The 4 Best 5.9 Cummins Performance Upgrades

The 5.9 Cummins has been around since 1989 and has powered some of the best-selling and most reliable Dodge turbo diesel trucks in history. Since then, it has been revised and improved multiple times, with injection pump upgrades and additional valves per cylinder. Alongside reliability, the 5.9 Cummins is known for one other important characteristic, modifiability.

While all versions of the 5.9 can handle ludicrous amounts of additional power over their stock output, later 24-valve versions of the engine with CP3 and VP44 pumps are the most capable compared to earlier 12-valve versions. In this guide, we’ll cover the most popular modifications for 24-valve 5.9 Cummins engines including upgraded intakes, performance tuning, exhaust systems, and turbo upgrades.

While this guide is targeted for later second and third generation 5.9 Cummins engines, the vast majority of these modifications also apply to earlier 12v Cummins as well.

What are the best performance upgrades for the 5.9 Cummins?

Since the 5.9 Cummins has been around for so long, there is a tried-and-true recipe for modifying the engine to get the most out of it at this point. This guide is organized around the best bang-for-buck Cummins modifications to get the most power per dollar. 

• Upgraded air intake

• Performance tuning

• Turbo-back exhaust system

• Turbo upgrade

With only a few performance upgrades, it is possible to get over 400 horsepower out of a 24-valve 5.9 Cummins. While some of the more advanced modifications are where the real power gains come from, it is a better idea to work your way up. An upgraded intake is the best place to start, as it serves as a building block for other modifications later on. The same goes for a quality turbo-back exhaust. Tuning and a turbo upgrade have the most power potential, but are more costly to execute.

Upgraded Intake

• 5-10whp+ gains

• 10-20wtq+ gains

• 30%-50% increase in air flow

• Better throttle response

• Faster turbo spool

• 1-2 mpg increases

• Cool turbo and intake noises

As a foundational modification to other more advanced modifications, an upgraded Cummins air intake alone won’t yield massive power gains. You can expect around a 5-10 whp gain and maybe a bit more torque. However, when paired with other mods like a tune and an upgraded turbo, those gains can be far more significant, as increased airflow can seriously aid performance later in your mod journey.

Outside of the mild power and torque gains, upgraded 5.9 Cummins intakes also provide some other useful benefits. Better throttle response and faster turbo spool are two of the most important, as they both improve drivability. Improving intake air flow also tends to mildly improve fuel economy as well, even if it is just 1 or 2 mpg. 

Turbo-Back Exhaust

• Decreased EGTs

• Improved fuel efficiency

• Marginally improved power and torque

• Deep and rich exhaust tone

• Pronounced turbo whistle

Alongside an upgraded air intake, a turbo-back exhaust is the best modification for engine breathability. Installing a turbo-back exhaust will ultimately decrease backpressure, allowing the turbo to operate more efficiently while reducing EGTs in the process. While there are other 5.9 Cummins exhaust options, a turbo-back provides the most noticeable benefits without breaking the bank.

A 5.9 Cummins turbo-back exhaust bolts directly to the turbo and goes all the way back to the exhaust tip. The additional piping diameter over the stock exhaust can decrease backpressure by more than 80 percent while also lowering exhaust gas temperatures by over 200 degrees. A 4” turbo-back is usually suitable for 5.9 Cummins pushing up to 500 horsepower. A 5” turbo-back is best for power figures beyond that. 

A turbo-back exhaust is another modification that won’t yield massive gains on its own. You’ll need a tune and an intake to see gains of around 15-20 horsepower and a similar amount of torque. However, you will likely notice improved fuel economy and quicker throttle response. The sound improvement alone is worth it for most people.

Performance Tuning

• Gains up to 180 horsepower and 350 lb-ft of torque

• Improved throttle response

• Preloaded performance and towing tunes

• Better fuel economy

• Doesn’t require any other modifications

There’s no question that performance tuning is the best modification available for the 5.9 Cummins. That goes for both older 12v variants of the engine, and especially newer CP3 and VP44 24v versions of the engine. Tuning is also one of the easiest modifications to do on the 5.9, with some great plug-and-play OBD tuners on the market.

