Cummins Upgrades You Can’t Live Without

The Upgrades Your Cummins Can’t Live Without

If you’re a Cummins owner, you know that performance and reliability go hand-in-hand. In terms of serviceability, durability and aftermarket support, the Cummins has been the most desirable engine of the lot for more than 30 years—and for good reason. From the original 6BT revolutionizing the diesel truck market to the legendary P-pumped 12-valve, and the introduction of the 24-valve head to common-rail injection, each rendition of this iconic inline-six enjoys a strong enthusiast following. As a result, the Cummins is not only the undisputed champion of making horsepower, but the most celebrated engine in the diesel industry. However, that doesn’t necessarily mean a few Cummins upgrades won’t come in handy.

Unfortunately, every engine has its shortcomings—even the almighty Cummins. If some imperfections go unaddressed, such as the killer dowel pin in ’89-’02 5.9L’s, catastrophic issues can surface. If others aren’t dealt with, you’ve got a truck that can barely keep up with traffic. And if you’ve added power but not tackled the simple supporting modifications that make that extra giddy-up safe or usable, you’ll never see optimal performance or million-mile longevity. From the mechanical 12-valve 5.9L to the 6.7L common-rail, the following Cummins upgrades aren’t just recommendations, they’re mandatory if you want your engine to live up to its full potential.

1989-2002 Engines:
Killer Dowel Pin

The killer dowel pin (or KDP for short) issue is well known among 5.9L 12-valve Cummins owners, but many don’t know that it can also strike in ’98.5-’02 24-valve engines, too. What happens, exactly? From the factory, a steel dowel pin was used to precisely locate the timing gear housing during assembly. This pin can work its way loose over time, and if/when it backs out of the block it can drop down into the cam gear, injection pump gear, and even the crank gear, causing catastrophic damage.

Available from Industrial Injection, this comprehensive kit includes everything you need to solve the killer dowel pin issue before it leaves you stranded. It goes without saying that accessing the killer dowel pin requires quite a bit of work, but in the end it’s totally worth it. Consider addressing the KDP the best preventative measure you can perform on your first or second-gen Cummins. Industrial Injection’s kit includes a KDP tab to lock the dowel pin permanently in place in the block, a new front crank seal, and a fresh timing gear cover gasket.

1989-1993 12-Valve

The first thing you’ll notice about a bone-stock first-generation Cummins other than its lack of rpm range (more on that later) is how conservatively it’s fueled. The factory mechanical distributor style Bosch VE injection pump makes use of a single 12mm plunger and only flows 105cc’s worth of fuel. Although the 6BT’s original power rating of 160hp might’ve sufficed in 1989, even basic VE pump tweaks are necessary to help get a first-gen truck out of its own way.

Making a fuel screw adjustment is the best way to get started with the VE injection pump, and it can add as much as 70 hp and 200 lb-ft of torque to the equation. Also known as the smoke screw, it’s located at the back of the pump (firewall side) and calls for the removal of the OEM tamper-resistant cover and locking collar before you can turn it. Just make sure you don’t adjust the fuel screw too far. If you do, the engine could run away on you…

In stock form, the VE governs the 5.9L Cummins’ engine speed to 2,500 rpm. However, many engines begin to de-fuel around 2,400 rpm, so there is virtually no power window to utilize with the aforementioned fueling mods. The age-old 3,200-rpm governor spring changes all of that, stretching out the engine’s power band and facilitating more horsepower up top.

For a significant increase in low-rpm fueling, an aftermarket or modified factory fuel pin (or fuel cone) can do the trick. A more aggressive profile ramps up low-end fueling as boost comes on, and is known to provide roughly a 30hp gain along with another 50 lb-ft. If you’re grinding the factory fuel pin yourself, be forewarned that once you remove too much material there is no going back. Don’t get carried away.

1994-1998 12-Valve

To appease NVH, emissions, and drivability requirements, the Bosch P7100 is extremely docile in factory form. Set to approximately 12 degrees of timing advance and moving just 135 to 170cc’s of fuel in stock trim, to say the ’94-’98 12-valve Cummins was conservatively fueled would be an understatement. Don’t worry though, the P-pump can be made to flow three times that with a few simple changes. Thanks to having one plunger dedicated to feeding each cylinder, tons of fueling potential exists—even without upgrading the 12mm plungers.

A lot of tinkerers get started with the pre-boost screw. It’s located at the rear of the air fuel control (AFC) assembly. Adjusting the pre-boost screw can add significantly more off-idle (under boost) fueling to the mix, which also helps bring boost on quicker.

