Best 5.9 Cummins 24v Performance Upgrades

Now long retired, the 24-valve Cummins turbo-diesel that was in production from 1998–2007 has officially obtained legendary status. The 24v Cummins was the successor to the 12v Cummins, and some regard them as the two best turbo-diesel engines ever made. Not only are they incredibly reliable and dependable, but they are very popular in the aftermarket and modding community, too. That’s because they can make gobs of horsepower and torque with just a few upgrades. Read on to find out the best 24v Cummins performance upgrades to make the most horsepower and torque from your 5.9 ISB Cummins. 

Make sure to check out our other 24v Cummins content, including our 5.9 Cummins vs 7.3 PowerStroke comparison, 5.9 Cummins intake manifold upgrade guide, and our most common 5.9 Cummins engine problems guide. 

24v Cummins Performance Upgrades Basics

The 24v 5.9 Cummins was in production from 1998–2007, most often appearing in the Dodge Ram 2500/3500. Depending on the year, it produced 235-325 horsepower and 460-610 lb-ft of torque. The 24v 5.9 Cummins, also known as the 5.9 ISB, is an inline-six engine with four-valves per cylinder. It has a single in-block camshaft, and both the cylinder head and engine block are cast iron. Compression sits at 16.3:1 in the standard 24v Cummins, or 17.2:1 in the high-output Cummins. 

The 24v Cummins used three different turbos during its run, all of them manufactured by the Cummins-owned Holset. From 1998–1999, it was the HX35W, which was upgraded to the HY35W Type D from 2000-2004, and finally to the HE351CW from 2004–2007. All of these used air-to-ar intercoolers to increase performance and improve cooling. 

In addition to different turbos, the 24v Cummins also used two different fuel pumps to supply its high-pressure direct injection fuel system. From 1998–2002, they used the problematic Bosch VP44. This was constantly prone to failure and probably the biggest flaw with the engine. Starting in 2003, they upgraded to the Bosch CP3 pump, which is vastly superior. In fact, Cummins still uses the CP3 on their 6.7 liter Cummins successor the 5.9. 

Overall, the engine is widely known as one of the most dependable and reliable turbo-diesels ever built. They are capable of exceeding well over 300,000 miles without needing a rebuild, and they are also capable of some extreme horsepower and torque numbers with the right mods.

24v Cummins Performance Upgrades’ Supporting Mods

If you plan on installing some 24v Cummins performance upgrades, you’ll definitely need a few supporting mods to go with it. First off, if you have a 1998–2004 Cummins with the VP44 fuel pump, you absolutely need a lift pump. The lift pump is a low-pressure fuel pump that supplies fuel to the high-pressure VP44. The stock lift pump is notorious for failing, leaving the VP44 starved for fuel, which leads to it failing and thus engine damage. An aftermarket lift pump will ensure a constant flow of filtered diesel fuel to the VP44, making sure it does not catastrophically fail.

Next up, you want to make sure you have a full set of gauges for you to monitor the health of your engine. You will want gauges for exhaust gas temperature (EGT), boost pressure, and fuel pressure, at a minimum. Your EGT gauge will tell you when the engine is beginning to overheat, and usually you want to keep it below 1,400° except for brief periods. The boost gauge will tell you how much boost pressure the turbo is outputting. This can tell you if you are underboosting (have a leak) or overboosting. 

Finally, the fuel pressure gauge will tell you the health of the VP44. If you start to see fuel pressure plummeting you’ll know the VP44 is going south, indicating you need to lay off the throttle and start figuring out a replacement. 

For those looking at running more than 40 PSI of boost, you’ll want to look into head studs to keep the engine together and prevent head gasket failure. With that being said, if you want to run more than the stock boost levels, you’ll need to upgrade to an aftermarket boost elbow to allow for the wastegate to be adjusted. 

Top 24v Cummins Performance Upgrades

Our top 24v Cummins Performance Upgrades are:

• Tuner
• Turbo-back Exhaust
• Cold Air Intake Upgrade
• Turbo Upgrade

It only takes a few mods to transform the 24v Cummins from its OEM specs into a behemoth. In order, we suggest tuning, a turbo-back exhaust, a cold air intake upgrade, and a turbo swap to a larger blower. With these mods, you can make more than 450 wheel-horsepower. Importantly, you will want to make sure you have all supporting mods done by that point, but these engines are ridiculously capable. 

1) 24v Cummins Tuning

Hands down, the best 24v Cummins performance upgrade is tuning. Tuning was not an option on the 12-valve Cummins, and it really makes the 24v come to life. With just tuning alone and no other bolt-ons, you can add more than 200 horsepower and torque in minutes. That’s no joke and equates to more than 500 horsepower at the crank on later models. 

Flash tuning is incredibly easy and involves installing software from a handheld tuning device onto your truck through the OBDII port under the dashboard. This software has several “maps” or “tunes,” most of which either increase performance, fuel economy, or towing capacity on the 5.9 Cummins. In addition, if you end up adding more mods, you can maximize and optimize their performance with tuning, too. 

