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Oettle, Fister, Gundo ... and the PSE diode cut

GT4

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8 Nov 2008
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30,181
Oettle, Fister, FisterD, Gundo, ... which ever way you spell it, it sounds like a 911 should!

There are many names for the muffler bypass mod (Leland Pate and Pedro deserve mention too, for their work on 993/964 and Boxster/Cayman boxes respectively)


Before the words, hear the results:

http://oettle.org/mediapool/50/504167/videos/996_BYPASSANLAGE_STUFE_1.wmv





MP3s open in QuickTime or similar, may require downloading prior to playback.

http://homepage.ntlworld.com/dixonpj/911/3.4 exhaust-before.mp3

http://homepage.ntlworld.com/dixonpj/911/3.4 exhaust-after PSE mod.mp3


What is a bypass?

Basically a mod to mimic the sound of the factory PSE (Porsche Sports Exhaust) - code XLF.

The 996 has a relatively muted engine and exhaust sound, coming from the 993 or other aircooleds with their traditional flat-six sewing machine "roar".

This is partially down to the new water-cooled architecture and a lot to do with more stringent EU and other noise regs.

The PSE (switchable in most cases, although early factory and OEM retrofitted examples may not have the button or electronics fitted) allows some of the exhaust gases to bypass the muffler/silencer boxes and hence make a much nicer (deeper and louder), proper sportscar noise.


Outside a standard (non PSE) 996 muffler:

99622096330Slr.gif


Inside a (non-PSE) 996 muffler:
vlcsnap_2010_01_21_17h34m12s213_small_104.jpg


vlcsnap_2010_01_21_17h33m32s68_small_209.jpg



Two types:

The PSE has had two basic variants: PSE1 for the 996.1 (3.4) and PSE2 for 996.2 and 997 ( 3.6 and 3.8 ).

There is a good reason for this: between the 3.4 and 3.6/3.8 the muffler internals were changed. NOTE: the PSE2 mod is NOT compatible with the 996.1 3.4 mufflers.

Because the PSE2 design only works on one muffler design and the PSE1 design works on both (and is easier, quicker and cheaper to perform), the PSE1 style bridge bypass has become the universal standard.



OEM PSE1:

PSE1 uses a 1" diameter bridge bypass across entry/exit pipes (bypasses all internal muffler stages - stages 1,2,3)

3616_large.jpg


The design is easier to see on the bypass mod'd mufflers as there is no valve systems to get in the way (although some mod'ers do offer valving too).


PSE1 style Bridge Bypass (for a fixed diameter, the length and shape of the bypass have little or no effect on the sound):

"J" bypass (The "J" shape was only used in OEM PSE as the additional length was needed to add the valving)
ianexhaust3_300.jpg

post-8661-1176555495.jpg


Straight bypass (this is all you need if you have no plans of adding a valve):
1sc_154.jpeg

1sb_231.jpeg



OEM PSE2:

PSE2 uses a 2.25" corner nipple bypass to exit pipe (bypasses internal muffler stages 2&3)

996pse06dy0.jpg


The design is easier to see on the bypass mod'd mufflers as there is no valve systems to get in the way (although some mod'ers do offer valving too).


PSE2 style Corner Nipple Bypass (for a fixed diameter, the length and shape of the bypass have little or no effect on the sound):

post-24953-1209107872.jpg



The odd thing is that loudnesswise the PSE1 and PSE2 mod are almost the same due to the PSE1 smaller diameter 1" bypassing all 3 internal muffler stages and the PSE2 larger 2.25" bypassing only 2 of the internal muffler stages.

The loudness is only greater on the PSE2 due to the 3.6 fitted to it!

Static Volume(dB) 0.5m @ 45 degs @ 3/4 max rpm:

Using 1" bypasss
[3.4]103 dB - [3.6]106 dB

However, if a larger diameter pipe is used for the PSE1 bridge bypass (up to 2.25" matching diameter of the entry/exit pipes) then this does result in a louder more bassy sound.

