Diesel Tuner's Blog

Blow The Tires off Your L5P With These 4 Upgrades!

Posted by Ben Lawson on Sep 5, 2022 3:30:00 PM



With the L5P being the newest Duramax engine on the scene it's also one of the best performing right out of the box. Making 400hp and 850 ft-lbs of torque when tested on our dyno. This iteration of the Duramax engine has been redesigned in all the right ways. From a thicker crank shaft, to a more advanced turbo, and pistons that can handle more load and heat than we've ever seen come in a stock Duramax engine before. Not only do we get improved performance but we also get an engine that can handle way more power than it left the factory with. Which means with bolt on upgrades alone you can raise the horsepower way beyond stock without having to do any upgrades to the internals of the engine. We've seen L5P's pushing up to 900ph on the stock internals. Even trucks still equipped with emissions systems can gain about 300hp and 500ft-lbs of torque with just a few bolt on upgrades. Today we will show you what upgrades you want on your L5P to make the biggest difference for the least about of money. So if maximum performance is what you’re looking to get out of your L5P this article is for you.

Chris Stiltner - L5P Black - Emissions ON tuning


Here are the top four L5P upgrades!

  • Tune
  • Transmission
  • Turbo
  • Intake 


Tuning Options for L5P


If you want to bump up the horsepower right off the bat, then custom tuning is a great place to start. The L5P already has a lot of power from the factory. However, there is much more power to be had from the stock engine through tuning alone. When fist researching tuning options for L5P's rookie diesel owners may be tempted to go with a box tuner. These devices manipulate the ECM to increase the amount of fuel being added in each injection. While this can result in more power,  it does so at the cost of efficiency. What you really want for your L5P is custom tuning. Custom tuning is designed to bring every element of the combustion cycle to the peak of its efficiency. Custom tuning (offered by DuramaxTuner.com) can bring the horsepower of a stock truck with full emissions system equipped up to 595hp and 1180 ft-lbs torque. Making this a great way to get the maximum power out of an engine. Including engines with performance upgrades already installed. If your truck has a few bolt-on upgrades, a bigger turbo, or aftermarket intake, custom tuning is the best way to get the most power out of upgraded components. Simply because it can allow their efficiency to me maximized. 


Tuning the L5P GMC Sierra

If you use your truck to haul heavy loads on a regular basis there are also tunes designed specifically for you. They will allow you to get the maximum amount of torque and power out of the engine while keeping your engine safe from high exhaust gas temperatures generated from being under a heavy load. They can also improve fuel economy by providing more power which allows the transmission to stay in higher gear and engine at lower RPM. Less reciprocating mass will always improve fuel efficiency.  This is a great performance upgrade for your tow rig. 

For many, this is great to hear. If you're looking to take the L5P to its absolute limits. While some choose to delete their truck, most of us won't actually need to. You can still have a responsive truck that's fun to drive without the added cost of deleting. 


Learn More About L5P Tuning



The transmission is how you get all that power from the engine to the ground, and if your transmission isn't shifting where you'd like it too you could be giving up a lot of that power. Transmission tuning is the best way to fix that. By adjusting the shift scheduling and torque converter lock up scheduling, the transmission can more effectively take advantage of the engine's wider power band. Giving the transmission access to more top-end power. L5P transmisson work

This is especially useful when the engine already has a tune or other modifications installed on it that change the stock power band. Any time that the engine's power band or drive output ratios change, like putting on larger than stock tires, attention should be given to the tuning of the Transmission Control Module (TCM). That being said, any modifications that plan to be done to the truck should be done before TCM upgrade is done.


Transmission Tuning For L5P


Along with improving performance, transmission tuning can also improve the durability of your transmission. By increasing line pressure electronically stronger holding strength can be added to the clutch packs, overall improving your transmissions durability in lugging or high output scenarios. 

Blue L5P GMC Sierra Diesel

This all sounds great but if you don’t already know the L5P can be matched with one of two different transmissions depending on what year your truck is. If you have a 2017 - 2019 L5P Duramax, your truck came with the 6-speed Allison 1000 transmission. And if you own a 2020 or newer your truck is paired with the new 10-speed Allison 1000 transmission. Both of these transmissions are great however only one is currently tunable and sadly for the guys with the brand new trucks it’s not the 10-speed. Currently, due to software restrictions, only the 6-speed Allison 1000 is currently tunable. So if you’re thinking that transmission tuning is in your future you’ll need to make sure either your truck is a 2017 - 2019 model. Otherwise you'll have to have a physical shift kit installed in the transmission to get the same adjustability. While this process is much more involved, it is also well worth it!



