Sequential turbo information

[graywolf624]

it is less likely to ignite before it was planned (pre-igniton/knock/detonation)

to explain this better for our less technically inclined.

When gas or diesel is ignited it travels on a front.. aka a line that slowly progresses along the area.
Preignition.. is when the gas not on that front(beyond it) ignites due to heat. (causing an uneven burn)
In a diesel engine.. the ignition is actually done by pressure and heat.. while gas is done with a spark.

The benefit obvious from diesel besides btu content is the efficiency at 0 due to the unrestricted airflow by the way.

Just clarifying.. you seem to be doing a good job of describing.

[adamk24]

do you know the reasons for the large soot emissions in teh transient response of diesel engines. I guess it is due to the lack of instantanious boost pressure at rapid throttle pedal changes, and therefore the fueling is equivalent to that RPM at full boost rather than that RPM at whatever boost is specific at that moment in time.

Well actually, although that IS the reason (some of the time) the anwser my diesel pad instruction would give is no. Heres why.
In most modern diesel engines designed for large trucks and heavy equipment they have sensors to monitor things such as boost pressure, atmospheric pressure, injector pulse width etc... they can adjust fuel to follow what ever conditions the engine is currently running under, not just following a pre-determined fuel map, like most automotive engines. But yet, when you get in a diesel and step on it, it shoots out black soot. Why? Well basically these systems do not work as good as they claim to, and despite the sensor shouting at the ecu "Uhhhh.... we dont got boost yet idiot, lay off the fuel!" it tends to have a slow reaction time. So, yes, its because the engine expects boost, but it takes it a while to realize that it doesnt have it, but by then the turbo is spooled and everything works out.
The real question I have is why does it take so long for it to figure out that it is over fueling? I will ask my diesel instructor tomorow and see what he says, but logic would tell me that if a computer can adjust the spray of fuel, messured in milliseconds, over 100 times during a spray no longer than 15-30 milliseconds, then why does it take it over 1/2 a second to turn down the spike of fuel

[Wutputt]

Originally Posted by adamk24 but logic would tell me that if a computer can adjust the spray of fuel, messured in milliseconds, over 100 times during a spray no longer than 15-30 milliseconds, then why does it take it over 1/2 a second to turn down the spike of fuel

Maybe the response time of some of the sensors used to determine the exact amount of fuel injected is quite slow when there are some bigger changes, like when you suddenly step on it.

It's just a guess.

[coombsie66]

U find out nything more adamk24?

[adamk24]

Yeah I talked to my instructor last week and basically what he told me is that they pre-program an intentional overfueling when you mash the gas before the engine is at operating temp for two reasons.
First to help with faster catalitic converter light-off, and also to give a margin of safety to prevent underfueling when switching to the new higher load % fuel map. Basically that means injecting more fuel before retarding injector timing to help prevent detonation. (because the injector timing is what helps prevent detonation in a diesel). If there is anything else that you need to know about turbo systems or diesels feel free to ask