Part 1 of 2 I found this bulletin from a gm mechanic. It is for a Duramax diesel: INFORMATION Bulletin No.: 06-06-01-007B Date: June 27, 2008 Subject: Information On Identifying Duramax(TM) Diesel LB7, LLY, LMM, LBZ Overpower Engine Breakdown or Non-Function Due to Aftermarket Power-Up Devices vs. Non Overpower Engine Non-Function of Pistons, Cylinders, and Valvetrain Components Models: 2001-2008 Chevrolet Silverado 2003-2008 Chevrolet Kodiak 2006-2008 Chevrolet Express 2001-2008 GMC Sierra 2003-2008 GMC TopKick 2006-2008 GMC Savana with Duramax(TM) 6.6L V8 Turbo Diesel Engine (VINs 1, 2, 6, D - RPOs LB7, LLY, LMM, LBZ) Supercede: This bulletin is being revised to add additional information on identifying fuel related Aftermarket Power-Up Devices. Also a Caution statement was added regarding likely Powertrain damage and warranty. Please discard Corporate Bulletin Number 06-06-01-007A (Section 06 - Engine/Propulsion System). Caution: Customers should be informed if a hard part failure is observed in the engine, transmission, transfer case and/or other driveline components, it is likely that powertrain components were weakened to the point of premature failure, while subjected to the higher stresses from Aftermarket Power-Up Devices. Failures associated with the installation of Aftermarket Power-Up Devices, which have been verified, are not covered under the terms of the New Vehicle Warranty. General Motors Position On Aftermarket Power-Up Devices Important: General Motors does not support or endorse the use of devices or modifications that, when installed, increase the engine horsepower and torque. Refer to bulletin number 04-06-04-054 - Warranty Admin. - Non-GM Parts and Accessories (Aftermarket). Important: For further information on aftermarket power-up kits, refer to February 2006 Emerging Issues Course Number 10206.02D. In Canada, information on aftermarket power-up kits will be covered in the April 2006 TAC TALK program. Aftermarket power-up devices are non-approved by General Motors. These devices are usually piggy-backed in the main engine harness or remain connected to the diagnostic connector to upload the calibration to the ECM. Recent warranty reviews of returned engines show engine breakdown or non-function due to power-up devices that are utilized for increased horsepower and torque. The following information will assist technicians in identifying overpower engine breakdown or non-function due to aftermarket power-up devices vs. non overpower engine breakdown or non-function. Non-GM parts can alter the design of the vehicle. GM dealers need to be aware of the quality of parts being installed on vehicles. If failure occurs as a result of installation of sub-par parts, warranty coverage may be denied. Refer to Service Bulletin Number 04-06-04-054 Warranty Admin. Non-GM Parts and Accessories (Aftermarket). Installed Power-Up Kit Aftermarket power-up kits have become a very popular add on for performance-minded customers. These devices can add horsepower and torque and can add additional stress to the engine. These aftermarket calibrations take the Duramax powertrain outside of its design torque and horsepower rating. They do this by altering air/fuel ratios and injector timing, resulting in excessive cylinder pressure and temperature. When these calibrated parameters are altered, it will upset the design balance and can lead to a reduction of engine life expectancy. Generally, in inspection of Duramax engine failure due to power-up failures, two or more cylinders will be affected. Installed Power-Up Kit ^ Once installed, the calibration may mask itself with the factory original calibration ID and may remain the same. ^ A Tech 2(R) will not positively enable you to identify the use of a power-up device. ^ Some companies that offer power-up devices claim increases of 150 or more horsepower and 300 or more lb/ft pounds of torque. ^ A vehicle that is used to the power-up device potential 100% of the time will see earlier engine wear and breakdown. ^ A vehicle that takes advantage of additional power, but on a less frequent basis, may not see premature engine wear and breakdown until later in the engine's life. ^ A vehicle not pushed to its limits of the power-up device often may not encounter premature wear and breakdown until after the engine is out of warranty. Duramax(TM) Powertrain Horsepower / Torque Ratings The following horsepower and torque increase over the past years required new internal components to accommodate the increase. ^ LB7 - 300 hp with 520 ft/lb of torque for model years 2000-2004 ^ LLY - 310 hp with 605 ft/lb of torque for model years 2004-2008 ^ LBZ - 360 hp with 650 ft/lb of torque for model year 2006-2008 ^ LMM - 365 hp with 660 ft/lb of torque for model year 2007-2008 LBZ Improvements To reliably achieve an increase in 50 horsepower with 45 ft/lb torque, the Duramax(TM) diesel had to be revised in many areas. A few of the revisions on the 2006 LBZ were: ^ New pistons with a revised compression ratio. ^ Wrist pins that are larger in diameter. ^ Connecting rods with added material to increase the I section strength. ^ Engine block and machining changes. ^ Cylinder heads. Duramax(TM) Life Expectancy The Duramax 6.6L V8 Turbo Diesel Engine is sold with a warranty of 100,000 miles/160,000 kilometers. The Duramax has been tested to survive upwards of 200,000 miles/320,000 kilometers. The Duramax powertrain is designed for reliability, peak horsepower and torque within its design limits. When a customer installs a power-up device, it drastically reduces the mileage ratings. Important: Cylinder Wall Spotting (commonly referred to leopard spots) is from the induction hardening process of the top 1/3 of the cylinder wall. This is normal for the Duramax(TM) Diesel. Identifying Fuel Related Aftermarket Power-Up Device Aftermarket companies have developed a performance pressure relief fuel valve for Duramax diesel engines. Refer to above graphic illustration. The performance pressure relief fuel valve attaches to the fuel rail in place of the OEM valve and will not allow any fuel return to the tank, giving 100% of the fuel to be available for additional engine performance. This may cause additional fuel related driveability concerns and may set the following DTC'S: ^ DTC P1093 Fuel Rail Pressure (FRP) Low During Power Enrichment ^ DTC P0087 Fuel Rail Pressure (FRP) Too Low Aftermarket companies have developed a replacement performance/economy fuel injector nozzle. Refer to above graphic illustration. The performance/economy fuel injector nozzles replace the OEM fuel injection nozzles. The aftermarket companies claim increased horsepower, improved fuel atomization, lower exhaust gas temperatures and increase fuel economy. This may cause additional fuel related driveability concerns and may cause internal engine damage to the pistons and fuel injector nozzles.