(as PSE2 is already at maximum diameter, there is no further loudness available from additional pipe diameter)


Will it wake the neighbours?

If you leave with a full-bore getaway, then yes.

However, just pootle home at less than 2k rpm and partial throttle and it is quiet as a church mouse (or at least little louder than standard).

At low rpm and partial throttle the back pressure is not enough to utilise the bypass.

Don't believe me, listen out between 1:57 and 2:10 of that last YouTube clip (Blue French 996.2).


Further advances:

Of course with those basic principles, some people increase the diameter (it will be noisier and bassier) or number of bypasses (the closer you get to NO muffler the closer to maximum loudness you get).

Some are probably pointless, but here are some examples:


PSE1 but 1.75" pipe
post-8962-1210225944.jpg


PSE1 but 2.25" pipe
2sd_844.jpg


Hybrid PSE1+2 using 1.75"+2.25" pipes
mk_12_189.jpg


A novel switchable (sort of) bypass!
bypass_valves_343.jpg



What's with all the different names for this mod?

Markus Oettle (and his eponymous company) is the German who pioneered and championed the PSE1 clone bridge mod in Europe (and popularised it).

Darin Fister (FisterD) popularised the mod in the US, predominantly the PSE2 clone corner nipple bypass. The Fister DiPietro Motorsports (Darin Fister and Mark DiPietro) business sells all sorts of Porsche related stuff.

Gundo hack - your guess is as good as mine :dont know:

LPMM - Leland Pate Muffler Mod (back in the day, the same bridge method was applied to 993 boxes)


Who fits them?

You can buy whole systems from various vendors, including Oettle direct for circa EUR450.

Or just get your current mufflers mod'd for between £125-£350, depending on whether you remove and refit your own mufflers (ie the welder just welds!) or it's on a full-service drive-in-drive-out basis and of course who you use.

Oettle Tuning, Germany
http://www.oettle-tuning.de

Hayward and Scott / H&S, Essex
http://www.haywardandscott.com

Stainless Creations, Falkirk
http://www.stainless-creations.co.uk

Zorstec, Bradford
http://www.zorstec.com

Sports&Classic, Cheshire
http://www.sportsandclassic.com

WrighTune, Oxford
http://www.wrightune.co.uk

PowerSpeed (AKA Fast Road Conversions), Kent
http://www.powerspeed.co.uk/

Not exhaustive, and please add your own recomendations.

In fact, if you are yourself or know a competant TIG welder, then it may just cost you a drink.

Just mod using T304 stainless steel pipe of the relevant diameter and stainless steel solder.

The PSE1 mod is simply 10 cm of 1" pipe and two holes!

Roll the windows down, drop the hood or open the sunroof and "Happy tunnel hunting!"


GT4 at H&S:

jack_796.jpg



UPDATE: PSE relay pull or Diode cut (no PSE quiet cut off)

For European drive by noise regs, the PSE disables between approximately 2.5k and 4k rpm.

To prevent this nannying of you PSE enjoyment, either remove the relay (whilst the PSE is NOT in quiet mode), or better still perform the diode cut mod (then you still retain the console switch operation):


To pull the under-dash relay:

Remove #2 relay when the PSE is in loud mode (switched open).

LHD, but  you get the idea:

relays_191.jpg


j1a.jpg


996_relays_362.jpg



To perform the diode cut:

Make sure the car is turned off, remove relay #2 

It is black (see below) and printed "Abgasklappen" (German for "EXHAUST VALVE" or "EXHAUST FLAP"). 

Numbered: 996.618.980.01 or 996.618.980.02 or 996.618.980.03 

Take the relay indoors and sit down. It may be quite difficult to prize the relay open, just use a thin blade or jeweller's screwdrivers to lever open. Be careful, there is a PCB inside.

Cut out the chestnut brown/dark orange glass diode (side snips are good) that connects to Pin 1 (it's the diode nearest the PCB support strut). 

