Front/dump Pipe

[boiracer]

just a quick question. and feel free to give me grief and send me in the right direction, as i couldn't find the answers i was after.

which is best for a standardish setup (standard turbo R33), combined dump and wastegate? or the separate wastegate pipe till further down?

which then leads to the next question? pros and cons of using a one piece dump/front, or 2 piece? and does it really matter what brand it is?

[chris_82]

The belmouth front pipe in mild steel seem to be more popular (turbo to cat one piece) some believe the split dump pipe can jam up the flapper on the wastegate

[gotRICE?]

The belmouth front pipe in mild steel seem to be more popular (turbo to cat one piece) some believe the split dump pipe can jam up the flapper on the wastegate

The original split dump pipes did jam the flapper. But as far as im aware they have been fiddled with and work fine. Havnt seen any complaints since the 1st batch. I had one. Biggest PITA ever. But im guessing mine was the 1st batch of them.

[boiracer]

is this a specific brand you guys are talking about? or in general?

now that you guys mention it, the bell mouth is generally mild steel and the other is stainless isnt it? could the production cost with said materials be the whole and sole reason for the design difference?

and no reason not to buy a 1 piece? not that i need to remove half the engine just to get the 1 piece thru?

[gotRICE?]

The JJR ones.

But anyone that sells the same style. Probly comes from the same place.

Nothing wrong with the one piece ones. I'd go for mild steel anyway. The stainless ruined my narrowband sensor thread, and bent all the bolts holding the thing to the turbine housing.

This has made me not ever want another stainless steel anything near my turbo lol.

[GTSBoy]

It is my considered opinion that keeping the wastegate gases from messing up the turbine exit gases in the most critical region (ie, immediately after the turbine outlet) is very worthwhile.  The ideal turbine outlet is a nice smooth conical expansion from the outlet size up to some big size (like 3"), but of course no one has the room to do it like that.  For a start, they usually have to bend straight away.  Given this, I can;t see why you'd be happy to make the turbine exit development region any worse by spraying wastegate flow directly across it.  Seems daft.

The little short split wastegate dumps are probably a waste of time.  They poke the wastegate gases back in pretty close to the top.  Seems silly just to make them a simple replacement for the factory dump.  I got one of the cheap JJR long split ones (dump and front pipe in one) and it noticeably improved the spool response of the car.  Absolutely no clearance problems with the flap valve.  I didn't test it against a bellmouth, so I can't say for sure that it is better than a bellmouth, but I can't see how it would be worse.  Any time a Skyline is making power, the wastegate is open.  So spraying wastegate gases in cannot be a good thing for peak power.  The turbine exit part of the dump is a more regular shape in the split ones than it is in a bellmouth, so even though the bellomouth style is simply bigger, thus giving a bigger volume for the turbine exit gases to spew into when the wastegate is still closed and theoretically giving a better spool response, I think the smaller turbine pipe doesn't hurt the split ones at all.

Oh, and the 1 piece ones do not take any extra effort to fit.

Edited March 7, 2012 by GTSBoy

[boiracer]

It is my considered opinion that keeping the wastegate gases from messing up the turbine exit gases in the most critical region (ie, immediately after the turbine outlet) is very worthwhile. The ideal turbine outlet is a nice smooth conical expansion from the outlet size up to some big size (like 3"), but of course no one has the room to do it like that. For a start, they usually have to bend straight away. Given this, I can;t see why you'd be happy to make the turbine exit development region any worse by spraying wastegate flow directly across it. Seems daft.

The little short split wastegate dumps are probably a waste of time. They poke the wastegate gases back in pretty close to the top. Seems silly just to make them a simple replacement for the factory dump. I got one of the cheap JJR long split ones (dump and front pipe in one) and it noticeably improved the spool response of the car. Absolutely no clearance problems with the flap valve. I didn't test it against a bellmouth, so I can't say for sure that it is better than a bellmouth, but I can't see how it would be worse. Any time a Skyline is making power, the wastegate is open. So spraying wastegate gases in cannot be a good thing for peak power. The turbine exit part of the dump is a more regular shape in the split ones than it is in a bellmouth, so even though the bellomouth style is simply bigger, thus giving a bigger volume for the turbine exit gases to spew into when the wastegate is still closed and theoretically giving a better spool response, I think the smaller turbine pipe doesn't hurt the split ones at all.

Oh, and the 1 piece ones do not take any extra effort to fit.

pretty much my assumption too, but with the small amount of extra power im looking at either or prob wont be a big difference.

thanks for clarifying the fitment question so fast

and thanks everyone for your quick replies

[XKLABA]

this is what i use on both my GTRs and the only one I would recommend

ces racing