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By Dose Pipe Sutututu · Posted
And if it still spikes, just for now, turn off VCT completely by disabling it OR simply unplug the solenoid. Just to rule out excessive exhaust pressure. I recall a video from Motive DVD about a decade ago, where Hawkins original single Garrett GTX3582 or so turbo had boost control issues sub 1.4bar of boost as well. Food for thought? Is there anyway you can peg the WG completely open and/or dodgily not plumb it back into your exhaust system for testing purposes? -
I will endeavour to give it a crack sooner or later. I have the wastegate apart at the moment so I'll replace it with a smaller spring just to see what it does and if I have to go back then so be it. If it spikes to 23 but can then be controlled back to 20, then the gate must not be 100% open... So if it's not 100% open then why can't it drop the boost even further than 20psi (I understand it's not linear). What a headache this whole thing is. -
Either the WG is reaching full opening, or it is not. The "it is not" case could only occur if there was not enough time available to swing the valve fully open during that boost event. I would consider that to be unlikely, as this is a commercial product that is in use elsewhere, so it really should work. But in your case, because there is definitely SOMETHING wrong, it should not be assumed that things like that are working as they should. You should put a video camera where it can see the actuator (if at all possible) during a run to see how far it is moving. -
I think you're mostly on the ball there. With the straight gate, I suspect the weight of the spring will determine how quickly the gate can close, when not run with active pressure drive on both sides of the diaphragm. Otherwise, with drive on both sides of the diaphragm, you could almost go without a spring at all, only needing one to make sure that the thing was actually closed while completely off boost and not having pressure available to drive it closed. Butterfly valves have mostly symmetric loading when there is flow going through them, meaning that the gas hitting the upstream part of the blade is balanced by the gas hitting the downstream part of the blade, which means you don't need actuator torque to overcome any non-symmetric flow induced loads. But the gas flow does impart a purely normal load against the shaft, which transfers into the bush/bearing at each end of the shaft and does increase the torque required to make the shaft turn. Only a little, but it is there. I have no feeling for the amount of force involved in a WG application, but it certainly could make an argument for a decent spring weight being required. But all of this is just peripheral to the actual problem here.
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The answer to this would be I followed the documentation from Turbosmart which said each spring pressure could achieve a maximum of 5x it's rated pressure so the included smallest spring being the 6psi had a range up to 30psi. I went with the 12 because I figured it'd likely hover around 15psi as a base pressure however I was obviously wrong. I have a log here that I'll dig out that is purely wastegate and no Mac valve controlling anything. If it can't hold anywhere near 12psi, does that mean the straight gate is virtually wide open during a run? Or am I thinking about this all wrong. I could Tee Piece into the cooler pipe pre intercooler where the wastegate gets its feed, and send that to the ecu and see how that reads, I just don't have a spare pressure sensor currently that's all.
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