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2008 Scion xB RS 5 - Power Pages

Oct 1, 2008
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* Dynamomoter: MD Automotive
* Testing & Installation: Luke Munnell
* Text & Photos: Luke Munnell

2008 Scion XB RS 5
Dyno 1: Baseline
Peak HP: 125.7 / Peak TQ: 128.0

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2008 Scion xB RS 5
The second-generation xB features a slightly tweaked version of the 2AZ-FE engine-the aluminum inline four that can be found powering the Camry, tC, and Corolla, among other Toyota platforms. Producing a factory-claimed 158 hp from the 2.4L, the new xB mill represents a 50hp and 0.9L displacement jump from the previous stateside xB of '04-'07, not to mention gobs more low-end torque. Its time in the chassis of other cars (especially the tC) has led the aftermarket to develop many more performance parts for this engine than the previous-generation's 1.5L inline four. Engine internals, EMSs, and forced-induction solutions can all be retrofitted to the new xB with very little work, and platform-specific versions of all are just around the corner.

The new xB is bigger. Call us old-fashioned, but we kind of like driving the old xBs better. Sure, they were shaped like an air brake ... and the new-gen's pseudo chop-top appeal and gangster-esque profile does look more menacing, but its extra 600-plus pounds of curb weight seem to cancel out its additional power. Also sucking up power are automatic transmissions-ours had one-which might explain the apparently low baseline numbers.

Perhaps the biggest gripe we hear of the new xB is from die-hard first-gen owners who feel the new chassis design and 2AZ-FE engine "killed" the small-displacement, JDM-styled allure of the bB/xB. It's really a tough argument to counter. We like all that about the first box, and its 35mpg highway average wasn't anything to sneer about. But ultimately, we're fans of power and the current xB simply brings more of it, along with much more room to grow. Plus, being rated at 28mpg highway (we saw a 31mpg average after installation), fuel economy is still much better than possibly any other vehicle offering its size, style, and practicality.

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AEM V2 Intake
AEM performs genuine ground-up engineering and flow-bench testing when designing all of its intake systems-something not commonly found in other intake systems-so fitment, construction, and power production are always second-to-none. Our xB kit was no different; installation was straightforward, the unit features full mandrel-bent and TIG-welded construction, OE-spec fitment, and made power and torque across the entire rpm range.

None-xBs should really come with better intakes from the factory.

Intake tubing (two sections), couplers, hose clamps, MAF sensor mounting hardware, Dryflow filter, and instructions

Pocket knife, 10-, 12-, and 14mm sockets and wrenches, extension, pliers, flat- and Phillips-head screwdrivers

Installation Time:
30 minutes

Installation is easy but time-consuming. Do yourself a favor and don't half-ass anything-it will only lead to more problems down the road.

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Dyno 2
AEM Cold-Air Induction System
Peak HP: 134.4 / Peak TQ: 138.6

Horsepower Gain
* 4,000 to 5,500 HP range: 5.5 to 10.8
* 5,500 to redline HP range: 6.9 to 12.0

Torque Gain
* 4,000 to 5,500 TQ range: 4.3 to 14.8
* 5,500 to redline TQ range: 5.7 to 11.2

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TRD Sport Muffler
TRD's Sport Muffler is offered as a factory upgrade for the Scion xB, so it came as no surprise that quality construction and fitment were spot-on. The unit replaces the OE exhaust rear section with larger diameter piping and a straight-through muffler with a signature TRD tip constructed of mandrel-bent, TIG-welded stainless steel. Power production rose and the exhaust note grew only slightly more aggressive-no cop headaches with this one. Best of all, installation took only minutes-and we didn't even need a jack.

The TRD unit's piping was larger than stock, but since it is only an axle-back piece, the improvements in exhaust flow it brought were marginal-meaning power production wasn't as great as we could've found by installing a full cat-back unit. The real bottleneck in the xB exhaust system lies in the mid-pipe and catalysts.