The star wheel adjustment is a great way to fine-tune the drivability of a P-pumped Cummins. It’s accessed through the top side of the AFC housing, and rotating it toward the passenger side of the engine opens the P7100’s fuel rack further (the rack being what allows fuel to enter the plungers). Small, incremental adjustments of the star wheel are key to balancing smoke output with streetability.

For yet another increase in rack travel (and as much as 35 hp), the venerable Mack rack plug is a great option for 160hp and 180hp P-pumps (note: it’s known to retard injection timing on 215hp pumps). It’s not free, but at least it’s dirt cheap at just $14.95 when sourced from our friends at Pure Diesel Power. The plug increases rack travel from 18mm to 21mm, which effectively allows roughly 70 more cc’s of fuel into the plungers. Just note that unless you plan to pull the P7100 to install the Mack rack plug, the front gear housing will have to be slightly modified to install it with the pump still on the engine.

Governed to approximately 2,800 rpm stock, it’s a very far cry from the kind of rpm we know the P7100 can support (especially the 215hp pump), but like the VE-pumped ’89-’93 12-valve, the P7100 begins to de-fuel well before that (as soon as 2,500 rpm on some ’94-’98 engines). Installing the tried and true 3,000-rpm governor spring kit extends the power curve of the engine, allowing you to take full advantage of the free and cheap fueling mods you’ve already made to the P-pump. The 4,000-rpm governor spring kit is also a popular option, but just know that stiffer valve springs should be installed if you plan to run your 12-valve upstairs.

Because the AFC controls the P7100’s low-boost fuel rate, adjusting it into the full-forward position brings immense fueling in much sooner in the rpm range. When combined with the star wheel adjustment already mentioned, it can yield a 200 lb-ft gain—along with 60 to 70 horsepower. To bring low-boost fuel on even quicker, a lighter tension AFC spring can be installed as well.

Removing the fuel plate or running a true #0 plate allows for full rack travel and even more fuel volume to enter the P-pump’s plungers. To pull the plate, the AFC assembly has to be removed, followed by the tamper-resistant bolt and then the two bolts that actually secure the fuel plate in place. The added fueling that comes with ditching the fuel plate is known to be between 30 and 40 hp.

Not only is the P7100 configured to flow very little volume and hardly fuel at all under low-boost conditions from the factory, but it’s also set to a timid 12 degrees of timing advancement. It’s fairly involved and calls for a dial indicator on the delivery valve holder to pull it off, but bumping timing up to 18-21 degrees (BTDC) always produces impressive results. Advancing timing to 18 degrees on stock injector trucks usually frees up another 30-40 hp, drivability improves, and cold-starts aren’t a problem. To be sure, the P-pumped Cummins’ fueling mods are nowhere near exhausted at this point. You can also turn the barrels, install bigger delivery valves and obviously run larger injectors with optimized pop-off pressure to complement your specific setup.

Without a boost elbow or a disabled wastegate, all fueling mods performed on the P7100 are for naught unless the Holset HX35W (’95-’98 engines) can make more boost than stock. With the common, $25 boost elbow onboard, boost can be fine-tuned for a maximum of 35 to 40-psi instead of the 18-22 psi it sees stock. Not only will the elevated boost add 20-30 hp to your overall setup, it will cool off EGT as well.

1998.5-2002 24-Valve

Whether it’s the electric Carter lift pump mounted on the engine or the in-tank version Chrysler implemented as a “factory-fix” back in the day, OEM lift pumps don’t live very lengthy lives on the ’98.5-’02 24-valve Cummins. Worse yet, when they fail (or begin to fail) they starve the Bosch VP44 injection pump of the fuel it needs to stay cool and lubricated while performing its various jobs (pressurizing fuel, controlling injection timing, and regulating fuel volume).

Keeping the VP44 in good health begins with a reliable lift pump, and one that can provide the magical 12-15 psi worth of supply pressure the VP44 requires. FASS offers a sound replacement lift pump coined the DRP (for Dodge Replacement Pump), which is available in both chassis-mount and in-tank form to suit either application, and the company even offers an optional pump relocation kit to solve frame-mounting difficulties. For the ultimate in-tank lift pump solution, the Fleece Performance Engineering in-tank PowerFlo system features dual gerotor pumps within the supplied sending unit and float, and supports up to 800 hp.

