Backyard Power Mods: High-Mileage Duramax DIY for Under $500

It’s understandable that with today’s newer truck prices, more owners are opting to hang onto their five- to 10-year-old trucks, even when the mileage starts getting into the 200,000+ range. For many, it’s difficult to justify an $800 payment for a new truck when their current rig still fits their needs and runs well. Sure, the new interiors with air-conditioned seats and factory navigation are nice and the new engines are producing power levels never thought imaginable from the factory just a few years ago, but a good used truck is still something to hold on to.

With the longevity found in most diesel engines, regular maintenance and a few performance upgrades really can swing the pendulum in favor of your older diesel truck. The payments you would drop into a new truck will go a long way towards upgrading your older rig and will still cost you less cash in the end. Let’s take a look at a few things you can do to improve your well-loved and paid-for truck. The Chevy seen here is just one example, and many options are available for most brands of diesel pickups on the road today in the U.S.

1. The LB7 Duramax has proven to be a solid and reliable engine platform, outside of some early injector failure issues that could still be covered by GM under warranty. Offered in the 2001-2004 model year trucks, the LB7 is known for offering good fuel mileage and being emissions equipment free. With new truck prices soaring to more than $60,000, more and more owners are choosing to hang on to their current trucks just a bit longer. As the odometer continues to rack up the mileage, there are some worthwhile and inexpensive upgrades that can be made under the hood to only enhance that LB7’s performance and efficiency. — The LB7 Duramax has proven to be a solid and reliable engine platform, outside of some early injector failure issues that could still be covered by GM under warranty. Offered in the 2001-2004 model year trucks, the LB7 is known for offering good fuel mileage and being emissions equipment free. With new truck prices soaring to more than $60,000, more and more owners are choosing to hang on to their current trucks just a bit longer. As the odometer continues to rack up the mileage, there are some worthwhile and inexpensive upgrades that can be made under the hood to only enhance that LB7’s performance and efficiency.

2. This particular truck is coming up on 300,000 miles and shows its fair share of abuse and time spent on dirt roads hauling cattle, but for less than $500 and just a few hours time, minor upgrades can breathe new life under the hood and help save a little money at the gas pump. First off, the factory airbox can be removed and modified to allow better airflow to the stock-style air filter, which can improve throttle response, power and mileage. Best of all, it’s free. Here you see the airbox with the lid off and the filter removed. — This particular truck is coming up on 300,000 miles and shows its fair share of abuse and time spent on dirt roads hauling cattle, but for less than $500 and just a few hours time, minor upgrades can breathe new life under the hood and help save a little money at the gas pump. First off, the factory airbox can be removed and modified to allow better airflow to the stock-style air filter, which can improve throttle response, power and mileage. Best of all, it’s free. Here you see the airbox with the lid off and the filter removed.

The 2001-2004 model years of the LB7 Duramax has been extremely popular among light duty truck owners and for good reason. As the first Duramax platform offered by GM for their 2500HD and 3500 line-up, the LB7 offers a good mixture of power and fuel mileage. It’s not uncommon to hear claims of 18-20 mpg from LB7 owners, and even though the platform was plagued with semi-serious injector problems, some can be found with injectors that were replaced under warranty. In addition, if you have an extended warranty, it’s still possible that problem injectors can be replaced under the extended factory warranty.

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Another issue with any high-mileage truck is wear on the steering components and the wheel bearings. This is easily fixed and the upside is that with a diesel engine under the hood, you’ve got many more miles that can be put on the engine before a rebuild is required than with a gasser.

Diesel engines are fairly reliable and efficient and for those running trucks in near-stock form that are on a tight budget, there are a few upgrades that can be done for less than $500 bucks. With very little time invested, these modifications will breathe new life into an old diesel truck. Here are the upgrades to consider:

DIY Airbox Modifications

The first upgrade is a DIY Airbox modification. In stock form, the LB7 Duramax should produce 270-290 rear-wheel horsepower and with a mild tuner the can be bumped to around 400 hp safely. At these power levels, the factory airbox and paper-style air filter is sufficient, since it offers great filtration and fairly decent flow. While upgrading to a performance cold air intake has its advantages, when working on a budget, the factory airbox can be modified to improve flow through the filter, enhancing your engine’s performance and efficiency.

