Sam Manderine's car was the...
Sam Manderine's car was the perfect candidate to test SLP's 475 HP Performance Pac. Sam's baby performed perfectly running 12.9s at over 108 mph, giving us a solid and strong bone-stock baseline.
It seems like every Mopar maniac wants a new Challenger, and even Brand-X guys appreciate the styling. In fact, we've spoken to regular (any brand) folks who mentioned they like the Challenger's styling over the new Camaro. Many owners of these new dream machines modify them just like owners did back in the day. The aftermarket has jumped into this new market with their feet first-and that's a good thing! The first modification most people do to their new Hemi is to let them breathe and be heard. For this test, we checked out SLP's variety of exhaust system possibilities in decibels, power, and elapsed times.
This all started with a bi-annual visit to the folks at SLP Performance. At this point they had designed, installed, and tested their headers and exhaust on quite a few Challengers. We had already put SLP's goodies to the test on the Chargers we flogged in the May '09 issue of Mopar Muscle ("Hemi Hop-Up"), and were anxious to see what kind of results we'd see on the Challenger. Luckily we had a friend with an unmolested '08 Challenger SRT8. Sam Mandarine offered us his low-mileage Challenger SRT8 (1,600 miles before testing) to use. We thank him for letting us use it as a guinea pig for the install of the SLP 475 HP PerformancePac (Headers, exhaust, air intake, underdrive balancer/pulley and power programmer) as well as the before and after strip and dyno tests at SLP.
Here's the last look of the...
Here's the last look of the front pipes and cats. Maybe in 25 years restorers can use these pics for reference. Sam wisely decided to save all the original exhaust parts for his low-number '08 Challenger.
The 90-minute ride to Englishtown for baseline runs and the ride home was time well spent. The thrill drive to E-town helped us find optimum shift points. We noticed the automatic 1-2 shift point came in too early at 5,400 rpm, while the 2-3 shift point felt perfect at 6,200. After a one-hour cool-down, we made a pass while manually shifting at 6,200 rpm. We were stoked to see the scoreboard show a sizzling 12.90 at 108.27 mph. E-Town's starting line was well-prepped and we were blessed with good autumn air. We made a backup pass and slowed to a 12.97 at 108.07 mph. This was unlike the Hemi Chargers we tested in the May '09 issue, which ran quicker on the backup run. Another one hour cool-down and the 6.1 produced a 12.91 and a 12.97 backup pass.
This time around we would add a twist and sound-test the three different exhaust systems (Loudmouth, Loudmouth II, and PowerFlo) that SLP offers. If you choose to mix and match the mufflers, there's the possibility of six different levels of sound for anyone's personal preference. We used a sound decibel meter to test four exhaust configurations and different levels of noise. Interior decibels readings were observed at idle and at a full throttle 50 to 70 mph blast. Exterior audio was checked at 30 feet and 3,000 rpm. Decibel readings "going down the track" were only taken while strip-testing with the stock and PowerFlo exhaust system (final exhaust configuration).
After the front pipes are...
After the front pipes are the factory X-pipe and the too-quiet mid-muffler. Notice the reduced pipe diameter (3 to 21/2-inch) at the inlet and outlets of the muffler, which restricts exhaust flow.
Sam's choice of exhaust was the PowerFlo so his wife could clearly hear music from the Challenger's sound system. The underdrive balancer/pulley, high-flow air intake, and the power programmer were installed to complete SLP's 475 HP PerformancePac. Then the late-model Hemi car headed over to SLP's in-house dyno. There it made an SAE corrected 480 horsepower at the crankshaft, proving itself as a better than average strong runner. See the dyno charts for the gains.
Our track date was hindered with unfavorable weather conditions (higher humidity and a lower barometer than the baseline) not allowing the bolt-on components to show their full power punch. After our usual one hour cool-down, we ran a 12.59 at 112.29 mph. Despite the bad air, we picked up a full 4 mph in trap speed. That's impressive, considering the test weight of 4,200 pounds. With good air, similar to the baseline, 12.40s would have been possible. Nonetheless, SLP's simple upgrades once again prove to be a real performance package. Follow along for the complete results from the exhaustive sound, dyno, and strip testing.
The tailpipes and rear mufflers...
The tailpipes and rear mufflers keep decibels down to a too-quiet minimum. Most gear heads would rather hear their Hemi talk to them. We used a decibel meter to test (interior, exterior, and down-track) the stock and SLP's exhaust offerings. The factory chrome tailpipe extensions are reused when upgrading to an SLP exhaust system.
The mid X-pipe, mid muffler,...
The mid X-pipe, mid muffler, right-side tailpipe, and muffler come out in one piece because they are welded together at the factory. The SLP system will offer a weight reduction, improved performance, and sound.
Just like our vintage Mopars,...
Just like our vintage Mopars, the starter needs to be unbolted to install headers on the late-model Hemi. Not shown, but it is necessary to remove the splash shield under the engine, oil filter, and the front tires to gain accessibility to the header bolts. SLP includes easy-to-follow instructions with their header kits.
We removed the air cleaner...
We removed the air cleaner assembly and then moved the coolant reservoir tank back near the firewall and master cylinder for added access.
The headers go in from the...
The headers go in from the bottom on both sides. Notice the bung for the O2 sensor in the collector area. There's plenty of clearance for easy fitment. The hardest part of the installation is access to tightening the header bolts. It'll need to be done from the top, sides, and the bottom. Having a good assortment of different length 1/4-inch, 3/8-inch drive extensions and universals will help access to the header bolts.
SLP's new Hemi headers were...
SLP's new Hemi headers were originally developed for the SRT8 LX cars. They fit like a glove on the new Challenger and offer factory ground clearance and impressive power gains. The header kit features OEM-quality O2 sensor extension harnesses. After the 409 stainless headers, the high-flow cats and exhaust are made from 304 stainless and feature a lifetime warrantee. This header system will hook up to the stock exhaust and to any of the SLP after cats exhaust systems.