S&S Fuel System Planner: Injector and CP3 Sizing by HP
Most fuel system problems are not failures. They are planning mistakes. Somebody buys injectors first, finds out the stock pump cannot keep rail pressure, then buys a pump that does not match the injectors they already own. Now there is a box of parts on the bench and a truck that falls on its face at the top of third gear.
S&S Diesel Motorsport publishes a fuel system planner for every major platform. It does one job very well. It shows you what injector size and what high pressure pump combination live at a given horsepower number, so you can buy the whole system once instead of twice.
Below is every planner chart broken down into plain numbers, plus the parts we stock to build each stage. All horsepower figures are crankshaft horsepower and every one of them assumes the supporting mods are there. Turbo, tuning, lift pump, fuel lines, transmission. The chart does not care how badly you want the number.
How to read the planner
Two halves, one axis.
Top half is injectors. Sizes are listed as a percentage over stock nozzle flow. Each bar is the horsepower window that size actually works in. The left edge is the lowest sensible power level for that injector and the right edge is where it runs out of nozzle.
Bottom half is high pressure pumps. Each pump is shown three times, as a single, a twin and a triple setup. The bar length is how much horsepower that configuration can feed while holding rail pressure.
To plan a build, pick your horsepower target on the bottom axis, draw a line straight up, and take the injector bar and the pump bar that both cross it. If your target crosses a 200 percent injector bar and a twin 12mm bar, that is your system.
Two rules keep people out of trouble:
- Do not size the injector at the far left of its bar. Running a big injector at low power means tiny pulse widths, ugly idle and poor drivability.
- Do not plan at the far right edge of the pump bar. Leave headroom. Rail pressure drop under load is what kills injectors and pumps.
Where each pump lands
The pump side of the chart is nearly identical across platforms, which makes it easy to memorize.
| Pump | Single | Twin | Triple |
|---|---|---|---|
| 14mm CP3, 1850 mm3/rev | up to about 1,400 hp | up to about 2,800 hp | up to about 4,200 hp |
| 12mm CP3, 1590 mm3/rev | up to about 1,100 hp | up to about 2,200 hp | up to about 3,300 hp |
| 10mm CP3, 1325 mm3/rev | up to about 800 hp | up to about 1,600 hp | up to about 2,400 hp |
| SuperSport CP3 | up to about 500 hp | up to about 1,000 hp | up to about 1,500 hp |
| DCR 1250, 6.7L Power Stroke | up to about 700 hp | up to about 1,400 hp | up to about 2,100 hp |
Shop the pumps: S&S Duramax 14mm CP3, S&S Duramax 12mm CP3, S&S Duramax 10mm CP3 High Speed, S&S Duramax SuperSport CP3 and S&S Cummins 10mm CP3 High Speed.
High speed versions of these pumps are built for engines that spend real time above 3,500 rpm. If you are turning a race engine, that is the version you want. If you are towing and driving on the street, the standard pump is the right call.
5.9L Cummins fuel system planner
The 5.9L Common Rail is the platform where a stock pump carries you further than most people expect, and where a single injector jump buys real power.
| Injector size | Supported range |
|---|---|
| Stock | about 250 to 475 hp |
| 10 percent | about 275 to 500 hp |
| 30 percent | about 325 to 600 hp |
| 45 percent | about 375 to 675 hp |
| 60 percent | about 400 to 725 hp |
| 80 percent | about 450 to 800 hp |
| 100 percent | about 500 to 900 hp |
| 150 percent | about 650 to 1,150 hp |
| 200 percent | about 800 to 1,375 hp |
| 250 percent | about 975 to 1,600 hp |
| 300 percent | about 1,150 to 1,825 hp |
| 350 percent | about 1,300 to 2,075 hp |
| 400 percent | about 1,450 to 2,300 hp |
| 450 percent | about 1,600 to 2,525 hp |
| 500 percent | about 1,750 to 2,750 hp |
Typical 5.9L builds:
- 500 to 600 hp street truck. 30 to 45 percent injectors with a SuperSport or 10mm CP3.
- 700 to 900 hp. 80 to 100 percent injectors with a single 10mm CP3.
- 1,200 hp and up. 150 to 200 percent injectors with twin 12mm or 14mm pumps.
Note that all S&S CP3 pumps are 6.7L based. Running one on a 5.9L takes some modification to the factory fuel lines. Plan for that before the truck is apart.
See the full S&S injector lineup for the 2003 to early 2004 5.9L and 2004.5 to 2007 5.9L.
Browse every S&S Diesel Motorsport part we stock.
