With new technology and new trucks come new problems to work around when trying to add more power. For example, take the new '07 Tahoes from GMC; some of these SUVs come with active fuel management to cut down on how much fuel these hefty trucks drink. The AFM system deactivates four of the eight cylinders while cruising, effectively cutting the fuel load in half. While this is great for saving money on gas, it does bad things to the exhaust note. What was a nice V-8 growl turns into something that sounds more like a clapped-out fishing boat. We are not going to sit here and tell you a four-cylinder can't sound good because they can, but this truck is only a four-cylinder during cruising. So, you get this muffled burble, instead of anything that sounds high-performance, which GM hides by keeping the exhaust very quiet.
So, what happens when you add a high-performance exhaust system to squeeze out more ponies? Well, if you buy substandard parts, you end up just amplifying that nasty burble. Luckily for all of you power-hungry truckers, JBA Exhaust Company builds a full exhaust system that not only adds 14.5 hp, but it also keeps that burble under control. Mark Matthews from JBA says, "This AFM feature was something we tuned our products for to avoid an unpleasant exhaust drone when in four-cylinder mode. Once installed, the new headers and exhaust system were tested extensively on the dyno and in real-world road conditions to ensure the operation of the AFM was not affected."
The Cat4ward headers and stainless steel exhaust system are available for '99-'07 Chevy and GMC 4.8-, 5.3-, and 6.0L V-8-equipped trucks and SUVs. The headers feature all of the good things you want to hear from a set of pipes, thick CNC laser-cut flanges, mandrel bends, and stainless steel. To top that off, you also get a limited lifetime warranty. The muffler and tailpipe assembly share some of the same features, such as mandrel bends and stainless construction, but also come with a straight-through-designed muffler and a 3-1/2-inch chrome-plated stainless tip with rolled lip. You might be asking why JBA chromed a stainless tip: Stainless has a tendency to turn yellow, and the chrome prevents that from happening.
To complement this system, JBA also offers a set of the company's PowerCables, which feature less resistance than the factory wires for more spark energy, and 8mm jackets for higher temperature resistance. Because these wires are made by the same company that makes the headers, they have all the proper ends to fit the new pipes. The parts are designed to be installed at home with minimal tools needed, so don't be afraid to tackle the job yourself. But, if you are not confident in your abilities, a professional shop shouldn't charge you too much to put them in.
Headers: These headers have a one-piece design with 3/8-inch CNC laser-cut flanges and ma
Gaskets: JBA supplies the best gaskets available with each header kit. For the late-model
Wire Kit: JBA PowerCables are engineered with ultra-low-resistance wire-wound mag conduct
Muffler & Tip: If you take a look inside of JBA's high-flow stainless muffler, you can se
The only part of the exhaust that most people will see is the end of the tailpipe, and JBA
Part One: The Teardown
Now that you know about the parts, let us give you some advice on tear-down and installation. JBA supplies great directions with its products, so the following information is just a highlight of some key points. You won't need a lift to do this job because the headers load from the top. But, you will be under the truck a lot, so a lift would be nice-a jack and jackstands will be sufficient. Before you grab a tool from the toolbox, grab some penetrating fluid like WD-40 and spray all the fasteners and hangers.
1. To get the factory exhaust manifolds out, you will need to remove the six 13mm bolts fr
2. To get the tailpipe assembly out, you will need to remove the two 15mm bolts from the f
3. The rubber hangers do a great job in holding the exhaust system in place, but that also
Once the stock system was removed from the Yukon, we laid it out next to the new JBA system. Here's how they matched up:
1. Here is a comparison shot of the manifold and the JBA header. As you can see, the heade
2. The tailpipe and muffler assembly from JBA is not only constructed entirely out of stai
Part Two: The Install
Now for the installation of the new parts. As stated earlier in the story, both the left and right header feed in from the top. Be careful when you are sliding these into place, because one wrong move will break off a spark plug. You could remove them just to be safe, but as long as you are careful there is no need.
1. The driver-side header features a flat collector flange that JBA provides a gasket for
2. Because there is still a piece of the factory exhaust system in place, the converter as
3. Once you have the tailpipe right where you want it and you have made sure nothing is to
5. This is not necessary, but if you feel the need to tack-weld everything in place go ahe
The Final Word
After everything was installed, the truck was strapped to a chassis dyno to see how much power the Yukon has now. As you can see by the numbers to the right, the installation of the JBA parts added 14.5 hp and 17 lb-ft to the peak numbers. Look at the numbers below 3,500 rpm; the JBA stuff really added some low-end grunt right in the sweet spot.
Read It And Weep!
|RPM ||HP BEFORE ||HP AFTER ||TQ BEFORE ||TQ AFTER |
|2461 ||44.8 ||100.1 ||96 ||214 |
|2552 ||56.2 ||117.0 ||116 ||241 |
|2643 ||68.5 ||130.2 ||136 ||259 |
|2734 ||79.2 ||139.6 ||152 ||268 |
|2825 ||91.1 ||148.1 ||169 ||275 |
|2916 ||104.2 ||154.8 ||188 ||279 |
|3007 ||118.6 ||161.5 ||207 ||282 |
|3099 ||132.8 ||167.4 ||225 ||284 |
|3190 ||145.4 ||172.5 ||239 ||284 |
|3281 ||156.5 ||178.3 ||251 ||285 |
|3372 ||167.3 ||182.2 ||261 ||284 |
|3463 ||175.6 ||186.1 ||266 ||282 |
|3554 ||180.6 ||191.9 ||267 ||284 |
|3645 ||186.7 ||198.5 ||269 ||286 |
|3737 ||191.4 ||208.4 ||269 ||293 |
|3828 ||196.2 ||219.1 ||269 ||301 |
|3919 ||201.2 ||225.6 ||270 ||302 |
|4010 ||209.6 ||232.9 ||275 ||305 |
|4101 ||217.8 ||236.8 ||279 ||303 |
|4192 ||229.1 ||241.6 ||287 ||303 |
|4283 ||234.6 ||245.9 ||288 ||301 |
|4374 ||238.5 ||250.1 ||286 ||300 |
|4466 ||241.2 ||253.8 ||284 ||299 |
|4557 ||246.9 ||256.3 ||285 ||295 |
|4648 ||249.2 ||258.2 ||282 ||292 |
|4739 ||248.6 ||261.3 ||276 ||290 |
|4830 ||249.9 ||262.2 ||272 ||285 |
|4921 ||251.6 ||265.3 ||269 ||283 |
|5012 ||254.5 ||267.9 ||267 ||281 |
|5104 ||249.2 ||268.2 ||256 ||276 |
|5195 ||247.8 ||269.0 ||251 ||272 |
|5286 ||243.9 ||267.2 ||242 ||266 |
|5377 ||241.1 ||263.4 ||235 ||257 |
|5468 ||239.5 ||263.1 ||230 ||253 |
|5559 ||238.1 ||260.5 ||225 ||246 |
|5650 ||237.2 ||256.1 ||220 ||238 |
|5741 ||235.0 ||252.9 ||215 ||231 |
|5833 ||233.7 ||254.1 ||210 ||229 |