K&N's muffler is a straight-through design, but produced surprisingly little more noise th
Lastly, to retune the truck for maximum output and also recalibrate the annoyingly-low 98-mph factory speed limiter, which was shutting the engine down even though it was still climbing up the hp scale, we plugged in Hypertech's Power Programmer Plus. Following the Programmer's simple prompts we changed the following settings: improved the spark curve, moved speed limiter up to 110 mph, increased shift point rpm, and then we installed a 160-degree thermostat. The truck already had B&M's electronic shift improvement kit installed, so we didn't bump up the shift firmness setting. The results after the Hypertech reprogramming are somewhat skewed, but still indicative of the overall performance increase with all components.
The skewed results come from the fact that after reprogramming the truck was able to accelerate past 98 mph (this translated into a higher rpm, which the engine seemed to like) and kept on making power right up to the 110-mph limit. This tells us that the engine could probably make even more power with a higher speed limit, but we didn't want to spin the Pirelli Scorpion AT off-road tires any faster. If you look at the max power produced you'll note the huge jump to almost 234hp. But, check out the average power figure for the whole story. The final 201.3 average hp tells us that Hypertech's Programming was worth an additional 10hp over the exhaust and FIPK alone. Not too bad for about five minutes of tuning done from the driver's seat.
K&N recommends having its complete system tack-welded by a competent "muffologist" after y
This test taught us that while it's tough to beat the factory tuning on today's trucks, there's still some power to be found. Although you may not see the huge increases that had traditionally been gained when swapping parts on the restricted engines of the '70s and '80s. The bolt-ons we tried here offer several advantages beyond just a power increase. Especially the exhaust system because it is much more durable than the factory components. Add it all up and you'll get more power from a better looking and sounding truck than you could ever get off the showroom floor, and that alone is worth every cent.
Figures shown here reflect testing in Third gear only with power readings beginning at 65 mph (roughly 2,600 rpm) but not fully stabilizing until 70 mph so that's where our list begins. The last column shows the calculated crankshaft hp after factoring in a modest 15 percent drivetrain power loss.