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What happens when you make a two-degree timing adjustment on an L5P? Diesel legend Gale Banks invited Duramaxtuner.com's Nick Priegnitz and Paul Wilson to California to find out.
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Diesel and Fuel Economy - A Brief Article on DOC and DPF
Most of the 2007.5 and newer light duty and medium duty trucks are equipped with a Diesel Particulate Filter (DPF) and Diesel Oxidation Catalyst (DOC). The DPF is designed to filter particulate matter better known as soot.
Here is a quick break down how it works. DPF, diesel particulate FILTER. Yes this is a filter. It is a serviceable item. As the truck is running, the DPF is filtering and trapping the soot or particulate matter. Eventually by the use of sensors and programming, the engine management computer on your truck will sense and calculate when the DPF needs to be cleaned. On vehicle cleaning is called regeneration. These vehicles will give you a warning or a check engine light will be illuminated.
Regeneration is the process of burning soot. As the truck runs and the computer management system monitors the calculated amount of soot, the DPF has collected, the program will come to a conclusion when a DPF needs to be regenerated.
At this time the truck may display a message like DRIVE UNTIL CLEAN. The regeneration process better known as an ACTIVE regeneration will wait for the exhaust to be warm above 350 degrees F. The programming of the on board computer will command post injections to allow the piston in the exhaust stroke to push fuel into the exhaust where it will meet the DOC. The DOC will chemically react with the fuel in the exhaust and become very hot. This heat can exceed over 1000 degrees F. This high temperature will burn the soot in the DPF and convert it to ash.
Here is the interesting part, in order to run an active regeneration, the programming will command the fuel injectors to inject fuel into the cylinder as the piston approaches the exhaust stroke. Yes, fuel is being dumped into the exhaust to create an active regeneration!
Since fuel is sprayed into the cylinder it isn't surprising to see that a bit of this fuel can migrate around the piston and rings. Depending on temperature this fuel can become carbonized around the rings due to frequent regenerations. (see picture above left). This can be verified with engine oil is diluted and finding that the oil level is overfull above the mark on the oil dipstick.
If the piston rings are saturated with fuel in time they become full of carbon. Sticking or stuck piston rings can lead to lower compression and poor fuel economy. Customers will notice more engine blowby or crankcase gases.
Our technicians at Las Vegas Diesel LLC can help alleviate this issue by running a stationary regeneration using factory software and running a cleaner through the crankcase to bring back compression and lower crankcase pressure.