Duramax Crankshaft Woes Solved?

The Duramax 6.6L: A Workhorse Facing a Crucial Weakness

For nearly fifteen years, the 6.6-litre Duramax V-8 has been the backbone of countless General Motors trucks, earning a reputation for its robust nature and unwavering dependability. Over its extensive production run, this powerplant has seen numerous updates aimed at enhancing performance, improving drivability, and meeting ever-stricter emissions standards. The more recent iterations, such as the 2011-2015 LML Duramax, boasted significant internal revisions, including new connecting rods, pistons, advanced emissions control systems, and a variable-geometry turbocharger, collectively pushing its output to an impressive 400 horsepower. However, one critical component that has remained largely unchanged throughout its evolution is the Alternate Firing Camshaft. This seemingly minor oversight can lead to premature failure, particularly when the engine is subjected to extreme stress, such as in high-performance racing or competitive pulling scenarios.

The aftermarket has truly pushed the boundaries of what the 6.6L Duramax is capable of, achieving performance levels that were once thought impossible. It’s now commonplace to encounter drag racing and sled-pulling machines that harness over 1,500 horsepower from these engines. Achieving such colossal power figures is no small feat. Specialist Duramax performance shops have had to delve deep into the technical intricacies of the engine, developing ingenious solutions to ensure these power plants can withstand such immense forces. One such pioneering company is Empire Diesel, based in Dubuque, Iowa. Empire Diesel quickly rose to prominence in the competitive Midwest sled-pulling circuit, thanks to their expertly crafted custom engines and profound understanding of the Duramax platform. With their own sled trucks routinely producing around 1,000 horsepower, they too encountered the inherent limitations of the stock crankshaft.

Cracking the Code: The Crankshaft Failure Phenomenon

Empire Diesel's investigation into these persistent crankshaft failures led them to a critical observation: the factory firing order of the Duramax engine could be inducing significant stress along the crankshaft's plane. Their hypothesis was that by developing a new camshaft profile that altered this firing order, they could achieve a more uniform distribution of combustion stress across the entire crankshaft. To gain deeper insight, we spoke with Chad Remakel, CEO of Empire Diesel. Our conversation revealed fascinating technical details about the inner workings of the Duramax diesel and the extreme measures required to push these engines to their absolute limits.

DIESEL WORLD: What was the primary motivation behind developing the Alternate Firing Camshaft for the 6.6L Duramax?

CHAD REMAKEL: The main impetus for modifying the Duramax firing order with a new camshaft is to alleviate stress on the front section of the crankshaft in high-performance applications. The standard factory firing order is 1-2-7-8-4-5-6-3. Our new camshaft design reconfigures this to 1-5-6-3-4-2-7-8. It's worth noting that altering an engine's firing order isn't a novel concept; GM enthusiasts have been implementing the '4-7 swap' on their LS gasoline engines for years. We simply aimed to apply this principle to the Duramax to help mitigate component breakage.

We've observed these crankshaft failures across the entire Duramax engine family – including the LB7, LLY, LBZ, LMM, and LML. The common failure point is consistently located just behind the crankshaft snout, extending towards the No. 3 rod journal. These failures occur in a wide spectrum of vehicles, from mildly modified daily drivers to full-blown competition engines that utilise aftermarket billet cranks with internal balancing. The underlying issue appears to be related to the Duramax engine's harmonics at higher revolutions per minute and increased power levels, which, combined with the factory firing order, places an excessive amount of stress on the crankshaft.

The Genesis of the Alternate Fire Camshaft

DW: When did Empire Diesel first identify these crankshaft issues, and what prompted the development of this new camshaft design?

CR: By 2009, we were continuously encountering Duramax crankshaft failures when engines reached the 1,000-horsepower mark. It presented a significant roadblock to further performance development. We convened to brainstorm, seeking a straightforward and cost-effective solution to eliminate broken crankshafts permanently. Drawing parallels from similar engine failures we'd encountered in our earlier performance gasoline engine projects, we concluded these issues were likely rooted in the engine's harmonics and internal stresses. There are essentially two viable avenues to overcome this: either reduce the engine's power output or engineer a way to distribute the existing stress more evenly across the crankshaft.

DW: Once the decision was made to alter the firing order, how did you go about determining the optimal sequence for the injection events?

