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Hey all, I am attaching some interesting reading from GM's SI. From the Description and Operation of the Exhaust Aftertreatment System section:


Normal DPF Regeneration
Over time, the soot trapped on the cell walls acts to restrict exhaust flow through the DPF reducing its effectiveness as well as reducing engine efficiency. This restriction in exhaust flow produces a pressure drop across the DPF that increases as the once porous cell walls become saturated with trapped soot. A DPS monitors the pressure drop across the DPF and provides the ECM with a voltage signal proportional to soot buildup. Once soot buildup reaches a specified limit, (usually around 22 - 25 grams) as signaled by the increased pressure drop across the DPF, the ECM commands a regeneration event to burn-off the collected soot during normal vehicle operation. Regeneration events occurring during vehicle operation are known as normal regenerations as they occur automatically and without driver knowledge. In general, the vehicle will need to be operating continuously at speeds above 48 km/h (30 mph) for approximately 20–30 minutes for a full and effective regeneration to complete.
The frequency of normal DPF regeneration is a function of the engine run time, miles driven, and fuel consumed since the last regeneration event. Under normal operating conditions, the normal DPF regeneration is initiated after approximately 85 gallons of fuel used or a maximum distance traveled of 2009 km (1250 miles.) To initiate a normal DPF regeneration event, the ECM commands additional fuel via post-injection in order to create the additional exhaust heat in the DOC necessary to promote regeneration and burn-off the collected soot.
During regeneration exhaust temperatures may exceed 550°C (1,022°F) due to the rapid catalytic combustion of soot within the DPF. Conversely, under low engine speed or light loads, exhaust temperatures may be too low to promote proper regeneration. To protect the DPF catalyst from thermal damage due to excessive soot combustion or from sulfate poisoning at low temperatures, the ECM monitors EGT sensors upstream and downstream of the DPF during regeneration. If the vehicle is slowed to idle speed during a normal DPF regeneration, the engine may maintain an elevated idle of 800 RPM until the DPF is cooled to a calibrated temperature.
Should the EGT sensors indicate that regeneration temperatures have exceeded a calibrated threshold, regeneration will be temporally suspended until the sensors return to a normal temperature. If regeneration temperatures fall below a calibrated threshold, regeneration is terminated and a corresponding DTC is set in the ECM.
Under most conditions, the soot collected within the DPF burns off during normal regeneration cycles. Periodic regeneration prevents the buildup of soot from reaching a level where its burn-off could produce damaging high temperatures within the DPF. Vehicles operated at prolonged low speed or low loads where normal regeneration does not occur will eventually reach a high soot load condition. When the increased pressure drop across the DPF is detected by the DPS, the ECM illuminates the DPF lamp in the instrument cluster and sends a Clean Exhaust Filter message to the driver information center (DIC). The owner manual diesel supplement describes how the vehicle should be driven in order to enable normal regeneration.
 

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The CTD idles at 800rpm all the time so Im confused by the statement calling that elevated
The CTD also does not have a post fuel injection system. I am guessing that this is possibly a Duramax writeup? However, it is likely very similar in fucntionality to ours.
 

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The CTD also does not have a post fuel injection system. I am guessing that this is possibly a Duramax writeup? However, it is likely very similar in fucntionality to ours.
I wonder if that's just a poorly worded way of saying post combustion injection (exhaust) stroke but yeah I'm familiar with the actual injector pre-dpf that the duramaxs have and it might just be written for that.
 

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Discussion Starter · #6 ·
That is exactly what it is saying. Post-injection is fuel being injected after a main injection. In our case the injectors are dumping additional fuel into the cylinders after the main combustion injection to raise the temperature of the DPF to burn off the soot. As mentioned some vehicles have additional injectors in the exhaust system such as GM's trucks.
 

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The post mentions the DPF lamp, in 42,000km mine has only illuminated once at around 6,000km and never since, although occasionally when I park the engine fan roars for a while, even in winter.
 

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Does it mention anything about the 30 second window I discovered, when it starts the regen process (evident by a reduction in manifold absolute pressure to vacuum levels), but the regen indicator is not on yet, and if you shut the car off during this period it can clog the DPF?
 

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Does it mention anything about the 30 second window I discovered, when it starts the regen process (evident by a reduction in manifold absolute pressure to vacuum levels), but the regen indicator is not on yet, and if you shut the car off during this period it can clog the DPF?
I don't think the US Cruze diesel has the light. I have the Australian built Cruze which has a different engine.

View attachment 172657
 

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I don't think the US Cruze diesel has the light. I have the Australian built Cruze which has a different engine.
off topic but i really like your engine cover more so then ours in the USA
 

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off topic but i really like your engine cover more so then ours in the USA
Even though my car was the first diesel in Cruzetalk, the engine is a newer design with chain driven cams. I bought it new 3 1/2 years ago and it has been great. I also don't have DEF so I can carry a full size spare. When touring in australia there many cell black spots so a spare really is necessary so you won't get stuck miles from anywhere.
 

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our eco tech cover looks cheap and the style is off. i hate that gm made our diesels belt drive and gave that POS 1.4 turbo chains... so the more expensive motor gets cheaper components? i don't mean to call out the 1.4 but man was the belt on the 2.0 a bad decision
 

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They used an existing engine and altered it to meet the US emission standards so I suppose that the newer engine wasn't ready when they started designing the extra gear that it carries. The engine in mine is actually the second generation diesel in the Australian Cruze, the earlier 2009 - 2011 engine was a 4 valve single cam belt driven design. The turbo was at the back of the engine and it looked quite different.
 

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Hmm interesting.i know we are single belt drive cam and the other cam meshes with a mechanical gear at the rear of the cams. It just gets me why any one that's designing a diesel motor starts with " lets make it belt driven"
 

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Hmm interesting.i know we are single belt drive cam and the other cam meshes with a mechanical gear at the rear of the cams. It just gets me why any one that's designing a diesel motor starts with " lets make it belt driven"
The US diesel isn't a new design, it is an engine that was used in Europe for some time and altered for use in the US and DEF was added.
 

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I understand that but what gets me is when the engine is being originally designed why belt drive not chain?
 

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yes that's very interesting and ive seen it here before, but im wondering from a engineering stand point why when the engine was being drawn up did they choose belts not chains. only upside i can see is less parasitic loss since a belt is not as heavy as chains
 

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yes that's very interesting and ive seen it here before, but im wondering from a engineering stand point why when the engine was being drawn up did they choose belts not chains. only upside i can see is less parasitic loss since a belt is not as heavy as chains
They may have used belts to reduce noise, although the engine in my car, while obviously a diesel is still fairly quiet mechanically, it seems to just be the injectors that are a bit noisy.
 

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with today modern direct injection and high pressure common rail noise of the old diesels are long gone, plus the cruze diesel has tons of insulation
 
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