Purpose of Energising time SOI correction in negative temp

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Re: Purpose of Energising time SOI correction in negative te

Postby ceecee » Thu Feb 03, 2022 1:45 pm

almetr wrote:The advice is correct, but the reasoning is wrong. I tuned such an old motor with a phased noise meter, and the offset of the pilot injection did not help, increasing the ramp helped a little, and a little early main injection (by 2 degrees) helped. The exhaust support (boot in the pipe) immediately calmed the detonation both in the version with stock injection and with early, equally


Well I didn't say about pilot, may be you refered other guy. Anyway pilot has big relevance (specially on engines with pilot-main). I can feel sound and smooth changes from little pilot tune on cold. Different labo studies say the same -> attached.

About phase noise meter is really interesting. What do you mean with exhaust support boot in the pipe?
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Re: Purpose of Energising time SOI correction in negative te

Postby almetr » Thu Feb 10, 2022 10:50 am

[ceecee my experience, in my "laboratory" is an Opel Vivaro, and I shared my experience with you, how by forcibly closing the exhaust pipe with a cork (the sole of my shoes), I got a reduction in noise at idle in the cold. I will clarify about the injection setting: but the quietest option turned out to be the pilot injection setting from the car manufacturer, my change in the phase and pilot amount only made it worse, apart from the fact that it became a little quieter from the main injection shift. This is what I reported earlier, just what is my experience with tuning in a pilot-main system.
But why does a demanding engine work smoothly with Reinforced EGR (forced exhaust boost)? For me, the answer is obvious - the injection process is accompanied by ignition without the disappearance of the flame until the entire cyclic supply burns out, which means that areas with an explosive fuel-air mixture do not have time to accumulate. A phased sound level meter helped me see this. When the engine is running quietly, all the noise falls before TDC and lasts a little beyond TDC, and when bubbling, the noise amplitude is increased just beyond TDC and lasts longer. That's why I disagree with your opinion "With the EGR off, combustion is faster and harder, because the pressure the temperature in the cylinder is higher."

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Re: Purpose of Energising time SOI correction in negative te

Postby ceecee » Thu Feb 10, 2022 1:09 pm

Thanks for explaining Almetr.
some comments...

forcibly closing the exhaust pipe with a cork (the sole of my shoes), I got a reduction in noise at idle in the cold.


Yes, when exhaust is blocked there are back pressure and engine breathing is blocked = lower clean air = lower recirculated dirty air = lower MAF/MAP read = lower injection and retarded injection = lower fuel injected and lower cylinder pressure = lower sound

but the quietest option turned out to be the pilot injection setting from the car manufacturer, my change in the phase and pilot amount only made it worse, apart from the fact that it became a little quieter from the main injection shift.


May be, usually manufacturer settings should be the best balance for street use, but not the best for consumption or performance. It's easy to get 3db up/down or 0,5L up/down. It depends on injector technology too.

But why does a demanding engine work smoothly with Reinforced EGR (forced exhaust boost)? For me, the answer is obvious - the injection process is accompanied by ignition without the disappearance of the flame until the entire cyclic supply burns out, which means that areas with an explosive fuel-air mixture do not have time to accumulate. A phased sound level meter helped me see this. When the engine is running quietly, all the noise falls before TDC and lasts a little beyond TDC, and when bubbling, the noise amplitude is increased just beyond TDC and lasts longer. That's why I disagree with your opinion "With the EGR off, combustion is faster and harder, because the pressure the temperature in the cylinder is higher."


Of course, with EGR ON combustion is smoother, cylinder pressure is lower and usually heat release lower, then combustion sound is lower, its one of the basics with recirculated gases as lower NOx, higher HC and so on. EGR increment delay up to 4 times and retard pressure and heat release various grads, noise always follow that, you can not has noise combustion without cylinder activity and with EGR it happens later and lower.

I attach tests from other well known engine 2.7 V6 CRDI Siemens.
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