One of the biggest performance drawbacks of the 24-valve Cummins is the VP44’s inability to support higher rpm. From the factory, the VP44 only fuels to 3,200 rpm—and many aftermarket programmers, modules, and fueling boxes fail to address this issue while adding power. One option that does provide full fueling comes from Edge Products. Level 7 of its Competition Juice with Attitude fuels all the way up to 3,600 rpm and adds as much as 150 hp and 380 lb-ft to your ’98.5-’02 second-gen’s bottom line. With proper fuel pressure being supplied to the VP44, we’ve seen stock injector trucks make 315-rwhp (vs. 180-rwhp stock) courtesy of Edge’s full-fuel tuning.

Just like the 12-valve, delaying when the turbocharger’s wastegate opens (or disabling it) is key in building enough boost to capitalize on any extra fueling. On 24-valve engines fitted with the HX35W, which includes all manual transmission versions and ’98.5-’00 automatics, the same 45-degree, adjustable boost elbow used on ’95-’98 engines can be employed. Once again, it’s wise to keep maximum boost between 35-40 psi to keep the HX35W from overspeeding.

For control over the wastegate on the HY35W turbo found on ’01-’02 automatic trucks, the common J-hook or BD’s X-hook is recommended. On the HY35, the wastegate pod connects to the compressor housing via a hard steel line, which makes it hard to swap out the wastegate for any kind of boost control upgrade. This is where the J-hook or X-hook comes in, bolting to the compressor housing and increasing pressure on the valve.

2003-2007 Common-Rail

Some might not remember, but inadequate fuel filtration was a fairly common issue with the ’03-’07 common-rail 5.9L from the factory. It’s rumored that both Bosch and Cummins highly recommended Chrysler equip its fuel system with a 2 to 4-micron filter rather than the 7-micron it settled on. The high-pressure fuel system’s tight tolerances made any sizeable contaminant a big problem, with the result being eventual damage inflicted on the injectors (and sometimes even the CP3). To ensure your common-rail 5.9L’s injectors go the distance (usually 200,000-miles or so), switching to a quality, lower micron filter or adding a second auxiliary fuel filter to the mix definitely increases their chances.

The factory HE341W (’03-‘04) and HE351W (’04.5-‘07) turbochargers aboard the common-rail 5.9L Cummins can support 500-rwhp, and in some cases a little more—but not without a boost fooler or wastegate resistor in the equation. If your tuning doesn’t keep your truck from throwing an overboost CEL, a boost fooler is necessary. On ’03 and ’04 models, physically modifying the wastegate to allow more boost is necessary. On ’04.5-’07 engines, an electronic boost fooler that installs in-line with the MAP sensor is most common.

2007.5-2018 6.7L Common-Rail

Whether your ’07.5-’18 6.7L Cummins is tuned or tows heavy at the stock power level, your 68RFE needs help. To optimize the six-speed automatic transmission’s shift schedule, holding capacity, and longevity, it pays to invest in good transmission control module (TCM) tuning. Available from companies like GDP Tuning and through KT Performance to name a few, TCM tuning ramps up line pressure for improved clutch holding capacity, optimizes shift points (eliminating the ‘68s common short-shifting issues) and dials in torque converter lockup with a fine-tooth comb. If you want your 68RFE to live with added power and/or stress being sent through it, this is your best option outside of spending big money on a billet transmission build.

Thanks to its increased stroke over the 5.9L (4.88-inch vs. 4.72-inch), pound-for-pound the 6.7L Cummins produces more torque. Unfortunately this additional cylinder pressure makes head gasket failure much more common. If babied, a tuned 6.7L can get roughly 200,000 miles out of the stock gasket and head bolts, but trucks that are abused lift the head much sooner. Here, ARP head studs are a must-have item. In addition to adding head studs during a head gasket job, many 6.7L owners opt for fire-rings, too.

SOURCES

ARP
800.826.3045
ARPDIESEL.COM

EDGE PRODUCTS
801.476.3343
EDGEPRODUCTS.COM

FLEECE PERFORMANCE ENGINEERING
317.286.3573
FLEECEPERFORMANCE.COM

GDP TUNING
877.223.5018
GDPPRODUCTS.COM

INDUSTRIAL INJECTION
800.955.0476
INDUSTRIALINJECTION.COM

PURE DIESEL POWER
715.204.3115
PUREDIESELPOWER.COM

SCHEID DIESEL
800.669.1593
SCHEIDDIESEL.COM

FREQUENTLY ASKED QUESTIONS

What are the essential upgrades for enhancing the performance of a 3rd generation 5.9L Cummins engine?

