Lean??

[GreenF350]

So I saw the post about "can you get too much air", and the guy building the 2 filter intake and the not so certain responses, that is what sparked this as I have been wondering for awhile. Coming from gas engines I have always wondered, can a diesel run too lean? If it does, will it damage anything? I know on gas engines that is a good way to put a hole in the piston, especially with a turbo or nitrous. After reading and learning I have NEVER heard anyone ever mention that you could damage anything running too lean. Since there is no throttle plate, it would seem to me that they are running lean at idle. In fact, I distinctly remember an article in a Diesel Power awhile back that said the only danger to running nitrous was that the power was easy to come by and addictive and you could easily overcome the HP threshold for the engine. (Not exact wording) SO, true or false....You cannot damage a diesel by running too lean.
-Aaron

[vitalidle]

Well the way the turbo diesel works if you don't get the fuel to turn the turbine you won't get any boost, so yeah you would seriously lack some go juice if you ran lean seems to me. Im sure one of the techs will chime in with a definate answer.

[vitalidle]

Here is a good article Diesel-Central.com the technical source for Diesel Truck information, Truck Pulling, and Drag Racing

[ABOBB]

While gasoline (and other spark) engines are throttled on air, diesels are throttled on fuel. What this means is that the amount of fuel that is metered into the engine controls rpms, power, etc... not the amount of air.

On a stock, or even a fairly wild street, diesel engine it is highly unlikely that you will do damage due to a lean condition.

Highly modified diesel engines however can do damage. That is the reason why you almost always see them spewing a lot of black smoke. They are using the excess fuel to keep things cool.

[GreenF350]

Allright, thanks everyone. I guess that answers the "$64,000 question".
-Aaron

[cotton]

vitalidle is joking, right?



"Highly modified diesel engines however can do damage. That is the reason why you almost always see them spewing a lot of black smoke. They are using the excess fuel to keep things cool."

I was under the impression that most modified diesels blow black smoke because of the delay in providing air to the fuel supply. In other words, the turbo doesn't spool fast enough to offset the quick increase in fuel.

[vitalidle]

Originally Posted by cotton

vitalidle is joking, right?



"Highly modified diesel engines however can do damage. That is the reason why you almost always see them spewing a lot of black smoke. They are using the excess fuel to keep things cool."

I was under the impression that most modified diesels blow black smoke because of the delay in providing air to the fuel supply. In other words, the turbo doesn't spool fast enough to offset the quick increase in fuel.

Hey cotton I didn't write that article so like Ronald Reagan said you can trust but you must verify. So thats up to you to decide if its valid or not

[GreenF350]

Ok...So on a side note and for the sake of argument. Why are my EGT's so much cooler with my wastegate disconnected? Somewhere in the range of 300-400* at full throttle? I know the theory about more of the fuel being burned inside the cylinder instead of the burn being in process as the exhaust valve opens. But if being lean can (not necessarily will) damage the internals. Wouldn't that mean that EGT's would be higher with the same amount of fuel but more air? For instance, if 1500* EGT's can weaken pistons to the point of breaking ring lands, etc. Shouldn't a leaner engine with it's hotter combustion temps show a hotter EGT? The temps can't cool that much after the burn, right?

Sorry to be asking so many ""stupid questions, but I have been listening, reading and learning stuff for about a year (Since i bought my truck) and I am finally asking some of the questions that have been rattling around in my head for awhile. I am a "I need to know WHY something is the way it is, not just that that's the way it is" person.

[vitalidle]

Originally Posted by GreenF350

Ok...So on a side note and for the sake of argument. Why are my EGT's so much cooler with my wastegate disconnected? Somewhere in the range of 300-400* at full throttle? I know the theory about more of the fuel being burned inside the cylinder instead of the burn being in process as the exhaust valve opens. But if being lean can (not necessarily will) damage the internals. Wouldn't that mean that EGT's would be higher with the same amount of fuel but more air? For instance, if 1500* EGT's can weaken pistons to the point of breaking ring lands, etc. Shouldn't a leaner engine with it's hotter combustion temps show a hotter EGT? The temps can't cool that much after the burn, right?

Sorry to be asking so many ""stupid questions, but I have been listening, reading and learning stuff for about a year (Since i bought my truck) and I am finally asking some of the questions that have been rattling around in my head for awhile. I am a "I need to know WHY something is the way it is, not just that that's the way it is" person.

Well this is pure speculation on my part but if your wastegate is disconnected your talking about the red pressure line right? That means your going to build more boost or the turbine wheel is going to spin faster which in turn makes the compressor wheel go faster which will pull more cool air from the intake which will cool the egts. If the wastegate is connected and it opens the opposite will happen you will have the same amount of fuel going to the cylinders but not as much air to cool them