Long storkes, under-square conditions(morb|d is right!), and sparkless ignition created by unreal compression ratios... these things tend to slow crank rotation, but the long stroke gives torque out the booty. Diesel burns at a slower rate than gas too - it's like the difference between magnum powders(slow burning) and regular powders(faster burning) if you are into shooting pistols/rifles. Slower burn rate makes it difficult to achieve complete combustion during the expansion stroke, because the period(time) of that stroke decreases as crank speed increases.

Or so I'm told!

 

ah, hadn't considered the slower burning rate of the diesel.

btw, if it's a long stroke it's usually referred to as "under-square". and it's less a factor than you might think.

 

I believe this might have something to do with diesel fuel producing more power from the same volume than gasoline.

Diesels, nowadays, are produced for a single purpose - torque, and not horsepower. For horsepower you spin the engines fast. For torque, you don't need to spin them fast. So the quest for torque dictates the design/properties of the engine.

For large TQ you get large displacement (as you pointed out in another thread). For trucks, it is about 975 ci - which is a lot of engine to spin at high RPMs. Cylinder/rod load increases exponentially with increase in RPM, and these engines last 1,000,000 miles - for longetivity, revving it low is also good. TQ usually means towing - you do not want to stall right off the line - you want as much power off the line as you can get, otherwise you'll be burning your clutch plates.

Most diesels are also using turbos. If you take a look at gasoline turbo cars, such as the ones offered from Audi, their peak torque arrives at a whopping 1850 RPM, and stays until usually 5000 or so and then drops. So the design of the turbo is a factor, and in diesels it is to create good environment for towing/drivability.

Having said that, would they be able to produce a high-revving diesel engine for pure horsepower, such as Nascar? Everything indicates that they should. Shorten the stroke (by a LOT), increase piston size. The question is, has this been tried? And why are they not in use in race cars?

 

i think what's hold back diesel's HP numbers are other limitations which are difficult to overcome rather than the configuration or "tune" of the diesel engine, like stroke/displacement. I wanted to know if anyone had insight into what those limitations might be. the burn rate of diesel vs gasoline fuels in particular makes good sense (if true). also, i was mainly talking about passanger diesels, not truck or locomotive engines. it goes without saying why those engines would be setup the way they are.

 

I'm partial to Vancouver myself. It's just that I have a problem with an area where the bars have to close at 1!

 

That's the understatement of the year ... at least in my area we are a mecca for university students. Makes for an interestly night life. Guionm ... bars here don't close early ... if you ever find yourself lost on the North Atlantic, give SharpShooter_SS and I a call. We will treat you to some Maritime hospitality.

A round of Lobsters for everyone!

Ted

 

The only thing you guys got there is Coors Light....

 

If it makes you feel any better, Pacer, I'm stuck in Michigan right now. I think you got the better end of this deal .

 

Where in Michigan?

 

Dee-troit. And I forgot my handgun.

 

You can borrow one of mine.

If you're still in Detroit, and I manage to escape in the next day or two, let's meet up for lunch or something.

 

Sounds good . I'm probably leaving tomorrow though.

 

here's some food for thought... I was out on Michigan's Silver Lake Sand Dunes (dirt biking/four wheeling) today and there were about 8 H2s out there. My friend asked one of them if they were part of a Hummer club or something... the response: we are from GM [and he proceeded to punish it up the biggest sand dune]