6.7L Cummins fuel system planner
The 6.7L carries slightly more power per injector size than the 5.9L across the whole chart, and it tops out higher.
| Injector size | Supported range |
|---|---|
| Stock | about 325 to 575 hp |
| 10 percent | about 375 to 625 hp |
| 30 percent | about 425 to 725 hp |
| 45 percent | about 475 to 800 hp |
| 60 percent | about 525 to 900 hp |
| 80 percent | about 575 to 1,025 hp |
| 100 percent | about 625 to 1,125 hp |
| 150 percent | about 800 to 1,400 hp |
| 200 percent | about 975 to 1,700 hp |
| 250 percent | about 1,150 to 1,950 hp |
| 300 percent | about 1,300 to 2,250 hp |
| 350 percent | about 1,550 to 2,500 hp |
| 400 percent | about 1,625 to 2,800 hp |
| 450 percent | about 1,800 to 3,075 hp |
| 500 percent | about 1,950 to 3,350 hp |
For trucks that tow and still need to behave, the S&S TorqueMaster injector for 2007.5 to 2018 6.7L Cummins is the one to look at. It is built for low end response rather than peak flow, so you get torque where you actually use it without the drivability hit of a big nozzle.
Worth knowing about S&S injectors: nozzles are flow matched to 1 percent variance per set and complete injectors are flow matched to 3 percent, checked at four different pressure and energizing points. At 200 percent and above the bodies are internally modified, because a bigger nozzle slows the open and close event and the body work fixes the injection rate shape. That is the difference between a set of injectors and a set of holes.
See the full S&S injector lineup for the 2007.5 to 2018 6.7L and 2019 and up 6.7L.
6.7L Power Stroke fuel system planner
Ford guys get a fourth pump option on the chart in the DCR 1250, plus the standard CP3 lineup for conversions.
| Injector size | Supported range |
|---|---|
| Stock | about 300 to 500 hp |
| 10 percent | about 375 to 550 hp |
| 30 percent | about 425 to 650 hp |
| 45 percent | about 475 to 725 hp |
| 60 percent | about 500 to 800 hp |
| 80 percent | about 525 to 900 hp |
| 100 percent | about 625 to 1,025 hp |
| 150 percent | about 775 to 1,250 hp |
| 200 percent | about 950 to 1,500 hp |
| 250 percent | about 1,125 to 1,750 hp |
| 300 percent | about 1,300 to 2,000 hp |
The practical read on this chart: a single DCR 1250 covers most street and tow builds through roughly 700 hp. Past that you are into twin pumps or a CP3 setup. If you are adding a big single or compounds and planning past 800 hp, size the pump for where the truck is going, not where it sits today.
Running an earlier 6.4L Power Stroke? Start with the S&S 80 percent over 6.4L injector set.
See every S&S injector for the 6.4L, 2011 to 2019 6.7L, and 2020 and up 6.7L Power Stroke.
LB7 and LLY Duramax fuel system planner
The two oldest common rail Duramax engines share a chart, and it runs the full spread from stock to 500 percent over.
| Injector size | Supported range |
|---|---|
| Stock | about 225 to 475 hp |
| 30 percent | about 350 to 600 hp |
| 60 percent | about 450 to 725 hp |
| 100 percent | about 550 to 900 hp |
| 150 percent | about 700 to 1,125 hp |
| 200 percent | about 850 to 1,350 hp |
| 250 percent | about 1,025 to 1,575 hp |
| 300 percent | about 1,175 to 1,800 hp |
| 400 percent | about 1,450 to 2,250 hp |
| 500 percent | about 1,750 to 2,700 hp |
For a moderate street build, a nozzle swap is often the smarter buy than a full injector set. We stock the S&S LLY nozzle set and, when a rail needs replacing on an LLY, the S&S LLY fuel rail for the left hand side.
See the full S&S injector and nozzle lineup for LB7 and LLY.
LBZ and LMM Duramax fuel system planner
Same range as the LB7 and LLY chart, with slightly more capability at the top.
| Injector size | Supported range |
|---|---|
| Stock | about 250 to 500 hp |
| 30 percent | about 350 to 650 hp |
| 60 percent | about 550 to 800 hp |
| 100 percent | about 600 to 1,025 hp |
| 150 percent | about 700 to 1,275 hp |
| 200 percent | about 875 to 1,525 hp |
| 250 percent | about 1,050 to 1,775 hp |
| 300 percent | about 1,175 to 2,025 hp |
| 400 percent | about 1,450 to 2,525 hp |
| 500 percent | about 1,750 to 3,025 hp |
The LBZ pump is the basis for the S&S Duramax CP3 lineup, which is why those pumps drop into so many builds. Nozzle sets are here: S&S LBZ nozzle set and S&S LMM nozzle set.
See the full S&S injector and nozzle lineup for LBZ and LMM.
