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Old 01-12-2015, 09:45 PM   #1
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New Engine

Here's an interesting new engine from Renault. Both turbocharged and supercharged ... and 2 stroke. The crystal ball is always interesting.


Renault doesn't sell any vehicles in the U.S.—unless you consider some Nissans that share a global platform—but there's a reason this tiny diesel from France is interesting: it gives us an idea of how internal combustion engines will evolve under pressure to increase relative output and efficiency at the same time. The humble two-stroke might be the engine of the future. What's old is new again, right?

Renault is a major small-diesel manufacturer, and it seems likely that with what the company calls the "POWERFUL" (POWERtrain for FUture Light-duty vehicles) concept, it might be first out the gate with a small two-stroke diesel for passenger cars.

y design, a two-stroke diesel is power-dense, with a power stroke every other revolution, and inherently cleaner than a gasoline two-stroke. A major drawback is a narrow powerband. And "clean" is relative; emissions and economy standards in Europe and North America are extremely exacting for diesels. Several companies are trying to meet these challenges and produce a two-stroke engine suitable for a light automobile, but so far none have come to market.

The POWERFUL is half the size of the company's basic 1.5-liter cDi turbodiesel passenger-car engine; it weighs a full 88 lbs less, and in its current form is capable of making 48–68 horsepower out of just 0.73 liters. The POWERFUL uses both a supercharger and a turbocharger, just like other twin-charged engines. For comparison, depending on tune, the 1.5-liter cDi makes 64–110 hp. And it's not merely a 1.5 cDi cut in half, because that engine is a four-stroke diesel.

That being said, Renault's not happy with the performance of POWERFUL yet. Further development is required before it's ready for prime time. France is reconsidering its love affair with diesel as we speak, but perhaps tiny two-strokes will show the way forward.
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Old 01-12-2015, 10:49 PM   #2
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More info: Renault Unveils Two-Stroke Twincharged Diesel Two Cylinder - Engine Builder Magazine
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Old 01-12-2015, 11:03 PM   #3
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Interesting how they eliminate the turbo lag at low speeds w the supercharger. My 2014 Jetta could benefit from that.
As I recall some of the late high output DD were twin-charged.
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Old 01-12-2015, 11:55 PM   #4
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"a two-stroke diesel is power-dense, with a power stroke every other revolution"

Wait a minute. What? Is it a two stroke or a four stroke
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Old 01-13-2015, 12:01 AM   #5
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Good Catch😊, that's still amazing horsepower out of less than a litre. I wonder how long of a service life you could expect out of an engine...


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Old 01-13-2015, 06:34 AM   #6
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The wave of the future seems to be a direct injection engine that burns Diesel (or kerosene or JP) but uses spark to ignite , not compression.

This gives the efficiency of using denser fuel , with out the structural requirement for compression ignition.

For their size they will probably have a long stroke to obtain every erg from the fuel..
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Old 01-13-2015, 10:46 AM   #7
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IMO those engines are intended for light duty and not suitable for boats.
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Old 01-13-2015, 10:58 AM   #8
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Bayview,
All our "marine"engines are of various levels of light duty and not designed for boats. But your'e probably right. I can't imagine my 1.8L Jetta engine (170hp) putting out a continuous 125hp. But I'm sure heavy duty engines would be built following this example. And the "Powerful" is not even near the production stage yet.
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Old 01-13-2015, 11:41 AM   #9
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Eric:

I would modify your statement to say that all automotive diesels are light duty and aren't really suitable for boats. It think that Yanmar proved this with their line of BMW based BY engines.

But construction, 18 wheeler and even pickup designed engines do well in boats. But you can't take one of the automotive engines that is putting out up to 100 hp per liter and run it at two thirds load and expect it to live very long.

Automotive diesels operate at about 15% average load so they have a very different operating environment than boats. Autos need high hp for only a few seconds at a time- passing, entering a freeway or just impressing the auto testers. Boats need it most of the time.

