitoring fuel consumption.

At two consecutive weekends running the car at a flat road, constant 80 km/h speed, and looking for the best adjustment, I got 23 km/l, very impressive for that engine, against something about 15 km/l (I am not quite sure) for the gasoline standard version. Contrarily to what one should expect for a lean mixture, I could no detect any lag when throttle were suddenly opening. However, if throttle was released fast engine used to falter for a while.

I didn´t sustained high loads for long time, but knock was not very common. By the way, my wife had to learn how to delay ignition when engine was knocking. Yes, she had to learn how knock sounds too. Fuel pump connection with tank was restored beforehand (she refused to feed the bottle). General fuel consumption was not that good, but it must be remenbered that automatic carburetor and spark timing adjustments were untouched.

After driving for some 6 months, I decided to sell the car. I asked my mechanic to open the engine and see if there was something wrong and restore engine original configuration. Besides being puzzled about what I was trying to do, his only remark was that combustion chambers and spark plugs were unusually clean. No signal of excessively lean mixture arising from slow and late combustion.

In my view, some of the principles applied by Smokey irrespective to their actual effectiveness:

-    lean burn to improve efficiency, to avoid knocking, and to reduce heat rejection;
-    heated lean mixture to reduce pump losses;
-    heated mixture to avoid misfiring;
-    partial heat recovery through intake compression and heating from cooling system and exhaust gases.

Few years later I did some cycle simulations (instantaneous combustion, no heat rejection, no friction, and no flow losses) with heat recovery in order to access how much I could get. In order to take advantage of intake heating you must compress the mixture before, just as it is compressed in the combustion chamber before  ignition. However, if you compress, intake temperature is higher, so less heat you can get from exhaust especially if you are using lean mixtures. On the other hand, stoichiometric mixtures can lead to temperatures that reach turbine limits. Water injection lowers exhaust gases temperatures, but efficiency deteriorates because of the worse fluid thermal properties. Once results should get worse with introduction of flow losses I did not pursued this subject further.

RE: Smokey's Adiabatic Engine

For whomever it was that wanted to see the patent:  http://www.delphion.com/details?pn=US04862859__

Whether or not it worked, it would not have passed today's emission standards.  I read an article from a college engineering dept. somewhere that tried to copy his work, and they got very high oxides of nitrogen emissions, which was to be expected due to the high combustion temps.

RE: Smokey's Adiabatic Engine

How did he keep the fuel from auto-ignighting at those temperatures. Avaition jet fuel's auto ignight about about 450 to 500° F.

RE: Smokey's Adiabatic Engine

Gasoline's autoignition temperature is somewhat higher. I don't remember the exact figure off hand, but I think its over a thousand degrees F.

But it's certainly less than 1600 deg F. As to why it didn't auto-ignite -- If old Smokey was telling the truth, perhaps because the fuel/air mixture was so lean?

RE: Smokey's Adiabatic Engine

What about fuel "cracking", that is breaking down the long string hydrocarbons into, basicaly methane.  Has anyone acyually tried building and testing these ideas?

RE: Smokey's Adiabatic Engine


The former government chief engineer here in Sri Lanka has fitted about 50 engines in cars, vans, trucks, generators etc. with small flash gasifiers (fuel crackers) which appear to give quite good improvements in fuel consumption. The people who are using them say they work.

Apparently the rapid cracking of the fuel gives a different mix of hydrocarbons and these act as a catalyst to improve the combustion process. I'm not a chem eng and am highly dubious about the claims but here is some info if you are interested in the topic:

The patent is 5,398,663 look on www.uspto.gov

I have put an old article about this invention at http://album4062.fotopic.net/p304369.html

He is trying to get the NOx emissions checked but others are lower (CO, particulates, hydrocarbons) probably due to lower fuel consumption. NOx may be a problem.

cheers, derek

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RE: Smokey's Adiabatic Engine

Did any of you bother to study Smokey's patent?

I did, and it was kinda scary.  He proposed having an enclosed intake manifold, full of a volatile fuel-air mixture and heated to close to it's autoignition temperature.  Do the words "KA-BOOM" mean anything to you?

Adiabatic engine concepts always sound great in theory, but they never pan out in practice.  

Here's the reality: to achieve optimum BTE, you can't beat a large displacement, slow running CI engine:



RE: Smokey's Adiabatic Engine

How about fuel injection, shut off the fuel and let the motor use up whats left.  I still would like to hear if anyone has actually built and tested one.  What happened to Smoky's cars?

RE: Smokey's Adiabatic Engine

Smokey's daughter has a VW rabbit with a working adiabatic engine. There's suppossed to be a display in the Smithsonian with some of his handiwork also. There is a bunch of Smokey stuff on display at the Don Garlits museum in Ocala, FL.----------Phil

RE: Smokey's Adiabatic Engine

Does anyone know what happened to the DeLorean which had Smokey's engine in it?

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