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[s12drifter]

currently I'm having a major boost spike issue. i have a divided manifold and a twin scroll turbo.

on the passenger side i have a 40mm wastegate but yet i still overboost (the valve opens at 15psi and spikes all the way to 25psi)

someone told me collect from both manifolds and have it merge into one big 60mm wastegate. someone else told me to just run two wastegates, i already have one done just do the other side.

im not too sure on what to do as if i dump too much exhaust gases i wont have enough to keep the turbo in boost? and if i dont dump enough i retain the same issue i started out with. The more I think about it the more I think I'm going to end up with under boost issues? Is that even possible? I know a lot about turbocharging but eh I know about what wastegates are suppose to do and thats it, not much more then that.

or?

my current setup is VG30ET; 9.1 compression, 450CC injectors, holset HX35 turbo, i think thats about it as far as intake/exhaust?

This post has been edited by s12drifter on May 5 2012, 05:46 PM

[Spaz]

The entire point of the wastegates is to control boost. If they're set at 15psi, that's what you'll run so long as they can flow enough exhaust when wide open to keep the turbine from further accelerating. As boost drops the spring will force the diaphragm closed again to stabilize the pressure. As long as the springs are loaded evenly you shouldn't see any pressure drop as a result of adding a second gate, since they'd more than likely not even fully open.

The reason you're still spiking with one wastegate is likely because of the efficiency of the twin scroll setup. If you're only venting exhaust pressure from one scroll, the other is still seeing full pressure from the other 3 cylinders which will continue to accelerate the turbine, which is why a single gate won't work. You need to vent from the other scroll as well to get adequate control over exhaust pressure and therefore turbine speed.

[s12drifter]

Adding another wastegate is fine? was gonna add another 40mm. idk people keep telling me to dump the dual wastegate setup and add one big 60mm i just dont know about merging manifolds.

yea, i think i'll go dual wastegate. i honestly dont thing 30mm per side is enough.

This post has been edited by s12drifter on May 6 2012, 06:26 AM

[HorizontalMitsubishi]

40mm on each side would be more then enough to control boost.

[sideways]

Be overkill if anything. On the upside you should have a nice flat boost curve once it hits full boost.