The 2017-2023 L5P Duramax horsepower numbers are impressive right out of the gate. Arguably the best diesel engine GM has ever built, it delivers a respectable 445 horsepower and 910 lb-ft of torque in its stock form.
However, for diesel enthusiasts, "stock" is simply a starting point. The factory emissions systems restrict airflow, limit fuel potential, and dilute engine oil with soot. This leaves owners asking one big question: What is this engine actually capable of when it's allowed to breathe?
Here is the deep dive into the real-world performance of a deleted and tuned L5P.
The Short Answer
A fully deleted and tuned L5P Duramax typically produces between 550 to 600 horsepower and over 1,250 lb-ft of torque on a standard "Street" or "Performance" tune. With a maximum effort "Race" tune and proper transmission tuning, the L5P can exceed 640+ horsepower at the crank using the stock turbo and fuel system.
Understanding the Factory L5P Limitations
To understand the gains, you have to understand what is holding the truck back. According to official 2017 Duramax L5P specs, the engine is equipped with a robust reciprocating assembly (stronger connecting rods and crank than previous generations) and a highly capable Denso fuel system.
However, modern EPA regulations force the engine to operate inefficiently. The exhaust is strangled by filters, and the intake air is heated up by recycled exhaust gas. By using an L5P delete kit, we aren't "adding" parts to make power; we are simply removing the barriers that prevent the engine from running at its natural efficiency.
What Exactly Gets Deleted from Your Duramax? (The Hardware & Essential Mods)
When we talk about a "delete," most people think of the "Big 3" restrictions: EGR, DPF, and DEF. While these are the primary emissions components, optimizing an L5P for maximum reliability and flow involves a complete ecosystem of parts.
At Spetuner, we provide a comprehensive range of L5P mods to address every bottleneck:
1. The Mandatory Deletes (The "Big 3")
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EGR (Exhaust Gas Recirculation): This system routes dirty exhaust gas back into your intake manifold to lower combustion temperatures. Removing this stops soot from entering your engine and keeps your intake air clean and cool.
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DPF (Diesel Particulate Filter): A massive filter in the exhaust system that traps soot. It creates significant backpressure, acting like a cork in your exhaust pipe.
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DEF (Diesel Exhaust Fluid): The fluid injected into the exhaust to reduce NOx. Removing this eliminates the complex heater pumps, tanks, and "Limpar Mode" countdowns associated with DEF system failures.
2. Performance Enhancers (Highly Recommended)
To truly "wake up" the L5P, you should look beyond just the basic pipe. The general specialized upgrades to perfect the build:
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CCV Reroute Kit (Crankcase Ventilation): The factory CCV vents oily crankcase gases back into your L5P turbo inlet, coating your turbo blades and intercooler in oil sludge. Our CCV Reroute Kit vents this to the atmosphere, keeping your turbo clean and extending its life.
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Downpipe & Up-Pipes: The factory downpipe is flattened and restrictive. Upgrading to a high-flow downpipe allows the L5P turbo to spool faster and reduces Exhaust Gas Temperatures (EGTs).
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Performance Muffler: If you want the flow of a straight pipe but want to reduce the "drone" on the highway, a high-flow performance muffler is the perfect middle ground for your L5P mods.
Shop All L5P Duramax Performance Parts
How Much Horsepower Does a Deleted and Tuned L5P Have?
To appreciate the gains, we must first look at the baseline. The Stock L5P Duramax is rated from the factory at 445 HP and 910 lb-ft of torque (Crank Horsepower). However, due to drivetrain loss through the heavy-duty Allison transmission, a stock truck typically puts down roughly 380-400 HP at the wheels on a dyno.
Once the restrictive hardware is removed, the real magic happens in the software. The factory Denso fuel system and stock turbocharger have significant headroom, allowing for massive gains without needing mechanical upgrades.
Below is the breakdown of L5P tune gains you can expect from professional custom tuning (included in our unlock bundles). These numbers represent the added power over stock.
Note: These are estimated Crank Horsepower numbers.
| Tune Level | Additional HP | Total Est. HP | Torque Gains | Application |
|---|---|---|---|---|
| 1. Optimized Stock | +20 HP | ~465 HP | +40 lb-ft | Heavy Towing |
| 2. Tow | +60 HP | ~505 HP | +100 lb-ft | Light Towing / Daily |
| 3. Street (Eco) | +100 HP | ~545 HP | +180 lb-ft | Best MPG / Daily |
| 4. Performance | +150 HP | ~595 HP | +240 lb-ft | Spirited Driving |
| 5. Max Effort (Race) | +200 HP | ~645 HP | +350+ lb-ft | Track Use Only |
The Crucial Step: E41 ECM Unlock and TCM Tuning
This is where the L5P differs from older models like the LML. GM locked down the L5P's computer (E41 ECM) with military-grade encryption.
- The E41 ECM Unlock: You cannot simply plug a tuner into a stock L5P. The ECM must be physically removed and "unlocked" by a specialist, or you must swap in a pre-unlocked unit.