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Old 01-13-2015, 11:57 AM   #10
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It's called "duty cycle". Very different in a motor vehicle, boat, industrial application, etc.
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Old 01-13-2015, 12:44 PM   #11
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But that's what we're running. Engines built for vehicles on the road. And some for generators and tractors. Both the latter in my case. In our world there are no marine engines. In 1950 there were many marine engines both gas and diesel. "Many" may be open to debate though. Marine engines frequently had a cast iron oil pan that included the gearbox and a flywheel mounted on the front of the engine where it probably sill belongs.
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Old 01-13-2015, 01:01 PM   #12
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Genset applications?
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Old 01-13-2015, 01:05 PM   #13
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This Renault is a different bird. Two stroke diesels typically have some ports on the liner for air intake, with exhaust valves in the head, e.g., Detroits, EMD, freighters. Or both intake and exhaust handled via ports and no valves, e.g., Polar NOHAB, Fairbanks OP, earlier single acting Fairbanks, other early stuff.

This thing has no ports on liner so no issues with lube crossing into process air. It has intake and exhaust valves like a four stroke, but the cylinder is scavenged by both sets of valves opening around bottom dead center and air being blown through the cylinder to chase the exhaust out. Not an easy task to do that, air will want to short cycle from inlet to exh valves and avoid going down into bottom of cylinder where some exhaust wants to hide. Requires clever shaping of ports and timing, etc. Probably short stroke, too. Side benefit is you get some free EGR!!

The articles make a statement about 2stroke reaching 50% thermal efficiency, and four stroke car diesels struggle to get 35%. Well they are comparing 2stroke SHIP ENGINES to little car engines. The efficiency of the ship engines does not come from them being two stroke, but by their size, slow speed and other engineered features.

Efficiency of a little 80hp 2stroke will likely be very similar to a little 80hp 4stroke.

Annoying reading those articles. Very little tech discussed. What was discussed was often wrong, misleading, shallow, etc.

One article spent more words discussing what kind of hat an engineer wore than actual tech details, like how the thing is scavenged, which is the critical element of the design. I only concluded the scavenging method from putting little bits together from a few sources. Modern journalism. ppfffft.

Rant off.

Cool idea. Big hurdle to get that thing to breathe right, though.
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Old 01-13-2015, 05:22 PM   #14
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Greetings: January the month of dreams. The French have always had a way with engines. The following site provides a real insight into their engineering skills.


http://www.engadget.com/2014/10/03/citroen-airflow-2l-concept-hands-on/?utm_source=Feed_Classic_Full&utm_medium=feed&utm_ campaign=Engadget&?ncid=rss_full&utm_content=gravi ty_organic_sitefeed&cps=gravity

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Old 01-13-2015, 08:42 PM   #15
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Ski,
Very informative post and much increased focus look into this very experimental engine. It will probably come to nothing along w lots of other experimental engines but new experimental mechanical stuff is always interesting to me and I wanted to share.
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Old 01-14-2015, 07:51 AM   #16
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In the future is may be that car engines will be more useful in boats.

Both gas and diesel have optimum power loading and the car of the future will probably be a hybrid .

It will operate at its 100% efficient speed with a CVT to the wheels.

Acceleration or hill climbing will be augmented with the electric drive, cruise will see the engine power generating electric for batt storage.

The GPS will know the road grade ahead and switch back and forth between engine drive and battery power.

The engine ,when operating will always be at 100% , so if that amount of power is what the boat needs it will work fine.
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Old 01-14-2015, 11:41 AM   #17
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I agree FF but I don't think the hybrid will be in existance very long. As soon as batteries are up to the task internal combustion will be out. Anyone's guess when that will be though.

But then would you run a propane car w/o a backup? Not much difference than an electric car. I suspect pure electric is coming fast. But hybrid would stay in boats longer for obvious reasons.
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Old 01-15-2015, 07:31 AM   #18
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" As soon as batteries are up to the task internal combustion will be out. Anyone's guess when that will be though."

THe world has been waiting 120 years with little progress so far.

Simplest efficient storage still seems to be a flywheel . Running in a vacuume at turbo charger RPM, re spin would be over an induction pad , no getting out to plug in.

The downside is the liars for hire as in a crash a fly wheel with 10-20 gal of gas worth of energy would be a problem.
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