PART FOUR: EXHAUST BRAKING AND FLUID PERFORMANCE
You have that 35-foot stock trailer in tow, loaded down with fattened calves headed for the auction, but a couple long 6% grades stand between the farm and the sale barn. This Ultimate Working Heavy Hauler project has come a long way from its stock days but there are still a few parts needed to really dial this truck in perfectly for the hard task at hand. While it already has the extra power needed thanks to the Duramaxtuner.com EFI Live engine and transmission tuning, keeping a heavy load under control on the downhill still creates some concern as the factory brakes have gotten hot a time or two in the past. Since this truck seems to always have a big trailer attached to it, trying to combat high fluid temps in the rear axle and maintaining optimal fuel quality to the Duramax’s injection system are important things that need to be addressed.
To avoid riding the factory service brakes down long, winding mountain passes, the addition of an exhaust brake can not only increase the life of your brake pads and rotors, but bring a little piece of mind when you’re behind the wheel hauling a heavy load. While Tow/Haul mode and the previously installed Tapshifter has helped with towing performance by helping maintain the optimum transmission gear while towing, over-revving the engine on a steep downhill is still possible when all that weight is pushing you from behind.
The addition of the BD Diesel exhaust brake system can safely cut downhill speeds without you ever having to touch the brake pedal. Maximum braking power can be experienced through the air-actuated, exhaust-mounted butterfl y valve that restricts exhaust fl ow and increases drive pressure within the engine to better maintain a safe engine RPM and vehicle speed. By tapping into the truck’s speed sensor, cruise control and throttle position sensor, the truck can still run and function as it did before adding the brake, but offer great hold-back power when engaged. The brake will automatically disengage at speeds under 15 mph for smooth stopand- go driving. Exclusive variable orifi ce technology and the offset butterfl y creates the best of both worlds with optimum braking when closed and maximum exhaust fl ow when open. Its tough cast iron housing and stainless steel shaft and hardware will also help it hold up to the heaviest abuse and harsh road conditions.
HIGH FLOW MANIFOLD
An often-overlooked but worthwhile upgrade for the Duramax power plant is the high fl ow BD Diesel replacement driver side exhaust manifold. The factory exhaust manifold on the LB7 Duramax creates an unneeded restriction in the preturbo exhaust stream, which really affects turbo performance. The stock driver manifold fl ows just 80% of that of the passenger side manifold; this difference causes an imbalance between cylinder heads and creates unneeded heat build-up preturbo. By eliminating the restriction and maintaining a constant internal bore size matching the passenger manifold, a more effi cient exhaust fl ow can be fed to the turbocharger to allow for better control of exhaust gas temperatures and exhaust back pressure, in turn allowing for an increase in power and engine effi ciency.
MAX FLOW FUEL PUMP
The LB7 Duramax platform has been plagued with injector failure issues for quite some time, so much so that GM had extended a warranty period for up to 200,000 miles on the injectors. A lot of these issues stem from fuel contamination and debris getting through the injection system. The factory CP3 also must do a lot of work to keep the engine running effi ciently, as it has to pull fuel clear from the tank on its own before pressurizing the fuel to 20,000+ psi for the common rail system. To improve the longevity of the fuel system and hopefully avoid expensive replacement parts and repairs, the BD Max Flow lift pump kit was bolted on to offer additional fi ltering plus a lowpressure fuel supply to feed the stock CP3.
The gerotor design within the pump can fl ow 150 gallons per hour for enough fuel supply to support up to 600 hp. While this truck is most likely around 400 hp in the highest EFI Live tune, power potential wasn’t the real reason for the Max Flow system. The optional 30-micron water separator fi lter and 3-micron high-fl ow spin-on post fi lter will help keep contaminants and debris out of the CP3 and fuel injectors. The ultra-quiet and compact system is easy to install and ties into the stock fuel feed line, so there is no need to drop the fuel tank. An additional advantage to the aftermarket fi ltered system is the expensive and problematic OEM fi lter can be bypassed all together, making fi lter services much less expensive and easier to do.
In heavy towing conditions, the rear axle goes through a lot of strain. With the massive amounts of horsepower and torque that Duramax engine can produce, transferring it all to the tires can generate a lot of heat within the rear axle housing. These metal axles, ring and pinion gears will wear with time and put extremely fine metallic debris in the gear oil, which can affect the longevity of the parts.
The addition of a performance BD Diesel differential cover can kill two birds with one stone: reducing fluid temperatures via its cooling fins and oil deflector to keep oil on the ring and pinion gear, and a magnetic plug that will also trap those small metal particles and keep them from being passed through the gears to reduce wear over time. Increasing fluid capacity and keeping that fluid cooler helps extend fluid life and increasing reliability within the axle, even under the heaviest of loads.
In Part 5 of this build the truck will gain some additional load control with a set of bolt-on Hellwig rear suspension airbags and a massive sway bar kit. The cosmetics will also see some improvements with a new set of Ultra Wheels and General Tires for better on- and off-road performance. Building the Ultimate Working Heavy Hauler may take some work and the perfect list of parts, but the end result will be worth it, we promise.DW