Split Dump Screamer Question

[matt47569]

I have a BA futura that's been converted to turbo running on 10psi that uses a bleed valve as boost control and has been tuned with a x3

It has a pacemaker 3.5" split dump pipe and I was wondering if I modify the split part that comes off the wastegate and dump it to atmosphere, will it affect the boost control/tune? ie will the car run normal.. and when will the gas startexiting that wastegate? when boost gets close to 10psi? thanks

Edited 06/05/11 07:39 AM by matt47569

[Bigkeels]

I haven't got a rear housing near me and can't remember if the wastegate and exhaust wheel are isolated from each other with a bridge in between, I don't think they are.

I saw somewhere a company can isolate the two from each other so it will control the boost better if you cut your wastegate pipe to atmo.

Hope that makes sense

[Henz]

There not a split housing, but people have still chopped the split dump into a screamer. It's a sh*t idea at 10 psi it'll sound like poo and won't help

Anything.

[matt47569]

the turbo I had was seperate because I remember the gasket off the rear housing had a bit going through the middle.. and the dump pipe had a bridge in between that lined up

I understand it wont make it go any quicker but it's so quiet at the moment.. have a 3" straight through exhaust with 2 mufflers but dont want to take one out because it will drone so bad.. love the sound of a screamer on boost

someone told me it will overboost but I thought the overboost comes from no restriction being on the rear of the turbine itself not the wastgate flap that opens and dumps the excess into the exhaust anyone confirm?

Edited 06/05/11 08:36 AM by matt47569

[Henz]

At 10 psi it will just burble, trust me dude sounds gay. You need big boost, 17psi+ before they sound good.

[matt47569]

sounds ok to me

anyway can people answer my question about the overboost?

Edited 06/05/11 09:27 AM by matt47569

[Benny]

What turbo are you running? If it's an OEM turbo then it wont seal between the turbine and wastegate sides even if you have a gasket and dump with the middle section. This will result in exhaust gas leaking constantly down the screamer pipe to atmosphere.

Also a "Bleed Valve" sounds concerning. Has the car ever been tuned on the dyno? I'm guessing it still runs the factory CPU if the X3 is being used.

Benny

[matt47569]

Factory GT35/40.. fair enough then I coulda sworn they were seperate hmm that wont be any good then haha

Yeah it's all fine was done by bruce heinrich performance in lonsdale SA and makes 272rwkw on 10psi with a 3k stally, correct all NA computer etc remapped with capa X3

Edited 07/05/11 02:47 AM by matt47569

[BFHOON]

with the split open air screamer apart from being illegal it will make it slightly easier for the wastegate to control boost.

the case of exhaust flow and wastegate performance is that to much flow in the exhaust allows the exhaust gas to follow the path of least resistance. so if the exhaust flow path is of lesser resistance than the path of the wastegate, exhaust gasses will flow around the turbine instead of bypassing the turbine and exiting out the wastegate making the turbo spike at an uncontrolable rate over boosting.

this is why people who have large exhaust systems port out the wastegate and put on a larger flapper this allows more gasses to be vented through the wastegate instead of going around the turbine.

so if you in theory allow the waste gate to flow to atmo it will have less resistance than the exhaust system maintaining easy control of boost but.

when you hard tune a 4 litre engine with 18 or 20 psi there is a hell of a lot more exshaust flow so turbo mods such as a ported wastegate are a mandatory addition.

[bjc]

Car sounds good to me matt47569

And BFHOON's right about the boost spike at higher levels. My BA Turbo has 3.5in xforce with the split dump, catless and straight through single rear muffler. No turbo mods at all and with 16psi boost was stable all the way, even on the highway loading the arse off it in 3rd but apply 19psi and she spikes to nearly 22psi from around 4-4500rpm.

Have to get motivated and do the turbo mods (8 or 12psi actuator and just flowing the wastegate with a little port, no flapper change), but first I have to fit the water meth kit I bought yonkers ago