While the airbox modification won’t cost you anything, a new replacement paper air filter from your local parts supply house is going to set you back $30-50 depending on the brand. But if your filter looks like this one, it’s money well spent, as the filter is your only real insurance policy to keeping the factory turbocharger, cylinders and pistons free of unwanted dirt and debris.

The factory airbox uses an opening on the passenger side to draw air from the fender well area. On the front side of the box, there’s a triangular-shaped portion that can be cut out and removed to allow an additional spot for the filter to draw air. This location is directly behind the headlight and has an open cavity that still draws relatively cool fresh air. Using a small cut-off wheel or something similar, the plastic box can be cut out and deburred with a file, then reinstalled into the truck. Depending on the condition of your current air filter, it may be worth it to install a new element from your local parts store or most performance intake companies offer a reusable, cleanable drop-in filter that could be used as well.

4. With the factory airbox removed from the truck, you’ll notice a small opening on the passenger side of the box where it pulls air from the inner fender well area. On the front side of the airbox, you’ll also notice a triangular-shaped section on the lower part of the box, seen here. This area can be cut out and removed to allow an additional spot for intake air to enter the box, adding some additional flow for the filter. Using a cutoff wheel, the plastic will cut easily. A small file can then be used to debur the edges before the box is reinstalled in the truck. While this may not seem like much, the added airflow can make an improvement over stock without costing you anything out of pocket. — With the factory airbox removed from the truck, you’ll notice a small opening on the passenger side of the box where it pulls air from the inner fender well area. On the front side of the airbox, you’ll also notice a triangular-shaped section on the lower part of the box, seen here. This area can be cut out and removed to allow an additional spot for intake air to enter the box, adding some additional flow for the filter. Using a cutoff wheel, the plastic will cut easily. A small file can then be used to debur the edges before the box is reinstalled in the truck. While this may not seem like much, the added airflow can make an improvement over stock without costing you anything out of pocket.

Eliminate Boost Leaks

While on the subject of intake air, it’s also a good time to check the charge air system for any boost leaks. With the airbox off, a simple leak detector can be built using some parts from the hardware store and a threaded tire valve stem. By installing the leak detector onto the factory intake horn, the charge air system can be pressurized with 30-35 psi so you can search for leaks with soapy water or just by listening closely, which is much simpler since the engine won’t have to be running.

With higher mileage motors it’s common for boost leaks to develop around the intercooler boots and intercooler end tanks (especially on intercoolers with plastic tanks). On the LB7 Duramax, it’s also common that the driver-side intercooler pipe rubs on a small hardline by the radiator; if it rubs enough over time it can create a large hole and substantial boost leak. Even the smallest boost leaks can affect turbocharger and engine performance, so they’ll want to be taken care of quickly to ensure you’re getting all you can out of that engine.

5. The next part of the DIY upgrade is more about general maintenance. The fuel filter is a commonly overlooked part of your engine’s performance and reliability on most diesel trucks. But a good clean fuel filter is extremely crucial in the Duramax application. Since the LB7 Duramax has no lift pump to help get fuel from the tank to the CP3 injection pump, any hint of restriction can really hurt performance and mileage. A dirty fuel filter can even send the Duramax engine into a limp mode if the proper rail pressure can’t be maintained under hard load. With this in mind, it’s always a good idea to keep up on fuel filter changes; 12,000-15,000 mile intervals is a good rule of thumb, but depending on the quality of fuel being used this could be done even more often than that. — The next part of the DIY upgrade is more about general maintenance. The fuel filter is a commonly overlooked part of your engine’s performance and reliability on most diesel trucks. But a good clean fuel filter is extremely crucial in the Duramax application. Since the LB7 Duramax has no lift pump to help get fuel from the tank to the CP3 injection pump, any hint of restriction can really hurt performance and mileage. A dirty fuel filter can even send the Duramax engine into a limp mode if the proper rail pressure can’t be maintained under hard load. With this in mind, it’s always a good idea to keep up on fuel filter changes; 12,000-15,000 mile intervals is a good rule of thumb, but depending on the quality of fuel being used this could be done even more often than that.