Clip back together and replace in relay carrier. 

Go for a drive  :D

img_0040_982.jpg


relay_pin_outs_861.jpg


pse_hack_cut_side_view_159.jpg


pse_hack_432.jpg
 
Thats a great write up, pretty much explains it all, I'm goin to book my 996.2 into infinity exhausts in Bristol next week for a PSE1 (seems little point in the 2 as it looks more complicated and pricey).

Will let you know how I get on.
 
Fantastic write up

Should note that this won't work on a Turbo if I'm correct?
 
They come with PSE so I can't see why not, all the changes are aft of the turbo's.
 
Fantastic write up and excellent photo's - very helpful - so much so I have just booked mine in :)

i thought the 996 Turbo couldn't have a PSE??
 
Very comprehensive GT4, and as I've just had mine done this week can highly recommend it (as those who have seen my video can testify :D )

might be worth mentioning that the boys at H&S would do a group discount and as quite a few have expressed an interest here, might be worth enquiring further with them as to what discount they can do?
 
Moonshine said:
They come with PSE so I can't see why not, all the changes are aft of the turbo's.

Sorry, they didn't come with PSE (which is why they sound more like a Hoover than a sports car), and can't have PSE.

This mod is NOT compatible with a turbo.
 
Moonshine said:
Thats a great write up, pretty much explains it all, I'm goin to book my 996.2 into infinity exhausts in Bristol next week for a PSE1 (seems little point in the 2 as it looks more complicated and pricey).

Will let you know how I get on.
When infinity did my car, they thought pse2 was easier than pse1 and so that is what I had done.
 
Moonshine said:
Thats a great write up, pretty much explains it all, I'm goin to book my 996.2 into infinity exhausts in Bristol next week for a PSE1 (seems little point in the 2 as it looks more complicated and pricey).

Will let you know how I get on.
When infinity did my car, they thought pse2 was easier than pse1 and so that is what I had done.
 
GT4 said:
Moonshine said:
They come with PSE so I can't see why not, all the changes are aft of the turbo's.

Sorry, they didn't come with PSE (which is why they sound more like a Hoover than a sports car), and can't have PSE.

This mod is NOT compatible with a turbo.

My bad sorry.
 
JKH112 said:
Moonshine said:
Thats a great write up, pretty much explains it all, I'm goin to book my 996.2 into infinity exhausts in Bristol next week for a PSE1 (seems little point in the 2 as it looks more complicated and pricey).

Will let you know how I get on.
When infinity did my car, they thought pse2 was easier than pse1 and so that is what I had done.

Generally PSE1 is the cheaper and easier mod as it is just a straight bridge. (plus you can make it as loud as you like, within reason, by going to 1.75" or 2.25" etc piping)

The straight bridge requires no mandrel bending or multiple curve welds and uses less pipe in both length and diameter. Additionally, the final result is probably neater, better hidden and more mechanically secure (being "internal" to the entry and exit pipes either side).

The issue with the PSE1 is getting the "internal" holes cut (although they are generally offset from centre, a option when only using half the 2.25" diameter)

The PSE2 uses "external" holes (ie to the exit pipe and cutting away the corner nipple capping).

There is no right or wrong way (as both are the respective clones of their OEM counterparts).

The only caveat being PSE2 will NOT work on 996.1 (3.4) mufflers.

996.1 muffler internals do not allow the corner nipple bypass to work effectively, or at least if one is performed it has little or no noise increase.
 
A simple mod and well worth it :thumb: This can be done DIY if you have a friendly welder and an angle grinder on standby to get the rusted nuts off.

Loving the corner nipple bypass :oops:
 
Once again the conversation digresses into nipples and nuts, keep checking to see if i'm still on 911uk.com or been taking through to a more seeder site :D
 
Well I'm booked in tomorrow for the exhaust to be done :mrgreen: I've gone for the pse1 mod with 1.5" pipe so should be a little louder than standard come tomorrow afternoon!!
 

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