Staged Diesel Performance

Nov 29, 2009

At this point, it is becoming old news that modern diesel-powered trucks are capable of impressive towing weights, while having the acceleration of a mildly expensive sports car. What is not always common knowledge is what an installer’s best upgrade path recommendation to their customer should be. Certain supporting components are often needed to ensure that the performance is delivered effectively and with the most sustainability.

So how does a diesel truck owner who needs to adhere to a budget effectively upgrade their vehicle in stages while keeping dependability in-mind? This article will cover adding base components to a completely stock truck, through midrange modification for towing and hot rod street driven trucks.

The Red Pill Or The Blue Pill?

The simplest point for a tuning shop to begin with a performance diesel customer is to interview them about what it is that they intend to do with their truck. Will this truck be strictly a tuned-up tow rig? Will the truck be used as a hot rod street driver or maybe even have some competition usage? Based on the customer’s intentions, the upgrade path can vary depending on the year/make/model of the truck. The continuing evolution of such things as fuel system types and computer controls has led to a wide array of available performance products.

Base Components For Power Building

A few initial modifications are similar between the different brands of trucks. Improving airflow and reducing restrictions in the intake and exhaust are key factors in maintaining durability. One of the most popular starting points for truck owners is to upgrade the exhaust system. This modification increases the pipe size from what is usually around a three-inch diameter to either four or five inches. Depending on the kit, this also may mean changing from the factory aluminized material to a stainless steel. This offers a stronger and more corrosion-resistant material.

On trucks that are factory equipped with catalytic converters, it is often a matter of installing a CAT-back style exhaust in order to conform to emissions requirements. While it may not be a magic bullet for fuel enhancement, the exhaust does allow the motor to breath more easily, which makes for some improvement. According to John Glasgow of Performance Diesel in South Carolina, using this springboard for other upgrades is a proven method that works very well.

“We will first recommend air, exhaust and fueling enhancements. The majority of our clients are more interested in fuel economy,” says Glasgow.

Although most customers of performance aftermarket shops will typically upgrade at least a few more items beyond the intake and exhaust, there are some that never venture beyond that point due to worries about their factory warranty. Many shops such as Alligator Performance in Nevada say that the majority of their buildups are not too extreme.

Alligator’s Chad Hall says, “In our area, the ratio is about 95% (of truck owners) that stick to the basic components: intake, exhaust and tuner. The other 5% is a mixed bag of in-between parts, from transmission upgrades only, to full-blown race motors.”

Hall’s primary starting points include a higher volume air intake kit by either S&B Filters, or aFe (Advanced Flow Engineering), along with free flow exhaust by MBRP or Magnaflow. One unique quirk of upgrading a Ram is the fact that the exhaust manifold tends to wear out over time and eventually develop cracks, which robs horsepower and can have adverse effects on exhaust gas temps. Trading out the stock design for a higher durability ported manifold is an important step.

With an air intake and exhaust upgrade in place, fuel enhancement can begin to be added. Dodge Rams with the 5.9L engine are some of the simplest trucks to upgrade. 1994-1998 pickups, which are powered by the 12-valve Cummins power plant, contain an all-mechanical fuel injection system. One of the easiest power upgrades involves replacing the stock cam plate inside the fuel injection pump with an aftermarket design. The replacement cam is shaped differently to allow expanded rack travel inside the housing which means more fuel output on demand. Access to the Ram’s motor on pre-2006 models is very open and straight forward when compared to the Ford and GM layouts, which makes the addition of larger exhaust and other upgrades somewhat less time consuming. This feature makes the Dodge a favorite candidate for upgrading by many shops.

On the mid-1998 and later Dodge truck the mechanical fuel/cam plate is replaced by electronically timed fuel injection. In the electronics department Hall says, “A smaller tuner, such as DiabloSport’s Predator, a Standard PPE Xcelerator, Bully Dog’s PMT, or Edge’s Juice with Attitude is on our list for a typical (tow only) build.”

Compared to electronic tuners for gas vehicles, that may add 20-25 horsepower increases at best, and diesel tuners can add over 100 horsepower to a truck! This level of torque increase is more than enough to cook a stock transmission or clutch and can damage stock turbochargers as well as other components. Customers need to be aware that they will not be ready to select the “race” or “extreme” settings on their box or programmer without further upgrades.

