Why did we test the Stealth box and not others? Other than the Banks Derringer, it’s the only other tuner available for the 2020 Duramax. So, what horsepower addition does Stealth claim? Going to the product page may leave you scratching your head. It’s not until you follow the links to their frequently asked question section to find a claim of 50-70 horsepower. Wait, 50-70 horsepower?
How do they not know precisely what their tuner adds? Their excuse, they say, is that it’s not designed to be dyno tested. This again, left us scratching their heads. It’s kinda like claiming you’re six feet tall but not allowing anyone to measure your height.
Banks engineers hooked the unit to a piece of test equipment to characterize the module, fingerprinting it by simulating the signals that the device would see during the operation of the vehicle. The system then checks what the module does with those signals throughout the range of the sensors that the device is trying to manipulate. Now that they understood how the box manipulated the signals, it was time for a dyno test.
Then they installed it in our 2020 Denali and where they measured a best gain of 42 horsepower. Let’s put it in perspective, the Banks Derringer for the 2020 Duramax add 81 horsepower, doubling Stealth’s actual gain. Derringer is also connected via OBD and closely monitors the engine and transmission, while the Stealth has no idea what it’s doing to the engine, transmission, EGTs, coolant temp, etc.
It makes you wonder just what the competition does for development and testing if they can’t even come up with a straight answer on what their own product does.