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Installing a High Performance Exhaust on the Porsche 911 Carrera
 
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Pelican Technical Article:

Installing a High Performance Exhaust on the Porsche 911 Carrera

Time:

8 hours8 hrs

Tab:

$4000

Talent:

*****

Tools:

All of them

Applicable Models:

Porsche 996 Carrera (1999-05)
Porsche 996 Carrera 4 (1999-04)
Porsche 996 Carrera 4S (2002-05)
Porsche 997 Carrera (2005-12)
Porsche 997 Carrera 4 (2006-12)
Porsche 997 Carrera 4 GTS (2012)
Porsche 997 Carrera 4S (2006-12)
Porsche 997 Carrera GTS (2011-12)
Porsche 997 Carrera S (2005-12)

Parts Required:

Exhaust

Hot Tip:

If your CAT's are toast, replace your entire system with a sport exhaust system

Performance Gain:

20-30HP depending on exhaust design and other factors.

Complementary Modification:

Replace oxygen sensors

Replacing the exhaust system on any car is a good way to make a little more horsepower and also enhance the sound of the engine. This is done by increasing the diameter of the exhaust tubing and/or smoothing out the angles and bends in the exhaust system. This has the effect of reducing exhaust system back pressure, which most of the time creates more power.

In this article, I'll go over the steps involved with replacing the stock exhaust on the 996 with a new unit from Fabspeed. This setup is manufactured out of stainless steel and is CNC mandrel bent for optimum flow and fewer restrictions than the Porsche factory exhaust. They feature 50mm header pipes that connect to a dual muffler system The Fabspeed exhaust system is low profile and weighs 30 lbs less than the Porsche factory system. While the 997s have a different style of fasteners for the exhaust, and use Torx screws in place of Philips, the basic geometry of the exhaust is the same as well as the procedures for removal and replacement.

Inside the engine compartment along the back shelf, you'll see two electrical connectors on either side. These are the electrical connections to the oxygen sensors for each side of the exhaust. Remove the airbox (see our article on replacing your air filter Pelican Technical Article: Replacing Your Porsche Carrera Air Filter (996/997)) to gain access to the connectors. The black connectors attach to the oxygen sensors before the catalytic converters. The gray connectors go to the oxygen sensors after the catalytic converters. Pull the red tab out on each connector to disconnect it. For each oxygen sensor, follow the wire back and open each clamp that holds the wire. There will be one clamp on the engine mount plate and also one on the engine shelf. Simply pry the clamp open and it will release the wire. Feed the wires for each oxygen sensor down and out from inside the engine compartment. If you are re-using the sensors in the new exhaust, unbolt them from the catalytic converter pipes. Use either an oxygen sensor removal tool or a 22mm wrench. Make a note of which sensor goes where.

The rear bumper cover has to come off the car for added clearance when removing the mufflers. Begin by removing the two Phillips head screws at the bottom of the rear bumper cover on both sides of the car, as well as the two screws on the very back edge. On the 997s there is an addition body support piece attached to the leading edge screw, you will need to remove this as well.

Once removed, open the engine lid and remove the Phillips head screws on both edges of the top of the bumper cover and then remove the black metal threshold strip. Now look underneath each black plastic bumperette. You'll see a small access hole with a 6mm hex bolt inside. Loosen the 6mm bolt and you will be able to swing the bumperette up and off the bumper from the bottom. At this point, you can give the bumper cover a good tug towards the back of the car and it will come off. Underneath, disconnect the electrical connection to the license plate lights. Place the bumper cover in a safe place to prevent damage to the finish. Underneath, you'll see the large aluminum carrier bar. Remove the two 19mm bolts holding the bar in place. As you remove the carrier bar, you'll also remove the lower heat shield.

Underneath the bumpers, you'll see the exhaust shields that cover each muffler on both the right and left sides of the car. Locate the seven 10mm nuts that hold the exhaust shields on each side of the car. Once the shields are removed, you'll see the mufflers on either side of the car.

