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...

Boost Testing your diesel is essential!  Common symptoms of a boost leak include Increased Smoke, Higher EGTs, Excessive Lag, and Loss of Power.  Every truck that comes in our shop here at Calibrated Power, gets a boost test.   It seems about 85% of them have a boost leak when they show up.  Most of the time customers report still seeing peak boost on their gauges despite a boost leak. 

If you work with diesel trucks long enough, you’ll see leaks just about everywhere in the charged air system at one time or another. Remember, the charged air system includes anywhere from the turbocharger to the intake manifold. Your Intercooler system, Exhaust Gas Recirculation components, and even the Turbocharger compressor cover can all develop boost leaks.

Does your diesel have High EGTs, Excessive SMOKE, Increased Turbo Lag, and Less Power than it used to? Let’s talk about boost leaks.

Your truck needs air! Not a little bit of air. Your diesel engine needs all the incoming air it can get. Increasing air in the combustion process will help manager your Exhaust Gas Temperatures, Limit your smoke output, and increase your power.

This is why boost leaks kill diesel engines. Boost leaks can result in a smokey, laggy, dog-of-a-truck, which runs hot and burns fuel. Basically, the exact opposite of what you want from your diesel.

Boost leaks commonly occur in boots and clamps throughout the charged air system. That’s anywhere from the turbocharger to the combustion cylinder. Your intercooler system, Exhaust Gas Recirculation components, and even the turbocharger compressor cover can all develop boost leaks over time.

Too often trucks come into our shop experincing high EGT's, turbo lag, excessive smoke output, and bad fuel mileage which are all symptoms of a boost leak. It is so common to develop a boost leak that we now require all trucks to have a leak down test done prior to strapping them down on the dyno. What's funny is, most truck owners that we do identify boost leaks on never even knew they had one. The reality is that even if you can hit peak boost, you may have a leak, especially if you have a variable vane turbo. Variable vane turbos will change vane position and other operations to try to compensate for the reduced level of boost pressure in the intake system. Leaving you driving around without an idea that your turbo efficiency has taken a hit.