Upgrading from the stock turbo is going to be one of the best ways to get the peak performance out of an L5P. Remember how you’ll only be able to get around 600hp out of the stock motor with tuning no matter if your truck is deleted or not. Well, this is your limiting factor. 


L5P Turbo

The stock turbo is capable of moving 60-62 pounds per minute (ppm). Typical power figures show that for every 1ppm we can expect to get 10hp. So we can calculate that the stock turbo is good for reaching a maximum of 600hp, maybe 620hp on the best day, with a proper tune. So if you want to see horsepower figures above the 600 mark you will need to upgrade from stock. With an upgraded turbocharger you can expect to get anywhere from 70ppm to 80ppm allowing for maximum horsepower to be raised up to the 700hp-800hp range. These horsepower figures are only achievable with a tune however and just upgrading your turbo on a stock tune will only net you an additional 20-25hp over stock. So tuning should also be a priority when deciding to upgrade turbos. 

Get Info On The L5P Stealth 67




When it comes to intakes on the market for the L5P there are many options, From cold air intakes to turbo intake horns, and knowing when and where to start is important for getting the most bang for your buck. Upgrading parts of your intake makes for a great supporting modification to other upgrades you may want to do to your truck as well.


If you are thinking about getting a tune or upgrading your turbo, then installing an aftermarket intake on top of either is a great idea. This is will get you the most power for your money as well as be able to maximize the performance you get out of your tune or turbo upgrade. Getting your truck tuned is definitely necessary to get actual performance out of an aftermarket intake. Without a tune, you may see a slight increase in performance as well as better fuel efficiency. But you won't be able to use it to its full potential without tuning. 


L5P After Market Intake Horns

If upgrading your stock turbo is in your plans then an upgraded intake horn is also a necessary upgrade. The stock plastic intake horn the L5P comes with you will choke any upgraded turbo. The upgraded intakes on the market all feature larger 3.5in tubing and a less restrictive opening. Providing more air volume and smoother flow to the turbo inlet. This less restrictive opening does come with a price though and that would be in the form of turbo surge. Since most aftermarket intake horns either don't include anti-surge features or have very poor supplements for the stock solution. Turbo surge, which will shorten the turbos life, is almost certain to occur. Therefore an aftermarket anti-surge ring is also something you won't want to go without if you are planning on upgrading the turbo along with the turbo intake horn. The upgraded surge ring simulates the stock anti-surge ring built into the stock intake horn but is redesigned to provide a larger opening to match the upgraded turbo’s larger compressor inlet. This will prevent any restriction along with providing better anti-surge performance than after-market intakes offer alone.


Find An L5P Anti-Surge Ring


L5P Anti Surge Ring


Cold air intakes are another possible upgrade to your L5P’s intake system. Aftermarket cold air intakes such as the ones offered by WC Fab, S&B, and Banks all feature enclosed air boxes that still use the factory ram air intake. All cold air intakes will keep intake air temperatures cooler which means better air density and more air entering the engine. Cooler intake air temps combined with improved designs for better flow and less restrictive filters all add up to being able to produce  more power with better efficiency. Some cold air intakes even claim to reduce soot output which will allow more time in-between re-gen cycles. Just by adding a cold air intake, you can expect to see a slight bump in power around 10-12hp however just like in any case adding a tune on top of the cold air intake will get you the most performance out of it. On a tuned truck that's only sporting a cold air intake you can expect to see an extra 30-40hp on top of what the tune could normally add. 


With these simple modifications, a lot more performance can be brought out of the L5P platform. Tuning is arguably one of the best ways to see a large increase in power right off the bat or get you the most power from a heavily modified engine. If peak performance is what you want out of your L5P then the turbo and intake are both limiting factors that will need to be upgraded. As well as the transmission which is another very important part of getting all that power you’ve made to the ground. All of these mods should be done together to get the best version of your L5P. Overall planning should be done so you can maximize the efficiency of the parts you choose to add as well as get the biggest power increase for your money. This list was made so you know what the potential worthwhile upgrades for your L5P are and how they can best be used together. If you're interested in learning more about the topics in this article please check out the links below for more information!


Topics: Duramax Performance, Duramax Power, Turbo, TCM Tuning, L5P, L5P Tuning, Upgrades