Oil & Fuel General diesel question

[RobJ]

As you press down on the "gas pedal" (or raise the lever) on a diesel, you are actuating a complex bit of machinery that increases the length of the stroke of each hydraulic ram, resulting in more fuel delivered to each injector.

Actually the gas pedal on a diesel is really called a speed control. And that complex bit of machinery is a simple spring and governor weights. This setup is still used today. Instead of weights on some small diesels like mine, it's a two pronged looking spring.

This is also why diesels are so well-adapted to turbochargers, as their exhaust gas temps are considerably cooler than on a gas engine, resulting in less stress on a turbo's bearing as well as on the oil.

Pretty sure exhaust temps run higher on a diesel. This heat helps gets things movings.

 

[RobJ]

Are you saying that the flyball governor is a computer of the analog flavor?

Never thought about it in that light, it may stretch the bounds of "computer" a bit.

hehe, a bit?? Everest is a bit of a climb.

 

[RobJ]

Boy, lots of comments. Some with repeat info, others clarifying an answer from a question, etc.

One thing not mentioned so far is combustion chamber design in diesel engines. Close 3 decades ago when I was reading up on diesel engine design, there were at that time 5 combustion chamber types, each with their own operating characteristics. Some designs permit high speed (close to gas engine speeds) operation, others that permit low compression ratio's not much higher than was common 20-30 yrs ago in gas engines. I seem to recall the Perkins in my MF was something like 15:1 and 10:1 wasn't that rare in some gas engines. Some designs require glow plugs for starting on a cool engine and other don't. Again, my perkins didn't have glow plugs.

Combustion chamber design plays a big part in how a diesel engine operates/performs. As has been stated several times, in a gas engine speed is controlled by the amount of air entering the engine. With diesels you control fuel.

Personally think the biggest problem here in the States when it comes to diesel engines is owner resistance. With self-serve refueling being the norm, owners don't want the stinky-oily mess to get on their hand and into the car.

I was hoping for a primer on the 5 different types. I know of 2 basic designs. direct injection and indirect injection or pre-combustion chambers. indirect injects the fuel into secondary chanber that flows into the main chamber. this allows extra time and air movement better mix and burn the fuel more effeciantly. These are used in mines, etc. They did not have the power of a direct injection. I think they were also lower in compression...it's been a while. Combustion chambers design slightly differ, the goal is to swirl the air more to get a better fuel/air mix.

 

[john_bud]

I know my old fords just have a dead flat head with 0cc combustion chamber and then a pocket in the piston. I would like to have the spare $$ to design a set of pistons with tumble inducing topology machined into the piston to promote more thorough combustion. Ahh, the fun you can have with money.

Everest a bit of a climb? More of an evening constitutional.

Oh, I think you will find that gasoline engines have a higher potential exhaust gas temperature. From memory, I think the diesel hits about 1800F max and the gas can get to 2400F max. That's typically done by mistake with too lean of tuning and results in long term reduction in compression ratio.

jb

 

[Soundguy]

Are you saying that the flyball governor is a computer of the analog flavor?

Never thought about it in that light, it may stretch the bounds of "computer" a bit.

This kind of thought reminds me of the mechanical difference engine.. IE.. a hand-crank mechanical calculator

soundguy

 

[ccsial]

Analog computer....Yeah, I'd say so.

It processes a frequency and controls a volume. It can be programmed by a mechanical adjustment or shim. It fits the definition.

 

[irvingj]

Pre-combustion chambers... my ol' 504D had the "highly efficient Ricardo pre-combustion chamber" according to info on the beast; looked like a cross between an ear canal and a vaginal tract, but I guess it worked.... that is, until it got overheated and one of them developed a teensy crack in it.... ended up replacing the head. And then the coolant overflow jug. And then the heater core. And then the..... amazing what a little diesel compression pressure can do once it gets into the water jacket!

 

[SnowRidge]

Analog computer....Yeah, I'd say so.

It processes a frequency and controls a volume. It can be programmed by a mechanical adjustment or shim. It fits the definition.

But it doesn't.

The term computer comes from compute, which means to determine something by mathematical means. In the case of a mechanical fuel injection pump, all the computations were done by engineers during the design process. The pump itself doesn't compute anything. It is nothing more than a bit of precision machinery that operates in an entirely predetermined manner and delivers the correct amount of fuel according to the position of the throttle and the engine speed at any given moment. The amount of fuel for any given combination of RPM and throttle position having been previously computed by the engineers.

 

[N80]

But it doesn't.

Agreed. Complexity does not make something a computer. A traditional mechanical alarm clock or a stop watch can be complex, but they do not compute anything.

 

[Soundguy]

I may have to disagree.

You can have a mechaincal 'computation' due to programmed variables.

Difference engine - Wikipedia, the free encyclopedia

Furthermore, the next step up from the difference engine was the analytical engine.. which is described as a mechaincal , general purpose computer, and an importnt initial step in the history of computing.

Analytical engine - Wikipedia, the free encyclopedia

Also.. google 'castle clock'.. it was made in 1206 and is widely accepted as the first programable analog computer. Note there were mechancal calculatng devices much earlier.. like an abacus and astrolabe...

soundguy