luke-44

I am new to this so bear with me....I am confused about the options for 964 after-market exhaust systems - I have been following a number of these threads. Let me take a stab at it - tell me if I am right:

The basic system as I understand is -> a) heat exchanger ->to b) catalytic converter, ->to c) primary muffler ->to d) secondary muffler, ->to e) exhaust pipe. Correct?

As I understand it, some common upgrades or swaps (regardless of brands - Dansk, Fab, etc,) are as follows:

1) replace a) heat exchanger with headers - either with or without a heater allowance? - This is kind of "hard core" - like for a racing appl'ns etc?

2) change the b) catalytic converter with a new b) - cat bypass, or replace b) cat with a b) low restriction cat. In either event, the b) part stays - possible not legal in some states...

3) bypass the c) primary muffler (covered in this post - https://rennlist.com/forums/964-forum/374878-dansk-primary-bypass-missing-part.html or change c) primary muffler to a c) dual exhaust setup - bypassing the d) secondary.

4) bypass the d) secondary muffler. - The so called "G" Pipe" - covered in this post - https://rennlist.com/forums/diy-964-1989-1994-911/197456-g-pipe-secondary-bypass-fitting-guide.html

5) change to new 5) tips - mainly for looks

Questions:

Is it possible to do all of 2), 3) and 4)? Wouldn't this be major loud - ie - no exhaust at all?

Or...
just do one of either 3) or 4). Or bypass both 3) and 4) - keeping 2) - (which would obviously be louder than just doing either 3) or 4).)

Assuming I am basically right, my final questions are:

If you do any of these, do any electronics have to be changed?

what is the difference in the result between bypassing c) primary muffler, versus bypassing d) secondary muffler?

Or, is that what all the debate is about - loud vs too Loud, vs performance increase, vs cost, etc...

Thanks in advance....

Cupcar#12

Is it possible to do all of 2), 3) and 4)? Wouldn't this be major loud - ie - no exhaust at all?

-Yes it is very loud depending on your tolerance it could be too much - ok for a track car or occasional car - with the right ECU tuning this is the prefered setup for a race car.

bypass cat and primary are the most cost effective - however the secondary is the most restrictive of the 2 mufflers but is a) ligher and b) place in a better area from a weight POV.
this setup sounds good as well

no ecu changes needed, for the above (provided a normal stock car) you are not optimized for your particular setup but in reality unless it is a setup for your car on a dyno - your generally waisting money

there are a lot of ways to look at it perf incress vs. sound etc.
your choice - just don't think you are going to gain a bunnch of hp (if any) by doing it

you can do other systems as well - but you need to a) design them to your car and your driving style and b) be ready to send a lot of time on a dyno to tune it (ECu and exhaust)


If you are going for a look or a sound - pick the one that meets thouse goals

ymmv and these are my opinions only

mark lintott

From what I understand its not recommended to bypass both the primary and secondary and cat as the lack of back pressure actually reduces bhp - a bad thing. Also the noise is unpleasantly loud - unless you live under the flight path to a major airport in which case you'll be used to it already.

IMHO change the cat to a sports cat (less restriction and still passes inspection) by Dansk or Bursch and change the primary to a bypass. Keep the secondary. Lovely burble and a bit more oomph. Changing the secondary is cheaper but losing the weight of the primary off the back may be of more use in the handling dept.

Of course change the exhaust tip to a drain pipe but thats just for looks!

Cheers

MisterRisky

Bruce, just for the record you seem to have a better understanding of the options than most people do

YES!

And congratulations on really good use of the search function! Seriously, you'd be surprised how many people ask questions that have already been answered 50 times in the last year. Welcome aboard and be sure and keep us posted on which of the above you choose.

Tom W

Yes, (1) is typically for race only. It is seldom done with keeping any of the stock exhaust. I currently have headers and Phase 9 mufflers and run about 96-97 db. {My sound numbers come from trackside measurements - about 20 feet from the car.} This car is way too loud for the street and I don't start it on weekends until after 9:30 or so.

If you do (2) + (4), I found you can get more hp and the sound stays reasonable (89 db). While Laguna Seca says it's 89 db, the neighbors said it was loud, but not too loud.

When I switched to a "fancy" dual outlet primary (and kept the cat bypass), I lost a couple hp.

Switching to a cat bypass (or 100 cell cat) and secondary bypass is the cheapest and easiest way to improve the sound and get what hp gains are to be had (IMO).

delftvanp

Hi Bruce, I replaced the primary muffler, with a Dansk bypass,and the secondary with a dansk sport muffler that I bought on sale from Vertex.
Sound is good however it is always better on the outside.
If you want to stop by and see or talk about , email me .
Paul

wf758

Paul. That is what I just bought. Looking forward to getting it all hooked up.

YYC930

A cat bypass and a free flowing sport muffler is all you will need.

DogInBlack

This is the best thread I've found on this topic. Thanks fellas for the intel. Cat bypass and secondary bypass it is.

etom

And your reason for the secondary bypass and not the primary bypass to go along with the cat bypass?

Just curious . . .

mpeters951

Too Loud ? Not for me me, maybe for the neighbors. My frame of reference may be way different than yours, but I love it. Can you be stealthy with this set-up ? Probably not. Can you return late at night after a boozer without waking the Dutchess ? Unlikely.

But, my context is a love of the sound of the well-tuned (excepting Harley, as that agricultural garbage and the term well-tuned seem mutually exclusive).

From direct experience with F1 at McLaren and experiencing the aural symphony at the Glen, Detroit and Montreal to my own past modded 951's, R6's and Duc's and now 964, I like hearing the bloody engine and what it's doing - emphatically. The former TriFlow set-up did absolutely nothing for me. Seemed a complete waste of money for PO, thankfully not for me.

So, anyway- yes this full Dansk system is bolted to stock cat. Next up will likely be Dansk sport cat. We'll see if the neighbors still remain friendly post install.

joey bagadonuts

I think this question was directed at Tom but I can tell you why I would choose the secondary over the primary: sound and midrange torque. IMHO, the primary bypass sounds like a wet fart (sorry guys )while the secondary is a bit smoother ... more of a growl. And adding the cat byapss will kick up the boominess, like a sub woofer.

jeff522

The weight difference between the primary and secondary muffler is 4 lbs. 16 vs. 20 lbs. The 4 lbs. difference in weight would be the same as gaining about 1/3 of a hp. As far as the change in handling, how much difference would 4 pounds in the rear make on a 3200 lb car with a driver?