Haulin_in_Dixie

Ok I did a lot of work with racing over the years and understand the operation of an engine pretty good. There is one thing that I do not understand about a diesel engine though. Advanced timing on a gasser gives a longer burning pattern, where the spark comes sooner thereby igniting the fuel sooner and haveing a longer period of time before the valves open. On a diesel the timing of the injectors is basically the same idea. Injecting the fuel sooner should ignite it sooner but this is not obviously the result. Why does earlier timing cause more smoke? The same amount of fuel is injected, just sooner which should increase the duration of the burn. But that would cause less smoke.

We have those on here that fully understand the engineering and can answer this. I really want to understand the difference.

apwatson50

I don't see how just advancing the timing will increase smoke.

Haulin_in_Dixie

It does though, more advance, more smoke.

gunracer1

on my truck more advance gets less smoke, and lower egts. mine has been at 11.5,16.5 and now 20.

HOHN

Yeah, I was was also wondering why HID thinks more timing means more smoke.

Now, if you advance it TOO FAR, then yes-- you will have GOBS of smoke, crappy performance, and less boost.

I don't see how bumping from 15 to say 18 would increase smoke, though.

Maybe someone could explain WHY it increases smoke, if in fact it does.

jlh

BigBlue

An EZ is a timing only box, right? If it is, then that's proof right there that advanced timing (at least on the properly valved engines ) increases smoke. If not, then I don't know.

Forrest Nearing

it has to do with piston speed... as piston speed increases, you need the ignition event to occur earlier so that you can get a complete burn and push down on the piston instead of still having fuel burning as the piston is headed down (or on the way back up on the exhaust stroke! LOL!)

it can cause more smoke down low and a nice rattle as the combustion process meets the piston on the way up

but more timing generally cleans up higher RPM WOT smoke

JStull

But an EZ can add fuel at various boost levels (different settings) It can't fuel beyond stock vp44 limits, but it can do it a lot sooner than stock.

J

G1625S

Maybe it's something to do with the lower boost that comes with advanced timing. Since starting the fire sooner leads to more heat in the combustion chamber and less in the turbine housing, boost generally goes down. Boost down with the same amount of fuel, even with a more efficient burn, may lead to more smoke guess it depends on the ratio of burn efficiency increase vs boost drop. Just a thought.

greg

JAFAW

http://dodgeram.org/tech/dsl/FAQ/timing.htm

Copy the above address it explains timing pretty good

signature600

Haulin...by more smoke do you mean at WOT or down in the peak torque region???

More timing will increase smoke at peak torque, but decreases smoke overall...I think the link above tells you this too!

Chris

roadranger

The EZ is both timing and additional fueling...

It adjusts 3 positions to control when MAX fueling turns on, in relation to boost pressure.
There is always a smaller percentage of additional fueling going on in all 3 positions.

So, this is NOT a good example of how increased timing can create smoke....

Haulin_in_Dixie

Ok the fact that it increases at peak torque is established and is well documented. The question is how does it create more smoke with a longer period of time to burn.

apwatson50

Advancing the timing will shorten the combustion event, retarding the timing will lengthen it and increase your EGT's

putzer

advancing timing puts fuel into the cylinder earlier. In a diesel it is the heat from the air being compressed that ignites the fuel, if you put it in too early the air temp will not be enough to ignite it properly. on the same token, retarding your timing too far willl produce similar results, the engine may run but will not be very efficient. these are extreme situations but it does happen. you see crazy things when you are a diesel mechanic for a living,