What CAT Injector Do I Need? Breaking Down 10R0958, 10R1273, 10R0957, 10R0955 for Your C15 or 3406E

What CAT Injector Do I Need? Breaking Down 10R0958, 10R1273, 10R0957 & 10R0955 for Your C15 or 3406E 🛠️💨

You ever stare at a list of injector part numbers and think, “What in the diesel-lovin’ heck is the difference between a 57 and a 58?” Yeah, we get that question a lot. Whether you’re trying to hit that 600HP mark or you’re building an 800+ HP monster, we’re here to break down CAT injector sizing once and for all.

Let’s make it simple. Straight talk. No fluff. Just the answers you need to get your CAT purring like it should.

🧩 What Do These Numbers Even Mean? (55, 57, 58, 73)

The numbers (like 10R0955 or 10R0958) are Caterpillar’s part numbers. But what most folks care about is that last two-digit number — 55, 57, 58, or 73 — because that’s where the fuel flow magic happens.

Here’s the quick breakdown:

• 10R0955 ("55s") – Stock injectors for older 3406E/C15. Good for 475–550HP.

• 10R0957 ("57s") – Slight upgrade over stock. Can push up to ~600HP.

• 10R0958 ("58s") – Popular performance injector. About 20% more fuel than 57s. Great for 600–700HP.

• 10R1273 ("73s") – Big boy injectors. Often used in builds aiming for 800+ HP. Built for big air and big fuel.

⚙️ What Injector Do I Need for My CAT C15?

It depends on what you’re building and what turbo you’re running. Here's a general rule of thumb:

💨 What Turbo Should I Match With My Injectors?

If you're upping fuel, you better up your air too. Turbo and injector combos should be balanced — too much fuel with not enough air and you're swimming in EGTs and smoke.

Common Turbo Pairings:

• 55s or 57s: Match with stock turbo or mild performance (like a BorgWarner 171702).

• 58s: Pair with a higher flow turbo ( 78mm BorgWarner S400).

• 73s: Big turbo or compound setup. Think 80mm+ or compound twin-turbos. These injectors need serious airflow.

Need help picking a turbo? Just holler at us — we do this all day long.

🚛 What Injectors Do I Need for My CAT C15 ACERT?

Ah, the ACERT. Dual turbos and all kinds of emissions magic. Most ACERTs will come with different injectors than the single turbo 3406Es.

• Many ACERTs use a variation of the 10R8501 or 10R8502 injectors.

• If you’re converting to a single turbo setup or tuning for power, you’ll often end up using 10R0957 or 10R0958 injectors in the conversion.

ACERT builds can be tricky — best to call us with your engine serial number and goals.

🧪 How Do I Know If My Injectors Are Bad?

You don’t need a lab coat — just look for these signs:

✅ Excessive white smoke on cold starts
✅ Fuel in the oil
✅ Rough idle or miss
✅ High EGTs under throttle
✅ Poor MPG, even after tuning
✅ Hard starts or no starts

You can also do a cylinder cutout test or have your shop run injector balance rates. But if your CAT’s running weird, it's usually fuel or air — and injectors are often the culprit.

📋 What Info Do I Need to Give Texas Truck Market for the Right Injectors?

To make sure you get the right injectors the first time, here’s what we’ll ask:

• Engine serial number (starts with MBN, 6NZ, etc.)

• Current injector part number (if you know it)

• Turbo setup (stock, aftermarket, compound?)

• Desired horsepower

• Any ECM tuning or upgrades done already

You give us that, we’ll get you dialed in — no guessing.

What are trim codes to cat injectors

🧠 What Are Trim Codes on CAT Injectors?

Trim codes (also called calibration codes) are unique alphanumeric codes assigned to each Caterpillar injector. These codes are used by the engine’s ECM (Engine Control Module) to fine-tune fuel delivery based on slight variations in manufacturing between injectors.

Even though all injectors of the same part number are designed to spec, no two injectors are 100% identical. The trim code helps the ECM adjust fuel delivery timing and quantity so your engine runs smoothly and efficiently.

🧾 Where Do You Find the Trim Code?

Each CAT injector comes with a barcoded label or etched code—usually a 7-digit alphanumeric string. It’s typically located on:

• The injector itself

• The packaging when you buy new or reman units

When installing new injectors, your mechanic (or you, if you're wrenchin' on it) will enter the trim codes into the ECM using CAT ET (Electronic Technician software).

🛠️ What Happens If You Don’t Enter Trim Codes?

Bad things:

• Poor fuel economy

• Rough idle

• High EGTs

• Misfires

• Potential engine damage over time

Basically, you’re flying blind without them — the ECM won’t know how to adjust for each injector’s specific flow pattern.

💡 Pro Tip:

When ordering new injectors from Texas Truck Market, make sure to:

• Ask if trim codes are included (ours always are ✅)

• Save that code! You’ll need it at install time.

Want help programming your new injector trim codes? Give us a shout at 832-867-3345, and we’ll walk you through it or connect you with a tech who can.

Let me know if you want an image explaining trim codes next!

📞 Still Have Questions?

Whether you’re building a towing workhorse or a dyno-crushing highway runner, the team at Texas Truck Market is here to help you get the right injectors, turbo, and tuning setup.

📲 Call or text us at 832-867-3345
🛒 Or shop online at texastruckmarket.com

Let’s get your CAT back to crushing pavement. 🐾💨