CR: The process of determining the new firing order was quite rudimentary, involving little more than a pencil, paper, and some rather unartistic drawing skills! We essentially had to connect the dots, analysing various patterns to identify which sequence would most effectively distribute the stresses generated by each cylinder's combustion event across the crankshaft.

From Concept to Reality: The Manufacturing and Tuning Challenges

DW: After finalising the firing order, was it as simple as manufacturing a new camshaft and replacing the stock unit?

CR: In theory, yes, but the practical execution was far from straightforward. At that time, the major performance camshaft manufacturers were primarily focused on gasoline engines and showed little interest in diesel applications. It was a protracted and arduous struggle to find a manufacturer willing to produce precisely what we needed for what they perceived as a 'limited market' at a reasonable price. After months of persistent calls and considerable legwork, we finally obtained the first alternate-fire order Duramax camshaft. However, this was not the end of our challenges. We still needed to figure out how to get the ECM (engine control module) to recognise the change in the camshaft profile. Through further investigation, we discovered that all the ECM required to initiate the injector firing order was to detect the trigger signal on the tone wheel. This trigger informs the ECM when to fire the No. 1 cylinder injector; thereafter, the ECM is indifferent to the order in which the remaining seven injectors fire. Therefore, if an injector signal was relocated from its original intended firing position, as long as the relocated injector signal coincided with the correct valve stroke (opening or closing) for that particular cylinder, the engine would operate as if it were factory stock.

DW: So, what electronic modifications are necessary to adjust the injector firing order when implementing this camshaft change?

CR: There are two primary methods for handling the electronic side of this modification. The first involves relocating and extending the factory injector wiring harnesses. The second entails repositioning the pins within the injection harness itself. We've been informed that EFILive is currently developing new tables within their custom tuning software that will facilitate firing order changes. However, even if this becomes a viable option, while it might simplify the process, we would still advocate for the pin-swapping method. This approach carries a lower risk of causing engine issues that could arise from the potential of loading an incorrect tune.

Performance, Reliability, and Future Developments

DW: Having successfully implemented this Alternate Fire Camshaft and supplied it to numerous customers over the years, has your initial camshaft profile remained consistent, or are you continually refining it to enhance performance and reliability?

CR: Over the past five years, we've experienced considerable success with this process, effectively contributing to the longevity of Duramax crankshafts and engines. Some customers theorise that this alternate firing order also promotes a more even distribution of air within the intake manifold, leading to improved combustion, although we haven't been able to empirically verify this. Since our initial testing, our camshaft profiles have become progressively more aggressive. We now offer distinct 'Street' and 'Competition' versions, and we also have the capability to engineer custom profiles tailored to a customer's specific requirements. The 2014 sled-pulling season was exceptionally successful for us and for our customers utilising our camshaft designs. While we would ideally share specific examples of our customers' achievements, many are direct competitors, necessitating that we maintain a degree of confidentiality regarding certain details. More recently, we've partnered with Wagler Competition Products, and the results we've witnessed when our cam profiles are paired with Jeremy Wagler's Duramax cylinder head program have been exceptionally impressive.

DW: What kind of performance gains can typically be expected from implementing this camshaft change?

CR: In our initial engine dyno testing conducted between 2009 and 2010, we immediately observed a noticeably smoother idle and a distinct change in the engine's tone at higher RPMs. To date, the most significant horsepower increase we've measured from this camshaft compared to a stock unit is approximately 28 hp on the engine dyno. However, it's crucial to understand that this modification was not primarily developed with the goal of increasing horsepower. Our main objective was to enhance durability at higher horsepower levels, a goal this technology has demonstrably achieved. While this Alternate Fire technology has brought about substantial improvements in durability and has enabled us to push the horsepower limits of the Duramax platform, it's important to remember that no solution is entirely foolproof. This camshaft design is not a 'golden ticket' that guarantees your engine will never fail; the choice of other components, the precision of the assembly, and the quality of the tuning are equally vital.

DW: Are alternate-fire camshafts exclusively required for full competition builds?

CR: We actually recommend this conversion for any engine build, ranging from mild towing and street applications to our all-out 1,500-hp+ competition builds. We have encountered entirely stock trucks with broken crank snouts at our shop, which is why we offer our Alternate Fire Camshaft in various profiles to suit every application. Our mild 'Street' grind is suitable for an otherwise stock motor with stock pistons, requiring no valve reliefs. These can contribute to an improved power and torque curve, making the truck more enjoyable for daily driving and towing. Our more performance-oriented grinds are considerably more aggressive and necessitate other engine modifications to function optimally. We also provide the camshaft as a 'blank,' allowing it to be purchased and sent to your preferred engine builder or machine shop to be profiled according to their specifications.

