Cup pipe?

SimonExtreme · Dec 14, 2004

I have been looking in the parts catalogue and also under my car and I suspect I have a cup pipe and didn't even know it! As I see it, the silencer across the rear of the car should be oval in section while mine is round. Am I right in assuming that I have a cup pipe. If so should I

a) Be very excited because my car is even better than I realised.

b) Take the car back and complain.

c) Curse my luck as a cup pipe just makes the car nisier without any performance gains.

d) Immediately change it for the standard unit as I am a law abiding citizen who doesn't want to polute the world with the excess noise.

e) Rev the engine even more first thing in the morning just to make sure everybody nearby is awake.

I hope I get more answers to this than I got from my last post. And if you couldn't be bothered to read it to the end, there was a question about brake pads in it[

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Elliot Davies · Dec 14, 2004

A cup pipe is about 3" in Dia normally in stainless steel.
Running across the car from one side to the other behind/under rear bumper
If you have space around/above and behind this pipe then its a 'Cup'
like attached..........

SimonExtreme · Dec 14, 2004

The reason for my doubt is 2 fold

1. Its not stainless
2. There is no mention of it in the history which is reasonably detailed.

However, it is round in section and seems to be about 3".

Matt · Dec 15, 2004

if you get rid of the silencer under the rhs wing you can make the car even noisier to amuse your neighbours & the local constabulary. think that ones called a G-pipe. mines had this done to it (not my choice btw) and it is a little anti-social however on a sunday morning.

standard set-up is too quiet, g-pipe is too noisy, cup pipe probably a good compromise so enjoy it..

Elliot Davies · Dec 15, 2004

but not both 'G' and 'Cup' together otherwise there will be no silencing at all except for the catalyst [

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Melv · Dec 15, 2004

If you're planning on track days almost anywhere, forget the Cup Pipe!!

Mine's hanging up in the garage and a 964 C2 silencer languishes in its place on the Cup Car.....

Before? 105-107db.

After? 98-100db.

Power difference? Slight lag upto 4200rpm that you would only notice if you could do a back to back comparison.

Ear plugs? Don't need to wear them in the car anymore....[

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And still 285bhp/tonne!!!![

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Mel

SimonExtreme · Dec 15, 2004

I had been thinking it was fairly loud! Maybe time for a change [

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RSR · Dec 15, 2004

Hi Simon. It should be fairly easy to tell. If its a cup pipe it will just be a "PIPE" running across the back. The silencer is obviously much bigger in diamter with a piece of pipe exiting from either end.

On the pads I prefer the feel of the Pagid orange, but they can be noisy.

SimonExtreme · Dec 15, 2004

Right, thats it then. I love the feel of Pagids so Pagid orange it is. Yes they can be noisy but if you follow the bedding in procedure, that helps and if the squeals return, bed them in again.

The exhaust is more interesting. I am sure its got a cup pipe on it so I have been doing some investigating. Simple and cheap would be to stick on a standard C2 section. However, we don't like standard and we don't like simple! So i have been on the phone to my old friends at Haywood and Scott. They do a nice shiny SS cat back system that replaces both silencers behind the cat with just one across the back and then out. They think that it should be trackday friendly and should be freer flowing than what I have already and all for the (gulp) sum of £450 + a bit for HMG. Now, I have had very good experiences with this company. has anybody got any comments?

Melv · Dec 15, 2004

"........£450 + a bit for HMG............."

Thirty quid cash for a C2 silencer......[

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Mel

SimonExtreme · Dec 15, 2004

ORIGINAL: Melv
"........£450 + a bit for HMG............."
Thirty quid cash for a C2 silencer......[]
Mel

But is it shiny! Seriously though, this replaces both the cup pipe and the rear box, gives acceptable noise levels and increases power. If I end up going for a Motec ecu and am trying to get 325+bhp, helping the engine breath will be fairly important.

Jamie Summers · Dec 15, 2004

Simon,
Thanks for doing the initial research for me ! I've got a cat bypass and cup pipe on my new 964 and it (allegedly) puts out about 105db (not tried on track yet), so was looking for a way to keep the hp benefit of the de-cat and cup pipe whilst wishing to remain 98ish db track-friendly. I was about to give H&S a call to see if they have something 'off the shelf' rather than a £1,500 full custom system that might do the trick - and it appears they have - great ! Standard back box sounds like a possibility, but I can't help but think that I don't need to suffocate my otherwise standard rebuilt engine more than it needs to be and frankly £450 for any Porsche part is something of a bargain ! Also, clearly a cup pipe has a resale value so the cost can be defrayed to some extent !

