Need exhaust help on 964

[si Banker]

I have a 1993 C-2 964 that has a stock exhaust system which has a cat by-pass on it'

I have heard people speak of a "G" pipe; what part of the exhaust system does it eliminate? Can you run a cat by-pass with it? I had the exhaust system off the car and was supervised at how heavy it is.

For the record I had my car smog tested with out a cat and it passed by 7 hydro carbons. A very small margin but it did pass.get

The goal would be to some additional performance and improve the exhaust note.

Any help would be appreciated

[iamtheari]

The stock 964 exhaust system consists of the following:

Cylinder 4-5-6 heat exchanger/header, which flows forward and then leftward to join the other side
Cylinder 1-2-3 heat exchanger/header, which flows forward and then leftward after the flow merges with the other side
Catalytic converter, which flows rearward, has an O2 sensor bung on its inlet side, and bolts to the heat exchanger assembly with a gasket and four bolts (this is the part that results in heat on the left side of the car such as steam after a drive in the rain)
Primary muffler, which sits inside the rear bumper and flows rightward, connecting to the catalytic converter with a spherical kind of fitting
Secondary muffler, which sits inside the right corner of the car, reverses the flow of exhaust gases coming forward from the primary muffler and then going rearward through the tailpipe, connecting to both of those with the same kind of fitting as the primary muffler and cat connect with (this is responsible for steam on the right side of the car after driving in the rain)
Tailpipe, which is supported only by its fitting to the secondary muffler
Heat cross-over pipe, which connects to the rear clean air side of both of the heat exchangers and has an inlet that is fed by the big electric HVAC fan on the left top side of the engine, which itself gets air from underneath the engine shroud that gets pumped in by the engine-driven cooling fan
Flexible ducts, one on the front of each heat exchanger, that direct hot, clean air from the heat exchangers up to the HVAC system

Common modifications:

1. Primary muffler bypass / "cup pipe": my car has this from a previous owner and sounds great, very livable but you know when the throttle is open
2. Secondary muffler bypass / "G pipe": this replaces the secondary muffler and is named for its general shape, just reversing the flow of exhaust gases without also muffling them, supposedly also sounds good
3. Cat bypass / "test pipe": this replaces the catalytic converter and should have an O2 sensor bung so your ECU does not get confused, which is not a problem because it is designed for the O2 sensor to read before the catalytic converter and thus the bypass has no effect on it
4. Replace the primary muffler and secondary muffler with a single, high-performance muffler that sits in the location of the old primary muffler: Fabspeed is one of the many offering this solution
5. Replace everything from the heat exchangers on with new headers: Fabspeed also offers this and it supposedly has a big impact on performance because the two cylinder banks do not have a merged exhaust flow as the stock system has

Nobody agrees on the actual benefits of any particular modification.

[Bill Verburg]

Here's a 964 exhaust.


Here is what is called a Cup bypass, replaces the primary muffler


Here is a G pipe left and cat bypass right


Cup by pass below muffler


G pipe installed on the intermediate muffler, secondary muffler is deleted


the most restrictive part is the primary muffler followed by the cat and then closely by the secondary muffler

[si Banker]

Iam and Bill thank you very much for the info on 964 exhaust. I am going to add a cup pipe to my exhaust; I have a mufffler that takes the place of the two mufflers one the car but it is just to dam loud. If anyone wants it I will let it go cheap. I also removed the heater blower from the engine bay.

Which would you buy "G" pipe or cup pipe?

[mikedsilva]

I'm glad this thread has just come about....
Recently, I bought a 964 in total stock condition...

First mod was to drill out the lid of the airbox... I ended up cutting a large opening in it.. Result was no extra noise until I really opened the throttle.. then I would get that nice deep throaty roar.. sounded great.. but wasn't enough.

Next mod was to buy a cup pipe. I bought one from Ebay... **********...
Easy install...
I was expecting the car to sound loud when I started it... but I was surprised how quiet it was at idle. In effect, at idle, the volume is hardly any different.. when driving though, the car now has a very pleasant note. Not loud but very "colourful"... Sounds like a nice porsche should sound.

My next options, are to consider the cat bypass and or g pipe. Assuming, I have all 3 components, would you run them all at the same time?

I've been told that a cat bypass, stock primary, and g pipe, give a loud note and best combo of performance...

Do these engines "need" backpressure at all?

[SouthCoastPhil]

to si and mikedsilva

first: How did I know that Bill V would provide superb insights? Maybe history? (Just giving Bill a hard time, for I've found his insights super helpful for my 1993 964 over the years.)

i cannot answer the back pressure question (but i bet i know who can and will!).

As Bill V and others have accurately pointed out, 964 exhaust (starting with the cat) is really just three pieces (plus some connecting parts of course).

FWIW, I've run my 964 with all possible combinations of exhaust parts from the cat and down. My car came with "cat delete" and "G pipe" (=secondary muffler bypass). I've since purchased the "cup pipe" (from Sid at Vertex. made by Schnell, IIRC), as well as a great OEM secondary muffler.

OK, so i now had essentially an exhaust sandbox in which to play.

Running the primary muffler bypass (="cup pipe") and the secondary muffler bypass (="g-pipe" or "swan pipe") at the same time resulted in headaches within 3 minutes for me. way too loud, outside and in, at any rpm range. and my BUTT DYNO indicated that there was only performance degradation in both HP and torque.
(Perhaps that's an indicator of need for back pressure, Bill V?)

more to come shortly

[SouthCoastPhil]

follow on...

so i have tried primary delete ("cup pipe") with secondary muffler in place, as well as primary muffler in place with secondary muffler bypass ("G-pipe" or "swan pipe").