Unlock Maximum Performance: Essential Upgrades for 3rd Gen 5.9L Cummins Engines

For enthusiasts eager to push their 3rd gen 5.9L Cummins engines to new heights, several key modifications are critical. These upgrades not only boost power but also improve overall efficiency and reliability.

1. Cold Air Intake

Begin with a cold air intake system to enhance airflow to your engine. Factory-installed intakes often suffer from restricted airflow and poor sealing. Upgrading to a high-quality aftermarket system can significantly improve air intake, lower temperatures, and ultimately increase engine efficiency. This modification is cost-effective, easy to install, and a perfect entry point for performance enhancements.

2. Custom Tuning

Another powerful tool in your performance arsenal is custom tuning. This tailor-made adjustment unlocks your truck’s full horsepower potential and offers adaptability to various driving styles. Custom tuning is especially beneficial whether your vehicle is largely stock or has additional bolt-on enhancements. Expect noticeable boosts in horsepower—up to 100 more—and torque improvements reaching up to 180 pound-feet from a standard motor.

3. Transmission Upgrade

Achieving significant power gains necessitates upgrading your transmission. The stock automatic transmission in these trucks can falter above 400 horsepower, and manual transmissions often struggle to manage excess power. Therefore, a built transmission is essential to handle the increased power and maintain reliability. Despite the higher cost, this investment is crucial for durable performance under enhanced power conditions.

4. Turbocharger Enhancement

Finally, consider enhancing your turbocharger. The stock turbo is adequate at standard power levels but quickly reaches its limits as you increase output. To exceed 400 horsepower, an upgraded turbocharger is necessary. This not only helps achieve peak power but also improves performance throughout the engine’s range. Paired with custom tuning and a strengthened transmission, it’s indispensable for those seeking substantial power boosts.

Implementing these key modifications will significantly elevate the performance of your 3rd gen 5.9L Cummins engine, pushing it to achieve remarkable power and efficiency.

What are the advantages of upgrading the turbo in a 3rd generation 5.9L Cummins engine?

Advantages of Upgrading the Turbo in a 3rd Generation 5.9L Cummins Engine

Upgrading the turbocharger in a 3rd generation 5.9L Cummins engine unlocks several performance benefits that can transform your driving experience. Here’s a closer look at the key advantages:

1. Enhanced Horsepower

The standard turbocharger is designed to handle stock power levels effectively but struggles with higher outputs. By switching to a larger turbo, you can push past the 400 horsepower threshold, opening up opportunities for thrilling acceleration and top-end speed.

2. Improved Engine Performance

A larger turbo offers more than just a spike in horsepower; it enhances the overall performance profile of your engine. You’ll experience better throttle response and increased efficiency across various RPM ranges, ensuring your Cummins engine runs more smoothly and powerfully.

3. Optimal Pairing with Custom Modifications

Pairing your new turbo with custom ECU tuning and a reinforced transmission can lead to substantial power gains. Custom tuning ensures that your engine operates in sync with the new turbo’s capabilities, maximizing both power and reliability. The upgraded transmission withstands the increased power output, preventing potential damage and extending vehicle lifespan.

4. Durability and Longevity

Upgrading to a higher performance turbo can also improve the durability of your engine. A better-designed turbo handles increased power loads with ease, reducing the strain on engine components and promoting a longer vehicle life.

5. Flexibility for Future Modifications

If you plan on further upgrades in the future, such as injectors or exhaust systems, a better turbo provides a flexible foundation. The increased power capacity allows for additional modifications without the need to immediately upgrade again.

By installing a more capable turbocharger, Cummins enthusiasts can achieve significant power enhancements while preparing their engines for potential future upgrades. Whether your focus is on performance or durability, the benefits of turbo upgrades are undeniable.

Why is it important to upgrade the transmission in a 5.9L Cummins engine?

Why Upgrading the Transmission in a 5.9L Cummins Engine is Crucial

If you’re looking to boost the performance of your vehicle equipped with a 5.9L Cummins engine, upgrading the transmission is a critical step. Stock transmissions, especially automatics, often fail to support power levels beyond 400 horsepower. This can lead to slipping, causing frustration and potential damage. Manual transmissions aren’t immune to these issues either, as their factory-installed clutches can falter under increased power demands.