LML Duramax fuel system planner
The LML has the CP4 problem, and the chart reflects how most people solve it.
| Injector size | Supported range |
|---|---|
| Stock | about 300 to 500 hp |
| 30 percent | about 425 to 650 hp |
| 60 percent | about 500 to 800 hp |
| 100 percent | about 625 to 1,025 hp |
| 150 percent | about 775 to 1,250 hp |
| 200 percent | about 950 to 1,500 hp |
| 250 percent | about 1,125 to 1,750 hp |
| 300 percent | about 1,300 to 2,000 hp |
Every pump on the LML chart is a CP3. That is the point. The S&S LML CP3 conversion kit with pump gets the CP4 out of the truck and puts a proven pump in its place. It is competition use only and requires tuning, so line up your tuner before the kit shows up.
See every S&S injector for the LML.
L5P Duramax fuel system planner
The newest platform on the list has the shortest injector chart, because the factory L5P injector is already a strong piece.
| Injector size | Supported range |
|---|---|
| 50 percent | about 475 to 900 hp |
| 100 percent | about 675 to 1,200 hp |
| 150 percent | about 850 to 1,500 hp |
| 200 percent | about 1,050 to 1,800 hp |
Same story as the LML on the pump side. The S&S L5P CP3 conversion kit with 14mm pump is competition use only, will not work on a stock truck, and cannot ship to California. Read that twice before you order.
See every S&S injector for the L5P.
Build it once
The order of operations that keeps people out of the parts graveyard:
- Pick a realistic horsepower target and write it down.
- Read the planner chart for your engine at that number.
- Buy the injectors and the pump together as one system.
- Make sure the low pressure side can feed it. A big CP3 with a starved inlet is a warranty claim waiting to happen.
- Get it tuned by somebody who has done that exact combination.
Not sure which column you land in? Call the shop at 865-640-2097 or email twalker@powerhouse-diesel.com and tell us the truck, the turbo and the number you are chasing. We will tell you straight whether the parts you are looking at will get you there.
Shop all S&S Diesel Motorsport parts at Powerhouse Diesel
Charts published by S&S Diesel Motorsport. Values are crankshaft horsepower and depend on supporting modifications. Ranges listed here are read from the published planner charts and rounded. Confirm final sizing with us or with S&S before you buy.
FAQ
What does injector percentage actually mean?
It is the increase in nozzle flow over the stock injector for that engine. A 100 percent injector flows roughly double the stock nozzle. The industry settled on that convention, so a 100 percent injector on a 5.9L Cummins and a 100 percent on a 6.7L Power Stroke are not the same physical flow number. Always read the chart for your engine.
How much horsepower will a single 14mm CP3 support?
Roughly 1,400 crankshaft horsepower with the right supporting parts. A twin 14mm setup takes that to about 2,800 and a triple to about 4,200.
When do I need twin CP3 pumps?
When your horsepower target passes the single pump bar for the pump you are running. For a 12mm CP3 that is around 1,100 hp and for a 10mm it is around 800 hp. If the truck is dropping rail pressure under load at your current power level, you are already past it.
Can I run big injectors with a stock pump?
For a short time, yes. It is still a bad plan. The pump will not hold rail pressure at the top of the run, you lose the power you paid for, and the pressure swings are hard on the whole system. Injectors and pumps get bought together.
What is the difference between a standard CP3 and a High Speed CP3?
The High Speed version is built to keep flowing above roughly 3,500 to 4,500 rpm, where a standard pump starts to fall off. Race engines that live at high rpm want the High Speed version. Street and tow trucks do not need it.
Do I need to replace the lift pump too?
If you are adding a larger CP3 or a second pump, yes. The high pressure pump can only move what is delivered to it. For high horsepower builds the S&S SP3000 mechanical supply pump flows up to 2,791 liters per hour at 400 psi and is designed to support as many as four 14mm CP3 pumps.
Are the CP3 conversion kits street legal?
No. The S&S L5P and LML CP3 conversion kits are sold for competition use only, they require tuning, and the L5P kit will not ship to California. Do not put one on a truck that has to pass emissions.
Will S&S CP3 pumps bolt onto a 5.9L Cummins?
All S&S CP3 pumps are built on a 6.7L base. Fitting one to a 5.9L requires modification to the factory fuel lines. Budget time and parts for that step.
Should I buy injectors or nozzles?
If your injector bodies are healthy and you are chasing a moderate power bump, a nozzle set is the cheaper path. If the injectors have high mileage, are leaking back, or you are going past roughly 200 percent over, buy complete injectors. Above 200 percent, S&S modifies the injector body itself to correct the injection rate shape, which a nozzle swap cannot do.
Where can I get help sizing my fuel system?
Call Powerhouse Diesel at 865-640-2097 or email twalker@powerhouse-diesel.com with your engine, turbo setup, transmission and horsepower goal. We build and ship these systems every week.