Diesel Tuner's Blog

With so many drop-in turbo upgrades to choose from it can be hard to make sure you're getting exactly what you want, and need, out of a drop-in turbo upgrade for your '04.5-'16 Duramax. Could your stock LLY, LBZ, LMM, or LML turbo be enough to crank out the power you're looking for if you really turned it up?  Do aftermarket replacements really live up to their claims? Today we'll take an in-depth look at what you can expect out of varying levels of drop-in turbo upgrades for your 6.6L Duramax and compare them to what the your stock charger can provide. Below is the data from our in-depth engine dyno testing of a Stock VVT/LML turbo, Stealth STR, Stealth Mach 1, and Stealth Mach 2 turbo. All tests were conducted on a built LBZ engine connected to our Dyno-mite water brake engine dyno.  This empirical data was gathered under real-world circumstances, with a serious effort made to control as many variables as possible for consistency. Installation, instrumentation, and operation of this engine through a gauntlet of tests that took several weeks.

Turbo and Test Descriptions

Dyno Engine: The platform that we will be using for this test is a 2007 6.6L LBZ Duramax that received the following upgrades before testing:

• Custom tuning
• S&B Cold Air Intake
• 100% over injectors
• 10mm CP3 pump
• Head studs
• Alternate firing order cam
• Upgraded pistons
• Upgraded crank shaft
• Upgraded connecting rods

These upgrades were necessary to be able to handle the power levels that we pushed this engine to during the testing of all 4 of these turbos. 

Testing: We performed three tests to gauge the overall performance of each turbo in comparison to each other. Obviously the bigger the turbo, the more top end power. But what about all the other factors that go into creating that power like drive pressure, EGTs, air/fuel ratio, etc? What about in towing conditions and all-around drive-ability? The first test that we will present is the "Max Power" test which is your traditional dyno and power test.  This test will provide a general comparison in terms of the difference in power that these different turbo options can produce. The second test presents spool up data and will give a good visualization of the difference in drivability and turbo lag that each turbo can provide. Finally our "Tow Test" is the ultimate data provider, providing insights on key data points including EGT's, drive pressure, air/fuel ratio Ect...

When it comes to turbochargers for diesel trucks, Stealth Turbos have made a name for themselves by offering performance, reliability, and quality upgrades across the board. Whether you’re driving a 6.6L Duramax, 6.7L Powerstroke or a 6.7L Cummins, Stealth turbos can provide solutions for a multitude of different needs and wants—from stock replacements to high-performance setups. In this blog post, we’ll break down the key differences between Stealth’s STR, Mach 1, and Mach 2 line's of turbochargers and help you decide which one is the best fit for your driving needs.

Over the years, GM has changed a lot regarding the turbos they use on Duramax engines. Not only have they changed manufacturers a handful of times but each RPO has its own unique measurements for key components. This can make it a headache when trying to track down exactly what the measurements of your stock turbo are. Luckily we've compiled this list of stock Duramax turbo specifications along with other helpful information so you can get a good idea of what you're already working with before you dive into the sea of turbo upgrades these trucks have to choose from. However, while some turbos may have the same peak power output, the size and shape of specific components can affect things such as exhaust gas temperature, drive pressure, and turbo efficiency range.  

One of the biggest advancements in turbo design since we first started applying them to diesel engines over 70 years ago has been the invention of Variable Geometry Turbos. These turbos utilize a set of movable vanes on the inside of the exhaust housing that allows the actuator to vary the area in which exhaust gasses can pass through them. This allows the exhaust side of the turbo to increase or restrict the flow of exhaust hitting the turbine wheel. In some designs it also changes the flow direction of gasses hitting the exhaust turbine as you can see illustrated below. 


When restricted, the velocity of the exhaust gasses increases which helps spin the turbine faster than a fixed geometry turbo would. This gives the turbo the ability to spool the turbine and compressor wheel up much better than it normally would even with a low volume of exhaust pressure traveling through the system. This helps to spool the turbo at lower RPMs to create boost where it would normally be lacking. This is why variable geometry turbos (VGTs) are such an advancement. They have the ability to significantly reduce turbo lag and provide much better response and turbo efficiency across a range of RPMs. 

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.

Here are the top four L5P upgrades!

• Tune

• Transmission

• Turbo

• Intake 

Turbocharging diesel engines is nothing new.  The most basic premise of a diesel engine is the more fuel and air you mix during compression, the more power you get. 

