Syndacate

I know this is a honda forum...but this forum is a "FI in general" forum. I'm talking about diesel turbo trucks, like the ram 2500 cummins diesel. I know for diesel engines it's better to let them idle for say 20 minutes, than to turn them off and turn 'em back on 20 minutes later. Though when you do that w/ a turbo, it's not like a gas engine where at idle the turbo's off, on a diesel the turbo's still spooling, but slowly, so oil gets built up in there. Then when you nail it and put it into OD, you get that big puff of smoke out the back (which is normal). I was j/w why this happend? I heard it was b/c of the turbo spooling at idle and it bunches up the oil then when u get on it hard it expells all that oil out the exhaust...but if it did that, wouldn't the smoke be blue? Seems in your rear view mirror it's more of a black/greyish color. Can anybody shed some light on this.

Yes I searched, no I can't find anything, because it's a scenario (after it's idling) opposed to just "smoking."

Thx in advance.

93supercoupe

U dont let the engine idle to drain the built up oil, but to circulate and cool the oil in the turbo.Even gas motor's turbos are still spinning at idle.


The black smoke isnt oil, but fuel.Im not exactly sure why, but remember, theres no throttle plates on deisles.The only thing that controls RPM is the amount of fuel be injected.

SOHCD16y8

Its really just from a tune that is not very refined. I remember reading an article about the Banks Power 800hp road race truck that does not smoke at all. They had a ton of time into tuning it to eliminate the richness so it sould not smoke, therefore allowing them to race with other trucks without it being a hazard. The quote I remember most was that the smoke is "Power you can see but not use"

awdgsx96

That, and I don't know if this is relevant to the topic or not, but diesel engines don't have spark plugs. They use a glow plug which is only used to help start the engine and than it's straight compression after that, correct?

matt k

the smoke is fuel diesel motors love fuel its very easy to make power by just adding fuel thats all most of the aftermarket boxes do

wantboost

iTrader: (2)

diesel fuel contains parrafin wax. run it too rich and you get the lovely black smoke which is caused by an incomplete burn... know how when you put something near a candle and it disrupts the flame and you get that sooty smoke?
diesels are sheer compression motors, they use compression to ignite the air/fuel mixture. when you get it too rich it burns too cold, which is what causes the smoke

dave@passenger

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by wantboost &raquo;</TD></TR><TR><TD CLASS="quote">diesel fuel contains parrafin wax. run it too rich and you get the lovely black smoke which is caused by an incomplete burn... know how when you put something near a candle and it disrupts the flame and you get that sooty smoke?
diesels are sheer compression motors, they use compression to ignite the air/fuel mixture. when you get it too rich it burns too cold, which is what causes the smoke</TD></TR></TABLE>

NO. The more fuel (rich if you would like to call it) the hotter your egt's are. The smoke you see (opacity) is merely unburnt fuel. The puff of smoke you see is excessive fuel that is being wasted, it usually goes away as the boost climbs and more air enters the cylinders. Smoke is the result of dumbass american style tuning. I build some of the highest hp vw diesel engines in North America, and they do not smoke.

Syndacate

Alright, maybe I was wrong, that's why I posted here. I'm not talking about idling to let it cool off or anything, it's just better to let a diesel idle than to turn it off then start it back up. Opposed to a gasoline engine where just the opposite is true. I for some blah reason the oil builds up in the turbo from the feedline, and all gets expelled/burnt out when you nail it. I was j/w why/how. It's probably just dark blue to the point where it appears black. A T-Diesel won't jet black smoke if you just nail it into OD (well at least not as much as it will ifyou let it idle for awhile). I heard it's b/c of the oil bunching up...so how does it get expelled?

blundar

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by dave@passenger &raquo;</TD></TR><TR><TD CLASS="quote">NO. The more fuel (rich if you would like to call it) the hotter your egt's are. The smoke you see (opacity) is merely unburnt fuel. The puff of smoke you see is excessive fuel that is being wasted, it usually goes away as the boost climbs and more air enters the cylinders. Smoke is the result of dumbass american style tuning. I build some of the highest hp vw diesel engines in North America, and they do not smoke.</TD></TR></TABLE>
You seem like you have more than half a clue. I've been doing some research into diesel tuning lately, maybe you can confirm/correct some of the conclusions I've come to.
1. Most modern diesels are compression ignition, direct-injection. This means that fuel is directly injected into the cylinder at/around/after the motor reaches TDC on the compression stroke.
2. Diesels have turbos in order to put more air in the cylinders. Diesels can run at much higher PRs than gas motors because there isn't a strong possibility of preignition/detonation (assuming relatively good cylinder emptying at the end of each cycle / complete combustion) because air is compressed without fuel present.
3. Given a fixed amount of air (displacement/boost level) there is a relatively fixed amount of fuel that can be burnt. Fuel beyond that point causes EGTs to rise (fuel still burning as it leaves the motor) and sometimes "smoke".
4. (??) Injection timing plays a role in how much fuel can be burnt by giving injectors longer to fire with advance. Injection timing too far retarded makes for poor power output and increased EGTs. Injection timing too far advanced ???
5. Larger injectors overcome limits of injection timing

School me