On each side of the car, locate the connection from the header to the catalytic converter pipe. This union is held together with three 13mm bolts and nuts. Loosen these bolts. If they are rusted, use a good penetrant spray on them. Also loosen the four 19mm nuts on the two exhaust clamps at the ends of the catalytic converters.

Now crawl under the car and begin to remove the six 13mm header bolts on each side of the engine. Once all the bolts have been removed, the header will just drop off the bottom of the engine along with the old gasket.

NOTE: It is very common for the nuts and bolts on older cars to rust, and make exhaust components very difficult to remove. This very well may be the case with your exhaust. If so, then you might need to grind off the nuts and/or heads of the bolts to get the headers off of the car. It's not an easy job, and it is complicated by the lack of room underneath the car. If you have extreme difficulty, then take the car to your local mechanic. The header bolts are very prone to breaking and if they are highly rusted, they should be heated up red-hot with an oxy-acetylene torch to assist in their removal.

On our project 996, we had a couple bolts break off as we tried to remove them. At first, we attempted to remove the reminder of the bolt with and easy-out, but found that just would not remove the remainder of threads left in the cylinder head. Our only option was to drill the remainder out and install a Heli-coil in place.

Now look at the mufflers on either side of the car. On the inside of the muffler is a mounting plate that holds the muffler to each side. There are three 13mm nuts on the inside of each plate in between the valve cover and the muffler. Use a ratchet and extension to remove the nuts. Keep in mind that the mufflers are rather heavy, so you may want to have a helper hold the muffler while you slide back the clamp that joins the muffler and catalytic converter. Now you can remove the muffler.

At this point, only the catalytic converters will be left on the car. These are clamped to the engine mounting plate. From behind, loosen and remove the 19mm bolt that holds the clamp in place. You may need to pry the clamp open a bit to slide it past the lip on the mounting plate. Once the clamps are removed, each catalytic converter will drop off the car.

Before we can fit the new exhaust, we will need to remove the mounting plates from each muffler and re-fit them to the new mufflers. The plates are held to the mufflers with two 13mm nuts and bolts. Remove each nut and bolt and pop the plate out of the old muffler. Re-fit the plates to the new mufflers, noting the position of each.

Crawl under the car and fit the new headers up in place. It can be a little tricky to fit the bolts through the holes in the header, through the new gasket and up to the cylinder head. You may need a helper to hold it in place while you thread the bolts in. At this point, we want to just snug up the bolts. You want the header to be able to move just a little bit so that we can get everything to line up. It's been my experience that no exhaust system ever lines up perfectly.

Take the new catalytic converter assembly and thread in the oxygen sensors, making note of which one goes where. There will be a small hex head plug in each sensor port. Remove these plugs and thread in the sensors snugly. We will tighten them down fully later.

Now place the catalytic converter assembly up onto the mounting plate and slide the new clamps over the lip on the plate. You'll just want to snug them up right now. You may notice at this point that the flange between the header and the cat assembly may not line up perfectly. That's ok. As we tighten everything up, the whole system will flex and bend.

Slide the new gasket between the header flange and the cat assembly. Take the new 13mm bolts and slide them through each of the holes. If the holes don't line up, move both the header and cat until they do. Once all the bolts are in, thread the nuts onto the bolts loosely.

Now crawl under the car again and tighten down the header bolts fully to 19ft/lbs. As you tighten, keep an eye on the header to cat flanges. Snug the bolts down as you tighten the header bolts to keep everything in line. Once all of the header bolts are torqued, fully snug down the header to cat flanges and torque them to 22ft/lbs. Route the wiring for the oxygen sensors up through the engine compartment and plug them back into the connectors on the engine shelf.

