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The problem with making choices is that there is always room for error. This is especially true when it comes to picking power parts for your truck. Magazines such as Sport Truck are chock full of advertisements with bolt-on parts for your truck. Many of them make claims about how much horsepower you'll gain with their products, but how do you know which ones really do what they claim? Or how about whether or not they will work in conjunction with other parts?
Most truck enthusiasts are confident that they can create power by adding a good aftermarket exhaust and improving the airflow on the intake side. In the old days, a computer chip was also a key element of performance. But with today's trucks and their OBD-II computer technology, making real power at the rear wheels is a little more complicated. Both the engines and the electronics are more sensitive to changes, and it's often easier to lose power than it is to gain it.
So as part of Sport Truck's never-ending quest to enlighten its readers and provide power solutions for their trucks, we've done a little dyno testing of some products that seem to work on late-model GM trucks. First and foremost, we'd like to spell out that this combination of parts is not the only set of parts that makes power. They just happen to be the ones we tested at the time. More importantly, it's the theory behind the parts that is the key to making power.
In a nutshell, we took a stock 6.0L GM truck and added an after-cat exhaust, air intake, and some computer programming, testing each addition as we went along. The results show that on this particular truck, on this particular day, with these particular parts, we made x amount of horsepower. More importantly, we made tremendous gains in the throttle response and picked up a little mileage to boot.
So can you accomplish the same thing with other parts? Yes. There are a lot of choices on the market, and you probably can duplicate our results with another combo. The main thing is that we used a combination of exhaust, intake, and programming improvements to make power. So without further ado, here's what we did and what we found.
EXHAUST
SOURCE: MagnaFlow / Car Sound Exhaust System, Inc
Since after-cat exhaust systems are proven power makers, we started our hunt for grunt by scrapping the stock exhaust system on our '01 Chevy 2500 HD Crew Cab and replacing it with a MagnaFlow 4-inch after-cat exhaust system. The MagnaFlow system features a polished muffler built from 16-gauge aluminized steel that is fully welded and contains no restrictive baffles, chambers, or louvers. The straight-through design of the muffler allows for maximum exhaust flow and reduces engine heat. This all adds up to a system that legitimately makes more power than the OEM system. Dyno testing revealed that with the MagnaFlow system in place, our engine picked up 17.5 hp.
REAR WHEEL HORSEPOWER GAINS OVER STOCK:
HORSEPOWER: 17.5 TORQUE: 14.2 LB-FT
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As with any performance test where parts will be swapped and numbers will be needed, we first ran our test vehicle on a chasses dynamometer.
What's wrong with this picture? Our truck already had a home-built after-cat exhaust system that was installed badly. Looking at the photo, we can see that the muffler is installed at a negative angle. This is bad because moisture will run back into the muffler from the exhaust pipe when the truck sits overnight, causing it to rust from the inside out in no time.
A close up look at where the muffler and piping meet shows that the muffler inlet is actually smaller than the exhaust pipe! The dubious installer simply slid the muffler into the piping and welded it. This is very restrictive and defeats the purpose of even installing a high-flow muffler in the first place.
Out came the Sawzall and off came the old after-cat exhaust system. The stock system on these trucks uses 3-inch piping and a restrictive, multi-chambered muffler.
Because it was routed over the axle, the exhaust system had to be removed from the rear of the truck.
The heart of MagnaFlow's system is in its high-flow muffler and straight-through design. There are no chambers, baffles, or louvers to restrict the exhaust flow, just a perforated piece of stainless piping that will create a nice exhaust tone and enable the engine to breathe easier.
The mandrel-bent MagnaFlow exhaust is first maneuvered into place, and the new piping is slid over the stock head pipe. A stand is placed underneath the exhaust to aid in positioning the system precisely.
Not wanting to duplicate the last installer's mistakes, MagnaFlow placed a level underneath the muffler to ensure that there would be no water draining back into the muffler after the installation was complete. This step is taken with every installation the company performs.
The system is welded into place. It exits behind the passenger-side rear wheel, in the factory location.
(10a & 10b) Before and after. The MagnaFlow system is visually pleasing, well-made, and makes excellent power.