Twin Dump Pipes-any performance gains?

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LeeSmith

Member
Just did a quick search on the net for you m8 and came up with this:

"This is a replacement turbo down pipe. The twin dump refers to the two pipes that allow exhaust gases to exit from the turbo. All down pipes have at least one! The second pipe is directly in line with the waste gate, which means at low revs when the waste gate is open, exhaust gases can exit more easily.

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The first thing you notice when you start the car is the presence of the turbo whine. You hear it spin up and down as you rev and change gear - brought back memories of 18 year olds in Renault 5 Turbos. The improvement is only at the bottom end, but makes the car even more drivable than it already is - you effectively get the same torque as before, but at 500rpm lower. It can save you changing down a gear at times."

There are pictures of this on the site below (on an subaru but u get the idea)
This was taken from:

http://www.steve.ukmail.org/car/twindump.html
 
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donpulsar

South Yorkshire Regional Rep
Thanks for all that m8, it made v.interesting reading :D Wonder if it justifies its £300 price tag (import from NZ) tho' :?: Oh for a better paid job :!: :roll:
 
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Sirnixalot

Guest
LeeSmith said:
which means at low revs when the waste gate is open, exhaust gases can exit more easily.
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that is completely wrong. The wastegate is only open when you are making boost...hence it opens to limit the boost to a preset ammount. At low rev's and off boost situations the wastegate is closed.

The pipes provide an easier path for the gases exiting the turbine housing to follow. Our standard one does quite well but for those with upgraded turbo's a little more flow is needed. If you were to just take a dremel to yours and polish up the inside it would be perfect for a standard turbo.

Don...nice find 8)
 
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skiddusmarkus

Active Member
Wastegate can be open at low revs too Nikko-say going up a hill in 5th and it levels out.Revs stay the same but the wastegate will open as boost is no longer needed due to decrease in load on engine.
 
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skiddusmarkus

Active Member
It looks like you need 2 parts for it to mate up to the cat-the price quoted is just for the one peice(there's a pic of other bit).
 
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daBOODA

Guest
My car was the donor car for the mecury pipe. I just got the twin pipe and a 3 inch pipe from the dump pipe to the cat. The rest of the system is a 2.25inch pipe.

Twin pipes definately make a difference over stock. I have my stock air box on the car now and I can still hear the turbo spool up (I never heard any turbo spool with the air box with the stock dump pipe). It's more responsive throughout the rev range.

The funny thing you'll notice is that your max boost drops because the wastegate is able to vent more exhuast gas. It spools quicker though and you can raise your max boost with a boost controller to counteract the drop.

I was on 15 psi, now it's 13 psi but I think I'll leave it at that as it still feels quicker.
 
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daBOODA

Guest
skiddusmarkus said:
It looks like you need 2 parts for it to mate up to the cat-the price quoted is just for the one peice(there's a pic of other bit).
Click to expand...
Personally I reckon if you get the twin pipe (you don't have to buy the dump-to-cat pipe) you can get your local exhuast shop to run the rest of the exhuast for you. The hard bit is making the dump pipe (and runing 3 inch over the rear axel :( ) so only get the dump-to-cat pipe if you just want to hook it up to a standard cat back exhuast.
 
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daBOODA

Guest
donpulsar said:
Could someone explain to me what advantages (if any) these have over the ordinary pipe and what makes them special?
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Arg, sorry about the triple post ...

Firstly, ideally you want to get a 3 inch dump pipe coming off the turbo into a 3 inch system. The standard pipe is a little small and somewhat restrictive.

The problem with GTi-Rs is that it's impossible to get a 3 inch dump pipe to fit if you want to keep your aircon. So what you do is split the exhuast outlet and wastegate up and run the waste gate pipe (which is small compared to the outlet's pipe) around the front and join it to the outlet's pipe about a foot down. This allows you to keep your aircon and have comparable volume to a full 3 inch pipe.
 
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323GT-R

Guest
skiddusmarkus said:
Wastegate can be open at low revs too Nikko-say going up a hill in 5th and it levels out.Revs stay the same but the wastegate will open as boost is no longer needed due to decrease in load on engine.
Click to expand...
The wastegate is controlled by boost pressure, it only opens once the actuator sees boost. No boost = closed wastegate.

The idea of the twin dump pipes is to get rid of the turbulence in the area just after the exhaust turbine, reducing back pressure. This also in theory allows the wastegate to do it's job properly, so you get better boost control. A good twin dump design will give better spool up, the key thing is that the if the pipes join back together, the join has to be smooth, otherwise you're just moving the turbulence, not getting rid of it. A single dump pipe with a splitter between the wastegate and turbine exit is much easier to build, and seems to work just as well, but it doesn't look as cool 8)
 
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donpulsar

South Yorkshire Regional Rep
Havin' read all that, I think I'll opt for Sirnixalot's option - the good ole
Dremel :p , and save the £300 for something else ... Unichip / H20 injection /
etc :!: :twisted: Unless I get one of these jobs I'm goin' for, then watch those mods fly :!: :lol: Well, I live in hope :)
 
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ashills

Active Member
i dremelled mine to an inch of its life and its good i think ill find out in a couple of weeks when shes mapped
 
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