At this point, it is important to check the fuel pressure of the 24-valve Dodge. Many OEM “lift” or “assist” fuel pumps will be in a weakened state from normal usage and will need replacement. Typically, performance shops will opt to negate the lift pump altogether by installing a stronger aftermarket pusher pump, such as the FASS System.

GM trucks with the Duramax engine are substantially different from the earlier Ram and Power Stroke platform when it comes to powertrain component placement, and all use an electronically timed fuel system. Modifications dealing with electronics come into play almost immediately in the upgrade process. While they lack many of the similarities to the first and second generation Dodge trucks in the area of mechanical performance upgrades, the key base components are still needed. Opened intake, free flow exhaust and gauges (if not already built into a power module), are the best starting point. If the customer opts for a fuel controller or tuner immediately, warning them about using it safely is paramount.

Many Duramax owners seem to have a false impression about the abilities of their stock transmission. Television commercials and word-of-mouth have led many GM owners to believe that their truck’s geartrain is what would be found in a military battle tank. The automatic transmission that moves the Duramax down the road is arguably somewhat stronger in OEM trim versus the Dodge or Ford, but it can easily be overpowered and damaged with a simple plug-in programmer.

For many shops, the popularity and sale of electronics for the GM far surpasses that of the Dodge and Ford, and it would seem a rarity to find a Duramax owner who had not done some form of tuning enhancement. The ability of the latest electronics to interact with the parameters of the vehicle is nothing less than impressive. Tuning everything from the pulse width, duration and timing of the fuel injection to altering programming for tire/wheel size changes is possible by simply plugging in to the on-dash port with a handheld box.

A Ford Power Stroke’s upgrade path initially follows that of the Dodge and the GM trucks. Mid-year 1999 through 2003 7.3L trucks differ somewhat in the area of the turbo. Due to intake restriction with the turbo’s compressor housing, a surge or fluttering effect can occur with very minimal upgrades in power. Under throttle, the turbine wheel inside the turbo will try to out speed the compressor wheel, and it can lead to broken shafts between the two. This problem can be remedied by upgrading either the compressor housing to one that is a larger diameter with more aggressive porting, or by changing the compressor wheel model. For the 6.0 liter Power Stroke, many truck owners have run into issues in the turbo department relating to soot buildup in the variable veins of the charger or failed solenoids.

Before beginning upgrades on the 2003-2007 trucks, it is advisable to check the travel and actuation of the solenoid that powers these VGT veins. Issues here can cause headaches and tail chasing as more parts are added. If stickage is occurring with the VGT turbo, there are alternative packages which will upgrade the charger to a non-variable or “straight turbo” to eliminate this complication. Addressing the housing on the 7.3L or the complete turbo on the 6.0L will also help with cooler operation once other fuel upgrades are in place.

Up Another Notch -“ Towing And Mild Hot Rods

Chances are, your diesel customer will advance into the next round of upgrades. Most truck owners will need to advance past the mildest base components mentioned in previous section, whether it is for towing trailers or for mild hot rod power.

A common next step that makes equal sense for all three brands of diesel trucks is to upgrade the torque converter on the automatic transmission or the clutch for the manual. Upgraded torque converters will prevent clutch pack slippage with the increased amount of power. Billet components and reshaped stators for better fluid control are a common feature between most of the aftermarket units available. Lockup clutch designs vary somewhat based on brand and are an important decision depending on what the final power output of the truck will be. The majority of the higher-end performance aftermarket torque converters available now utilize a multi-disc lockup system. Different brands will use a different number of clutch discs and designs, and this will determine how much torque they can support.

At this midrange point in the upgrade process, Glasgow from Performance Diesel also typically opts to upgrade the automatic transmission’s valve body to increase oil flow and to improve hydraulic clamping force to the transmission’s clutch packs. Commonly on the Ram trucks, the complete valve body is exchanged for a performance unit, and it is often an easier and more cost effective method for the seller/installer than purchasing internal kit pieces to install. Some electronic tuners will ‘defuel’ while the transmission is shifting gears which helps somewhat, but attending to clutch apply will still be important for long-term durability.

Depending on what the customer’s plans are for trailer towing, this may also be the time to look at upgrading the rest of the transmission. If a Dodge or Ford truck is coming to a shop with significant mileage (i.e. 80,000-plus miles), or if it will be doing heavy towing, it may be advisable to rebuild or swap the transmission to support their upgrades. Duramax trucks that have a lesser amount of miles on the clock can support this stage of upgrades by using the heavy-duty torque converter and either a valve body kit or electronic pressure controller to support positive clutch engagement.

