Photos: Kevin Wilson
Hushpower Turbo-Back Exhaust
Another area the stock 7.3L falls short in is the factory exhaust system. The 3-inch system is necked down just past the turbo outlet and continues on a kinky path to a chambered muffler, which robs even more performance. So improving on things is fairly easy with a quality turbo-back system since there’s now catalytic converter on this truck.
With several turbo back options on the table, we selected a Hushpower 4-inch, turbo back system for the 7.3L for one simple reason: the owner of the truck tows a lot and doesn’t want to have to crank the stereo to drown out the exhaust drone inside the cab. We’ve had some experience with the Hushpower muffler and it’s unique internal design when it was first introduced over a year ago, and owners have reported not only is the muffler quiet, it really picks up bottom end torque and flow. And in keeping with the budget theme on this truck, we figured it was a less expensive option that a stainless steel system.
Flowmaster, a recognized name in the performance exhaust industry for well over 25 years, initially developed the Hushpower muffler as a competition piece. It worked so well among the sled pulling teams, the company expanded its availability to include full turbo-back and cat-back systems for late model diesels. The setup for our F-350 dually is a full 4-inch, turbo back setup that utilizes mandrel-bent aluminized tubing and a 4-inch Hushpower muffler. The kit came complete with all the necessary hardware and some serious exhaust clamps. The hardest part of the whole install was removing the old system with the help of a Sawzall. The finishing touch is a polished 5-inch stainless steel tip.
At The Other End…
Since an engine is essentially nothing more than a giant air pump, improving the pumping efficiency at the other end (intake side) is just as crucial as fixing the exhaust side, especially on a turbocharged engine. On the 7.3L, the stock intake is the weakest link in the chain, especially since one of the engine’s batteries sits in front of it. This relegates fresh air intake to a small duct that runs past the batter to the firewall, and a small opening on the fender side of the air box. This setup is barely adequate on stock engines, let alone those that will be modified, so a good place to start is replacing the stock setup with an aftermarket air intake system.
There are a handful of aftermarket companies who offer air intake systems, but only a handful of them address a critical issue: filter size in relationship to the amount of air the turbo will draw at full song. Using a conical filter on top of the old stock airbox is better than stock, but will not support additional mods and boost level increases. For this reason, the owner of the truck purchased an Airaid intake system even before we got our hands on it. We outlined the typical install of the kit in our May 2009 issue so we’ll spare you the bolt-by-bolt details.
Airaid’s 400-222 system features a steel cold air dam that incorporates a battery tray, battery bump stop and stainless steel battery hold-downs. The Airaid air intake also replaces the factory bellows-style hose with a larger roto-molded inlet tube that draw air through a huge, Airaid premium filter. Airaid filters utilize hand-poured urethane and feature four layers of oil cotton gauze backed with a fifth layer of synthetic material called SynthaFlow, which improves filtration down to 2 microns, according to Airaid. And speaking of urethane, the air intake also comes with a urethane battery pad, complete with drain hole, to protect the intake from battery acid leakage.
The install is fairly simple although you have to remove the battery to bolt down the new intake. The rest is simple stuff and the end results of our effort are a better breathing 7.3L that’s ready for the next phase of mods and a trip to the dyno. Stay tuned.
Airaid Filter Company
Shell Oil Company