Bizman928

Quick Question...

I have just bought a twin tailpipe S4 back exhaust box to exchange for my single oval S4 tailpipe on my Black '88 S4. I have always liked the twin tail pipe version for looks but wondered if there was any real difference between the two back exhaust boxes or are they just a straight swop for looks only?

Many Thanks

Steve

MY89 928 S4 Stone Grey Metallic....gone but not forgotten......

My New 928 :-
MY88 928 S4 Auto - Black Analogue Dash .....- Back in 928 S4 ownership!

AO

First off, it's only the muffler that is single - that is to say the stock exhaust is dual pipse all the way back to the rear muffler. Then, I believe only the GT's were the only models fitted with a dual exhaust outlet. However, many people run Rear muffler Bypasses (RMB) which eliminates the rear muffler and has dual pipes.

As for functional differences, I am told that some of the early GT mufflers are actually quite a bit lighter than the oval mufflers. Later ones seem to be about the same weight. I don't think there's much functional difference between any of them.

Gary Knox

The GTS's also have the dual pipe extending from the rear of the rear muffler.

If I recall correctly, the S4 mufflers actually have the two pipes coming out the back of the muffler, but they are shortened vs the GT/GTS's, then collected in the single oval extension. Always thought the oval could easily be cut off, then extensions welded to the S4 stubs pretty easily! But, since I have an RMB on the '89, never did this modification.

Gary Knox

Jadz928

This thread will help with the differences.

Bizman928

Hi Guys

Thanks for the replies. I realise that the stock S4 Oval muffler has twin oulets before the oval - but they seem smaller in diameter than the twin oulet pipe version.....or maybe its just a visual hoax???

I will do a measure check over the weekend and see if they are the same outlet pipes.

Cheers & have a great weekend
Steve

Vilhuer

Twin outlet silencer was standard on '90-91 S4. This was done to simplify S4 and GT production.

Brett928S2

Hi Steve

Twin outlet was also standard on the 86 S2 if it helps...also...Paul Anderson does a special box with twin outlets and almost no silencing that replaces the S4 box (I have one as part of my race system)... think of it as a advanced version of an RMB...

All the best Brett

Hilton

That would be this one... made by Paul A. It's a bolt-on.

Sounds very good with large resonators and an x-pipe (from Richard A. of Ritech), and not too-loud like an RMB is.

I haven't tried it on my 89 with its small "GT" resonators yet - but sound comparisons of the two exhausts when stock showed the small resonators are 2dB louder so my plan is to try this once I get around to installing the cats on my 89's X-pipe (from Motorsport SLC). I don't want too loud an exhaust - I'll get pulled over (they're strict about it here).

Speedtoys

I have an 89 exhaust, with X pipe, and RMB.


Far too raspy sounding for me...would this humble down the note a little?

I want a nice low thrum of V8 whoopass, not what the current setup gets me.

Hilton

Yes, compared to a local friend's GT with x-pipe and RMB, this makes a much friendlier V8 "woofle".

X-pipe and RMB is just too loud - here it gets you pulled over by the police. If the police here feel like it, they can issue a Defect Notice that requires you to take the car to a testing station for measurements compared to legal road limits.. where they test all emissions, not just noise.

edit: I'd offer to post audio, but its not installed on any of my cars atm - I'm halfway through moving it to my 89, but being interrupted by TBWP/intake/HVAC/electrics on my red 87

Brett928S2

Hi

Wow , my 928 exhaust wouldn't last long there legally

Because I need a VERY free flowing exhaust for my Nitrous I have.....

A Richard Armstrong X-Pipe then NO front boxes , NO middle boxes and just that Paul Anderson new rear box....so the only actual silencing on mine is the small amount of silencing material inside that rear box...lol

It reads over 130 db at 6000 revs (not sure how much over 130 as my decibel meter wont read higher) and it sounds GREAT

And its my daily driver...

All the best Brett

SeanR

I traded out my RMB (X-pipe, sm resonators) to a GTS muffler, the sound is just perfect. I do miss the times when I could hit the gas and it was louder, but I'm much happier now.

Speedtoys

Awesome info..thanks.

Now..n00b question, where do I find this Paul Anderson...I know Mark online here...

Hilton

He's in the UK - www.928spares.co.uk

Speedtoys

Brilliant..however, I cant see shipping this from the UK.