Reader Question: A Gas-Steam Engine?

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Here’s the latest reader question along with my reply!

Ron asks: I have a question. If you take a V8 engine and only provide fuel to every other cylinder, will it run?

I ask this because I had an idea. What if every other cylinder runs on gasoline, which heats up the cylinder block to around 280 degrees Fahrenheit; so in other words, only four cylinders are getting gasoline. Then you inject water into the other four cylinders. If the cylinder block is hot enough, the water would turn into steam, and expand, just like the gas resulting from fuel combustion. So you could have two tanks in your car: one gas tank, and one water tank. Four cylinders would run on gasoline, and four cylinders would run on water. And a car that gets thirty miles to the gallon would get sixty miles to the gallon. It’s a steam and gas engine.The conversion would be easy. No machining; just redirecting four fuel injectors to the water tank. Do you think that this could work?

My reply: Several car companies (GM, Chrysler) offer a version of what you describe. It’s styled variable displacement or cylinder deactivation. GM was the first, I think, to bring the idea to market back in the (yes, really) 1970s with its V8-6-4. Early versions had lots of teething problems but today’s system operate pretty seamlessly.

Your expansion (had to go for that) idea is intriguing. It’d be interesting to experiment with the concept.

One of the issues you’d have would be figuring out how to deal with cold-start/higher (initial) load conditions. The variable displacement/cylinder deactivation systems in production shut off fuel to say half of a V8’s cylinders under light-load (steady cruise) conditions, when very little power is needed to keep the vehicle moving. But I am pretty sure you’d need the power of all eight to get moving – and until the engine gets hot enough to vaporize the steam in the inactive cylinders, you’d have an issue. It might require a pair of injectors, one for gas and one for the water, until the necessary temperature was achieved. And without spark ignition in the “off” cylinders, it might take awhile to achieve high enough temps. It might not ever get hot enough.

In other words, you might have some of the same driveability issues that the early variable displacement systems had.

Still, it’s something that’d be fun to play around with!

. . .

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  1. The engine I had in the Elco had water/methanol injection added to the mix. It allowed you to add a lot of timing without detonation resulting in more power and better mileage. That’s a 4300 lb dry weight vehicle with 3.73 gears and it would run well over 100 mph and get 12 mpg. I thought it was a dandy trade-off…..till the controller went apeshit and nearly drowned it. I still have the bright red reservoir tank that was mounted behind the grill. Everyone knew the vehicle on sight.

  2. There is no free lunch. Waste heat from an IC engine is more easily recaptured with a turbocharger- steam engines are specialized/optimized to work as they do- often dual acting and multiple stage. They can be more efficient than gas if you stack enough expensive hardware on top of them to recapture energy. Water or steam injection, if done right, is interesting. Haven’t heard much about it since the early 80s- it’s probably an analog solution to the problem of precisely controlling combustion when that is now done digitally.

  3. Probably not a gas engine, as the performance of gas explosion versus water evaporating would be too asymmetric. Maybe a diesel engine, as diesel burns more slowly. Water would have to be distilled/rainwater, as any contaminants found in normal drinking water (e.g. calcium and lime) would quickly become part of the cylinder walls. Lots of technical problems – water doesn’t play well with others.


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