Sunday, December 27, 2009 - 10:41 am, by: Scott Wilkes(Scottywilkes)
Plans are 1JZ, GT35R, how will a 38mm gate go at controlling boost? WIll it be able to hold a steady 16PSI of boost? Or will it be to small for a 35R with a .86 rear housing?
Monday, December 28, 2009 - 02:01 pm, by: Costa Tsimiklis(Driftshop)
The less boost you run, the more exhaust gas you need to bypass away from the turbo. A proper brand name 38mm gate will just cut it running 16psi. I would recommend a 44mm tial or similar to be safer. The valve will open and close as required to flow the right amount of exhaust for the boost level. If you are set on running a low boost, the spring pressure should be set at that boost level and the exhaust flow should be adequate enough through the valve so there is no boost creep when running the external wastegate.
Stay way from the chinese wastegates if you do not have a proper boost cut installed just in case it fails. The main issue with cheap and sh.it wastegates is the poor material used and poor tolerance causing the gate to seize from heat cycling, condensation and diaphragm failure.
Monday, December 28, 2009 - 02:18 pm, by: Scott Wilkes(Scottywilkes)
the wastegate in question is a tial gate, so quality isnt an issued. A mates got it for sale for quite cheap and would get me running while i save for a large gate, but for general driving it would be set on 16 PSI as it is now.
Tuesday, December 29, 2009 - 12:28 pm, by: Cihan Aday(Cihan)
Depends on the design of the exhaust manifold and the application (minimum desired boost pressure and exhaust manifold pressure)
Most manifolds are poorly designed with regards to wastegate position. In many cases its easy enough to correct, though.
A 38mm gate is fine for a GT35R on a 1JZ if there is sufficient room post 'collector' to bleed from all cylinders, and the position of the wastegate exit pipe is in the right direction.
If you're trying to maximise response and reduce manifold pressure, a 0.63 rear housing plus well designed 50mm gate setup is perfect on a 1JZ.
Tuesday, December 29, 2009 - 01:09 pm, by: Scott Wilkes(Scottywilkes)
Thanks mate, the manifold will most likely be a 6boost manifold, ive heard nothing but praise for him so id think he would of spent a bit of time designing the manifolds.
My plan is to hit 300RWKW, id like a bit of response, but id also like to not run out of push towards the top end, which ive heard the smaller .63 rear housing does towards the top.
ROughly what power levels at what boost would both housing be able to support, and roughly when would both come onto boost?
Tuesday, December 29, 2009 - 02:18 pm, by: Cihan Aday(Cihan)
A 4inch dump and free flowing exhaust, with the 0.84 rear you'll have 20psi by around 3800-4000rpm depending on the tune and camshafts.
6Boost manifolds are great. Because the merge collector is so effective, i've experienced boost creep in high revving engines (RB26 with cnc head etc) when a small-medium sized rear housing is used. Subsequently remedied by cutting and welding a second outlet and using a very big gate (2 x 40mm outlets into a 60mm HKS item).
If you use quality parts and management, 300rwkw is a walk in the park with great reliability.
Wednesday, December 30, 2009 - 01:02 pm, by: Chris Driver(Yakuza)
What about twin external wastegates on a 1jz maintaining boost on twin turbos? Custom manifolds with that, and downpipes of course. Is this setup better than single big?