Bursting:

[McRat]

Bursting is the condition when the engine coughs, power goes to zero, then power starts up again. It is accompanied by WHITE smoke, which is unburned diesel fuel that has been atomized.

When it was first seen, it was thought to be fuel starvation, but what actually causes it is not enough heat to ignite the fuel that is being injected.

The way to stop it, is to:

1. Keep the air hotter.
   • Cold engine cools down the air.
   • Lowering the compression reduces temp of air.
   • Preheaters and glowplugs can heat up the air.
2. Shoot the fuel in later.
   Too much timing is the #1 culprit. Air is hottest at TDC (or shortly after) and that's the best time to shoot in fuel if bursting. But you need timing to make power, so it's a trade-off. A DSP2 tune for low compression engines can work wonders, or a program that aggressively pulls timing when water temp is low. The problem with the second option, is that if you are called to lanes, you might not have the water hot enough to make big power.
3. Shoot the fuel in slower.
   What would be really good with a Common Rail, is to change the size of the injectors while the engine is running. But we can't. So we reduce the pressure instead. This brings the fuel in slower, since you can "put out the fire" by spraying the fuel in too fast. As fuel atomizes, it cools the air. So less fuel cools the air less.

 

[messejme]

Have you been experiencing this problem, Rat?

 

[McRat]

For about 4 years.

At first it was seen when stacking boxes. Experts said the rail was being pulled down to zero. That's not what was happening though.

Nitrous guys saw it too, since nitrous cools down the air. They blamed it on too much nitrous, when retarding the timing could have fixed it.

Now we are running dual fuelers, low compression, delete glowplugs, etc, we are going to see this more and more.

 

[WolfLMM]

thart makes me wonder why GM is lowering the compression of these engines. I know that they are not tuning for all out power like us, but these engines are getting stronger by the year.

 

[McRat]

Lower compression = lower Oxides of Nitrogen, the diesel's worst enemy with emissions.

They needed to add an intake grid heater to compensate.

There is not much we can do with Item #1, except to know that when tuning an engine that has low compression, deleted glowplugs, no preheater, that we must keep fuel pressure a bit lower and timing less advanced in the drivibility ranges.

 

[duratothemax]

interesting, thanks pat.

my buddy's 05 lly acts really wierd with his aurora 5000 on the stock tune. If you are cruising along at 60mph in 4th gear, tow/haul on, and stomp on it as hard as you can, the truck backfires/pops, and you get a big puff of white smoke. All the bigger tunes are fine?

 

[McRat]

That's bursting.

 

[SIKDMAX]

That would make me reallllly pissed off Ben LOL.

 

[McRat]

To add to this, retarding the timing too much will cause bursting also. There is a Happy Spot where the heat is enough to ignite the fuel and keep it lit. If you spray too late, the fuel might light at first then get put out when the pressure drops after TDC and more fuel cools the air. Big boost will light fuel very well, and it's why we can and do run big timing with big boost.

 

[sweetdiesel]

Bursting is the condition when the engine coughs, power goes to zero, then power starts up again. It is accompanied by WHITE smoke, which is unburned diesel fuel that has been atomized.

When it was first seen, it was thought to be fuel starvation, but what actually causes it is not enough heat to ignite the fuel that is being injected.

The way to stop it, is to:

1. Keep the air hotter.
   • Cold engine cools down the air.
   • Lowering the compression reduces temp of air.
   • Preheaters and glowplugs can heat up the air.
2. Shoot the fuel in later.
   Too much timing is the #1 culprit. Air is hottest at TDC (or shortly after) and that's the best time to shoot in fuel if bursting. But you need timing to make power, so it's a trade-off. A DSP2 tune for low compression engines can work wonders, or a program that aggressively pulls timing when water temp is low. The problem with the second option, is that if you are called to lanes, you might not have the water hot enough to make big power.
3. Shoot the fuel in slower.
   What would be really good with a Common Rail, is to change the size of the injectors while the engine is running. But we can't. So we reduce the pressure instead. This brings the fuel in slower, since you can "put out the fire" by spraying the fuel in too fast. As fuel atomizes, it cools the air. So less fuel cools the air less.

Great info Pat!

Do you think that Timing ECT and Fuel Pressure ECT should be used to adjust this for water temps?

After reading this info,I think i might have been makeing changes in the wrong direction as far as ECT tables?

Thanks for posting this

 

[McRat]

Great info Pat!

Do you think that Timing ECT and Fuel Pressure ECT should be used to adjust this for water temps?

After reading this info,I think i might have been makeing changes in the wrong direction as far as ECT tables?

Thanks for posting this

Especially Fuel Pressure is sensitive on the hot rod engines. Cold + High Pressure almost guarantees bursting with low compression engines.