Exhaust advice wanted for RS Rep

dean1057 · Post by **dean1057** » Wed Jan 12, 2011 6:34 pm

Hi,
Wondered if someone could give me some advice on who makes or where to get a exhaust for a 3.2 running SSI's for a RS rep.
Looking for the twin central outlets and possibly depnding on noise a third outlet on the left so pipes can be capped.
What sort of noise do the dansk twin outlets kick out? Would they be below 105db at revs lets say for a track day.

Any advice would be we welcome.
Regards
Dean

Nick Moss · Post by **Nick Moss** » Wed Jan 12, 2011 7:01 pm

What sort of noise do the dansk twin outlets kick out? Would they be below 105db at revs lets say for a track day.

No way, more like 110 dB. Ferry Man's 2.9 with SSIs and a triple outlet (with 2 capped) just gets in at 105 dB. The only safe way to get on track is a standard Dansk mild steel single outlet silencer. On my rally car, which had a Dansk dual, for track days I popped off the rear bumper and fitted a mild steel silence in about 20 mins, 105 dB

Northy · Post by **Northy** » Wed Jan 12, 2011 8:08 pm

I beg to differ... Kind of.

I have a dansk 1 out that I've modified to be a 3 out, with two centre exits that can be capped. Mine made 102db at Cadwell Park recently.

Mitch · Post by **Mitch** » Wed Jan 12, 2011 8:24 pm

FWIW my RS has SSI's and a S/S Dansk single outlet and is always around 105db.

Trouble is, noise measurement at circuits isn't an exact science. Depends on the device used (and the guy using it) the distance held, atmospheric conditions, how precise you are in holding the required revs... I try to be a little under!

hot66 · Post by **hot66** » Wed Jan 12, 2011 8:32 pm

Mitch wrote:FWIW my RS has SSI's and a S/S Dansk single outlet and is always around 105db.

Trouble is, noise measurement at circuits isn't an exact science. Depends on the device used (and the guy using it) the distance held, atmospheric conditions, how precise you are in holding the required revs... I try to be a little under!

My 2.4S, with steel HE & a SS single outlet measured 105 @ Goodwood

Of course an MFI early engine is different to a backdated 3.2 one, so not really comparable

Alan @ CanfordClassics · Wed Jan 12, 2011 8:42 pm

Hi,

We hope to have an easier answer to this soon as we have been working on an exhaust for this exact reason for a few months. If it helps and you can wait a bit longer we should have the results. We are building one right now around using a new Dansk mild steel exhuast but will have modified internals, dual central (below the over riders) outlet. This is for a HSCC race car so needs to conform to noise regulations.

Thanks

Alan

butzsi · Post by **butzsi** » Wed Jan 12, 2011 9:30 pm

Northy wrote:I beg to differ... Kind of.

I have a dansk 1 out that I've modified to be a 3 out, with two centre exits that can be capped. Mine made 102db at Cadwell Park recently.

Looks like you have captured the market if you are quick!

Chris

911hillclimber · Post by **911hillclimber** » Wed Jan 12, 2011 10:36 pm

For 18 years I've hillclimbed my 911 with a stock 3.2 with 2.7 Carrera 'ssi' design headers and a Leistriz (sp) 2 in, 3 out with centre 2 cappable.
It hits a hard 108dB with a 3.2 at 4800rpm 'fully open'.

I will be v interested in Alan's solution. The Dansk is far to loud at 108.

Sounds flippin' great mind.

Mike · Post by **Mike** » Wed Jan 12, 2011 11:31 pm

If your car's an RS rep, why would you want 3 outlets

hamishf · Post by **hamishf** » Thu Jan 13, 2011 7:59 am

I ran a Dansk two out for 10 yrs (on a 2.7MFI) which worked a treat, but too noisy here, so got turbo thomas to do a two out (one capped). So for track days put the cap on at noise testing (104db), and on the track take it off (its much louder, but I havent been pulled up yet) and with the cap off there is an appreciable difference in performance (and the noise difference goes from a comfortable driver to earplugs being a necessity).

It doesnt sound quite as good on over-run as the dansk, but it does seem to have more pull.

I'd recommend it, and lord knows he has plenty of experience with 3.2's.

911-32 · Post by **911-32** » Fri Jan 14, 2011 10:21 am

Another vote for Turbo Thomas. You can see lots of testimoials re his work on impact bumpers. Pics of my car with his twin centre out are here http://www.impactbumpers.com/forum/inde ... opic=14560

Mine is running Supercup cams so it doesn't quite get down to an honest 105db, even though that was what it was designed for. On a std 3.2, I think you would be fine though.

Nige · Post by **Nige** » Fri Jan 14, 2011 10:25 am

Definitely worth a call to Rich at Turbo Thomas, very reasonably priced and excellent skills.

Alan @ CanfordClassics · Sun Jan 16, 2011 7:47 pm

The prototype dual outlet exhuast was finished and fitted over the weekend. The next stage is testing back to back against a standard exhuast and also noise testing. Besides the outer shell/carcass of the exhaust all the internals, inlet and exhaust pipes are new.

Thanks

Alan

Sam · Post by **Sam** » Sun Jan 16, 2011 8:05 pm

As hot66 alludes to 3.2s have substantially less induction noise than MFI motors, so tend to register lower on static tests. But having said this I do agree with everything above - stick with one pipe if you want to stand a chance of getting on a track.

More importantly though, IME almost every two-exit stainless system has a boominess that creates nasty resonance in the cabin somewhere between 3 and 4krpm which is very tiring on motorway runs and can easily ruin the enjoyment of a car. I'm pretty convinced that mild steel systems aren't as bad for this.

All anecdotal of course, but from a pretty decent sample group.

911-32 · Post by **911-32** » Mon Jan 17, 2011 10:14 am

Completely agree. The thin walled M&K stainless mufflers are particularly bad for resonance. On the IB cars it seems to be more 2200rpm-2800rpm that is bad - which is a pity as there is so much else to like about Ben's product. As soon as they hit 2900rpm you are good to go though, so with some astute gear shifting you can avoid the worst of it. They also respond well to keeping the tailpipe sizes sensibly small and to inserts stuck up the tailpipes. Some IB cars have wrapped the muffler for some benefit and Ben even suggested using an insulating type of blanket around the muffler when I have chatted to him. I also thought that using one of the high tech type of ceramic exhaust paints took a little ring out of mine. Having said all that, even capping the rear pipes and using the 3rd exit alone was marginal on noise tests for my car and would be even worse on an S or RS type motor - hence my move to a custom TT system. I think that a long hard look at the engine noise is required and temporarily blocking off most of the grille area is the way thinking may be moving. Its a slightly more hi tech application of the apparently Tuthills suggestion to "throw a blanket over the motor".