Return of the Opposed Piston Engine

The San Diego based Achates Power is bringing back the opposed piston engine. Diesel, of course, but they just showed off a gasoline version at the ARPA-E conferance last week.

Niama-Reisser, has also tried to do so, with the “one-stroke” toroidal engine. Sounds like a bag of hammers, but… cool as. I reckon you can’t scale up a toroidal engine… but that’s what the linear one is for.

Fairbanks Morse still kicking.


I’m a Fairbanks fan. I even like to help change pistons.

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As a cadet I did a few weeks on the Mobil Lube, a small bulk LO delivery boat in NY harbor. High point of that was delivering LO to an SL7 over in Newark or Elizabeth. Got onboard for a quick tour of the engine room too. The Lube had 38 5-1/4 main engine if I recall correctly. Think it ran out of Newtown Creek in Brooklyn. I guess Mobil had a lube plant there or a tank farm at least. Long time ago. Later as assistant engineer on a biggish tug for Crowley that had 38 8-1/8 mains (2). Too many exhaust leaks on that one, make yourself sick standing a watch. Like anything else, need to be given time and parts to take care of them but I had no complaints against them.


My first cadet vessel was trading at Bayway refinery in Elizabeth City.

Never yet had the chance to see an opposed piston engine in the flesh, and we hardly mention them in school. What you reckon? Will we begin to see more of them?

miserable oil spewing infernal machines! and the need to lift the upper crankshaft each time a liner or piston needs replacing just adds to the stoopidity of them. fine if it is a Navy vessel with dozens and dozens of 20 year old kids to do that grunt wrenching but no old man should ever be inflicted with such labors


Ah gee, I love those beasts. Ankle burning cylinder reliefs are awesome. You haven’t lived until you’ve slipped a vertical drive.


There are several projects running with small 100kw high speed dual crank diesel engines but I hear in the industry just about all small diesel engine development put on the back burner worldwide.

I remember sailing with these as a (Deck) cadet way back when; endlessly fascinating to watch.


Regardless of whatever experience you’ve had on these engines, you will not find many other engines with a higher power to weight ratio. One of the considerable advantages these engines enjoy.


The best thing about a Fairbanks OP is that it is the fastest and most reliable direct reversing engine that I’ve ever seen. Often faster than a reverse gear with clutches.

I don’t understand how any two stroke engine can meet Tier IV. I also have to wonder whether they have ruined the engine with too much unreliable and unrepairable-at-sea electronics.

On land, we have past the point where the life cycle cost of owing a computerized diesel in a small to midsize truck exceed the lifecycle cost of running a gasoline engine. Excessive computerization of Diesel engines has made them too unreliable and too expensive.

The price gouging on ultra low sulfur fuel has also had a negative economic impact.

all fine for a diesel electric submarine for which the engines were designed but I see no advantage to any other application

isn’t the Navy the only customer for these engines today who don’t have to comply with EPA regulations?

According to Fairbank Morse’s website, their OP’s are more efficient, have fewer components than comparable sized engines and are (or can be) Tier IV compliant. Plus 40,000 hrs between major service intervals. Interesting claims to be sure.

Just curious on my part, but just what is your experience with these engines?

I have sailed on several tugs that had OP engines and found they are horrible for low speed running…black oil blowing out of the stack all over the vessel plus they guzzle fuel…worse than an EMD

You just had to go Doxford. . . .

like 2 stroke outboards once dirty now E-tec cleaner than any 4 stroke

Once seen, never forgotten; but then I never had to work on them.

EMD makes a Tier 4 two stroke engine.

“The [EMD] E 23 meets US EPA Tier 4 Final and IMO III regulations, with Dual-Fuel options available and a Natural Gas option to come in 2017.”

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The EMD 710 Series E 23 — now EPA Tier 4 Final Certified.
I guess its real unlike European diesels that say they are but not really when tested.

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