Airflow improvement beyond a simple intake kit will become important at this stage. Stock turbochargers are sized and designed for output that supports just that, a stock truck. When upgrading the customer’s turbo, the size of the charger and its configuration will need to depend on the planned usage.

On the 7.3L Ford, those customers that have opted for the compressor housing or compressor wheel upgrade may be in good shape. The 6.0L Ford, as well as the Dodge and Duramax, can benefit by changing the complete charger for an upgraded model. The stock turbo is designed to give effective boost reaction for off-the-line performance, but it typically won’t have the more aggressive midrange and top-end air volume of a performance charger. It is important that customers realize that they will usually sacrifice at least a little bit of bottom-end reaction time when upgrading. The benefits of cooler overall exhaust gas temperatures (EGTs) and increased power often help ease concerns in that area.

One of the popular upgrades at Performance Diesel for the Cummins engine is a compound turbo kit. A typical dual turbo setup works well for mildly upgraded trucks towing trailers through mid-range hot rod setups. The ample supply of air on-tap, as well as the lower exhaust gas temps makes them a highly desirable upgrade for many truck owners. While there can be a significant cost increase over and above a single charger upgrade, there are also great advantages. Most setups will feature a smaller turbo connected directly to the engine’s exhaust manifold, which then feeds the larger bottom turbo. This layout means that spool time is relatively fast (generated by the smaller charger), and the larger unit enhances midrange and top-level boost. While compound systems or dual turbos are not very common for the Ford engine, the 6.0L truck is often in desperate need of a new single charger. Upgrading the customer to a non-variable turbo will mean cooler operating temperatures and alleviation of other issues.

With increased fuel and air levels the intercooler is a great area to steer diesel owners towards. According to Hall at Alligator, “Intercoolers become increasingly important as a midrange build item. As you prepare to upgrade the stock turbo, the boost pressures will increase and the factory intercooler will not be able to keep up with demand, plus you lower your EGTs in the process while awaiting the next big upgrade.”

In addition to some stock intercoolers using plastic tank components, which sometimes crack, airflow can be inhibited and lead to unnecessarily high temperatures due to higher fuel levels. While a “lean condition” is not an issue with the diesel engine as it is for a gas motor, it is still important to ensure proper fuel flow. If it was not one of the initial modifications made, a pusher pump or assistant pump should be considered to aid in fuel supply at this point (if not upgrading the complete fuel system).

These midrange upgrades may be a stopping point for many truck owners who will build their vehicle exclusively for trailer towing. Popular upgrade items for this crowd also often include exhaust brakes and propane injection systems. While the braking systems attached to the wheels of the light duty diesel are impressive, hauling a 15,000-pound trailer down a mountain pass using only the wheel brakes can be a harrowing experience. Since the diesel does not feature the “engine braking” or deceleration compression of a gas motor, it can difficult to slow down a heavy load.

Aftermarket exhaust brakes which mount downstream of the turbo allow for a flap to close off the exhaust port during deceleration to create backpressure that retards the engine and causes assisted braking. Several quality brakes have been on the market for some time and offer slightly different features depending on shop preference. Customers who tow on a regular basis have no problem understanding the value of this improved braking ability, and the prevention of wear-and-tear to the wheel brakes.

One More For The Road

With the current fuel prices today, every shop seems to tout electronics and exhaust kits as a miles-per-gallon (mpg) savior. While these other upgrades can help significantly, the biggest mileage gain upgrade is often a propane assist system.

Since the diesel engine is not able to completely burn or use all of the fuel that goes into the engine, the propane, which is injected into the air stream, is able to catalyze and make use of the remaining diesel. Most of these propane systems advertise mileage gains of three to four mpg (or more in the case of some kits). Hall at Alligator stresses, “Our typical customer is between 25 and 50 years old, and he wants a little more power, better fuel economy and not to blow anything up. Many of these guys don’t know how these products work, and it is our job as an industry to school them with the dos and don’ts”.

Word of mouth is always one of best forms of advertising. In the diesel community a customer whose truck is built properly from the ground-up will be a great billboard out on the road and will continue to come back to that shop for their next “fix.”