Stonkin

Hi, i partly asked this question on another thread but thought i should really start a proper one, i asked what the difference was in the above, Nelson kindly replied with:

Stonkin - you are quite correct in your assumption mate that the twin dump is exactly what it says. Basically the Magnex one that I bought has two exits - one for the Turbo and one for the wastegate gasses. The 2 pipes then join farther along the pipe...does this make sense ? Whereas the open neck is one much larger exit which encompasses both the turbo and wastegate. I was very tempted by the open neck but decided to go for the twin dump having read problems others have had with having to remap etc.

Hope this helps ?

Can anyone ellaborate as to the differences between the 2, what problems can it cause with re-mapping, what advantages/disadvantaged coem with both?

many thanks,

Flat Faw

I researched this thoroughly (when the search facility worked!) before taking the plunge.

I bought a Jap Innovations open neck for my MY00, and have not had a single problem. You shouldn't need a remap if you're just decatting. Just use Optimax or similar to be on the safe side. If you are running an import thats mapped for Jap 100 Ron then its probably a different story.

Many of the blokes on here running massive BHP's all seem to use open neck designs, and I remember reading John Banks having all sorts of problems with a Magnex twin dump he fitted. On a mildly tuned car, there is probably little or no discernable difference between the 2 designs.

The_Judge

I think Flat Faw has summed up pretty well there. I have no experience of twin dump, but currently use the Hayward & Scott open neck. The only other thing you need to consider is whether to go for a "splitter" or not. It apparently helps the gases a bit more, making them less turbulent...

Stonkin

where does this splitter go and what exactly does it do Judge, thanks for your help? this is the first time i have tuned a turbo car, every little thing i dive into with this seems to open up to a whole bunch of different options available, which is a good thing, but makes things a little hard to get to grips with

The_Judge

I know what you mean mate

The splitter's basically a small piece of thin rectangular metal, welded vertically into the mouth of the open neck exhaust. It supposedly helps the turbo exhaust gas and wastegate exhaust gas flow better by separating them.

AndrewC

Have a look at http://www.users.bigpond.net.au/msgo...stsystems.html

Andrew...

The_Judge

Nice one Andrew, I couldn't find a picture anywhere...!

Stonkin

thank u people, another thing off the list explained!

ChristianR

iTrader: (1)

i have a bpm td-38 for sale for classic impreza if anyone is interested, drop me an email

Floyd

iTrader: (9)

IIRC the latest STI8 PPP DP is a twindump design so Prodrive have obviously done a lot of testing to settle for this method. Mike Wood wouldn't say if it had a splitter or not. You'd have to ask a freindly dealer!

F

JIM THEO

Yes, divorced wastegate exit:



JIM

Floyd

iTrader: (9)

Thanks for the pic Jim. So the DP is not just split but completely enclosed. The waste gate does seem a bit restricted still - very small aperture exit.

F

RRH

isn't there a power versus torque situation associated with this?

JIM THEO

Divorced gases from main exit and wastegate means to me more torque, better spool up and as the exhaust isn't completely free (as on decated systems with splitter causing - probably - overboost/spikes) is the best compromise with cat.
JIM

RRH

I'll agree with Jim as that went completely over my drunken head