996 C4S X51 Manual - Exhaust Replacement - Advice Request

I have a 2003 996 C4S with the X51 engine. I am very happy with the factory PSE system that’s on the car, but after 15 years it needs replacement. I am looking at replacing the existing X51 headers with the X51 OEM replacements. I am undecided about the mufflers. I will either find good condition / low km PSE replacement mufflers, or choose aftermarket, lighter, stainless steel mufflers like Cargraphic, NHP, AWE, FVD, etc (not Fabspeed, Billyboat). I don’t particularly want the high pitch sound of IPE etc. Any suggestions or first hand experience with this would be great. I also want to put 200 CEL cats on (no X pipe system). Any suggestions or first hand experience on what works well etc would be great. Many thanks, all.

I have an 04' Carrera C2 with a cargraphic exhaust system. Couldn't recommend them enough. You can get non x-pipe 200cel cats from them. Their mufflers also come in 3 sound stages: TUV, TUV sound and Super sound. I've had TUV sound and recently upgraded to Super sound. If you're after a really great note without an obnoxious sound that's why I'd recommend TUV sound. Super sound can be a bit much at times, but I love it - to each their own.

Thanks Dan. I appreciate the feedback. Cargraphic seem to be the front runner. Did you buy direct? You don’t want to sell the TUV sound mufflers that you originally had on it do you?

Yep got it direct, although you have to add the cost of import duties + gst etc. Becomes a very costly exercise unfortunately.

Thanks. I’m chatting to Cargraphic now on the emails. They are recommending the X cats over the crossover cats (suggested it would be better performance and not as loud as the crossover cats). From the last few weeks of trawling through forums, there seems to be a view that the X cats can lose low end torque. What are your thoughts? By the way, are you in Sydney? I’d love to spin around to hear your set up. The $$$ of it all is phenomenal, so I don’t want to cock it up. Cheers, Chris

I had thought I lost some low end torque but the car adapts and you forget about all the "low end torque loss talk" fairly quickly. Not sure about crossovers being louder than the x-pipe though. Is that what Cargraphic have said? The x-pipe claims more hp gain than the crossovers on their website. I'm in Melbourne unfortunately - I do have a few sound clips if you want to hear them but they really don't give you much information. I'd recommend the "TUV sound" version of the mufflers - over the "super sound" that I have - the super sound can be a bit much sometimes its given me ear aches on occasion. Anything Cargraphic isn't cheap the whole system can be close to 8k+ including taxes etc. To be honest I'd do it in sections rather than going all out - there isn't much advantage in buying it all together. I'd do mufflers first, then x-pipe, then headers. Although it depends on what you want and how much you'd like to spend.

Yeah. They said: In my personal opinion you will reach the very best combination in sound and performance by installing our 200 cell sport catalytic converter “X” with our flap-controlled sport rear silencers. The same combination with the requested “crossover” catalytic converters might be too loud as there is no gas stream collision inside the catalytic converters.

Hurmm that's interesting. I couldn't be bothered with the flap controlled mufflers thought they would be a waste. Anyway they told me the xpipe has more performance than the crossovers for what it's worth. I'm following them up on that for clarification they had always said that the xpipe was better all round. Also that the xpipe provided a more "refined" sound than the crossovers too.

I agree. My PSE system has the valves with a button on the dashboard. I closed them once on a trip to Canberra (it was very quiet). They are open (loud) all other times. I assume the valves open will be the same sound as the equivalent version without the flaps, but have asked the question. I won’t be getting the valves this time. The X pipe is definitely more power (10KW and 18nm) compared with crossovers (7kw and 10nm). It says improved mid and high end torque (so low end torque must therefore be the same or reduced).

It concerned me when I first installed the xpipe that I had lost some low end torque but the ECU adapts and I can't feel the loss if there actually was any - I dont give it any thought anymore as it sounds and drives fantastically. Are you going to keep your mufflers and just do the xpipe or what setup/components are you thinking about?

