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So … why not thake the gas powered car and use the heat from the engine to create steam to help power the car… then take the steam and condense it back to water and re-use it to re-power the steam turbine … connected to a flywheel between the engine and torque converter then into the transmission… the entire exhaust system could also be used to create the steam… making the car 35 percent more efficient… anyone have any ideas in this reguard?



why would it need substantially more water that it already uses to cool the engine… if the water were to be re-used by re-condensing it down… after it is run through the turbine?

Ever look at a steam engine? The size dictates the horse power. Besides, a gasoline engine doesn’t provide enough heat to boil the water to create the steam to produce that horse power. It’s a simple matter of you can’t get more energy out of something than the energy that’s put in.


35%? Where does that figure come from?

Also this idea ignores several laws of physics that i’m sure Isaac Newton could tell you all about.

An internal combustion gasoline engine utilizes about 33% of its fuel to make power from heat energy. About 33% of the heat energy is lost out the exhaust system, and about 33% of the heat energy is lost in the cooling system.


Also this idea ignores several laws of physics that i’m sure Isaac Newton could tell you all about.

Nah, Newton was dead long before that.

Another couple of reasons besides weight:


What you’re talking about is really a different type of hybrid. Using an electric motor, batteries, and regenerative braking are basically accomplishing what you’re talking about, only more efficiently and with less hassle. And I still don’t want one of those due to the complexity.

But a steam engine simple enough to fit in a car would at best probably only recover about 5 to 10 percent of that wasted exhaust heat so it certainly wouldn’t make the car engine 35% more efficient.

tintom606, you might be interested to know a version of extracting power from the exhaust energy has already existed for over a half-century.

Known either as “turbocompounding” or a “power recovery turbine,” it works like a supercharger in reverse: it’s basically a turbo, spinning in the exhaust, that uses its recovered power to spin the crankshaft a little faster. You’ll find them on newer over-the-road diesels, as well as piston aircraft engines in the immediate pre-jet era (i.e. Lockheed Constellation).

The downsides: weight, cost, complexity…as well as reliability: flight crews were known to derisively refer to these devices as “parts recovery turbines” due to the effect they had on reliability.

P.S. trying to capture “waste” heat and do something useful with it is a good idea: the barriers not being technological so much as cost and reliability, given the amount of maintenance most car owners prefer to allocate their vehicles (ie. 0).

P.P.S. If you want to look at what is theoretcially possible in this regard, look at “prime mover” engines (engines on supertankers and such): since such engines put out so much power, for extended periods of time, the fuel savings from a 10% gain in efficiency would be worth a large expenditure, where it wouldn’t be worth it for a leafblower, for example.

Something like what you’re describing is used in the California heavy oil fields to generate both steam and electricity. It’s called ‘cogeneration’, but it requires massive facilities:

As to why not in a car, everybody else has summed it up pretty well. What you want is a car with a gas engine that can run in a boiling water mode (requires high temperature and pressure, easy to overheat the cylinder head) attached to a steam turbine (very expensive and large) and a large condensor (the same). The turbine would then be geared into the transmission, but would only help power the car during those periods of heavy use, and would not be able to quickly respond to the throttle, a major problem in a car, not a factor in a train or steam/electrical generation facility.

A problem not yet discussed all the heat lost while moving the steam around - it’ll be significant, a major hit to the process efficiency. So what you propose is maybe possible, but impractical.

Plus the temperatures we’re talking about losing due to heat aren’t all that high, and with the volume of steam we’re talking about here, you’d probably lose any extra energy you recovered in friction losses from spinning the turbine.

Not only that, but in order to impart any appreciable energy, you have to pressurize the steam. That’s yet another component for owners to neglect, and a little research into the history of steam-powered tractors will show you why you really don’t want pressurized steam in the hands of neglectful owners.

Because we aren’t buying enough BMWs. They were playing with this in the last decade and called it “turbosteamer”

I don’t like that idea. Using a steam turbine to power the cooling system instead of a timing belt chewing water pump is a good idea. But using it as supplemental power requires quite a bit of plumbing under the hood. I’d be interested to see waste heat powering a Stirling generator. This enables continuous supplemental power while cruising as well as regenerative braking.

If we “boil this down” (pardon the pun), 100% of the energy used to power the car will still come from the gasoline. You’re talking about recovering some of the 33% (estimates vary, but they all state 25% to 33%) that exits the exhaust ports and converting it to additional motive force. I’ll use 28%.

The concept is actually sound. It’s been played with for the better part of the last century. But the reality is that a steam engine is only about 5% to 8% efficient. So at best you’d be recovering 5% to 8% of the 28%, or about 1.9% of the energy contained in the gas. The added vehicle weight would more than eat up the gains.

The better way to use the exhaust is the current design philosophy, turbochargers. With the proper injectors and ECU program, they can induce a 30-40% improvement in engine power with little additional fuel use, because most of the energy is recovered energy that would have headed out the tailpipe. And they do so with very little added weight.

TSMB (and others) is exactly right. In fact, turbochargers are being use by just about all the automakers now to improve their mpgs. For example, in the near future just about all the engines you can get in a BMW will be turbocharged. While these new turbo engines test well, I’ve yet to see actual usage tests that back up the claims. It appears that the magazine testers (at least) make full use of the extra power from the turbo, eliminating the potential mpg benefits.

Thanks for the compliment.

I did want to make one clarification to my post for the benefit of the OP. I made the statement that turbochargers induce a 30% to 40% with little additional fuel use because most of the energy is recovered energy that would have gone uot the tailpipe. That isn’t really accurate. The additional power comes from the additional fuel that’s brought along with the additional air that the turbocharger pumps. Only the power to drive the turbo, the power used to compress the air, comes from the exhaust. It’s efficient because other ways of making more power, increased compression, increased bore, supercharging, etc. all take power directly from the engine as opposed to using the exhaust.

I’m not even sure that this explanation is better. Perhaps I should take my fingers off the keyboard now, before I make a fool of myself…

ok … I get it, a standard steam engine is large and heavy… why not use a tesla style steam engine … again recycling the steam by condensing it back down to water using an aluminum condenser to be re-used by the system. After all the exhaust can get to 1300 degrees according to google…more than enough to create up to 150psi at 11000 rpm. Through gear reduction converted to 2500 rpm which is about 15 hp…that is more than is required to move the car at highway speed… the speed and hp that my 4 cylinder runs at 65 in 5th gear

But the reality is that a steam engine is only about 5% to 8% efficient

I find this a little dubious. A modern coal fire power plant is capable of 42% efficiency

this is what I am talking about

 "But the reality is that a steam engine is only about 5% to 8% efficient" 

I find this a little dubious. A modern coal fire power plant is capable of 42% efficiency

Assuming for the moment that that’s true, what’s the normal cruising speed of a coal fire power plant?