- TCM Tuning (Transmission): The Allison 10-speed is incredible, but when you push past +150 HP, stock clutches may slip. We recommend TCM tuning to increase line pressure for safety.
Performance Benefits of Deleting L5P Duramax
L5P Duramax horsepower is just a number on a sheet of paper. The driving experience changes in other ways:
- Improved L5P Delete MPG: Without the DPF "Regen" cycles dumping raw diesel into the exhaust to burn off soot, and with a more efficient air/fuel mixture, most L5P owners report a 3-5 MPG increase on the highway.
- Engine Longevity: By deleting the EGR, you stop feeding abrasive soot back into your cylinders. Your oil stays golden and clean for thousands of miles, reducing engine wear.
- Throttle Response: The turbo lag is significantly reduced. The truck feels lighter and more responsive to pedal input.
- Sound: A 4" or 5" straight pipe allows you to finally hear the V8 diesel rumble.
How Much Does It Cost to Delete an L5P Duramax?
The 2017+ L5P is more expensive to modify than older generations (like the LML or LBZ), primarily due to the locked ECM. However, budgeting correctly prevents surprises during the install.
Below is a realistic cost breakdown of a full L5P delete project using premium parts from Spetuner. We believe in transparency—here is exactly what you are paying for.
1. What is the Price Breakdown for L5P Delete Parts?
| Component | Estimated Cost | Why You Need It |
|---|---|---|
| GM Duramax L5P Tuner & Unlock Tool | $2,699.00 | The Brains. Includes ECM Unlock Service, tuning hardware, and credits. |
| DPF Delete Exhaust Kit | $298 - $1,099 | The Flow. Choices: Race, DP-Back, w/ Muffler, or Duals. |
| EGR Delete Kit | $159.77 | The Health. Removes EGR cooler/valve. |
| L5P CAN BUS Plug Kit | $140.00 | The Protection. Seals open connectors to prevent corrosion. *Essential.* |
| CCV Reroute / Downpipe / Up-Pipe | $219 - $249 ea. | Optional upgrades for reliability and flow. |
2. How Much Should I Budget for the Full Kit?
You might be wondering: "Do I have to buy all of this separately?" Not necessarily. Most owners opt for our All-in-One Bundles to handle the "Big 3" limitations (EGR, DPF, DEF) in one go.
Here is the total estimated cost depending on your build goals:
Option A: How Much Does the Standard "All-in-One" Kit Cost?
Includes: All-in-One Kit (Tuner + Unlock + Exhaust + EGR) + CAN BUS Plugs
This setup gets your truck deleted, tuned, and reliable. It removes all emissions failures and adds the horsepower you want.
- All-in-One Kit: $3,166.99 – $3,667.99
- CAN BUS Plug Kit: $140.00
- TOTAL: ~$3,300 – $3,800 USD
DPF/EGR/DEF Delete 2017-2023 L5P 6.6L Duramax All-in-One Kit
L5P delete kit
$3,166.99 – $3,667.99
Buy Now
Option B: What Does a "Full Performance" L5P Build Cost?
Includes: Everything in Option A + CCV Reroute + Downpipe + Up-Pipe
This is for the owner who wants to maximize longevity and airflow efficiency.
- Essential Total: ~$3,300 – $3,800
- Optional Upgrades: ~$720
- TOTAL: ~$4,000 – $4,520 USD
Check Current Prices for L5P Delete Kits Here
Is Deleting Your L5P Worth the Investment?
Deleting an L5P is an investment. Between the delete pipe, the muffler delete, the ECM unlock service, and the tuner itself, the cost is higher than older trucks.
However, if you plan to keep the truck for the long haul, yes, it is worth deleting your L5P. You are trading the upfront cost of modification for the long-term removal of expensive emissions failures (DEF pump failures, clogged DPFs) and gaining a truck that runs cooler, stronger, and more efficiently.
Frequently Asked Questions (FAQs)
Q1: Will deleting my L5P void the factory warranty?
A1: Yes. Deleting the emissions system and flashing the ECU will void the powertrain warranty. This is recommended for trucks out of warranty.
Q2: Do I need to upgrade my turbo or injectors for a delete?
A2: No. The stock L5P Denso fuel system and turbo are capable of handling up to 600-650 HP safely.
Q3: How much MPG will I actually gain?
A3: While it varies by driving style, most owners see an improvement of 3 to 5 MPG on the highway.
Q4: Can I delete my L5P without unlocking the ECM?
A4: No. The 2017+ L5P ECM is encrypted. You must perform the E41 ECM unlock service.
Q5: What happens to the DEF fluid tank?
A5: It becomes dead weight. You can leave it or remove it. Just ensure you use the L5P CAN BUS Plug Kit to seal the connections.
Disclaimer: All products and information provided are for closed-course competition use only. Removing emissions equipment is a violation of federal laws for road-going vehicles. Please check your local regulations.
