Intake and Exhaust Systems: 7.3L Power Stroke

Performance And Reliability Upgrades For The 7.3l Power Stroke

Vincent Uriah is a concrete contractor from Summerville, Georgia, who purchased a used 2003 2WD F-350 with just over 120,000 miles on the clock. The big Ford is fitted with the stout and reliable 7.3L Power Stroke diesel and eventually the truck will be used for work versus play. As is the case with many small business owners, Uriah is feeling the pressure of mounting fuel prices and wanted to get more efficiency and performance out of his new/old work truck, so he has handed his rig over to the folks at Swamp’s Diesel Performance in LaVergne, Tennessee, for some upgrades.

Like most diesel truck owners, Uriah is upgrading his truck in stages and we’ll follow along with the build and the 7.3 Power Stroke horsepower increase as it progresses from a basic stock work truck to a high-performance work machine. First 7.3 upgrades up: an Airaid intake system, DiamondEye Performance turbo-back exhaust with optional polished stainless steel tip and a TS Performance chip loaded with Swamp’s Diesel Performance custom tunes to optimize the truck for everyday driving as well as for towing.

1 This Airaid cold air intake system uses their oil-less SynthaMax filter media and comes with everything needed to install it on your 7.3L Super Duty including the battery tray, heat shield and hardware.
2 To make things easier on the budget, Uriah went with the aluminized steel version of the Diamond Eye 4-inch turbo-back exhaust system. They also offer a kit in stainless steel if your budget allows.
3 Swamp’s Diesel uses the TS Performance six-position chip as the basis for their tunes, giving customers six custom tunes to choose from on the fly through the control knob.


4 & 5 When Chris Murra was inspecting Uriah’s truck he found that the right front brake line was leaking from a previous repair. In addition to repairing the leak, he also bled the brakes and repainted the shock tower where the brake fluid stripped the paint.
6 Murra also found that the joints in the steering linkage were very worn with nearly an inch of slop in the joint connecting the drag link to the steering box (see arrow). If you have excessive play in your steering wheel as this truck did, be sure to check your steering components as a failure could be catastrophic.
7 A sharp blow with a sledgehammer will typically free the tapered tie rod end links from the steering knuckles.
8 When installing the new suspension components be sure to use the new hardware included in the kit and properly tighten each fastener, then secure them with new cotter pins; never re-use old cotter pins.
9 Not much to see here, but things will improve and wake up the 7.3L Power Stroke engine to deliver more power and better efficiency.
10 Murra started work on the engine by replacing the leaking fuel drain valve and changing the fuel filter with a new Motorcraft filter. Be sure to use the supplied O-rings when changing your fuel filter and make sure it’s fully seated in the housing before installing the cap.
11 He also suggests filling the new oil filter with fresh oil before installing it on the engine to prevent any dry running while the oil system is pressurized after the oil change.
12 The metal work for the Airaid kit goes together as indicated using the supplied hardware.

To improve the performance and efficiency of the Power Stroke engine the crew at Swamp’s starts by helping the engine to breathe more freely with a free-flowing cold air intake system. The Airaid intake system they installed features a non-oiled SynthaMax conical filter with more surface area than the factory panel filter as well as ductwork to channel cool outside air to the filter and block hot air from the engine compartment to make more power and increase efficiency on the inlet side of the turbo. On the exhaust outlet side of the turbo, flow will be improved by replacing the restrictive factory 3-inch diameter downpipe and 3.5-inch exhaust system with an aluminized steel 4-inch turbo-back Diamond Eye exhaust system that features mandrel bends to further enhance exhaust flow. The 4-inch-diameter downpipe has almost double the surface area as the stock 3-inch downpipe to allow the turbo to exhale spent gasses with ease.

With additional airflow you can also add more fuel to make more power, but that requires tuning of the PCM. Using a TS Performance six-position switchable chip the team at Swamp’s writes custom tunes to the chip to optimize performance for the owner’s desired truck operation that matches the performance modifications made to the truck. They can also re-flash the tunes to grow with the owner as he/she continues to modify and upgrade their truck. For Uriah’s current configuration with stock injectors and stock turbo, Robert Breedlove set up the chip with stock, high idle, economy, light towing (under 10,000 pounds), heavy towing (over 10,000 pounds) and extreme performance tunes to allow him to select the best option for his needs on the fly.

13 Remove the stock filter housing and all of its components including the battery cover, battery and battery tray to make room for the new Airaid components.
14 Then the Airaid battery tray and filter assembly can be lowered into the factory location and secured to the truck with the original mounting hardware.
15 With the inlet tube installed, the large air filter can be mounted in the assembly.
16 After putting the housing cover and seal on, Murra installs the supplied warning decal to help prevent witless techs from discarding the cleanable and reusable SynthaMax filter element.
17 While Murra works on the truck, Robert Breedlove burns six custom tunes to the TS Performance chip from the vast Swamp’s Diesel library of tunes.
18 After loosening the harness bolt from the engine compartment side of the firewall and the interior mounting bolts, Murra removes the PCM to prepare it for the chip installation.
19 After disassembling the housing to access the circuit board, he very gently cleans the surface of the board on both sides with Scotch-Brite pads. Be careful not to remove too much material; simply remove the protective coating from the board, not any of the tinning on the copper traces!
20 He used a high-speed rotary tool to cut a hole in the plastic PCM mount to allow the chip to slide in with the PCM installed in the truck so future upgrades and tuning changes will be easier.

