GARAGE NOTES

FOUR BOLTS TO BETTER BREATHING


Dan Kruegel of Sommer’s Subaru took us through the installation steps, using a lift. Note 1 Before removing the old system, spray the hangers with silicone lubricant so that the system’s brackets slide through easier. Note 2 Remove the old system by unbolting four bolts – two where the intermediate pipe attaches to the back of the catalytic converter (retaining the springs) ... Note 3 ... and two where the intermediate pipe attaches to the muffler pipe.
That leaves the pipes hanging. Dan popped the pipes off the hangers. You might have to use Channellock pliers to push the bracket flanges through the hangers. Note 4 Replace the gasket at the end of the converter pipe.
Pop the intermediate piece onto the hanger and loosely bolt it onto the converter pipe. Don’t forget the springs; the collars on the bolts will remind you. Note 5 Pop the muffler piece onto the three hangers. Make sure to use the gasket that comes with the system between the two pipes. Note 6 Notice two things here that help make the system better than average: First, the bolts on the intermediate pipe are welded to make the installation easier. Second, the nuts are made to resist corrosion. Note 7 The installation fits perfectly, with plenty of room between the pipes, muffler and underbody – even though the tubing is larger in diameter than the original. Dan mentioned that he’s had to modify the subframe for some other aftermarket kits. Not so with this one!
Installation notes: If you’re doing the installation yourself, Bosal suggests connecting the two pieces before installing them on the car. Note 8 Then Dan used a Subaru Select Monitor to clear the engine control module so it would accommodate the change in the system.

CLEAR THE ECM

A tag accompanies the system. It says, “PERFORMANCE INSTALLATION NOTE: To insure proper engine performance: If the vehicle has 500 miles or more, the engine control module (ECM) memory must be cleared before starting the vehicle. To clear engine control module (ECM), please follow procedures outlined in the Subaru Service Manual.”

Driving the car a few hundred miles will have the same (though not immediate) effect, as will disconnecting the battery for at least 10 to 15 minutes. If you use the disconnection method, you’ll have to reset the clock and radio.

WHADYATHINK?

On its own, the WRX Performance Exhaust System won’t change your driving life that much … or will it? Here’s the owner’s reaction:

“I knew that I had something pretty cool when I saw my wife’s eyes roll when she first heard the car with the SPT system installed. I knew it would be louder, but I wasn’t sure how much. It’s a low-pitched sound that I like a lot more than some of the tinny-popping sounds from other systems.

“After driving with the new system for a while, I’ve found it helping my shifting accuracy, because I can better hear engine output through the muffler.”
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WRX PERFORMANCE EXHAUST SYSTEM

arrows STARTING AT THE BACK - KICKING OFF PERFORMANCE UPGRADES WITH A FREEFLOWING EXHAUST SYSTEM.


Exhaust System

UPGRADING PERFORMANCE FROM THE EXHAUST FORWARD MIGHT SOUND BACKWARD, AND MAYBE TOO SIMPLE. BUT IT’S THE IDEAL PLACE TO START. HERE’S THE LOGIC: FREEING UP EXHAUST FLOW – THE BACK PART OF BETTER ENGINE BREATHING – PREPARES THE CAR FOR PERFORMANCE MODIFICATIONS ON THE INTAKE SIDE OF THE ENGINE.

Our WRX Performance Exhaust System came from Subaru Performance Tuning. The SPT system installs behind the catalytic converter, so we weren’t going to have to deal with emissions or warranty issues.

We had the work done by Sommer’s Subaru in Mequon, Wisconsin, which is an SPT Authorized Dealer. But this is the kind of modification that you can do yourself without a lift. Even with this seemingly quick and simple installation, though, there are some things to consider, as we’ll see.

arrows THE VEHICLE FOR OUR MODIFICATIONS

One of the Drive Performance project vehicles is a 2002 Impreza WRX Sport Wagon. Before getting started, we cleaned up the underside so our technician, Dan, didn’t have to ward off mud, dirt, salt and other debris. This WRX has been well maintained, with about 29,400 miles on the odometer when we started work.

arrows THE NEW SYSTEM

The SPT WRX Performance Exhaust System consists of an intermediate pipe and muffler assembly that installs behind the catalytic converter. It was designed to fit WRX models without modifications to the emission system or the underside of the car, using the existing system’s hangers.

Subaru Performance Tuning worked with Bosal Performance of Whippany, New Jersey, (www.bosalperformance.com) to develop the cat-back package to improve gas flow and engine breathing. Bosal explains how the system is tuned to function:

  1. Escaping exhaust gas creates a pressure wave that moves to the end of the exhaust system.
  2. Hitting the end causes a “suction wave” that returns to the engine.
  3. The suction wave hits the cylinder and reverses direction just as the exhaust valves open. The wave helps pull exhaust gases from the cylinder, improving engine breathing and volumetric efficiency (the ratio of actual airintake volume compared with ideal volume).

Installing this system will increase horsepower by a small amount on its own, along with giving the car a healthier exhaust sound. More important, though, is that it prepares the vehicle for engine modifications that require a free-flowing exhaust to be effective.

arrows THE PIPES

The SPT system’s tubing increases the diameter from 3.0 to 3.5 inches, which helps to dissipate heat from hot turbo gases. Pipes are made of 16-gauge 304 stainless steel, adding to durability. Laser-cut flanges improve sealing.

Along with the other quality manufacturing techniques, the pipes are mandrel-bent. Maintaining the same interior diameter helps to prevent friction and the buildup of turbulence in the flow of exhaust gas.

arrows THE MUFFLER

The muffler is computerdesigned for efficient gas flow. Its inner tubes are designed for sound quality and to ensure that material won’t blow out. A double-wrapped shell makes the muffler quieter. Because it’s thicker, this also results in a more durable unit.

Bosal tests each muffler to ensure that it doesn’t leak, using custombuilt machines to fill it with compressed air. The pressure test is part of Bosal’s extensive quality-control process.

arrows THE DESIGN

The SPT system is designed to fit the original brackets, making installation easier. Bolts and flanges line up. However, the system will NOT fit if the vehicle has a rear differential protector or trailer hitch

SUBARU SPT TESTING

The engineering staff at Subaru is involved with the development of every SPT item so that fit and function are correct. Subaru engineers ran the proposed Bosal exhaust through four tests:

  1. Drive-by noise test (SAE J1470) – measure 80 decibels or less on a drive-by between 40 and 60 miles per hour.
  2. Static test (SAE J1169) – measure 93 decibels or less at idle.
  3. Horsepower – positive increase.
  4. Static emissions – measure emissions at idle.

The SPT system from Bosal passed all four tests.

  1. Noise emissions on the drive-by were 80 decibels, which is in compliance in all 50 states.
  2. At idle, noise emissions were at 93 decibels – again, meeting 50- state compliance levels.
  3. The system shows an increase of about three peak horsepower (at about 70 miles per hour) – from 227 horsepower to 230 horsepower.
  4. There were no changes in emission levels in the static test.

 
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