I do recall seeing some data, either here or on RL, about the the impacts of those configs on torque and HP, but i dont have that data handy right now. (IIRC, one config provides more torque and the other provides more HP.)

for me and my car, both at track (PCA DE, yellow run group) and on the street, i prefer the secondary muffler bypass in combo with stock primary. the differences in sounds at various RPMs are apparent, no question. but its a matter of taste/preference, right?

HTH

[mikedsilva]

phil
when you tried your primary and secondary combinations, was that with the CAT bypass both times?

I'm going to order the fabspeed cat bypass and dansk gpipe from Pelican Parts.

I guess the only way to really find out for your self is to buy all the bits and play away!

[Justin@Athens]

I just ordered the cup pipe off ebay from vertex. I used the "make offer" button and bought it for $200 even shipped. I feel that is a decent price since schnell wants $259 new, and Vertex has a Buy it Now price of $239.

I already have a g-pipe, and cat bypass, and am running a flowmaster primary muffler.

I have the car apart for major service at the moment, so I thought I would take the opportunity to see if I like the cup pipe. I will report back in a week or two after the part arrives and the car is back on the road.

[Vandit]

^Justin, so you're going to be running no mufflers, just a straight through exhaust? I imagine it's going to be ridiculously loud.

[Vandit]

Which would you buy "G" pipe or cup pipe?

I don't remember if you've heard my car at Cars & Coffee, but I have a G-pipe only (secondary muffler delete). I still have the primary muffler and the cat.

From what I've heard on my car and others, Primary muffler + g-pipe = lower exhaust tone, hot rod sound. Cup pipe + secondary muffler = tighter exhaust note, sounds more authentic Porsche.

[Justin@Athens]

Originally Posted by Vandit

I don't remember if you've heard my car at Cars & Coffee, but I have a G-pipe only (secondary muffler delete). I still have the primary muffler and the cat.

From what I've heard on my car and others, Primary muffler + g-pipe = lower exhaust tone, hot rod sound. Cup pipe + secondary muffler = tighter exhaust note, sounds more authentic Porsche.

I will probably end up going the Cup pipe + secondary muffler route, but I wanted to have all the options at my disposal. I do not have a cat, so I cannot play with that option though.

If anyone wants to hold out and see if I use the G-pipe or not, ill let it go for $110 shipped. Its practically brand new, probably less than 100 miles on it.

[SouthCoastPhil]

In reply to Mikedsilva,
Yes, cat bypass with all three configs. My 964 came with a cat bypass and I've never seen the need to remove it, especially since emissions laws in MA were changed a while ago to not require emissions testing on cars 1995 and older.


Comment to Justin's last post:
When I used the cup pipe + secondary muffler, i could not for the !@#$%^& life of me get rid of what I'll call a "whine" or "squeal" at around 2500rpm, +/- ~500rpm.

I had that witch apart countless times, tightened everything, loosened everything, installed new "donuts", took new donuts out and greased them, etc., all to no avail. so now it's G-pipe for me. Swan pipe does the same thing, just provides mounting arms, IIRC.

Pretty much ticked me off, since I did like the sound, but driving around town, as you well know, is usually in lower rpms range.

I am curious to know if any other cup pipe users had a similar experience and, if so, how did you solve it?

TIA, as always, for your help.

Phil

[si Banker]

I ordered a cup pipe today and I will post the results. btw Does anyone have any interest in the sport exhaust I have for a 964. It eliminates both of of the existing mufflers and saves a ton of weight but it is very loud.

It is made of stainless..........$100. I am located in Fort Worth

[RedCoupe]

Originally Posted by SouthCoastPhil

In reply to Mikedsilva,
Yes, cat bypass with all three configs. My 964 came with a cat bypass and I've never seen the need to remove it, especially since emissions laws in MA were changed a while ago to not require emissions testing on cars 1995 and older.


Comment to Justin's last post:
When I used the cup pipe + secondary muffler, i could not for the !@#$%^& life of me get rid of what I'll call a "whine" or "squeal" at around 2500rpm, +/- ~500rpm.

I had that witch apart countless times, tightened everything, loosened everything, installed new "donuts", took new donuts out and greased them, etc., all to no avail. so now it's G-pipe for me. Swan pipe does the same thing, just provides mounting arms, IIRC.

Pretty much ticked me off, since I did like the sound, but driving around town, as you well know, is usually in lower rpms range.

I am curious to know if any other cup pipe users had a similar experience and, if so, how did you solve it?

TIA, as always, for your help.

Phil

Had the cup pipe (primary bypass) on my 964 for about 8 years without any problems like that. Recently, however, my original cat has started to rattle, especially at lower revs. Suspect it's used up all of it's 9 lives!

[trak ratt]

This

http://forums.pelicanparts.com/uploads23/964exhaust11411509887.jpg

nice sound, legal almost everyplace...

[Justin@Athens]

I am going to need a stock cat after all as my through pipe has been modified to fit the flowmaster that is on the car.

Anyone looking to sell their catalytic converter?

[pantera]

I'm running a Fabspeed by pass pipe, stock primary muffler, stock header exchangers with a Dansk G pipe on my 964 DE car. The car sounds great and lots of compliments. More importantly this combination really uncorked the motor. No dyno graphs but by its on track performance this combo makes the motor really pull strong throughout its rpm range

[si Banker]

FYI; I got my Cup Pipe last weekend and installed it. The sound is great and the car feels as if it pulls a little harder'

thank you to everybody for the feed back

[notfarnow]

My car has a hollowed out cat, and when I purchased it also had a g pipe. I found it too loud to use as a DD. I currently have a stock setup, albeit with the hollowed cat, and find it nice if a bit tame. May try a cup pipe or a homebrew flowmaster system I picked up in the pelican classifieds a couple years ago.