With no additional modifications, it is possible to gain up to 180 horsepower and 350 lb-ft of torque with just an OBD tuner. In addition to just the power and torque, the preloaded tunes can also improve throttle response, optimize towing capabilities, and improve fuel economy, all with the touch of a button. Combined with other modifications like an intake and exhaust, tuning can yield over 200 horsepower and 400 lb-ft of torque.

There are a few quality tuners on the market for the 5.9 Cummins. The MADS Smarty Junior is the go-to budget tuner option for the 24v Cummins and provides the benefits of a more expensive tuner at a fraction of the price. It has 3 preloaded tunes that can provide gains of up to 100 horsepower. If you are looking for a more advanced option, the VP44 Edge Comp Box Tuner requires a bit more setup but the payoff is massive. It comes with 5 preloaded tunes with a maximum tune that adds up to 150 horsepower and 350 lb-ft of torque. It also allows you to change your tune on the fly from your iOS device.

Turbo Upgrade

• Massive power and torque gains

• Reduced EGTs

• Increased turbo health and durability

• Increased turbo flow

• Immense amount of customizability and build options

If you are looking for performance and performance alone, it is hard to argue with a turbo upgrade for your 5.9 Cummins. It is important to mention that while you’ll likely see major power gains from a larger turbo, that comes at a cost to bottom end torque. If you do a lot of towing, a large turbo might not be the best option. 

That isn’t to say that there aren’t good turbo upgrade options for those that want OEM+ performance. Smaller options in the BD Power Iron Horn range are a fantastic upgrade option for those that don’t want to sacrifice towing ability while gaining a heap of additional power. Generally, 62mm turbos are the best option if you aren’t trying to sacrifice too much spool time in favor of ludicrous power.

Ultimately, you can take a turbo upgrade as far as you want to. From more manageable turbos like a 63mm S363 with a power limit of around 450 horsepower, to true titans like 67mm Stealth turbo with a power ceiling around 750 horsepower. It all depends on your application and what you intend on using your truck for.

With that being said, supporting modifications are critical here. There are some moderate 5.9 Cummins turbo upgrades that can operate on stock fueling with no issue. However, you’ll want to upgrade your injectors, lift pump, and anything else that needs replacing on the air side of the engine if you are looking at a more serious turbo upgrade. Research is always the key to success here.

What are the best supporting mods for the 5.9 Cummins?

While most of the 5.9 Cummins performance upgrades that we covered above will work on their own without any additional supporting modifications, there is a point where you’ll want to start thinking about some additional mods to not only keep power consistent, but also monitor the overall state of your truck.

The second-generation VP44 5.9 Cummins needs the most help when it comes to fuel flow to match performance. While there are conflicting reports on when a lift pump is needed to ensure that the VP44 high pressure fuel pump is receiving adequate fuel pressure to sustain a higher amount of power, it is generally a good upgrade to have anyway. If you are planning on doing any kind of serious modification to your second gen 5.9, like a tune or turbo upgrade, an upgraded lift pump is a necessity. Upgraded 60-100 hp injectors are also critical for a turbo upgrade.

Monitoring is extremely important when it comes to building a reliable 5.9 Cummins build. Monitoring things like exhaust gas temperature (EGT), boost pressure, and fuel pressure is critical to make sure that your engine is healthy and performing within acceptable windows. Monitors like the Edge Insight CTS3 can display all of those important readings at once, ensuring that you’re never in the dark if your EGTs are getting too high, if you are overboosting, or if your lift pump is failing.

FAQ

What are the best 5.9 Cummins mods?

The best modifications for the 24v 5.9 Cummins include an upgraded air intake, a turbo-back exhaust, performance tuning, and a turbo upgrade. While more advanced upgrades like a tune and turbo upgrade will yield the highest power and torque gains, it is better to get the supporting modifications, like an intake and exhaust, out of the way to get the most out of the more advanced mods later on.

How much power can the 5.9 Cummins handle?

Without any serious modifications, the 5.9 Cummins can generally handle 450-500 horsepower, daily driven, without issues. With that being said, there have been reports of unopened 24v 5.9 Cummins holding up to 700 horsepower for short periods of time.

How can I get more power out of my 5.9 Cummins?

Some of the best mods for the 24v Cummins are tuning, turbo-back exhaust, cold air intake, and a larger turbo swap. With the proper supporting mods and a larger turbocharger, the 24v Cummins can make more than 550 wheel-horsepower.