In addition to peak numbers, a 5.9 Cummins tuner will improve the entire power band of the engine. This means you’ll have more horsepower soon and it’ll hold out for longer, and the same with torque. Besides maps that offer high-power numbers, there are also some that are focused on improving gas mileage or towing capacity. This makes 5.9 ISB tuners helpful for a variety of purposes.  

Best 24v Cummins Performance Tuning

Previously, we looked at the best 24v Cummins tuners, so we’ll just summarize here. Make sure to check out the article for the full breakdown. 

There are three different options for tuning the 24v Cummins: Smarty, Quadzilla, and Edge EZ. Of them, we recommend Smarty. The Smarty comes in three different versions, the MADS Smarty Junior, Smarty S-03, and the Smarty Touch S2G. These range from the cheapest to the most expensive, and also in terms of performance. The Smarty Junior will add up to 100 horsepower depending on the tune level you choose. Both the S-03 and S2G are capable of an incredible 210 horsepower gain. 

The Smarty tuners are very easy to use, and the S2G has a full 480p touchscreen that allows you to monitor several different gauges at once — eliminating the need to buy aftermarket versions. Other options include the Quadzilla and the Edge EZ Tuner, which are both excellent products, too. 

2) Turbo-Back for 24v Cummins

After tuning you’re going to want to start opening up the exhaust. This will reduce back pressure and improve airflow, helping your 24v Cummins to breathe and exhale much easier. It can also help reduce EGT by allowing for better cooling of the turbo. The exhaust connects directly to the exhaust housing on the turbocharger, and routes all the way back to the mufflers. 

Typically, most 24v Cummins owners will go for either a 4” or 5” turbo-back exhaust. If you plan on staying below 500 horsepower, a 4” pipe will be perfectly fine and will not restrict power. For those looking at going over 500 horsepower, a 5” pipe will be more your size. You can use a larger 5” on a build below 500 horsepower for the extra volume, but you won’t see a ton more power. 

Best Turbo-Back Exhausts

For the top 24v Cummins exhaust upgrades, we suggest looking at MBRP’s offerings. They have a few different options, both with and without mufflers, depending on your level of comfort with sound. In addition, MBRP also sells the popular Diamond Eye branded turbo-backs, which have a great reputation in the community. In reality, the difference will be related to tone, as they will both perform pretty similar to each other. Both are great options and will really let your Cummins scream.

3) Cold Air Intake Upgrade for Cummins

After opening up the exhaust, a good place to continue with 24v Cummins performance upgrades is a cold air intake. Previously, we looked at the top options in our 5.9 Cummins cold air intake upgrade guide, so make sure to check out that article for the full breakdown.

Adding an upgraded cold air intake is the best way to increase the flow of air into the turbocharger. The OEM system can become a bottleneck once you start turning up the boost and adding a larger exhaust. Getting something with a larger filter that can suck in more air with less restriction will help the engine breathe better, allowing the turbo to work easier and more efficiently. 

Best Cold Air Intakes

For the 24v Cummins, the most popular intakes are the Sinister Diesel intake and the S&B intake. Both of them perform very well, with the biggest difference being the airbox on the S&B unit. This is supposed to help reduce intake temperatures, but on a turbocharged engine with an intercooler that’s not too big of a deal.

Both of the intakes will completely outflow the stock intake by as much as 40%, which is a pretty significant upgrade. In addition, you will also see gains of around 5-15 horsepower and torque. A cold air intake is a great way to increase performance on the 24v Cummins, and they are extremely easy to install and tune for. 

4) 24v Cummins Turbo Upgrade

For our final 24v Cummins performance upgrades recommendation, we suggest getting a larger turbo. Besides tuning, a turbo swap will give you the largest horsepower and torque gains. Importantly, you will need to do all supporting mods to swap on a turbo, as well as upgrade the injectors. Depending on the turbo size, you’ll also want either 100 hp or 150 hp injectors to adequately keep up with fuel. 

There are many different options in terms of turbo upgrades for the 24v Cummins, and you’ll want to keep in mind what you plan on using the truck for. Typically, if you plan on doing a substantial amount of towing, a turbo upgrade might not be the best option for you. You do not want to sacrifice low-end torque for top-end horsepower, which is what larger turbos will do. If you do plan on towing, you’ll want to stick to a 62mm or below turbo for the best low-end response. Even 62mm is pretty big for towing, but it’s hard to find smaller turbo upgrades for the 24v. 

One of the most popular bigger turbos to upgrade to is the ATS Aurora 3000. This will add significant horsepower over stock while still maintaining a pretty good spool. It has a 62mm compressor wheel and a 58mm inducer for quick response but solid top-end power. 

Ultimately, if you want even more performance you can get an even larger turbo. Many 24v Cummins are topping the 500-550 wheel-horsepower mark with a turbo swap, showing these engines are more than capable. 

24v Cummins Performance Upgrades FAQ