amr89c4

QUOTE>>>Cup pipe + G-pipe gives too low back pressure and loss of performance(hp/torque) as a result...(from what I found here by Rennlisters that tried) __________________

I tried the cup pipe and g pipe and loved the sound. It was pure business and not too loud, compared to the Harleys that drown you out. BUT, I found, as velocitylover mentioned above that car got pretty soft from idle to 4500 and I didn't want to give up the bottom. It was strong 4500 on up though.

I put the secondary muffler back on and I was back smiling again. My opinion, worth what you paid for it, is that soundwise it still sounds about like a full cat, primary and g pipe.

The 'hot set up' is supposed to be a cat bypass, cup pipe and secondary. I am looking for a decent cat bp now.

velocitylover

That is my set up exactly : Cat Bypass + Cup pipe + secondary

Lynn, why don't you try vertex bypass it looks the buss. and has great quality/fit for $279.00 (no affiliation etc.)

forklift

Funny this comes up right now....although it has come up many times throughout the years as I have searched this subject and performance chips for many hours and just dyno'd this set up on Thursday and found:

running the secondary bypass in addition to the cat and primary bypass (all 3 bypassed) resulted in a *loss* of 11-12 rwhp. .....so I am just back to the same set up I have had for the last 4 years or so which is the cat and primary bypassed and the secondary muffler in place...and stock headers/heat exchangers.

I know the cupcars ran both the mufflers bypassed, but I think they had the cat in place, so maybe there is some truth to the need for some back pressure. I'm not sure, but the dyno said a loss of 11-12 w/ all 3 bypassed vs. the secondary muffler in place.

Also, I have cracked two secondary mufflers over the years so I bought an extra and will probably buy another one when my currnet muffler cracks.

tdatk

I'm going this route as well with great advise from Jim. Sounds like I'm gonna need some spare secondary mufflers.....

biggles

What about the performance with the cat bypass, primary muffler and G-pipe? Does this result in a lost of hp/tq? Did not plan to dyno my car, because I assumed that any increase in hp/tq with these changes plus a chip would be minimal, but a potential loss in hp/tq would certainly warrant a dyno given the car's base amont of 250 hp.

biggles

amr89c4

I have not run a cat bp, primary and g pipe, but IIRC, my searches found that combination netted basically stock hp/torque results.

There was 5-6 hp with a stock cat, primary and g pipe.
There was about 7-9 hp with the cat bp, cup pipe and stock secondary.
There was a loss of bottom end torque (it was obvious to me anyway) with the stock cat, cup pipe and g pipe.

I have not experienced any problems with the secondary, thus far.

Others flow test showed the stock exhaust system and the secondary was the least restrictive, followed by the cat and then the primary. I'll see if I saved the actual flow numbers.

I did forget to mention I have a 93 octane, stock limit, Wong chip.

tdatk

Installed the primary muffler bypass tonight. I recorded the before and after sounds. I've linked the videos here. Sorry about the squeeky belt, I had the fan off and need to re-shim the pulley.
http://www.youtube.com/watch?v=nPv3vJp96f0
http://www.youtube.com/watch?v=WO4KZzZah4g

enjoy...

wellcraft290

tdat that only the primary or you have anything else done?

tdatk

The cat is gutted too. I went with the Maxspeed bypass, quality is good and the price is way more in line for this type of pipe. You can also buy the pricey cat bypass, but since I live where there is no sniffer testing, I just gutted the stock cat,
HTH
Tim

raspberryroadster

sounds nice.....will you leave the cat stock, or replace with race cat or do cat bypass?

tdatk

I will leave the stock one on there until I find a reason to change it out....like a 993 exhaust ....

wagonface

Morning all. I was hoping people could give me some volume advice. I have owned my 964T for about a month now and want to get to the bottom of why its so loud at idle.

The previous owner told me the engine internals have been modified: C2 Camshafts, Larger K29 Hybrid Turbo, Power Valve Headers (I have googled this last one but cant find the company and there are no invoices for this work as it was done a few owners back).

In terms of exhaust, I know it has non standard heat exchangers, and a g-pipe. From the photos below it looks like a standard primary muffler. I dont know about the cats, and wouldnt know where to start looking. Can anyone see from the photos below if the cats are present or have been deleted?

I do like the current sound when driving around: its throaty and burbles and pops when you ease off the throttle. But at idle it is very very loud.

Listening to tdatk's youtube videos (above) made me realise how loud my car is at idle. I want something louder than stock, but I dont want to be as loud as I currently am. I really like the slight change tdatk achieved, but dont know if the result would be the same on a turbo?

At idle my car sounds like this 965 with sports cat & g-pipe, which is in contrast to this normal 965 sound. Annoyingly I cant find a youtube of just a cup pipe on a 964T.

Any advice would be very gratefully received:
1) can you tell from the photos if I have a cat delete?
2) do people think the g-pipe alone would cause the massive increase in noise at idle?
3) if I put a secondary silencer back on and fit a cup pipe instead, will the noise at idle be much quieter? (I wont bother changing everything if there isnt much difference)

Thanks for any help / advice, Josh