6. On a high-mileage turbocharged engine, it’s always a good idea to look over the charge air system to be sure there are no boost leaks; even the smallest boost leaks can affect turbo spool-up, power and EGT. Using some plumbing pieces from the local hardware store, a few clamps and a metal threaded tire valve stem, this homemade tool can be made to help pressurize the charge system to help you search for leaks without having the engine running. By clamping it onto the intake horn, setting the regulator on your air compressor to, say, 35-40 psi, you can use an air chuck to fill the charge pipes and intercooler with pressure and use a good ear or some soapy water on the connection boots to track down leaks. The driver-side intercooler pipe is prone to rubbing on some hard lines running nearby, which can create a significant hole and major boost leak. — On a high-mileage turbocharged engine, it’s always a good idea to look over the charge air system to be sure there are no boost leaks; even the smallest boost leaks can affect turbo spool-up, power and EGT. Using some plumbing pieces from the local hardware store, a few clamps and a metal threaded tire valve stem, this homemade tool can be made to help pressurize the charge system to help you search for leaks without having the engine running. By clamping it onto the intake horn, setting the regulator on your air compressor to, say, 35-40 psi, you can use an air chuck to fill the charge pipes and intercooler with pressure and use a good ear or some soapy water on the connection boots to track down leaks. The driver-side intercooler pipe is prone to rubbing on some hard lines running nearby, which can create a significant hole and major boost leak.

PPE Boost-Increase Valve Upgrade

Unlike the 2004.5 and later Duramax engines, the LB7 did not come equipped with a Variable Geometry turbocharger, it actually uses a simpler but very effective wastegated IHI turbocharger that works well at stock and slightly above stock power levels. The OEM IHI turbo has been known to support around 500 hp while offering good towing manners and quick low-end response. So, for applications such as this truck, the factory turbo is sufficient, even when a mild performance tuner is thrown into the mix.

One disadvantage to the factory turbo is the fairly light wastegate actuator, which allows the wastegate to start opening around 18-20psi boost. The factory motor can support around 40-psi in stock form, so allowing that turbo to build more boost can lead to better power, cooler EGT and better efficiency.

To keep the actuator from opening so soon, Pacific Performance Engineering (PPE) offers this simple Boost Increase Valve that can be spliced to run in line with the boost reference hose on the actuator head. By restricting the boost pressure being fed to the head of the wastegate, the actuator will stay closed longer, which allows the turbo to build and maintain higher boost levels. It’s a simple 10-minute install and an increase of 8-10 psi can be expected depending on the fueling and tuning being used.

7. With the system checked and any leaks repaired, the next upgrade for the LB7 is this small Boost Increase Valve made by Pacific Performance Engineering. Retailing at around $30, the small valve is placed in line with the hose that runs boost pressure to the turbocharger’s wastegate actuator. The valve basically restricts flow to the actuator, which allows the wastegate to stay closed longer. This will allow the turbo to hold more boost under hard load and help with power and EGT. — With the system checked and any leaks repaired, the next upgrade for the LB7 is this small Boost Increase Valve made by Pacific Performance Engineering. Retailing at around $30, the small valve is placed in line with the hose that runs boost pressure to the turbocharger’s wastegate actuator. The valve basically restricts flow to the actuator, which allows the wastegate to stay closed longer. This will allow the turbo to hold more boost under hard load and help with power and EGT.

8. The PPE Boost Increase Valve is an extremely easy installation that takes five to 10 minutes max, especially if the airbox system is already off the truck and out of the way. The factory hose is simply cut in the center and the valve is put in line. Small hose clamps are included to seal the hose around each end and you’re done. Depending on the additional fueling (we’ll get to that next) the small valve can be good for up to 10-psi more boost. — The PPE Boost Increase Valve is an extremely easy installation that takes five to 10 minutes max, especially if the airbox system is already off the truck and out of the way. The factory hose is simply cut in the center and the valve is put in line. Small hose clamps are included to seal the hose around each end and you’re done. Depending on the additional fueling (we’ll get to that next) the small valve can be good for up to 10-psi more boost.

