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An Achates Engine is Hitting the Road

An Achates Engine is Hitting the Road

RE: An Achates Engine is Hitting the Road

Love your comments (you might be a cat guy but you're a top dog) but that was a year ago. Have there been any updates?

RE: An Achates Engine is Hitting the Road

Diesel Progress had an article in the latest issue, apparently there were some delays is regards to permitting and CARB. I did ask someone I know at Southwest Research, seems the expectations keep changing. The truck is supposed to operate somewhere in the central valley according to what he knew, I expect after some road time there will be some public info on how it worked out.

This release from Achates is more up to date, https://achatespower.com/achates-walmart-launch-op...


RE: An Achates Engine is Hitting the Road


The Achates Power engine, which is based on architecture initially considered and then rejected back in the 1930s, demonstrates as much as a 30% fuel efficiency improvement compared to other diesels, with comparable or better emissions and cost.
I wonder who rejected the architecture? Junkers certainly went into production.

je suis charlie

RE: An Achates Engine is Hitting the Road

As did Tilling-Stevens, Leyland, Rolls-Royce, Coventry Climax, Fairbanks-Morse, and many others. . .

RE: An Achates Engine is Hitting the Road

If the rate of expansion has benefit, OP expands twice as fast.

This is much more promising than the other engine designs that try to maximize torque by increasing mechanical advantage of the crank.

This design made the rounds while I was in college.


Funny thing, college taught me about thermodynamics and what goes on in the cylinder doesn't really care about what goes on under the cylinder. Expansion ratio determines everything.

RE: An Achates Engine is Hitting the Road

As you alluded, the rate of expansion does not affect the cycle analysis, on paper. However, it might affect the reactions and hence the effective expansion ratio, beneficially or otherwise, depending on the fuel and overall combustion recipe.

"Schiefgehen wird, was schiefgehen kann" - das Murphygesetz

RE: An Achates Engine is Hitting the Road

The rate of expansion matters if heat transfer matters ... which it does. The opposed-piston layout has the theoretical advantage of the geometry of an extremely long-stroke cylinder, which has a better surface-to-volume relationship in the part of the cycle where it matters the most (near max compression).

I still have doubts about how significant this will be, and I still have reservations about the effect of piston-porting on emissions due to engine oil unavoidably getting involved in the combustion process.

RE: An Achates Engine is Hitting the Road

turbo motor: Actually I did; the Commer engine was designed at Humber in Coventry in the early 1950's, but manufactured by Tilling-Stevens in Maidstone, and typically ended up in Rootes-Commer trucks.

Regrettably, I failed to mention my favorite OP engines: the Napier Deltic and the Doxford marine engine.

RE: An Achates Engine is Hitting the Road

Ah, the Napier Deltic was an amazing machine, worked on a pair in a converted yacht, the chief engineer on the vessel had been working on Deltics since they came out as marine engines in England.

Here is a pretty interesting YouTube on the Deltic if anyone interested, https://www.youtube.com/watch?v=-vV-YaKsIGk


RE: An Achates Engine is Hitting the Road

I don't think much will come of this, it just doesn't fit into the electrification of vehicles plan.
So is there any news on this engine?

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