Yes, some guys with twins are using blow-off valves. They aren't nearly as helpful on a diesel as on a gasser, since there's no throttle slamming shut, the turbo doesn't slow down as quickly.

 

Merrick did a great jbo of answering, so I don't need to type my standard 2000 word spiel again

Thanks, Merrick!


Justin

 

1. The lift pump supplies fuel to the injectors?Why not use a cheaper electric fuel pump, in-tank?

It's also my understanding that the diesel requires the lift pump because of the fact that diesel is a heavier fuel than gasoline. In order to get enough fuel for an even spray from the injectors, could this be part of the reason?

 

Oops, MCummings already covered that. Hey billg- thanks for those great sites!!

 

couple more questions:

Why do diesels take so darn long to warm up?

Is it wrong that i have one and i don't use it to tow or haul anything but just love to have a diesel?

Why are they so loud, is it the actual combustion process that is so loud. Is the diesel combustion similar to detonation in a gasser?

What would happen if you put regular gas in a diesel engine?

Why are the powerbands so small, why such a low rpm operating range?

 

I don't tow a whole lot either, I bought mine for economy and longevity. If you put ragualr gas in a diesel, you can kiss your injector pump goodbye, and thats if you'r lucky. The pump relies on the diesel fuel for lubrication. Without that, it will quickly destroy itself.
It is the combustion process that makes the noise. You're injecting fuel at several thousand psi into a 17.5:1 combustion chamber. Thats gonna make a little noise. The diesel combustion is very similar to detonation in a gasser.
The powerband is not that small. Our Cummins engine peak at 1600 RPM with 460+ lb/ft of torque, that doesn't drop off until about 3000. Your typical gasser, lets say a Chevy 350, will create its peak torque around 3700 rpm, and in most cases, that engine will be done making power around 5000 rpm. And you're only gonna peak with maybe 375 lb/ft. The diesel engine is designed for working hard, with long overhaul intervals. Hence the low RPMs, the lower the RPM, the less wear on parts. A gasoline engine is not necessarily designed to work as hard as a diesel, and will not last as long when it is required to operate at its maximum capacity for long periods.
HOpe this helps.
-Dave

 

A couple of more things to add to the gas in a diesel. Diesel has a higher combustion temperature than gas. This is why they run warmer than a gasser. If you introduce gas, into the hotter combustion chamber, it has a more violent explosion. It would be like trying to light a cigarette, with the blue flame in an oxy-cetalene torch. This, combined with the higher compression, destroys heads, pistons, and pretty much everything else inside.

 

1,000 pounds of cast iron vs. 550 pounds of cast iron for a gasser 5.9 liter = longer warm-up. Also the combustion temp is much lower during low power and idle than on a gasser, which means less heat transferred into the larger mass of cold iron and coolant.

I don't see anything wrong with it. I just drive mine back and forth to work. I'd drive a full size pickup anyway, so why not a diesel that gets better fuel economy and lasts longer?

Some of the noise is the knock from combustion. Also, the Cummins has solid lifters, so there's some valve noise. The injector pump is loud as well. The 2nd gen 24 valves have a pump that's almost as loud as the whole rest of the engine. Diesel combustion is more violent due to the high pressures involved, but it is not an uncontrolled explosion like detonation. Diesels can go into detonation, too - that's what happens when you feed too much propane into one.

Detonation, basically.

Mainly because we are so RPM limited at the top end. The big heavy parts needed to handle the high combustion pressures don't like to spin fast. If you think the powerband on your Dodge is narrow, the Cat in my work truck has 760 RPM between peak torque and peak HP. That's why I need 10 gears.

 

Somewhere in here somebody posted a link to a website detailing the world's most powerful and largest diesel engine. 1 cylinder has a displacement of 1800 cc (18L). It idles at 260 rpms and operates at somewhere around 600 (don't quote me on that). The bigger the parts, the slower it needs to turn to put out lots of torque.

Here's something to think about....next time you're near a dump truck in traffic, listen to see if it's a gas or diesel engine. Usually only the older dump trucks have gas engines...why? Because the gas engines have less torque and don't go anywhere very fast w/ a load of dirt or w/o...it took them a few years to figure out that diesels are better. A diesel dump truck can take off a whole lot easier than a gasser w/ the same load. Also, a lot of those diesel engines idle around 500 rpms and red line at 2000 rpms, and they're governed to around 1300 rpms so they don't self-destruct!