Tuner Tweak

The new F4 Flashpaq from Superchips is the perfect entry-level performance tuner for the budget-minded diesel owner in need of a little extra power and mileage. The simple hand-held tuner offers multiple tuning levels along with custom end user adjustable settings for calibrating larger tires, gear ratio changes and transmission shift strategies. The F4 can also be used to read and clear diagnostic trouble codes and offers a limited two-year powertrain warranty for your vehicle, giving end users peace of mind against future problems. The Superchips F4 is also fully CARB compliant for most diesel applications, meaning California residents no longer need to fear the extra performance from the tuner getting them in trouble with their local EPA office.

For the LB7 Duramax, the Flashpaq offers four power levels above stock: Mileage XS, Tow, Tow/Perf and Performance. While up to 119 hp and 206 lb.-ft. of torque can be added to that Duramax engine in the Performance tune, this particular truck is used on a daily basis to tow trailers around town and across the state to rodeos on the weekend. With this kind of abuse and nearly 300,000 miles on the odometer, the 50-hp Tow tune was chosen to offer the safest overall performance and efficiency improvement for heavy hauling. After taking a few minutes to select the specific user adjustable settings in the Advanced Tuning tables of the Flashpaq, the Tow tune was downloaded into the truck’s ECM and the Flashpaq could be unplugged and put away. The first initial test drive showed immediate improvements in throttle response and turbo spool-up. Even when unloaded, the added power offers great drivability improvements around town and on the freeway.

9. With the small upgrades made on to the airbox, the addition of the PPE Boost Increase Valve and the boost leaks repaired, the engine should be getting more air than in factory form and some minor tuning changes could be made to further enhance the engine performance without hurting longevity or the bank account. The Superchips Flashpaq F4 is the perfect option for this high-mileage truck as it offers tuning versatility for improved throttle response, added power and better fuel mileage along with a two-year limited powertrain warranty. — With the small upgrades made on to the airbox, the addition of the PPE Boost Increase Valve and the boost leaks repaired, the engine should be getting more air than in factory form and some minor tuning changes could be made to further enhance the engine performance without hurting longevity or the bank account. The Superchips Flashpaq F4 is the perfect option for this high-mileage truck as it offers tuning versatility for improved throttle response, added power and better fuel mileage along with a two-year limited powertrain warranty.

10. The Superchips F4 is very user-friendly and can be installed in less than 10 minutes without having to pop the hood or get your hands dirty. The F4 is first plugged into the OBD-II port located under the dash just to the left of the emergency brake release. The Flashpaq F4 offers four power levels for the LB7 Duramax. Mileage XS (30 hp/60 tq), Tow (50 hp/90 tq), Tow/Perf (80 hp/140 tq), and Performance (119 hp/206 tq). Within each of these four power levels, the end user has the ability to create custom files specific to their vehicle, raising the speed limiter, adjusting for tire size, and more. — The Superchips F4 is very user-friendly and can be installed in less than 10 minutes without having to pop the hood or get your hands dirty. The F4 is first plugged into the OBD-II port located under the dash just to the left of the emergency brake release. The Flashpaq F4 offers four power levels for the LB7 Duramax. Mileage XS (30 hp/60 tq), Tow (50 hp/90 tq), Tow/Perf (80 hp/140 tq), and Performance (119 hp/206 tq). Within each of these four power levels, the end user has the ability to create custom files specific to their vehicle, raising the speed limiter, adjusting for tire size, and more.

11. Another nice feature found within the Superchips F4 is the ability to read and clear diagnostic trouble codes (DTCs). Should you ever have a check engine light pop up on the dash, the F4 can be plugged into the OBD-II and used to read the ECM to help diagnose or erase the trouble code. So, for around $350 you get a scan tool with free performance tuning. — Another nice feature found within the Superchips F4 is the ability to read and clear diagnostic trouble codes (DTCs). Should you ever have a check engine light pop up on the dash, the F4 can be plugged into the OBD-II and used to read the ECM to help diagnose or erase the trouble code. So, for around $350 you get a scan tool with free performance tuning.