• Wastegate Turbocharger
• Fixed Vane Turbocharger
• VVT/VGT Turbocharger
• Compound Turbocharger 
• Twin Turbocharger
• Dual Scroll Turbocharger

Between 1885 and 1916 a few patent applications were submitted for products that address the general concept of turbocharging, but it was in 1925 that Swiss Engineer Alfred Buchi put the first commercially available turbo on a 10 cylinder diesel engine.  Turbochargers use exhaust gas pressure to drive a Turbine Wheel that is connected to a Compressor Wheel. The compressor wheel forces cold air into your engine. You're using exhaust pressure to create boost pressure. 

We all ask the question at some point, should I upgrade my turbocharger?  Improving performance is always something us diesel owners are thinking about.  Maybe your charger blew up or maybe you just want to help cool your truck's EGTs a bit more.  There are a ton of different reasons why you may want to upgrade.  With that comes a ton of different variables that go into which turbo you SHOULD buy.  Let's take a look at three big areas to consider. 

#1: How Do You Use Your Truck?

You've probably heard this one before, if you're new to the diesel world maybe you haven't.  Either way its a very important topic to consider, especially when choosing a turbo upgrade.  Do you commute 20 miles to work and back daily?  Do you haul any toys?  Maybe you hotshot as a career, all these are some of the ways a driver uses his diesel truck.  A driver that tows a lot would best be suited for the Stealth 64, why?  It runs more efficiently at higher horsepower numbers while loaded.  The truck will sustain a heavy load for longer because the heat that the turbo is introducing is lower than a stock charger.  Lower piston temps, lower EGTs equals more time and a larger buffer before the truck is affected by the added heat.  

Duramax VVT Upgrades:

The 2004.5-2005 LLY was the first model Duramax to be equipped with a Variable Vane Turbo (VVT).  VVT  technology provides quicker spool-up, better EGT control, and better overall boost control.  This is also commonly referred to as a VGT or Variable Geometry Turbo. 

To understand the basics of a VVT or VGT technology take a look at this VIDEO on YouTube.

The stock Duramax VVT turbo from 2004.5 until 2010 is similar.  Slight changes to each model (LLY, LBZ and LMM) were made in compressor size, aspect ratio, blade profile and other features.  Despite these changes, you will find the same peak power potential of approximately 530 RWHP.  As a Duramax performance enthusiast this is probably just not enough power to keep your interest for long. 

There are many upgrade options on the market.  Deciding which one is the best for you can be tough.  An endless amount of forum threads and user stories makes it challenging to decipher fact from opinion.  

Stealth 64 Turbo Product Links:

• Stealth 64 LB7
• Stealth 64 VVT
• Stealth 64 LML

Stock Duramax Turbo Upgrades!

Duramax owners are generally proud of how their stock turbos perform.  They spool quickly, run hard and are capable of over 500 RWHP (once you tune it and make a few supporting modifications to handle the power).  However, after driving your truck around 520 RWHP for a while, the addiction will creep in and you may find yourself shopping for more power.  We all do it!  For some, it may not even be about more power, it may be about EGT control under load, or it may just be the factory turbo had an issue and needs to be replaced.  If you are anything like me, you will not want to replace it with the factory components if there is an upgraded, after market, charger available. 

Drop-In Duramax Turbo Options

In the old days, there was no such thing as a "drop-in" turbo.  You pretty much had to buy a turbo that was designed for a different application and convert it to run on your Duramax.  Meaning the requirements for installation included several custom fabricated pieces to make it work.  

As technology in the diesel performance industry has advanced, our options for parts have expanded.  No longer do we have to use semi turbo's and roal coal to make power.  Now with the common rail injection system and variable vane turbo advancements there is a real need to find a turbo that makes more power than stock, while retaining all the benefits of a stock turbo. 

Benefits of a stock turbo:

• Quick Spooling 
• Clean installation
• Reliable
• Serviceable by any dealer or reputable shop
• Requires no custom fabrication

However, they do lack peak power, and peak power matters!  When looking for which upgraded unit to replace the stock turbo, we recommend matching the replacement as close as possible to the desired power level to minimize compromising drive-ability.  Any extra capacity you buy in peak for performance will cost you low end response.  Example: Looking to make 650rwhp? Buy a turbo that can just barely squeak out 650rwhp, do not buy something that's good for 850rwhp because it will drive poorly a light load.