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YOUR RESEARCHMilltek Catback mod?
Reported or suspected cause
like many other's who have early production cars
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Read evidence and context
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Reported cause
My cat problem was like many other's who have early production cars with the 400 cell cats...they just go.
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Then we slipped then into place and made a tack weld and then adjusted the system to make sure all was aligned and the tips were in the right place.
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BOTH cats (both sides) have to be replaced due to lackluster cold start operating temps.
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I do know that the dealership (Pfaff) has performed the same modifications for MANY customers since - both for new and used Porsches.
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Suggestion
The passenger side is leaking so I auumed that i would need to change that one but they are changing both sides.
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Milltek Catback mod? **now done...with pics**
Has anyone thought of cutting out the small, pre mufflers from the milltek system and replacing it with simple stainless pipe to increase the sound a bit?
Anyone done this or something similar? I'd love a bit more snarl out of my system and wondered what this would yield.
Thoughts?
Sounds like fun, let us know! I know Milltek is going to have a louder option at some point, this might be similar to what they end up doing... just a guess...
Hey K-Man,
Do you know any more about this louder option? Any thoughts on if this would hurt performance or how much louder this could be? I wonder how effective those little pre-mufflers are?
So I think I'm going to go through with the pre-muffler bypass mod. The pipes are 2.25" OD and I am sourcing some nice stainless steel pipes to insert instead of the little mini mufflers....and a weight savings to boot!! Hopefully this will give me the added sound i'm looking for. Keep you posted...
Chris
Only thing is you will probabaly loose some HP maybe just 2 or 3. that pre-race muffler is adding back pressure that they designed the system to have. The 2.25" pipe is allowing the exhaust gasses to escape faster. Maybe too fast so thats why they use the "offset" muffler because it is compensating for the larger diameter piping. That is another reason why there is so much piping the exhaust gasses have to flow through, to keep the back pressure the engine needs. That is why the Kreisseig exhaust has so many sharp breaks in the piping. It helps maintain back pressure even when the valve is open.
You can have an exhaust with no muffler produce the same amount of back pressure as an exhaust with a muffler. It would have to be designed correctly and it would have alot of sharp turns to slow the gasses passing through (which is what the muffler does) I bet the milltek will sound alot nicer, I almost bought one just to put valves on it. I cant wait to hear how much louder it will be. I dont expect much change in the noise though, those are really so small.
I doubt that I will lose any power with this small resonator/muffler removed. This whole idea that our cars need a ton of back pressure is kinda lame. You have to create more flow to make more power, it's as simple as that. All aftermarket manufacturers are using larger diameter pipes, free flowing muffler and cats to make more power. Removing a straight through pre-muffler or baffle, will surely not harm anything. I am keeping the same OD pipe and the length will be the same. If anything there might be a slight improvement in power since I am (hopefully) removing a restriction for the air (as it is swirled around in the pre muffler). You know, better scavenging effect with the same size pipes but less turbulence...All speculation thought but I'm not too worried...
I just hope it sounds a bit more aggressive!!
Chris
Why not just reduce the size of those huge cannister mufflers? I think that's the route I'm going, shooting for a size between a Tubi and stock Miltek.
Chris,
FWIW, I have a the stock exhaust system (with Fabspeed headers) that was customized by the dealership when I purchased the CS. Essentially they removed the internal baffles of the stock exhaust with a "straight" pipe of some geometry, and the result is much improved sound, and a slight, but noticeable, increase in power. I drove CS's back to back with the stock exhaust and the modified exhaust, and there definitely was an increase in power with the modified exhaust, so that is what I purchased. I think you are talking about doing something very similar - if not identical.
I do know that the dealership (Pfaff) has performed the same modifications for MANY customers since - both for new and used Porsches. I'm not aware of any problems, and my experience with this "mod" has been very good.
Done!
Ok so as I said above, I wanted to gain a bit more sound from my Milltek cat back system and I thought that the easiest way would be to remove the pre-mufflers. Sooooo I bought a 5' lenght of 2.25" stainless pipe, cut off the pre-mufflers, made a measurement and welded back the straight pipes.
Take a look...
After cutting off the pre-mufflers:
Next we measured the pre mufflers and decided that we would use 9.5" per side and flare the sides so as to slip it over
Then we slipped then into place and made a tack weld and then adjusted the system to make sure all was aligned and the tips were in the right place.
Then we welded it all in place properly
And then its all done and done!
So the sound is WAY better...no more resonance at low rpm and a much nicer and more aggressive snarl all through the rev range. It's louder for sure but not unreasonable at all. This is what it should have sounded like IMO. I'm really enjoying the sound for sure!!
On an unrelated note, I think I have the dreaded cat problem..the passenger side has what sounds like a leak from the manifold or the cat. It's actually not coming from the manifold but what seems to be (one) of the pipes that goes into the cat converter. It sounds like **** and I now have my first ever CEL...
The good with the bad I guess.
Chris
Side note...the pic i took of the final product has some kinda ugly welds...the spool was stiking and making it all chunky and ugly. The other side is nicer...'cause I KNOW someone will comment on it.
Chris
Chris[/QUOTE]
Quoting Chris
{On an unrelated note, I think I have the dreaded cat problem..the passenger side has what sounds like a leak from the manifold or the cat. It's actually not coming from the manifold but what seems to be (one) of the pipes that goes into the cat converter. It sounds like **** and I now have my first ever CEL...
The good with the bad I guess.}
Chris, what kind of headers do you have? I have Fabspeed with cats and have had some problems with the cats coming loose in the cansiters...also CELS.
andy
Update:
BOTH cats (both sides) have to be replaced due to lackluster cold start operating temps. The passenger side is leaking so I auumed that i would need to change that one but they are changing both sides.
I'll try to get a quick video and upload it. It sounds AMAZING.
Ok..I'm in information overload!
I am in SHOCK(!) it got rid of the low end drone (between 2-3K I assume) I would have thought the primary purpose of those mufflers would have been to remove some of that drone. If they got rid of it, I'm cutting them out of my car ASAP.:banana:
I'm suprised you are noting cat damage, considering you have stock headers, has anyone else experienced this?
hey guys,
Sorry for the delay, I've been busy at work.
The car has no more resonance or drone than it did before (which I found way, way too quiet). As it is, the car is not too loud but sounds great. It passed sound chck at Calabogie and Tremblant with a 95db (blipping the gas to about 43000rpm or so) at about 15' away.
I do not have a sound clip, unfortunatly.
My cat problem was like many other's who have early production cars with the 400 cell cats...they just go.
Anyway, I love the sound of the car now, it sounds great inside and out and is totally fine (IMO) for cruising on the highway and straight up wails at WOT on track.
Good luck!
Chris
Calling Milltek...
That sounds great if you have got rid of the resonance problem.
Calling Milltek... can you guys chime in and comment on this? Have they ever tried this? Good, bad otherwise?
Good work, brother. I think that's the way it should have come. And the best news is that i still pass all the sound tests at the track! A stock 997 GT3 got black flagged the other day...
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