Attn diesel guru's: How much fuel do we use idling? (1 Viewer)

[HZJ60 Guy]

i can honestly say i have never had a reason to run a diesel at idle for 3 days straight but if the need was there i would have no problem at all doing it.
bring the idle up to where you have decent oil pressure, at idle most of our Toyota diesels produce poor presure, even at 1200 rpm you have much better oil pressure.
as for glazing the walls, if the engine is burning the fuel being delivered and if you have the fuel setting properly set, why would the fuel wash the walls?

it is MUCH harder on an engine starting not plugged in cold weather than any amount of idling will do.

just my view of the matter.

If you'd have been on the Russian front with the German Army in WW2 like my dad was you'd have had reason to run ALL your engines 24-7! They never shut anything off!

 

[dieselcruiserhead]

I haven't read everything here but looks like it has been posted that idling will hurt your engine. Cummins factory manual suprizingly says 10 minutes tops! Very few diesels can produce the heat required to keep the diesel healthy at idle, coking, oil thinning etc are all by products. Plus it is bad for the environment. Here is a recent picture of lovely Salt Lake City. It is said that if idling was reduced by busses alone it could knock down something like 10-20% of our NOx emissions annually. Don't quote me on this but I seem to recall this off the top of my head.

 

[Behemoth60]

as for glazing the walls, if the engine is burning the fuel being delivered and if you have the fuel setting properly set, why would the fuel wash the walls?

Like you, I don't necessarily believe in the 'diesel fuel washing the cylendar walls' explanation of glazing. This, however, is a different and more understandable explanation of glazing due to cold idle. The article is in the context of new engine break-in, but I think the concept applies to all cold idle situations...

"Running the engine under very light or no load prevents the oil film placed on the cylinder wall from being scraped away by the expanding compression rings. The rings will instead “hydroplane” or ride over the deposited oil film, allowing it to be exposed to the cylinder combustion. The oil film will then partially burn on the cylinder leaving a residue that will build up and oxidize over time. Eventually this leaves a hard deposit on the cylinder wall that is very similar to the glaze left from flash burning."

They describe glazing thusly as caused by running an engine too hot...

"...the engine oil, lubricating the cylinder walls, will flash burn when it contacts the very hot rings. The burned oil will leave a hard, enamel like residue on the cylinder wall, commonly known as oil glazing. When the rings are permitted to operate under such high temperatures, oil glazing of the cylinder can happen very quickly."

Peter Straub

 

[brownbear]

Hey Peter, thanks for the info.

How about the excess soot at idle? I have seen chunks of crap in a cummins at work that idles all day.............BIG CHUNKS.

I am told the head will get lots of carbon build up. Plus our engine is on a bush road, so it never gets to giver hard to blow this junk out.

 

[nickw]

Hey Brownbear,

What would happen if you were to start runing that Dodge harder, until eventually you gave it a good work out? Would it clean everything out?

Just curious,

Cheers,
Nick

 

[Behemoth60]

Hey Peter, thanks for the info.

How about the excess soot at idle? I have seen chunks of crap in a cummins at work that idles all day.............BIG CHUNKS.

I am told the head will get lots of carbon build up. Plus our engine is on a bush road, so it never gets to giver hard to blow this junk out.

I don't really have anything to add to idle-soot thing. It seems reasonable, however, that with low exhaust gas speeds and temps, it will be easier for soot to settle all along the exhaust track. But that's just a guess.

Peter Straub

 

[dieselcruiserhead]

here is an example of soot and carbon buildup in my cummins. I don't know how much idling it did but the truck had about 146K miles on it when I got it. Don't know if the odo was reset when cummins installed it into the breadtruck in 1992. If it was not reset then this engine has ~70K miles is my guess, if it was then it has about 140K miles on it. But it was amazing how much buildup there was, on the cyl walls, top of pistons, injector tips, etc. Diesel really does collect and soot up and again, per factory manual, it says do not idle more than 10 minutes otherwise engine operating temp (even if coolant is at operating temp) drops too low to effectively burn without deposits. On injectors etc. So my $.02 on it...

Here are some photos from when I did a new head gasket. You can also see neat piston design - these pistons actually come just above the top of the block and into the head gasket area some. The head is totally flat of course. This means top of piston are within thousanths of inches from hitting top of head. Cummins sells a thicker headgasket to compensate for this if you have had machine work done. So, in this 3.9L engine (nearly 4.0L) -- it takes about 1L per cyl of air, that is already pressurized by the turbo to as high as 20-25psi, and compresses it into the tiny little space bored into the middle of the piston here. Talk about pressure... Hence the obsurd compression ratios of diesels. I guess this is normal for diesels, this was my first time doing a head gasket on a diesel. It makes sense of course...

 

[lowenbrau]

Cool pictures. Now imagine an indirect injected engine with all that air getting squeezed up into the precup by the flat top piston. No wonder precups fail!

 

[Tapage]

Cool pictures. Now imagine an indirect injected engine with all that air getting squeezed up into the precup by the flat top piston. No wonder precups fail!

you thought ...

 

[dieselcruiserhead]

wow I never realized it was all squeezed into the precup. Yes no wonder they fail.. All makes sense interestingly enough...