NZ951

I was bored so went to see a mate at a shop... So here it is... I am not sure if I will leave it with a tip or cut it shorter and turn it down, but its a start... I will change the design when the GT35 exhaust work gets down.

So here is the important stuff, we got some MORE empirical data and tested the pressure in the exhaust system as we did last time. This time around, the pressure was less than one psi! This is down from around 6 psi with the WG line plumbed in! Thats HUGE! The car is noticably faster, like MUCH faster. It will light the bags (new SO2's 265) up through the gears with frisky shifting.

I honestly think to feel the change I did, the gains must have been at least 20WHP. The next dyno run will tell exactly what happened, should be in a couple of weeks.

I also included a pic to indicate the size of ST's member... 1 and 3/4 inch.

Oh and it cost around USD90 including the SS tip. It makes a very cheap alternative and actually drops the pressure in the system by a lot. I may not even need a 3 inch system with this, if only the GT35 outlet was not 3 inch! lol

Fen

Those pressure figures are pretty impressive. How much noise does it make?

NZ951

The noise is not that bad, its obviously only when you are in high boost that you notice it, otherwise its as quiet as stock on cruise, idle etc. Mind you I have only bee driving a few hours with it like that. If it gets really annoying (which I doubt it will) I will put a little resonator in. I think this is a very cheap exhaust mod, you may not even need the full 3 inch setup if at 19psi there can be less than one psi in the exhaust with this mod.

Fen

Where in the system did it join before the mod? You got me thinking that in my 3" Hayward & Scott system the WG is plumbed in on about 6" of pipe rather than the stock one which (IIRC) ran pas the centre silencer and joined behind it. I'm wondering if the design I have now is bad for back pressure... Porsche must have run 3 feet of parallel pipe for some reason.

I'm also worried about how it would affect the dB level for noise-limited track sessions though, but I guess it wouldn't be louder than stock at a static noise test as no load=no boost=WG closed.

Fen

BTW I'm soooo jealous of you being bored in the shop. My shop time this week has been 100% fabricating a cam trigger and now I find we need to fabricate an alternative crank trigger... I hope this Autronic SM4 is as good as it's supposed to be because it's been a fight making it fit (I'm sure it will be though).

NZ951

I think with the 3 inch system the pressure would not be an issue no matter where the WG plumbed back in (stock is just after the front muffler for me). You do get better response and more stable boost control with a long / dedicated WG pipe though, as well as a greater flow area of course. dB would be louder for track sessions, but a resonator would take care of most all of that, and as you say static noise is stock level...

NZ951

I was bored at home... so I went to a mates shop and he had an idea...

Epic2112

I would imagine that they just did this to get around the catalytic converter (although I don't know if you guys have them on ROW cars). If you do have them, you can look and see that the WG pipe has its own cute little catalytic converter. At least if memory serves me correclty. Just a guess, but it makes sense.

NZ951

My car did not come with a cat... no NZ new cars did.

The longer WG tie in / screamer pipe is all about performance. Corky Bell lists several advantages to it having its own system... let me go look.

NZ951

PG138 A WG with its own tailpipe in general will be more positive in response and more effective in controlling boost pressure and effectively increases the exhausts total flow area...

Fen

Does it need to be long or would a pipe out the side of the car under the sill work just as well?

Eyal 951

Unless NZ says otherwise, I beleive a short dump tube is just fine. It will just be louder in the cabin this way. You can buy one for a few bucks.
~Eyal

Fen

I'm trying to imagine what the noise is like but I'm not sure I can. It's effectively venting off intake pressure so it shouldn't have combustion noise mixed in, right? Is it just a loud whoosh?

J1NX3D

i think NZ may have done his his way because in New Zealand by law the exhaust on a road registered car must extend out from the body of the car from the back or behind any windows that open, eg drivers window on a 951

badass951

I want videos!!! Or at least sound clips!!!