Now slide the old muffler clamps onto the ends of the cat assembly. Take the new mufflers and place them on the mounting brackets while also fitting the pipe into the cat assembly. As before, it can be a bit tricky to line everything up. Once in place, re-fit the 13mm nuts on the back of the muffler mounting plate and slide the muffler clamps over both ends of the muffler and cat pipes. Now tighten down the clamps. At this point, you'll also want to tighten down the oxygen sensors and the clamps that hold the cat assembly to the engine mount plate.

Take the new exhaust tips supplied with the car and secure them to the muffler outlets with the supplied clamps. Here's where it gets a little tricky. It will be easier to tighten the 11mm nuts on the clamps with the bumper cover removed from the car, however with the bumper cover installed, you have very little room to get a wrench inside. I would recommend marking both the exhaust tip and also the muffler outlet with a sharpie or use painters tape to give you a reference line. Put the bumper cover back on, align the tip then mark the position where you want it to sit. Then remove the cover, tighten up the exhaust clamp and enjoy the new aggressive sound coming from your car.

Here is aPicture of a complete exhaust system.
Figure 1

Here is a picture of a complete exhaust system. You can tell this exhaust is from a 997 as it has the newer style joiners as well as the rear fender support bracket, but the layout is exactly the same as the 996. For demonstration purposes we are following the exhaust from the left side of the engine. The exhaust leaves the engine via the headers (yellow arrow), enters the catalytic converter (blue arrow), travels to the muffler on the right side of the car (green arrow) and exits the tail pipe on the right side (red arrow). The lower bumper fasteners, in this case Torxs, but on the 996 they will be Philips (purple arrows) are also shown.

Now open the engine decklid and remove the airbox.
Figure 2

Now open the engine decklid and remove the airbox. Begin by loosening the hose clamp holding the boot to the throttle body (green arrow), then squeeze the tabs on the MAF connector to release it (yellow arrow). Now open the two harness holder clips (purple arrows). Finally, unbolt the 13mm bolt holding the airbox inside the engine compartment (red arrow, 996 only) and carefully lift the airbox out of the car. If you have a 3.8L don't forget to remove the wire connection for the resonance valve.

Loosen and remove the four Phillips head screws that hold the bumper threshold strip in place.
Figure 3

Loosen and remove the four Phillips head screws that hold the bumper threshold strip in place. Remove the strip and set it aside. Picture 4: Also remove the Phillips head screws along the bottom edge of the bumper cover as shown here (green arrows) and also on each side of the bumper cover.

Look underneath each black plastic bumperette.
Figure 4

Look underneath each black plastic bumperette. You'll see a small access hole with a 6mm hex bolt inside. Loosen the 6mm bolt and you will be able to swing the bumperette up and off the bumper from the bottom. At this point, you can give the bumper cover a good tug towards the back of the car and it will come off.

Once the bumper cover is removed, you'll need to remove the bumper itself.
Figure 5

Once the bumper cover is removed, you'll need to remove the bumper itself.

Remove the 10mm nuts holding each exhaust shield over the mufflers on each side of the car and take the exhaust shields off.
Figure 6

Loosen and remove the two 19mm bolts shown here (green arrows). Then remove the bumper with the heat shield attached.

One the shields are removed, you'll be able to remove the mufflers.
Figure 7

Remove the 10mm nuts holding each exhaust shield over the mufflers on each side of the car and take the exhaust shields off.

Remove the three 13mm bolts (green arrows) that mate the exhaust headers to the catalytic converter pipes on each side of the car.
Figure 8

One the shields are removed, you'll be able to remove the mufflers. This Picture shows the mufflers as they are mounted on the car.

Crawl underneath the car to remove the six 13mm bolts on each side of the engine.
Figure 9

Remove the three 13mm bolts (green arrows) that mate the exhaust headers to the catalytic converter pipes on each side of the car. You'll need to use a 13mm wrench to hold the nuts as you remove the bolts.

Pull up on the red tabs to separate the connectors going to each of the four oxygen sensors on the rear engine shelf.
Figure 10

Crawl underneath the car to remove the six 13mm bolts on each side of the engine. It's a good idea to soak these bolts in penetrating oil for a few days before trying to loosen them as they have a tendency to snap off.