I need to replace the headers as the flanges are getting thin (due to rust). From what I’ve read the X51 engine needs the 48mm diameter X51 headers that are on it, so that’s what I’ll get. The rest of the system is okay, but on the way out. I’m a bit stuck on what to do with the mufflers. Will be PSE (second hand, as the new ones make Cargraphic look cheap) or Cargraphic mufflers. Based on the emails from Catgraphic and our chat, I’m thinking the X pipe with the 200 Cel cats might be the way to go.

Hurrmm rusted headers?? Did the car live by the sea? Or a UK import? Haven't really read about exhaust systems rusting on 996s in Australia yet! The headers are the only thing I haven't pulled the trigger on. Will probably get them this year sometime. IMO mufflers make the most significant gain in performance and sound. Any exhaust part from Porsche seems to be ridiculously priced.

Exactly. She lived in London for a few years and the salt on the roads ate it up. I’ve already replaced the entire suspension with Ohlins Coilovers, new engine and gearbox mounts, etc. The exhaust system is the only thing left, showing the UK scars. Yeah the aftermarket world has thrived because of crazy OEM prices.

Ahh yep that would explain it! X51 is a rare option though Keep us posted on what you decide if you need any additional help let me know! Are you planning to install it yourself? Took me a day to do mine but I was working slowly. It's relatively straightforward although if its rusty id allow for extra time and extra WD40 + an overnight soak on all the nuts/bolts.

I got in touch with them as well they told me the same thing - xpipe provide more performance but the crossovers can be louder. Always wanted more sound and my only issue is under 3k its not very loud but to be honest that's probably a good thing! Talking to them about the headers as well now.

Yeah will fit it myself. Will need a couple of days of penetrating oil to get into all the bolts (especially on the manifolds) before I touch anything. Cheers for the chat!

No worries! Also few tools to have on hand if you don't have them already: - good spanner set + torx screwdriver set - torque wrench + extensions - manifold to xpipe bolts can be tricky to torque down without the extensions - crows foot set for torquing down O2 sensors - which id recommend replacing as you've got it apart anyway Also the O2 sensors should face toward the front of the car - I've seen some mechanics install them facing outwards - this is incorrect Keep us posted!

CJC - just be very wary of removing the header bolts from the alloy cylinder head. If the bolts look rusty and misshaped (and they will if its a UK car), be prepared for them to shear off and for you to have a painful episode removing what remains of the broken bolts. There used to be quite a few utube "how to" vids. outlining the procedure but it ain't easy, cheap or quick. Stomski Racing in the US has a pre fabricated template guide available to help drill out the offending bolts and install threaded inserts, but its not easy laying on your back drilling out the remains of steel bolts corroded into expensive alloy cylinder heads.....

Quotes source post: 279271

+996 i'm worried about doing mine and they aren't even that corroded... If they are bad i'd send it to a dealership or a reputable independent, of all the exhaust bolts the headers to block are the ones you don't want to get into trouble with...

