You can do this in Gretio but it only works so as long as the phone is hooked up.I remember the early days of VW TDI engines when you could use VAG-COM software to turn down the EGR flow to where it was minimal. It wouldn't trigger a CEL and the flow was so low that the intakes of the engine would never clog up.
You mean like sharp Diesel clatter in cold ambient temperatures?this can cause sound problems warming up
*some problemsYou mean like sharp Diesel clatter in cold ambient temperatures?
That's not an unexpected side effect. The EGR cooler bypass is there to feed more of that hot exhaust gas into the intake during cold starts. You want hotter intake air so you can get reliable, stable combustion when the fresh air intake temperature is cold.
It's a similar trick that Mazda uses in their Skyactiv-D engines with 14:1 compression ratios - the variable valve timing keeps the exhaust valve open a bit after the exhaust stroke so the intake stroke sucks some of that hot exhaust gas back into the cylinder to mix with the fresh air intake charge. It raises temperatures to get those cylinders lighting off better when it's cold.
We used to just have 21:1 compression ratios and those engines could crank and fire in almost any temperatures without glow plugs!
yes. it is topside and easy to change the egr valve. I looked at the instructions on alldatadiy.com a while back - factory service manual info is on-line. The egr cooler on the other hand - that looked like a bit more work.Anyone have tips for removal, inspection, and cleaning of the EGR valve? It's topside on the engine, right? A fairly easy job to do?
The EGR cooler was replaced under warranty. I don't recall the exact mileage, but it was maybe 25,000 miles or around there. It was some CEL codes that the GM technical HQ said replace it, and it was a new part number that presumably has some changes made to it. A few other people here had that done.The egr cooler on the other hand - that looked like a bit more work.
I think it's a fine balancing act and the engine flip-flops between EGR cooling depending on needs.On these small diesels the EGR is basically the only way we can retain heat.
The idea of egr emissions wise is having some inert gas (inertish) for combustion heat to mix into.Then, when everything is running at temperature you want the EGR to be cooled as much as possible so that you can have it cooler when being fed into the intake for lower combustion temperatures for lower emissions. High levels of NOx are formed with high combustion temperatures so you want a lean intake air mixture to lower combustion temperatures, and you have to cool that EGR gas down to lower intake temperatures as much as possible.
Lastly, I'm not 100% certain but I believe the EGR is entirely bypassed when the DPF is going through a regen cycle. You want the hottest exhaust gas possible to heat that DPF up, so the EGR is closed off to make sure the cylinders get the cleanest intake air possible for high combustion temperatures. Those high temperatures are then spiked a little bit more with some extra fuel injected during exhaust strokes to bring the DPF up to temperatures that burn the soot off. NOx probably spikes during regen, but the EPA gives waivers for temporary engine operating conditions that are rare and limited and don't often happen. DPF regen is where it has to be done and NOx output is allowed to be higher to make that happen.
To regenerate the DPF you have to heat it up really hot. You want in-cylinder combustion temperatures to be as high as possible, and to do that you need 100% clean intake air so the EGR doesn't quench the temperatures with inert gases. Then, you are also injecting excess fuel to heat it up even more, and you need as much O2 as possible for that extra combustion. Lastly, you want the soot in the filter heated up as much as possible to combust and flow out the exhaust as CO2, and for that you need extra O2 so the carbon (soot) can combine with that and flow through.Anyway yes EGR shuts off for most of a Regen. I don’t exactly know why