Comparative Table: Stock vs. Alternate Fire Camshaft

Frequently Asked Questions

How does the condition of the crankshaft affect the outcome of using an alternate-firing camshaft?

The condition of the crankshaft is paramount. A used crankshaft may have already experienced considerable stress from the standard firing order. Introducing a new firing pattern can impose unfamiliar stresses, potentially increasing the risk of failure. Conversely, a new crankshaft, even a standard one, can significantly enhance engine harmonics when paired with an alternate-firing camshaft. However, reports suggest that some new stock crankshafts still experience breakage, indicating variability in how they handle the introduced stresses. For maximum resilience, a billet, narrow-rod crankshaft design is often recommended, as it fortifies the fillet radius for greater resistance to failure.

What role do major crankshaft companies play in developing alternate-fire camshafts?

Major crankshaft companies are instrumental in the innovation of alternate-fire camshafts. They conduct research and design camshafts that optimise engine efficiency and power output, collaborating closely with engine builders to ensure correct selection for various applications. Through rigorous testing and customisation, they fine-tune profiles for compatibility and performance, providing expert consultation to help users make informed decisions.

Can alternate-firing camshafts completely prevent Duramax crankshaft failures?

No, alternate-firing camshafts are not a guaranteed solution for preventing all Duramax crankshaft failures. While they significantly reduce harmonics and help extend bearing life, they do not entirely eliminate the risk. Failures can still occur, underscoring the importance of component selection, precise assembly, and quality tuning. They are a critical enhancement for durability but not a foolproof fix.

What is an alternate-firing Duramax cam?

An alternate-firing Duramax cam is a camshaft designed to alter the engine's firing order from the stock sequence. The primary goal is to redistribute the stress generated by combustion events more evenly across the crankshaft, particularly in high-performance applications where the standard firing order can lead to premature crankshaft failure, typically behind the snout towards the No. 3 rod journal. This modification aims to improve engine harmonics and reduce stress on the crankshaft.

What is the general industry perspective on this modification?

The industry perspective is that while alternate-firing camshafts don't typically yield significant horsepower gains, they are a valuable modification for enhancing engine stability and longevity, especially in high-stress applications. Engine builders focus on developing profiles that efficiently manage force dispersion, though specific details are often kept proprietary.

What is the impact on power gains?

Unlike cam swaps in gasoline engines, altering the firing order in a Duramax diesel engine does not result in substantial power increases. The primary benefit is improved engine stability and durability, rather than a direct increase in horsepower.

How does the alternate-firing camshaft help alleviate the problem?

By modifying the firing order, the forces exerted on the crankshaft are more evenly distributed. This strategic shift redirects energy away from the vulnerable front end of the crankshaft, allowing it to be absorbed by other components, such as the flexplate, and mitigating the internal stresses that build up with RPM.

Why do these failures occur?

These failures are primarily caused by engine harmonics. In high-performance Duramax engines, internal vibrations intensify with increasing RPM, placing significant stress on the crankshaft and leading to eventual failure.

What is the specific issue with the Duramax crankshaft?

The Duramax crankshaft is particularly prone to failure in the section located behind the snout, extending to the No. 3 rod journal. This area is most susceptible to structural compromise under high stress.

What are the potential drawbacks or risks associated with using an alternate-firing camshaft on a used crankshaft?

Using an alternate-firing camshaft with a used crankshaft carries a risk. Used crankshafts have already adapted to the stresses of a standard firing sequence. Introducing a new firing order can impose unfamiliar stresses, potentially increasing the likelihood of failure. While new crankshafts can also fail, opting for a billet, narrow-rod design can enhance durability by strengthening critical stress points.

How do alternate-firing camshafts affect the synchronization of injectors and valves in a Duramax engine?

To ensure optimal engine performance, the engine's ECM must be informed of the camshaft's altered profile. This requires synchronizing the injectors to fire precisely with the opening and closing of the valves. This synchronization is often achieved by swapping pins in the injector harness to align the signals correctly. While software solutions are emerging, the mechanical pin-swapping method remains a reliable approach to prevent misfires and potential engine issues.