When we arrived at the Swamp’s shop, Chris Murra gave the truck a quick inspection before beginning the installation. Before beginning any modifications on your truck, it’s a good idea to give it a thorough inspection to make sure there are not any problems that need to be resolved first, especially if you just bought the truck used. Murra found a leaky brake line as well as worn steering linkage adding time to the work day, but adding safety to the truck at the same time. He also changed the fuel filter and leaking fuel bowl drain valve, and changed the engine oil and filter using a Motorcraft filter and 15W-40 Motorcraft diesel oil.

Based on Swamp’s vast 7.3L Power Stroke experience, the team estimates that stock trucks like Uriah’s ’03 put down about 200 hp to the rear wheels. With the new intake, exhaust and custom tunes on the truck, they estimate that it’s now capable of putting approximately 300 hp to the rear wheels. Bearing in mind that late 7.3L engines like this one use powdered metal rods rather than the stronger forged rods of the earlier 7.3L engines, Uriah’s ultimate power goal for his truck will be a safe 400 horsepower to the rear wheels with great drivability, efficiency and towing ability. He regularly tows heavy earth-moving equipment weighing in at more than 10,000 pounds with the truck.

21 Then he reinstalls the PCM in the truck. Do not forget to mount the housing inside the cab and secure the harness under the hood.
22 Murra carefully drilled a mounting hole in the dash near the steering column so that Uriah will be able to easily select tunes but will not bump the control knob with his knees.
23 After mounting the control knob, Murra routes the cable to the PCM and installs the switch onto the circuit board through the hole he previously cut in the mounting bracket (see arrow).
24 When finished, you hardly know the knob is there, but turn it a few clicks to the right and mash the loud pedal and you sure can feel a difference.
25 Not only is the factory exhaust system small, it’s also ugly and the bends are made with a crimp-type bender that compromises exhaust flow even more. No wonder these trucks only make around 200 hp stock.
26 Removing the old exhaust system is easiest when the truck is on a lift and you have access to a reciprocating saw with a fresh bi-metal blade (be sure to wear proper eye protection). Since the factory system is pretty much scrap metal, it doesn’t matter where you cut it as long as you’re not trying to reuse it for something.
27 If you’re working on your garage floor you will probably have to make more cuts and remove the old system in smaller sections. Be careful, the parts are heavy.
28 The difference in size between the factory 3-inch downpipe and the new Diamond Eye 4-inch downpipe is clearly evident both in the size of the pipe as well as the smooth mandrel bends that do not impede exhaust flow.
29 The large downpipe bolts to the factory turbo with the original factory clamp as seen by the arrow.
30 When hanging the rest of the new exhaust system it’s best to start with the muffler and its rear mount, then work forward and rearward from there. You’ll likely need to trim some of the pipe at either or both ends for proper fit for your particular cab and chassis configuration.
31 Murra aligned and installed the optional 5-inch-diameter polished stainless steel Diamond Eye exhaust tip to give the system a great look from behind.
32 After tightening all of the clamps and hangers, Murra gives each joint a tack weld to hold them firmly in position.
33 Looking under the truck you can see the new steering linkage components as well as the bright aluminized exhaust system.
34 To prevent overboost codes and defueling, Murra installs a Swamp’s pressure regulator inline with the boost reference hose to fool the PCM into thinking there’s less boost.
35 The engine bay is starting to look better with the new intake system in place. Stay tuned to these pages to follow along with more upgrades next month.

The next step in the upgrade path for Uriah and his F-350 will be to beef up the stock transmission before going much further and adding more power, which would stress the transmission even more. After the trans upgrades attention will be turned back on the engine where the fuel system will be targeted for improvement to deliver even more fuel to the engine. Finally he’ll look to add some more boost by upgrading the turbo to wrap up his work truck project. Follow along with the progress right here in Diesel World over the next few months as the truck is transformed from a run-of-the-mill work truck to a tire-burning workhorse ready to tackle anything Uriah demands of it.

Driving up to Swamp’s shop the truck averaged 15.5 mpg with the stock intake, exhaust and factory tuning. Then on the trip back from Swamp’s following the same route at similar speeds the truck averaged 16.7 mpg, including many full throttle blasts to feel the effects of the additional power it’s now making. We expect that driven normally the mileage improvement will be even better. The throttle response is greatly improved and he says feels noticeably more powerful, especially when climbing grades. The big truck no longer feels labored under its weight, and we’re confident it will tow much better as well.

The intake and exhaust systems and even the PCM chip are products that the vast majority of diesel enthusiasts can install themselves in their own garage or driveway with basic hand tools. But if it’s beyond your skill level or you just don’t have the time to invest in performing the work yourself, we’re sure your local performance diesel specialist shop will be more than happy to perform the installation for you. DW


Airaid Filters
Dept. DW
2688 E. Rose Garden Lane
Phoenix, AZ 85050

Diamond Eye Performance
Dept. DW
107 W. Main
Athena, OR 97813

Swamp’s Diesel Performance
Dept. DW
304 Sandhill Road
LaVergne, TN 37086



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