Today's diesel scene is very reminiscent of the end of the muscle car era. Much like in the early 1970s, manufacturers now have to meet stricter federal emissions requirements, which has led to the use of exhaust gas recirculation systems (EGR), lowered compression ratios in engines, and most recently, diesel particulate systems. Back in the day, car and truck owners simply removed EGR valves, catalytic converters, and smog pumps. However, today's electronically controlled engines present a unique challenge, and most will not function once these components are removed. Every technological marvel your new truck comes equipped with is essentially tied in with its emissions package. Now it's to the point that running any form of fuel other than ULSD (Ultra Low Sulfur Diesel) is risky and can leave you waiting for a tow on the side of the freeway. While the circumstances have changed and the situation is more complex due to modern electronics, people haven't changed. Aftermarket enthusiasts still want all power-robbing components removed from their vehicle.
This cutaway image of a diesel particulate filter shows the unique core pattern that exhaust gases are forced through before exiting.
WHAT WE ARE UP AGAINST
We all know how diesel particulate filters work right? Well for those who don't know, or need refreshing on the subject, we will explain. The DPF is trying to eliminate soot (unburned hydrocarbons from diesel fuel). The fact is that over time, soot and particulate matter (PM) build up in the DPF element, causing backpressure sensors mounted before and after the DPF to send a message to the ECU to enter an active regeneration mode. In active regeneration mode, fuel is injected during the engine's exhaust stroke, allowing unburned fuel to enter the exhaust and burn up the soot within the DPF. When this occurs, the heat created in the particulate filter often reaches more than 1,000 degrees F, turning particulate matter into a fine ash. You may have also noticed the oversized tailpipe on the new LMM Duramax or the twin outlet on the new 6.4L Power Stroke's exhaust. These exhaust tips are designed to draw cool air from underneath the truck to mix with the hot regeneration gases before they make their escape. This complex process in which additional fuel is used greatly reduces fuel efficiency in new diesel trucks, namely the 6.7L Cummins, 6.6L Duramax, and the 6.4L Power Stroke. In addition, the DPF element itself will need to be replaced at some point during the life of the truck due to ash buildup.
This photo shows the typical components of a DPF-equipped vehicle's exhaust system. The downpipe flows into the catalyst (1), then through the DPF element (2) and the muffler, and out the tailpipe.
OFF-ROAD USE ONLY
All aftermarket companies offering diesel particulate filter (DPF) delete kits are forced to specify that they are for racing applications only and are not to be used on public roads. Removing the DPF or any emissions equipment violates federal law and will void your factory dealer warranty. In addition, anyone wanting to purchase a delete kit will have to sign a waiver that makes the purchaser liable in the event of fines or civil punishments, not the aftermarket company. And unless you are present in the company's shop you are ordering from, you will more than likely have to print out the form from your computer, sign it, and return it before you can place your order. Gone are the days of simply entering your credit card information and receiving your parts a few days later.
THE PROS
Obviously, everyone wants to breathe cleaner air, and the latest emissions regulations have directly led to some of the cleanest diesel technologies we have ever seen. Through the use of EGR, catalyst, and DPF systems, drastically reduced emissions of nitrous oxides (NOx) and hydrocarbons have been made possible. In factory form, we as truck owners get the best of both worlds-clean-burning diesels with more power than ever before.
THE CONS
First and foremost, the active regeneration mode in new diesels leads to lower fuel economy. Second, when the power rating offered from the factory isn't enough (and for most diesel enthusiasts it isn't), adding a true performance exhaust system is something most power-hungry truck owners do first. Bolting on an exhaust system has never been so fraught with headaches. Conventional performance exhaust systems are no longer compatible. A diesel particulate filter system can't be replaced with a simple straight piece of piping. Besides entering a limp-mode where the truck's power will be virtually non-existent new tuning software is needed to complete the job. Not only is this an expensive endeavor, but as stated before, it will void your truck's factory warranty.