The 5 Best 6.7 Cummins Performance Mods
Zach is one of the founders of 8020 Media and a lead writer for DieselIQ. He’s been in the automotive industry for over a decade and has published more than 400 articles for DieselIQ, TuningPro, BMWTuning, & more. His blend of automotive knowledge, writing & research skills, and passion make him an excellent resource for fellow diesel owners. His expertise goes beyond writing and includes a deep knowledge of Cummins and Powerstroke engines, as well as nearly 10 years of DIY experience. Zach is also experienced with tuning and has a wealth of technical knowledge that he brings to every article he writes.
Launched in mid-year of 2007, the 6.7 Cummins initially produced 350hp and 610-650lb-ft. of torque, depending on the transmission. The engine had a number of small changes in the early years with the biggest changes coming in 2011 when SCR and all the other emissions systems were added. Still in production today, the 6.7 Cummins produces 420hp and 1,075lb-ft. of torque in high-output Ram 3500 versions.
While these performance numbers are quite stout, you might still be looking for a little more power. Whether you are chasing power, towing capacity, or fuel economy, performance modifications are a great option to give your 6.7 Cummins a little extra bite while improving engine efficiency.
6.7 Cummins bolt-on mods are simple, affordable, and effective. With just a handful of bolt-on mods you can add 150+whp and wtq to your Ram for only a few thousand bucks. While producing more power is possible, it starts to get a lot more expensive. Fueling becomes a limitation which requires an upgraded high pressure fuel pump, a lift pump, and high-flowing injectors. Additionally, you’ll need an upgraded turbo and a built transmission. All in total, breaking pas the ~500rwhp mark will require about $20k in mods.
Fortunately, getting to 500rwhp on the 6.7 Cummins can be done with these 5 simple bolt-on performance mods.
Best 6.7 Cummins Performance Mods
- Cold air intake
- Intake horn/manifold
Supplemental upgrades for >500rwhp:
- Upgraded turbo
- Lift pump
- Fuel pump
- Head studs
- Built transmission
The two limitations of big power are fueling and the transmission. The 68RFE auto trans is safe and reliable at 500rwhp, but anything above that and it will start to cause problems. If you have a manual transmission, simply upgrading to a dual disc clutch should be enough to support 800rwhp or more. Additionally, the Aisin transmission is a bit stronger than the 68RFE, but will still need to be built for high-power applications.
Secondly, above the 500rwhp mark you’ll need to upgrade your fuel injectors which is an easy $3k. With larger injectors, the stock CP3/CP4 fuel pump won’t flow enough for the injectors. Therefore you either need to add a 2nd fuel pump or upgrade which is another $2k or so. You’ll then need a lift pump for about $1k. So, all in all you are looking at about $6k in fueling mods alone.
1) 6.7 Cummins Tunes
If you were only going to add one mod to your 6.7 Cummins, a tune would hands down be the way to go. Tunes offer the biggest power gains and the best bang-for-the-buck. Additionally, all of the other upgrades we mention are best accompanied with a tune to unlock their full potential.
At a high level, a tune adjusts various engine parameters such as timing, fueling, and boost to improve power and engine efficiency. Plug-and-play tunes will come with a handful of pre-built maps with various purposes such as power, towing, fuel economy, and so on. Additionally, a tune will properly adjust engine parameters to account for the other performance mods you have, such as an intake, to maximize engine efficiency and power output.
If you are just looking for a bit of extra power, a plug and play unit is perfect. However, if you are chasing specific goals then custom tuning with EFI Live is a must. Additionally, getting the transmission tuned via EFI Live is highly recommended if you plan on daily driving near the 500rwhp range.
6.7 Cummins Tune Performance Benefits
- 30-175rwhp and torque gains
- Multiple maps for different goals/uses
- Ability to tune transmission (with EFI Live)
- Improved engine efficiency
- Better fuel economy
- Plug-and-play and can be turned on and off easily
Best 6.7 Cummins Tuners
- EFI Live (for custom and transmission tuning)
- Bully Dog
2) 6.7 Cummins Cold Air Intake Upgrade
Second favorite on our list is an upgraded intake system. Tunes primarily improve power by increasing turbo boost levels. When running higher boost levels bringing more air into the engine is necessary to reduce stress on the turbo and improve its ability to spool quickly. Therefore, we recommend going with a performance intake system to increase airflow into the engine.
An intake will provide about 5-10hp and 20-30tq gains through improved efficiency caused by the increased airflow into the engine. With most coming in south of the $400 price point, this is a solid mod to increase power, improve efficiency, and even slightly improve gas mileage.
Choosing an Intake
First off, we recommend a full intake system over just upgrading the air filter. An upgraded air filter will increase air flow by about 10% compared to 50%+ for full intake systems. Therefore, the performance benefits are minimal compared to a full system.
The 2nd option you have is to choose either an open or closed intake system. In an open system, the air filter is directly exposed to the engine bay air. In closed systems the intake filter sits within a box that protects the filter from hot engine bay air. Open systems will flow more air since they don’t have the restriction from the airbox and therefore will provide slightly better power gains.
Open systems however will make a lot more noise which can be somewhat annoying if you frequently tow or drive long distances. Unless you are chasing 800rwhp+ then it really doesn’t matter if you go with an open or closed system. We prefer open systems for the increased airflow, but the reduced noise of a closed system could be a big reason to go that route.