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TRD Sport Muffler with axle-back piping

14mm socket and extension, WD-40

Installation Time:
10 minutes

Upon firing the xB back up after installation and powering through some runs on the dyno, we noticed a ton of smoke emanating from the exhaust's tip-excess muffler packing dust that burns away under operating temperatures. Don't worry about this; it's normal and only lasts a few minutes after installation.

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Dyno 3
TRD Sport Muffler
Peak HP: 135.6 / Peak TQ: 138.9

Horsepower Gain
* 4,000 to 5,500 HP range: -1.3 to 3.0
* 5,500 to redline HP range: -1.7 to 2.2

Torque Gain
* 4,000 to 5,500 TQ range: -1.1 to 3.3
* 5,500 to redline TQ range: -1.6 to 1.8

Impp_0810_16_z+2008_scion_xb+strup_header Photo 8/11   |   2008 Scion xB RS 5 - Power Pages

Strup is probably a new company to a lot of you; it was to us prior to installing their header on our xB. Header design is absolutely critical for fitment of all other exhaust parts, making power, and maintaining vehicle street legality and longevity-and the Strup xB header met these challenges beautifully, with full mandrel-bent, TIG-welded, polished stainless construction, perfect fitment, and increased power and torque across the entire powerband.

The Strup unit removes one of the xB's two catalytic converters, meaning it's not legal for highway use in California. Additionally, removing one or both catalysts will prompt a check engine light (CEL) in the xB-a minor inconvenience at worst.

Strup header, CEL Eliminator

12- and 14mm short- and deep-well sockets, swivel, extension, 22mm wrench or sensor socket, pocketknife

Installation Time:
30 minutes

The '08 xB uses two catalytic converters and two O2 sensors to monitor engine vitals. The primary catalyst is welded to the OE header, so replacing it with one that brings power gains means removing the first catalyst altogether. Since doing so will throw off the proportions of O2 read by both cats, Strup includes a trick CEL Eliminator kit that fits between the second O2 sensor and catalyst to cure the problem. Driving with the CEL won't hurt performance or damage the vehicle, but it's annoying to deal with ... and you won't be alerted to any engine problems that may occur for other reasons down the road.

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Dyno 4
Strup Performance 4-1 Header
Peak HP: 140.9 / Peak TQ: 139.8

Horsepower Gain
* 4,000 to 5,500 HP range: -0.5 to 4.8
* 5,500 to redline HP range: 0.7 to 6.9

Torque Gain
* 4,000 to 5,500 TQ range: -0.6 to 2.0
* 5,500 to redline TQ range: 0.3 to 6.2

Impp_0810_19_z+2008_scion_xb+final_dyno Photo 10/11   |   2008 Scion xB RS 5 - Power Pages

After improving output by over 16 whp and 18 lb-ft of torque at points throughout our xB's powerband, we consider this installment of Power Pages a complete success. Eliminating the restriction of the stock airbox and piping brought instant power, as did eliminating the car's primary catalytic converter. The TRD muffler helped out a little, but served to bring out the 2AZ-FE's deep tone in a subtle, mature manner. Most impressive is that these gains were realized with one of the car's catalytic converters still inline, and half of its stock exhaust bolted up. Imagine what power could be found by adding a racing exhaust and a little tuning ... some forced-induction ... maybe building the block...

Impp_0810_07_z+2008_scion_xb+engine_bay Photo 11/11   |   2008 Scion xB RS 5 - Power Pages
MSRP Total $1,039.79
125.7 128.0
AEM COLD-AIR INDUCTION KIT 134.4 8.7 138.6 10.6
TRD SPORT MUFFLER 135.6 1.2 138.9 0.3
STRUP PERFORMANCE 4-1 HEADER 140.9 5.3 139.8 0.9
FINAL 140.9 15.2 139.8 11.8


Hawthorne, CA 90250
MD Autmotive



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