When is it advisable to install an alternate-firing camshaft in a Duramax engine?

It is advisable to consider an alternate-firing camshaft for any Duramax build, from mild towing and street use to high-horsepower competition builds (1,500 hp+). Even stock trucks can experience crankshaft failures. For street use, a mild grind can improve the power and torque curve. For competition builds exceeding 1,000 hp, it's a highly recommended upgrade for added reliability. It provides peace of mind for performance builds by potentially extending the life of the crankshaft and bearings.

How do alternate-firing camshafts impact the durability of Duramax crankshafts and bearings?

These camshafts significantly reduce engine harmonics and help extend bearing life by smoothing out mechanical stresses. This contributes to overall engine longevity. However, they are not a complete guarantee against crankshaft failure, as other factors like component quality, assembly precision, and tuning remain critical. While beneficial, they should be part of a comprehensive approach to engine building.

What are the benefits and limitations of alternate-firing camshafts?

Benefits: Reduced engine harmonics, extended bearing life, improved engine stability, and enhanced durability in high-stress applications. Limitations: Do not completely prevent crankshaft failures, may require ECM modifications, and do not offer significant horsepower gains on their own.

What additional components can enhance durability alongside alternate-firing camshafts?

Using a billet, narrow-rod crankshaft can significantly enhance durability. This design strengthens the fillet radius, a critical area prone to stress, thereby increasing overall engine resilience.

How does the crankshaft’s condition affect durability with alternate-firing camshafts?

A used crankshaft, having already endured the stresses of a standard firing order, may be more susceptible to failure when subjected to the new stresses introduced by an alternate firing order. Even new stock crankshafts have occasionally failed under these conditions, highlighting the importance of considering the crankshaft's material and design.

What modifications are necessary when using alternate-firing camshafts?

The primary modification involves the engine's ECM, which needs to be adjusted to recognise the new cam profile. This ensures injector signals are synchronised with valve timings, often requiring pins to be swapped within the injector harness. Some tuning software may also accommodate these changes.

How are alternate-firing camshafts used in practice?

In practice, these camshafts are installed in Duramax engines, particularly in performance-oriented builds, to mitigate crankshaft stress. For example, Diesel Power Challenge champion Richard Coker incorporated them into his compound-turbocharged engine to reduce harmonics and extend bearing life. The implementation requires careful attention to ECM programming and injector synchronisation.

Why might a used crankshaft be more susceptible to failure with an alternate-firing camshaft?

A used crankshaft has already experienced the cyclical stresses of the standard firing order. Introducing an alternate firing order imposes new, potentially uneven stresses on areas that may have already undergone material fatigue or microscopic damage. This can exacerbate existing weaknesses, increasing the risk of failure compared to a new or purpose-built crankshaft designed to withstand these altered stress patterns.

How do harmonics factor into the use of an alternate-firing camshaft?

Harmonics are the root cause of many crankshaft failures in high-performance Duramax engines. The alternate-firing camshaft is designed to alter the engine's firing sequence to disrupt and reduce these harmful harmonic vibrations. By redistributing the firing pulses, the camshaft aims to create a smoother operational balance, thereby lessening the resonant frequencies that can lead to crankshaft stress and fracture.

What technical solutions can mitigate the risk of failure?

Technical solutions to mitigate failure risk include using a billet, narrow-rod crankshaft, which offers increased strength in critical areas like the fillet radius. Additionally, ensuring proper ECM calibration and injector synchronisation, along with high-quality assembly and tuning, are crucial for overall engine reliability.

How do new crankshafts compare to used ones in terms of susceptibility to failure?

While a new crankshaft, even a stock one, is generally less susceptible to failure than a used one, they are not immune. Reports indicate that new stock crankshafts can still fail when subjected to the stresses of an alternate firing order. This suggests that the material quality and design of the crankshaft, regardless of its age, play a significant role in its resilience.

What are the effects of new stresses introduced by an alternate firing order?

An alternate firing order introduces a new pattern of torsional and bending stresses to the crankshaft. While designed to be more evenly distributed, these stresses are different from those the crankshaft experienced with the original firing order. If the crankshaft’s material properties or design are not adequately suited to these new stress patterns, especially in conjunction with other performance modifications, failure can occur.

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