Update / Current Status: Have now (almost) completely removed the existing exhaust system. All corroded. Took off the wheels. Removed the rear lights (C4S), rear bumper and heat shields. Then removed the exhaust pipes and tips from the mufflers (cut the clamps with a grinder and then spread them apart with a large flathead screwdriver). So far so good. 2 hours down. Opened up the engine bay and removed the big black plastic air box / intake / filter to access the plugs for the O2 sensors. Removed the plugs and opened up the small flexible metal clips that hold the wiring in place. Pulled the sensors through from the bottom. Cut each of the bolts heads / nuts (x3 on each side) from the cats to the headers. Many were rusted through / non-existent. Levered the cats and headers apart and wriggled them loose. Cut the bottom clamps and sleeves connecting to the flexi-pipe on the mufflers. Pulled them off sideways from the flat metal brackets mounted to the engine case. Then pulled / lowered each of the cats (O2 sensors connected) out. More difficult. 2 plus more hours. Removing the mufflers was a nightmare. Very difficult to get access to each of the 3 x bolts that mount the brackets to the mufflers. Heavily corroded / stuck on bolts. No access to lift the vertical bolt (closest to the rear wheels) up because it hits the body. 3 hours plus of trial and error and using different tools (PB blaster, sockets with and without extensions of different sizes, open ended spanners, hammer and flathead screwdriver, etc) and they came out. Now more concerned about removing the  12 x header bolts. Lathered in PB blaster (multiple times over 24 hours) and a socket set ready to go, work starts. 2 came out clean and 4 bolts sheared off at the head on the right. 4 bolts came out clean and 2 bolts sheared off at the head on the left. Was patient with it, but the ones that sheared off did so with such little torque on them. 6/12 in total. Could be worse. Pulled the existing headers down over the remaining bolts and slept on it. 2 - 3 hours. Bought a 1/2” drive stud extractor from T&E Tools in Sydney ($50) that looks like the chuck of a drill with 3 jaws that clamp down onto the stud as you wrench the drive on and a Butane blowtorch ($30). Heated the bolts up for a minute or so (maybe not quite hot enough, but was a little nervous) and put the tool on. Worked a treat. 4/6 broken bolts came out clean. However, 1 x broken bolt snapped just about flush with the block, and the other broken bolt was just under 6mm so couldn’t get a grip on it. Have ordered the 1/4” drive stud extractor, so hoping to get this one with that. The snapped bolt has been centre punched and drilled with a pilot. Will increase the size of the pilot tomorrow and then try a 6mm or 7mm easy out on it tomorrow. Stay tuned. Also, I have found some stock 996.2 C4S mufflers in excellent condition, however, the flexi-pipes have been cut. If any of you have stock 996 mufflers that have had their day, so I can cut the flexi-pipes off and weld them onto the mufflers I have, please let me know? I’m located in Sydney. I’m also considering either the Gundo / PSE / banana hack OR the Fister Modification on the mufflers. Although, with the beefy X51 headers and the X pipe I’m nervous it might all get too loud / aggressive (since I won’t have the valves to quieten it down like on the Genuine PSE mufflers that have come out). Thoughts? Have new titanium studs and K nuts ready for the new OEM X51 headers (48mm diameter) that I’ve had ceramic coated and new X Pipe 200 Cell Cats from FVD Bromacher / M&M and Bosch O2 sensors ready to go. If the easy out doesn’t work on the snapped header bolt, does anyone have a stomski jig I could borrow? Cheers, Chris

I have a set of cargraphic TUV sound mufflers if you're interested - PM me

Update: All header bolts are out! Had to drill the last two out, as the easy outs wouldn’t look at it. Now the fun part starts. Installing new titanium head studs and K nuts so I never have to repeat this activity again. New gaskets. New X51 factory OEM headers (ceramic coated for corrosion protection and heat reduction in the engine bay). See photo below. Old vs new.

Headers in. X pipe / Cats in. New Bosch O2 sensors in. PSE mufflers reinstalled. Exhaust tips, bumper etc on tomorrow. Then we can fire her up. Does anyone know how long the ECU will take to re-map itself after the install (in particular with the X Pipe / 200 Cell Cats and new O2 sensors installed)? I assume I should let it run for 5 - 10 minutes to settle in before driving.

You can disconnect the battery to assist the learning process and reset the values stored.

As Dan says above. 1) Disconnect battery for a couple of min. 2) After reconnecting battery switch on ignition so all dash lights illuminate (do not start engine) for +/- 30 seconds. You will hear fuel pump run & throttle body module resetting. 3) Switch off ignition and remove key. This should reset your throttle body and ECU parameters, though (I think) the car has to go through several start / stop and heat cycles to complete the stabilisation.

Heat shields and bumpers back on. Tips realigned. Will follow the steps above to reset the ECU (thank you both) and go for a drive 😉

Update. The system breathes a lot better with the X Pipe and 200 CEL cats compared to the original cross over pipes. Bit more of a burble just off idle (much like a V8 speedboat at idle) and a bit more raspy above 4,000/4,500 rpm. Much more willing to rev, and noticeably faster. Haven’t had the need to hit the PSE switch to activate the actuators and close the valves to quieten it down (although I tested this to make sure all is well, and it was working nicely). I would put it into quiet mode on the highway. I expect the new Bosch O2 sensors have also made a difference in efficiency. Will try and take / upload a video.