Jamie

SimonExtreme · Dec 15, 2004

I know that to some £450 seems a lot but H&S really do know what they are doing. They are pretty confident that their system will out perform the cup pipe and "final" silencer combination and be a lot quiter. All that and its in shiny SS [

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I have found another possible route and that is to get a 100 cell sports cat. This shouldn't see any performance difference but will drop the db's. I believe that this route will cost about £150 exchange.

However, I think that leaving the cup pipe in puts a lot of back pressure strain on the final box so a "total" solution is better and keeping the cat off the car seems the right way to go as they were never designed as a muffler.

Jamie Summers · Dec 15, 2004

Do you think H&S would do a 'try before you buy' ? Frankly, because if it doesn't get the db below 100 then it's not really worth having !

As to the simple 100 cell race cat swap I'm not sure if that would do the trick on its own ? As I already have a bypass (and no cat left to swap) I doubt they would do a £150 exchange. New they are more like the same cost as the £450 complete rear section - and then you would be able to sell cup pipe too.

Let me know how you get on - I'm sure I'm going to have to go down the same route - if there is a saving to be had for a group purchase then I'm certainly keen.

I believe my car has been allowed on track at Bedford before, but if it is genuinely 105db then either the sound tester wasn't watching the rev counter (

!!!!!!) or the previous owner wasn't giving it full beans on track. I'm doing a day there on 5th Feb, so am slightly tempted to leave it until then and see how it goes - even if it means having to drive like a granny to be allowed to stay on track !!!!!

Jamie

Laurence Gibbs · Dec 16, 2004

I have been thinking on this for a while now and it's suddenly come to me. I think maybe Mel's 105db may not be the same as other's. Let me explain. Mel's is a cup car with absolutely no sound deadning at all and possibly a less well insulated rear bumper section too. So in "theory" mels car could read slightly noiser than our "slightly" more "damped" RS's. Also if Mel is still running the final silencer that came with the car he might find that it's not quite the same internally as the standard item!!! Just thinking out loud.

Melv · Dec 16, 2004

In the words of Miles Davis, 'So What?'

Rgds
Mel

SimonExtreme · Dec 16, 2004

Laurence

Nice theory but, sorry, NO! Having checked the parts book it seems that the rear bumper is the same and there is no extra sound deadening in areas that would make a difference. The final silencer is the same as well.

Howver, it is possible that Mel is running a non standard final silencer without knowing it. 105db seems high and I am going to try to upset 'er next door with my own sound check. Now, how many rpm and from how far away?

Jamie Summers · Dec 16, 2004

Should be 1m away from the back of the car (not sure if it's from the tip of the exhaust or back of car itself) and upwards at 45 degrees (if I remember rightly ????). They usually ask you for 4,500 revs on the clock, but I think in theory it is meant to be 75% of maximum revs - you do the maths, can't remember the rev limit on the RS !

Jamie

Melv · Dec 16, 2004

Rumour and conjecture -get the facts right or you ain't doing any track days at all!!

Goodwood -either 98db/ten car per session or 105db/6 car per session day -75% max rpm at 0.75m;

Bedford - as 105db above (I think....)

Donington 'quiet' day 98db on DRIVE BY (so don't worry.....) Noisy day is 105db DRIVE BY -ouch!!!

Castle Combe -100db at 75% max rpm at 0.5m.....

These are the only tracks that I've been noise tested on in ten years of track days.....

The weather, humidity, barometric pressure and proximity of other buildings, also makes a difference.

BTW -the standard exhust on my 964 C4 came in at between 98 and 102db, so 105 is easily attainable by removing the rear silencer and fitting a Cup Pipe....does sound good though....also bare in mind that intake roar will also be recorded and with an air filter box looking like a Battenburg cake, that also must enter in to the equation.

If u r in Surrey and want a test, can arrange in exchange for a donation to my wife's school fund -she supplies the noise meter.

Rgds
Mel