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I can't remember exactly what it was with the 2-stroke diesel pollution issue. I know there was SOMETHING that was a big issue.

Non-turbocharged detroit 2-strokes don't have perfect cylinder evacuation. Adding a turbo will definately blow the cylinder out, though.

Also, something like 40% of the friction of a 2-stroke is involved with turning the blower.

To change the subject completely, you know what I would like to see? A decent-power diesel in a Jeep Wrangler.

camshaftprelube wrote:Non-turbocharged detroit 2-strokes don't have perfect cylinder evacuation. Adding a turbo will definately blow the cylinder out, though.

Are you talking about spark-ignition?

2-stroke diesels have to have some kind of supercharger; they're not self-aspirating.

EGR is a common way of countering NOx in any lean-burn type of engine, be it gas or diesel since it's an easy way of bringing more hydrogen and carbon to the party without punching in more fuel.

2-stroke diesel would pollute more than a 4-stroke of the same size simply by means of having twice the power strokes per revolution, therefore burning more fuel. Just to be anal.

Steve

Steve - Not in terms of emissions per mile though.

2-stroke diesels do have higher BSFC-per-hp numbers than 4-stroke diesels.

And yes, I was talking about diesels back there. Even though they have a blower on the engine for cylinder evacuation, it doesn't get it all out. A turbo on top of the blower makes this problem much, much smaller.

This according to my diesel textbook, which is five years old and probably outdated a little now.

Why is that? Less required rpms allowing higher gearing?

Steve

I can't make my arguement sound right. Stupid textbook says 2-strokes use more fuel per horsepower, but don't say why, dancing around the differences between the two designs, like shorter effective strokes, blower drive losses, crap like that.

I still agree that 2-stroke diesels kick ass.

Much of the information we have in the US just isnt correct. Our deisels suck becuase development stopped. Look at the popularity of diesel in EU. They have solved many of the problems and our technology has been left in the dust.

evolutionmovement: Not correct. If you have double the power available you only need to open the throttle half as much. The amount of energy extracted for the gallon of fuel is nearly the same

camshaftprelube: Modern superchargers have very little drag compared to the power produced. On a normal gas engine many even have a bypass which use more like 2% to turn.

So my argument only applies under full throttle - but you'd make more power than a 4-stroke at that point, too so the efficiency would actually theoretically be better anyway ignoring pumping loss differences that I'm unfamiliar with. Cool. I assume these could rev higher, too, so they would make more hp as well as torque. Must require a fairly substantial cooling system.

Did anyone see the Monster Garage where they made a trike from a semi? I thought it would be rediculous, but when they were done I wanted to drive that thing so bad.

Steve

Acording to the textbook again, up to 30% of a 2-stroke diesel's cooling is accomplished by the scavenging of the cylinders by the blower.

Still need a big radiator, though.

But it blows in compressd air, which is heated. Fuel itself is a good cooling agent, but that doesn't factor in either as it's such a lean burn and is ignited so quickly anyway. The high combustion pressures themselves would also add heat.

I hope I don't sound argumentative as I'm just figure this thing out. I never even knew there were 2-stroke diesels before and it sounds pretty cool. Diesels in general are new to me and I've only just become interested in them maybe this past year due to the things I've been reading about them doing with 4-stroke cars in Europe.

Steve

You should look at the specs of the TDI Jetta Wagon. That has to be one of the coolest commuter/family cars available. Too bad it doesnt get the bigger engine!

Or the 6-speed...

Yeah, not to love VW, but they have turned their direct injection tech to gas engines, too.

But anyway, did you see the diesel V10 for the Phaeton and Touareg? Everything's going diesel there. It's getting so they don't have the best mileage anymore as they move towards maximizing performance so people will buy them, but the torque is incredible and the mileage still isn't bad considering. The engine's likely longevity would pay for itself, too.

Plus if the world goes to hell, it'll likely only be diesels and freaks like me who'd build a steam car that would be able to get around.

If I only had the money to experiment with a turbo diesel conversion to a Subaru closed-deck turbo block...

Steve