Performance Intake Benefits
- 5-10hp gains
- 20-30tq gains
- Improved airflow
- Reduced stress on turbo / better turbo efficiency
- Increased gas mileage
Best 6.7 Cummins Intake Systems
- Banks Power
- Wherli Custom
3) 6.7 Cummins Intercooler Upgrade
Intake air is heated up as it’s compressed by the turbocharger. In order to cool it down before it enters the combustion chamber it’s passed through the intercooler which cools the charged air. The stock intercoolers in the 6.7 Cummins, especially 2013-2018 models, is pretty small. When you are running a tune and have an intake, you are now bringing a lot more air into the engine and therefore a lot more air that needs to be cooled.
The stock intercooler can become overwhelmed easily due to its small size. Therefore, one of the best upgrades is adding a larger intercooler. While this is the most expensive mod on the list and it doesn’t offer a ton of power gains, it is one of the most important. Heat and high EGTs are the killers of diesel engines. An intercooler that can’t properly cool the air before it enters the combustion chamber causes higher engine temps and EGTs. Therefore, an upgraded intercooler is an important reliability modification.
Not only is it important for reliability, it is also a great mod for frequent towers. Colder air entering the engine and lower EGTs result in an all around healthier engine. An intercooler will also prevent heat soak and high EGTs during heavy towing.
Intercooler Performance Benefits
- Approx. 25hp and 50tq (per Banks Power)
- Lower EGTs
- ~50% increase in airflow
- Slight MPG improvement
- Improves reliability
Recommended Intercooler: Banks Power
4) 6.7 Cummins Exhaust Upgrade
With more air flowing into the engine along with higher boost levels, we need to reduce restriction in the exhaust system to improve exhaust airflow. Exhaust backpressure increases when air and boost are added. Backpressure reduces the turbos ability to spool and therefore adds stress to the turbo and reduces its efficiency.
The best way to reduce exhaust backpressure is to upgrade to a 5″ exhaust system. Gains will be best on 2007.5-2010 versions that don’t have all the emissions equipment. 2011+ models will see less gains due to the DPF and other emissions equipment. Your two options are a 4″ or 5″ system. A 5″ will flow better and therefore have lower EGTs but it also might require upgrading the downpipe as well.
If you have a 2012 or new 6.7 Cummins, upgrading the downpipe is one of the best ways to reduce backpressure since it bolts directly to the turbo. However, the downpipe for these years features a diesel oxidation catalyst which is an emissions component and technically illegal to remove.
Overall, a larger diameter exhaust system will lower EGTs, improve exhaust airflow, and reduce backpressure. In turn this improves turbo efficiency and reliability and also improves turbo spool.
6.7 Cummins Exhaust Benefits
- Power gains dependent on year, size of exhaust, etc.
- Faster turbo spool
- Reduced backpressure
- Lower EGTs
- Improved turbo reliability
5) 6.7 Cummins Intake Horn Upgrade
The intake horn is the same thing as the intake manifold. If you are just looking for some simple bolt-on power then we recommend ignoring this mod and sticking with a tune, intake, exhaust, and intercooler. However, if you are looking to push additional power then an upgraded intake manifold is a great modification.
An upgraded intake horn will improve airflow by 25-50% and help reduce EGTs by 50-100°F. This can add around 15rwhp and 25wtq while also increasing reliability through lower EGTs. Additionally, some intake horns have bungs for methanol injection, nitrous, etc.
The one caveat is that upgrading the intake horn may also require the EGR system to be deleted. Various years of the 6.7 Cummins have EGR valves and other emissions equipment that attaches to the intake manifold and therefore needs to be deleted for it to be upgraded.
If you want to read into this further, check out our 6.7 Cummins Intake Horn Upgrade Guide.
Intake Horn Upgrade Benefits
- 5-15hp gains
- 10-20+ torque gains
- 50-100°F lower EGTs
- 25-50% increase in airflow
- Bungs for meth injection, nitrous, etc.
Bonus: 6.7 Cummins DPF Delete
Deleting the DPF and other emissions systems is really only for people chasing serious power levels, or for those who want to improve reliability by removing these expensive to replace parts. However, keep in mind that it is totally illegal, won’t pass emissions, and will make it difficult to sell your truck.
With that being said, deleting the emissions systems removes all the restriction within the exhaust system and therefore improves turbo and engine efficiency. It also removes the need for regen cycles and saves you from expensive repairs when these systems fail.
We have a full 6.7 Cummins DPF Delete Guide you should read if you plan on going this route.
DPF Delete Benefits
- 15-30hp gains
- 50-100wtq gains
- 2-5mpg increase
- Reduced exhaust backpressure
- Better turbo spool and more reliable turbo
- No regen cycles
- Less maintenance and repair expenses
6.7 Cummins Performance Mods Summary
Four simple bolt-on mods: a tune, intake, intercooler, and exhaust, can get you over 200rwhp gains on your 6.7 Cummins for just a few thousand dollars. However, one of the biggest limitations of the 6.7 Cummins is the 68RFE transmission which can only handle about 500rwhp when tuned.
Getting over 500rwhp will require a significant amount of money in the form of a built transmission, upgraded fueling system, bigger turbo, and various other supporting modifications. Additionally, an intake horn and DPF delete are items we only recommend upgrading if you plan on chasing power goals in excess of these numbers.
Overall, the 6.7 Cummins produces solid power from the factory. It can get a nice boost through bolt-on mods, however, achieving serious power gains becomes very expensive due to transmission and fueling limitations. With that being said, the four mods we recommend should provide adequate power and performance benefits for the majority of folks, all without sacrificing much in the way of reliability.
Excellent, thorough and un-biased article!