Mafia Secrets
Straight stacks for newer rigs? What’s up?

By Bryan Martin

Well, sports fans, this is most definitely one of the “top five” frequently asked questions here at Chrome Shop Mafia HQ. When our friends in Washington mandated all the emission changes, the aftermarket exhaust providers had to completely reinvent the wheel when it came to jumbo chrome pipes.

Since trucks will now be sporting those sexy diesel particulate filters, called DPFs, it isn’t enough that you have to deal with more operating costs, poorer fuel economy, and more downtime in the dealerships getting your exhaust filters cleaned. No, you have some pretty tough obstacles to overcome regarding the beloved, and highly sought after, straight pipes.

High heat: Exhaust gas temps went from an average of 500 to 900 degrees to well above 1,000 degrees. Since traditional chrome plating starts “bluing” after constant exposure to temps above 750 degrees, this was the main issue in designing new pipes.

Fortunately, in 2010 with the introduction of the diesel exhaust fluid, exhaust temperatures were decreased somewhat. However, they are still well above the temps that our pre-2007 trucks operated at.

New exhaust connections: For decades, all exhaust piping was connected using band clamps. You know the type. Slide one pipe inside another. Then wrap a thin 3-inch or 4-inch wide band clamp around it, tighten down the two bolts on the clamp and watch as the thin metal stretches around the connection to quickly and cheaply seal it off.

These band clamps were available at every truck parts store from here to Timbuktu for under $10. Life was easy, and one style of clamp worked for just about every truck on the road.

Once the new emission standards kicked in, the exhaust elbows went to a “Marman flange” clamp style where they connect to the DPF. This clamp would remind you of the same style that holds your exhaust pipe to your turbo charger. It requires very specific piping with the proper flanges, and allows virtually no room for fudging or using generic piping or flexible pipe.

Changes, changes, changes: Since the early versions of DPF trucks were somewhat trial-and-error, there were many changes in DPF locations on the chassis. That led to piping changes and updates as the OEMs tried to make the emission systems function more efficiently. Each change required a different exhaust elbow, which led to many variations. So offering a set of chrome pipes to fit all Peterbilt 389s was an impossibility. My, how times change.

Our friends at Lincoln Chrome and at DynaFlex have engineered exhaust kits to accommodate Peterbilt 389s from 2008 to 2013.

Stack Kits for your 2008-2010 ½ Pete are available in 7-inch or 8-inch diameters. Kits for the 2010 ½ and newer are only available in 7-inch, as the clearances around the elbows won’t allow for the fat 8-inchers.

Lincoln Chrome exhaust kits use jumbo elbows that feature their Never Blue technology and include “one piece” stacks that totally eliminate the possibility of any exhaust leakage around the top-mounting clamp, due to the deletion of this extra connection.

DynaFlex Exhaust kits employ their Air Kool technology. The double-walled piping uses a Venturi design that draws cool air in at the bottom of the elbow, pulls it upward as it travels through the double walled area of the pipe, and shoots it out at the top of the stack. The movement of the cool air through the outer wall of the stack cools the outer pipe, which pulls the exhaust gas through the stack at a higher velocity than would otherwise be obtained with the cooling.

Both Lincoln and DynaFlex Peterbilt exhaust kits for these late-model 389s are year specific to ensure the correct elbow configuration and allow for a trouble-free install, so have your year model and, in some cases, VIN number available when you call to order your pipes.

OK, OK, OK, Kenworth and Freightliner owners: Don’t shoot the messenger. There are no exhaust kits “in a box” developed for your trucks yet. Not to say that jumbo pipes for KWs and Freightliners are a no-go. But at this point each truck would need to be evaluated individually because a good deal of fabrication, modification and test fitting would need to be done per each truck.

Both Lincoln and DynaFlex have design plans in the works for Kenworths and Freightliners, but it will likely be 2013 before production is completed.

In closing, I’m not saying these are the only two pipe brands out there. I am sure other exhaust manufacturers out there in this big ol’ world have stack kits available for late model trucks. These two brands are the ones I am familiar with and can speak for with confidence.

Lastly, let me make this declaration: Change isn’t waiting on me or you to endorse it before it moves forward. Regardless of what we think is best, change keeps on truckin’ at a high rate of speed. So we don’t have to like it, but I reckon we better climb aboard, suit up, strap in and make an attempt to ‘roll with it’ as best as us ol’ truckers can. C’mon?  LL