Top 5 Performance Upgrades for Cummins

Most performance gains on a Cummins come from one place: airflow. Get more air in and out of the engine and the fuel you already have burns more completely, exhaust gas temperature drops, and the truck pulls harder without working as hard. These are the five upgrades that do that, ranked by where most builds should start.

1. Exhaust Manifold

Why replace a factory Cummins exhaust manifold?

The factory manifold is the most common restriction on a stock Cummins and the most common failure point on a modified one. Heat cycling warps and cracks cast manifolds, and once a manifold leaks you lose spool and drive pressure.

Diesel Power Source® manifolds are cast in HSMD (High Silicon Molybdenum Ductile iron) and designed with Computational Fluid Dynamics testing rather than copied from the factory casting. The 6.7L T4i manifold flows 72 to 75 percent better than factory. The 5th Gen manifold flows more than 75 percent better. The ISX15 / X15 manifold flows 22 percent better than factory and drops exhaust gas temperature 75 to 100 degrees F on its own.

What you get:

• Measured flow improvement over the factory casting
• Resistance to the warping and cracking that kills factory manifolds
• Lower exhaust gas temperature
• Multiple coating options

Shop Cummins exhaust manifolds, or go straight to 5.9 manifolds or 6.7 manifolds.

2. Single Turbo Upgrade

What is the best single turbo for a Cummins?

A larger single turbo is the direct path from a stock or lightly modified truck into the 450 to 750 horsepower range. Diesel Power Source® singles are built on the S300 and S400 platforms, then modified, machined, and balanced in house.

Pick by power target, not by the biggest number:

Turbo	RWHP Range	Best For
S362/68/.70	Stock to 450	Daily driven, stock to mild fueling
S363/68/.70	375 to 525	Towing with added fuel
S363/73/.80	400 to 575	Heavier towing, sustained load
S366/73/.80	450 to 650	Street and strip, larger injectors
S369/73/.80	500 to 750+	High horsepower single turbo builds

Oversizing a single turbo costs you spool and drivability, which is why the ranges above matter more than the model number. Shop S300 single turbos and S400 single turbos. For 2003-2007 5.9L trucks specifically, see the S300 turbo for 5.9 Cummins 2003-2007.

3. VGT Turbo Upgrade

What does a variable geometry turbo do on a diesel?

A variable geometry turbo changes its effective turbine size as load changes, so it builds boost early without choking at the top of the RPM range. On 2007.5 and newer 6.7L trucks the factory HE300VG is already a VGT, so an upgrade is a direct replacement rather than a conversion.

Turbo	Compressor Wheel	RWHP Range
Factory HE300VG	60mm	Stock to 400
DPS HE363VG	63mm	Stock to 550
DPS HE366VG	66mm	425 to 650

The Turbonator® VGT is a different product: a variable geometry turbine housing that fits S300 and S400 platform turbos on any 5.9L or 6.7L Cummins from 1988 to 2018. Every version spools the turbo at least 200 engine RPM earlier than the same turbo without it, and the electronic actuator version adds exhaust brake capability.

Shop HE300VG and HE400VG VGT turbos or Turbonator® VGT upgrades. Running an ISX15 / X15? See the DPS HE400VG for Cummins ISX15 / X15.

4. Compound Turbo Kit

Are compound turbos only for high horsepower builds?

No, and that misconception costs a lot of owners the single best upgrade available to them. A compound system runs a small turbo and a large turbo in series. It widens the usable RPM range of the engine and splits the load between two turbochargers instead of putting all of it on one.

The number that matters: exhaust gas temperature drops 200 to 400 degrees F. That is what you feel pulling a fifth wheel over a grade in August. Compounds protect the engine rather than stress it, and when sized correctly they work at any performance level, including completely stock fueling. Plenty of Diesel Power Source® customers run compounds on stock fuel with nothing else changed.

6.7L stage pairings:

Stage	Pairing	RWHP Range
Stage 1	S363 over S475	450 to 650
Stage 2	S363 over S480	500 to 700
Stage 3	S366 over S480	550 to 1,000
Stage 4	S369 over S480	600 to 1,200+

5.9L stage pairings:

Stage	Pairing	RWHP Range
Stage 1	S362 over S475	400 to 625
Stage 2	S362 over S480	425 to 700
Stage 3	S363 over S475	475 to 750
Stage 4	S366 over S480	600 to 1,000
Stage 5	S369 over S480	700 to 1,200+

Most Diesel Power Source® compound kits include a DPS manifold, and on 2010 to 2018 trucks a patented cast and machined hot pipe that removes the fabrication step other kits leave to you. DPS is also the only manufacturer offering a bolt-on compound kit for 1st Gen 1988 to 1993 trucks.

Shop compound turbo kits, or read the complete guide to Cummins compound turbos.

5. Add-A-Turbo Kit

Can I add a second turbo and keep my emissions equipment?

On 2007.5 to 2018 6.7L trucks, yes. The Add-A-Turbo kit keeps the factory manifold and the factory turbo as the high pressure unit and adds an S400 platform atmospheric turbo underneath it. EGR, DPF, and the factory exhaust brake all stay in place, so the kit is emissions compatible and the truck keeps its third stage engine brake.

Atmospheric Turbo	RWHP Range
S475/96/1.32	Up to 600
S480/96/1.32	600 to 700

Shop Add-A-Turbo kits.

What About Intakes, Tuners, and Injectors?

They belong to the fuel and induction side of the build, and they come after the air side is sorted. Adding fuel to an engine that cannot move enough air gets you black smoke and rising exhaust gas temperature, not usable power. Diesel Power Source® designs and manufactures the airflow side: turbochargers, exhaust manifolds, compound kits, and conversion kits.

Diesel Power Source® also does not sell emissions delete components of any kind. Many DPS turbos and manifolds are emissions compatible, including the 6.7L Add-A-Turbo kit above.

Before You Order

More air means more cylinder pressure, and cylinder pressure finds the weak link. Plan for these thresholds:

Engine Years	Head Studs Above	Fire Rings or O-Rings Above
1988 to 2002	45 psi	55 psi
2003 to 2007	55 psi	65 psi
2007.5 to 2018	48 psi	55 psi

Two more limits apply broadly: the transmission usually needs attention around 400 RWHP, and the fuel system usually becomes the limit around 500 to 550 RWHP.

Kits are built for a specific engine and year range, so confirm fitment at the time of order. Start with the Turbo Selector or call 801-930-8404. ISX15 / X15 orders require an engine serial number. Verify your ESN with DPS before ordering. If you are on a 1994-1998 12V truck, start at the 5.9 12V Cummins 1994-1998 category.

Want the longer version with every category broken down by engine and power target? Read the performance diesel parts buyer's guide for Cummins. Chasing high exhaust gas temperature specifically? See what causes high EGT on a 6.7 Cummins.

Diesel Power Source® designs and manufactures Cummins turbo and exhaust systems in West Jordan, Utah. Free shipping on orders over $350. Cummins is a registered trademark of Cummins Inc. Diesel Power Source® is not affiliated with Cummins Inc.