There are a few solid reasons that trucks are beating passenger cars out the showroom door. Today's pickups and SUVs are more reliable, cost effective, and powerful than ever before. Sure, the price of gas may be at an all-time high, but there's no denying that people are willing to trade that inconvenience for the utility and comfort that comes with a new truck. Add to this the fact that GM has done a great job optimizing power and economy in its new line of haulers and you can see why pickups are in high demand. But that's not to say that there isn't still room for improvement...there is!
That's where companies like K&N Engineering come in. K&N has worked hard for many years designing products that improve a vehicle's breathing capabilities and have recently stepped into the exhaust business centering around new trucks and SUVs. We wanted to test K&N's new exhaust system on their in-house DynoJet chassis dynamometer to see what kind of power benefits it offers and the cool sound it would create. But, before we bolted the new stainless exhaust system behind our cats, we installed K&N's new Fuel Injection Performance Kit (FIPK) so the engine could breath a little easier. Since K&N designed its exhaust systems to complement the FIPK kits, we felt it made the perfect power addition. Then, to make sure we were getting all that we could out of our better breathing truck, we reprogrammed its stock computer using Hypertech's Power Programmer Plus and gave it the ultimate five minute electronic tune up.
In With The Good
When GM configures a new vehicle they are limited by design parameters. The aftermarket is less restricted in its design criteria, and therefore can improve things the factory was forced to handicap. One of those areas is an engine's air inlet system. The factory usually muffles a stock vehicle's air inlet so the car will drive down the road making barely a whisper. But, to make more power we need more air, and higher volumes of oxygen rushing into the engine will make a noise similar to an airplane on a bombing run. So, to keep the mass consumers happy and make their vehicles quiet GM designs complicated air boxes to silence the wind. These present a major restriction to incoming air and removing them will almost always add power. But, unfortunately unbolting the air box usually means removing the air filter, so a new one must be adapted to fit. K&N designs new inlet systems, adding its own reusable air filters to bring out the most power without sacrificing noise. Although you'll definitely hear it after installing a K&N FIPK, you won't be disappointed with the additional power it unleashes.
Out With The Bad
Exhaust is another area the OEM's are restricted in their design flexibility. More attention is usually paid towards cost and ease of manufacture, than it is to sound quality and power. But, if you're anything like us, you'd gladly accept a slightly louder vehicle if it knocks down better mileage and makes more power. According to K&N, its new truck exhaust is completely legal because all the components bolt on after the catalytic converters. Also, your truck will benefit from the superior 304 stainless steel K&N manufactures its exhaust components from. Your truck's exhaust will never rust and the muffler and associated tubing won't change colors as it heats up like lesser quality stainless can. Each K&N system is designed for an exact fit and can be installed in your driveway using minimal hand tools. When finished you should have the system tack welded together by a competent muffler shop to insure it never falls off if a clamp loosens.
Every car built today is computer-controlled. That means that the key to unleashing any additional power ultimately lies within the computer. Unfortunately, you can't just plug a laptop into your car and hit the "more power" key to download performance. You can, however, plug in a unit like Hypertech's Power Programmer and get better performance in a matter of minutes. Besides reprogramming the fuel and spark curve there are other items that the Power Programmer can tweak. With it you can change your vehicle's top end speed limiter, alter the automatic transmission's shift points and shift firmness, recalibrate the speedo for new gears or tires, and raise or lower engine-operating temperature for max power. You have the option of programming in any number of these features individually or all together depending on what your vehicle and/or heart desires. And all of the new programming can be removed and your factory-stock settings reinstalled in just minutes because the Power Programmer saves the stock information in its own memory, which cannot be erased or overwritten, ever.
Real World Power
Before you read the power chart from our dyno test remember that a chassis dyno measures power at the rear wheels, which can be anywhere from 15 to 25 percent less than measured at the flywheel. That's simply because it takes power to turn the transmission, driveshaft, and differential and that power cannot be recovered. To clarify this point, if you calculated the observed power figures from a chassis dyno session, factoring in a 15 to 20 percent drivetrain loss, the improvements would more closely match those claimed by manufacturers in their advertisements.
First, we baselined the truck to get some stock power figures for comparison. Surprisingly, the 45,000-mile '97 Chevy 4x4 we tested produced unexpectedly high rear-wheel power figures. GM rates the truck's 5.7L Vortec V-8 at 245 flywheel hp. K&N's chassis dyno revealed that this truck was putting 212.3 of those hp on the ground. Some simple calculations tell us that if the engine was indeed making 245hp at the crank, then we're only losing 13.3 percent through the drivetrain. However, peak power numbers hardly tell the whole story when you're testing street components and we prefer to use average power figures to determine if a bolt-on was really worth it. Stock, the truck averaged 180.2hp, so this figure will become our baseline. It should be mentioned that all components were tested in both Second and Third gear, but the best power was produced in Third, so that's what we'll list.
With a baseline established, in went K&N's FIPK system then we drove the truck around town and on the highway for approximately 100 miles to let the factory computer adapt to its better breathing components. After strapping it back on the dyno we were immediately rewarded with an average 8.3hp increase bumping the average peak output to 188.5. Even more impressive was the 10 to 15hp gains observed between 65 and 75 mph, where many of us spend most of our time. So not only did the FIPK bring the entire power curve up, it fattened up the middle where it will do the most good.
Next we installed K&N's new stainless steel exhaust system which consists of a flow-through design muffler with 3-inch mandrel-bent stainless tubing leading in and out and finished with a chromed-stainless exhaust tip. Since it does not change the location of the O2 sensors or the catalytic converters, K&N says its exhaust is legal in all 50 states. After another 100-mile test drive and a few pulls on the dyno the exhaust did not net a huge power improvement, but in the time we've spent behind the wheel following the test we've been rewarded with improved fuel economy and much more attractive acoustics. With the new exhaust in place, there was as much as 10 additional hp gained at the rear wheels on the dyno.
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.
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.
After reprogramming the computer were we able to squeeze out an average over 200hp. Factor in the 15 percent drivetrain loss and you'll see we've added 24hp or roughly 10 percent to the factory 245hp rating.
All this new power and mean sound wouldn't be worth diddly if we didn't look the part. So we added a set of Weld Racing's new Velociti 6 EVO wheels and Pirelli Scorpion A/T 265/75R16 tires. These 16x8 one-piece forged aluminum wheels are chrome plated to withstand road abuse, can be cleaned up with ordinary window cleaner, and will never need repolishing.