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.