questions about my new upgrade.

[zenki_myles]

I just got my new set up all hooked up and everything.

its a rb25 s2 t3/t4 50 trim. 38 mm wastegate and gay little ebay manifold. (i know )

anyway my question is i was trying to tune my car and watching the boost controller and it when i spool up it spikes to like 24 psi. this seems like way to much.

ive read that the manifold is really crappy and does sometimes allow boost spike. but i didnt think it would be this bad

i was told that my wastegate has an 8psi spring but idk the validity of that.

im like afraid of driving it like this so i guess i was wondering how safe you guys thought it would be to get on it, with it spiking.

it doesnt feel that like its getting 24psi.

stock head gasket fyi

[Kansei240sx]

I've had the same problem with this manifold on a few customers car, including my own.

The only real way to deal with this problem effectively without modifying the manifold is loosening the wastegate spring or get a weaker spring and loosen it as much as possible, but enough to where it builds about 3 or 4 psi of boost. Use an Apexi AVC-R to control the boost to a perfect level adjusting the duty cycle of the solenoid. Basically the AVC-R cuts off the wastegate signal and opens it on and off very fast to modulate the boost pressure, doing this turbo response increases but is still laggy.

The best thing to do is modify the manifold right where the runners collect and have an extra tube to feed the wastegate tube and help divert exhaust gas and keep the turbine from creeping.

Its hard to explain, but the way your manifold is designed, which is the same as mine, has the wastegate tube at the bottom of the collector, which is the opposite direction of exhaust gas flow and actually creates a turbulence in the collector of the manifold and causes lag and poor boost control through the wastegate, thats where adding the extra pipe comes in.

These images are from another member here "Turbot304" but you get the idea.
Modified by Kansei240sx at 8:37 PM 10/11/2008

[zenki_myles]

thank you, that really helps out alot.

i have a friend who can weld that up for me. Im just kinda worried about how well it will mount in an s14 with that extra tube coming off like that.id think it might hit the strut tower.

and this would obviously put the wastegate in a different spot, so what about the clearance with that?

thanks for responding with so much information

[Kansei240sx]

It might take a few tries to get the clearance right, but most of the time it should be clear as long as you avoid the steering shaft.