12. When it comes time to actually flash the truck’s ECM with the Superchips tune, you’re given the option to use the precalibrated “Quick Tunes” or create your own version of them in the “Advanced” section. Since this particular truck is mostly stock, but running a 265/75R16 tire instead of the factory 245/75R16, we opted for the Advanced Tune, which allowed us to recalibrate for larger tires or adjust the speed limiter. — When it comes time to actually flash the truck’s ECM with the Superchips tune, you’re given the option to use the precalibrated “Quick Tunes” or create your own version of them in the “Advanced” section. Since this particular truck is mostly stock, but running a 265/75R16 tire instead of the factory 245/75R16, we opted for the Advanced Tune, which allowed us to recalibrate for larger tires or adjust the speed limiter.

13. The Flashpaq basically walks you through the entire process step-by-step with instructions on cycling the key to gain the ECM access the tuner needs. Once it’s connected with the vehicle, it will then save your truck’s factory ECM file, which you could then use to return your truck back to stock form at a future date if ever needed. Once the stock file has been saved, the Flashpaq will ask you to input the new information on your vehicle; the tire size just needs to be measured and input. — The Flashpaq basically walks you through the entire process step-by-step with instructions on cycling the key to gain the ECM access the tuner needs. Once it’s connected with the vehicle, it will then save your truck’s factory ECM file, which you could then use to return your truck back to stock form at a future date if ever needed. Once the stock file has been saved, the Flashpaq will ask you to input the new information on your vehicle; the tire size just needs to be measured and input.

14. The Flashpaq tuner will even allow for calibration of the tire diameter, within a given range. Just plug in your tire diameter and your speedo will read correctly, even with a tire diameter change. — The Flashpaq tuner will even allow for calibration of the tire diameter, within a given range. Just plug in your tire diameter and your speedo will read correctly, even with a tire diameter change.

15. With all the new information entered, it then asks which tune you want downloaded into the truck. Since this truck is used primarily on a family ranch and to haul heavy cattle trailers and horses on the weekends, the 50-hp Tow file was chosen as it would offer the best all-around performance without being too much for the engine while towing a heavy load. Superchips spent a lot of time fine tuning the custom files to offer the best drivability and efficiency without unwanted smoke out the exhaust. The tuning runs extremely clean and should be safe for the engine and transmission, but with any tuner the addition of a pyrometer gauge for monitoring EGT while towing is always a good idea. Within five minutes, the new Superchips Tow file had been downloaded and the truck was ready to drive. The owner immediately noticed an increase in throttle response and turbo spool-up and, over the course of the following weeks, showed significant mileage increases, jumping from an average of 15 mpg unloaded to just over 18 mpg highway and from 9.5-10 mpg towing to 12.5-13 mpg. — With all the new information entered, it then asks which tune you want downloaded into the truck. Since this truck is used primarily on a family ranch and to haul heavy cattle trailers and horses on the weekends, the 50-hp Tow file was chosen as it would offer the best all-around performance without being too much for the engine while towing a heavy load. Superchips spent a lot of time fine tuning the custom files to offer the best drivability and efficiency without unwanted smoke out the exhaust. The tuning runs extremely clean and should be safe for the engine and transmission, but with any tuner the addition of a pyrometer gauge for monitoring EGT while towing is always a good idea. Within five minutes, the new Superchips Tow file had been downloaded and the truck was ready to drive. The owner immediately noticed an increase in throttle response and turbo spool-up and, over the course of the following weeks, showed significant mileage increases, jumping from an average of 15 mpg unloaded to just over 18 mpg highway and from 9.5-10 mpg towing to 12.5-13 mpg.

The Outcome

This truck’s owner was extremely happy to see increased fuel mileage after the DIY upgrades had been completed. Between the air intake upgrades, a new fuel filter and the Superchips tuning, fuel mileage has increased nearly 4 mpg overall, up to more than 18 mpg highway when not towing and more than 12 mpg with their 14,000-lb horse trailer in tow. For less than a $500 investment, some elbow grease and two to three hours in the driveway, these simple upgrades can be worth the effort and will rekindle the love you have for that old worn-out truck that’s still just too good to trade in. DW

SOURCES:

Superchips

888.227.2447

SuperChips.com

Pacific Performance Engineering

714.985.4825