Key Reasons for Transmission Upgrades

1. Handling Power Increases: With a stock transmission, the vehicle’s ability to manage substantial horsepower enhancements is limited. Upgrading can significantly improve this capacity, allowing for more power without the risk of slipping or failure.
2. Ensuring Durability: A more robust transmission not only copes with added power but also enhances the longevity of your vehicle’s drivetrain. This durability is pivotal for those who use their Cummins-powered vehicles for towing or heavy-duty tasks.
3. Reliability in Performance: For enthusiasts aiming for reliable performance, especially in competitive or off-road scenarios, an upgraded transmission ensures consistent power delivery and responsiveness, reducing the chance of breakdowns.

Investment in Stability

While upgrading a transmission might seem like a substantial investment, it’s absolutely necessary for achieving desired performance levels and maintaining the integrity and reliability of your vehicle. Investing in brands like ATS Diesel or Suncoast can provide peace of mind, knowing that your transmission will stand up to the demands placed on it by increased engine power.

What are the benefits of upgrading to an aftermarket intake for a 5.9L Cummins engine?

Upgrading the intake system in your 5.9L Cummins engine can unlock several benefits, especially when you choose aftermarket solutions over the stock components.

Enhanced Airflow

Factory-installed intakes often limit airflow due to their design constraints, which can hinder your engine’s potential. Aftermarket cold air intakes address these limitations by boosting airflow, thus allowing the engine to breathe more efficiently. This increase in airflow translates to better combustion and enhanced engine performance.

Lower Intake Temperatures

Aftermarket intakes are designed to draw cooler air into the engine. Since cooler air is denser, it contains more oxygen, which is crucial for optimal combustion. This helps in not only improving power but also in safeguarding the engine from high temperatures that could lead to wear and tear.

Improved Engine Efficiency

Another significant advantage of upgrading is the improvement in overall engine efficiency. With better airflow and cooler air intake, the engine can operate more smoothly, leading to increased horsepower. Additionally, this enhanced efficiency often results in improved fuel economy, offering savings over the long run.

Easy Installation and Cost-Effectiveness

Aftermarket intakes for the 5.9L Cummins are relatively easy to install, often requiring no more than basic mechanical skills. They are also relatively affordable, making them a cost-effective modification that does not break the bank. This combination of ease and affordability makes them an attractive upgrade choice for many enthusiasts.

In summary, choosing an aftermarket intake system for a 5.9L Cummins engine is a smart move to unlock better performance, efficiency, and fuel savings with minimal hassle.

How does custom tuning improve the performance of a diesel truck?

To optimize the six-speed automatic transmission’s shift schedule, holding capacity, and longevity, it pays to invest in good transmission control module (TCM) tuning. Available from companies like GDP Tuning and through KT Performance to name a few, TCM tuning ramps up line pressure for improved clutch holding capacity, optimizes shift points (eliminating the ‘68s common short-shifting issues) and dials in torque converter lockup with a fine-tooth comb. If you want your 68RFE to live with added power and/or stress being sent through it, this is your best option outside of spending big money on a billet transmission build.

But enhancing your truck’s performance isn’t just about transmission tweaks. Custom tuning emerges as a game-changer across the board, offering a comprehensive upgrade to your diesel truck’s capabilities. Here’s how it transforms performance:

• Tailored Performance: Unlike generic tunes, custom tuning provides specific enhancements tailored to your vehicle’s setup. Whether your truck is stock or equipped with upgrades, custom tuning unlocks its maximum horsepower potential.
• Adaptability: Custom tuning allows for switch-on-the-fly capabilities, letting drivers adjust tunes on the go according to driving preferences and conditions, ensuring optimal performance at all times.
• Significant Power Gains: Expect substantial increases in power, with gains of up to 100 extra horsepower and 180 additional pound-feet of torque, even from a stock motor.

For those looking to extract the most from their diesel truck, coupling custom tuning with TCM tuning offers a holistic approach to performance enhancement. This combination not only fine-tunes your transmission but also maximizes overall engine output, providing a seamless driving experience that is both powerful and responsive.

What additional capabilities does custom tuning provide?

Custom tuning allows for on-the-fly adjustments, giving drivers the flexibility to change tunes based on their driving needs.

How does custom tuning compare to other tuning options?

Unlike generic tunes, custom tuning provides personalized performance improvements specific to the vehicle’s setup.

Is custom tuning beneficial for both stock and modified vehicles?

Yes, custom tuning is beneficial for vehicles in both stock condition and those with modifications like a cold air intake.

How does custom tuning affect horsepower and torque?

With custom tuning, a stock motor can gain up to 100 additional horsepower and 180 extra pound-feet of torque.

What is the primary benefit of custom tuning for diesel trucks?

Custom tuning is an economical way to boost the performance of a diesel truck significantly.