11
Figure 11

Pull up on the red tabs to separate the connectors going to each of the four oxygen sensors on the rear engine shelf. The black connectors attach to the oxygen sensors before the catalytic converters. The gray connectors go to the oxygen sensors after the catalytic converters. If you plan on re-using your oxygen sensors, remove them from the exhaust at this point.

Now remove the three 13mm nuts holding each muffler to the exhaust brackets on the engine.
Figure 12

Loosen the two 19mm exhaust clamps on both sides of the car (green arrows)

ThisPicture shows the exhaust bracket with the holes for mounting the muffler (green arrows).
Figure 13

Now remove the three 13mm nuts holding each muffler to the exhaust brackets on the engine. It's very difficult to get aPicture of this, so I've included twoPictures here. ThisPicture shows the studs mounted on the back of the muffler mounting plate (green arrows). Once the nuts are removed, work the muffler pipe out of the exhaust clamp on the cats if they didn't already come off with the mufflers. Save the muffler clamps as we will be reusing them.

Now loosen the 19mm clamp that holds each catalytic converter to the car (green arrow) You'll probably have to pry the clamp open slightly to get it over the lip of the mounting plate (purple arrow) At this point, lower the catalytic converters off the car.
Figure 14

ThisPicture shows the exhaust bracket with the holes for mounting the muffler (green arrows).

Remove the 13mm nuts and bolts that hold each of the muffler mounting plates to the old mufflers (green arrows) and pop the mounting plates off the old mufflers.
Figure 15

Now loosen the 19mm clamp that holds each catalytic converter to the car (green arrow) You'll probably have to pry the clamp open slightly to get it over the lip of the mounting plate (purple arrow) At this point, lower the catalytic converters off the car.

Place the mounting plates in the new mufflers as shown here.
Figure 16

Remove the 13mm nuts and bolts that hold each of the muffler mounting plates to the old mufflers (green arrows) and pop the mounting plates off the old mufflers.

Now crawl under the car and install the new headers making sure that the new exhaust gasket is oriented correctly.
Figure 17

Place the mounting plates in the new mufflers as shown here. In our case, we had pry the ears of the new muffler slightly open in order to fit them.

Mount the new catalytic converter on the engine mounting plate and use the supplied clamps to secure it to the plate.
Figure 18

Now crawl under the car and install the new headers making sure that the new exhaust gasket is oriented correctly. It's a good idea to use new bolts here with just a slight dab of anti-seize compound to prevent them from seizing up in the future. Torque these bolts to 19ft/lbs.

Bolt the header flanges to the catalytic converters using the supplied copper hardware.
Figure 19

Mount the new catalytic converter on the engine mounting plate and use the supplied clamps to secure it to the plate. You'll probably have to pry the clamps open somewhat to clear the lip on the plate.

Now fit the old exhaust clamps to the ends of the catalytic converter (green arrow) Slide the end of the new muffler into the clamp along with the studs of the mounting plate into the bracket on the engine.
Figure 20

Bolt the header flanges to the catalytic converters using the supplied copper hardware. Torque these bolts to 22ft/lbs.

Now fit the exhaust tips to the ends of the mufflers and secure them with the supplied clamps.
Figure 21

Now fit the old exhaust clamps to the ends of the catalytic converter (green arrow) Slide the end of the new muffler into the clamp along with the studs of the mounting plate into the bracket on the engine. Tighten the exhaust clamps down and re-fit the three 13mm nuts on the back of the muffler bracket.

Here's a shot of the new catalytic converter assembly with the bumper cover re-fitted.
Figure 22

Now fit the exhaust tips to the ends of the mufflers and secure them with the supplied clamps. It helps to do a bit of measuring and aligning before you tighten the clamps down fully.

23
Figure 23

Here's a shot of the new catalytic converter assembly with the bumper cover re-fitted.

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