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jwasbury jwasbury is offline
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Join Date: Jan 2008
Location: Weehawken, NJ
Posts: 3,624
Quote:
Originally Posted by 16Volt View Post
Questions:
1. The overboost switch is supposed to kick in at 1.2bar correct?
2. For those folks running 1bar springs or even more boost, are you just grounding the switch and running bareback with no protection?
3. There are two lines to the WG, one is a signal line from the intercooler and the other is a vent line. The vent line is just open to atmosphere in my car, the thinking being it just needs to be open to allow the underside of the diaphragm to move down correct?
4. I have a small regulated air supply, in theory I should be able to dial in 14psi to the WG signal line off the intercooler and should feel air exit the WG exhaust pipe correct?

If I feel air escaping the vent line we know that the diaphragm is torn thus the WG is not opening creating an overboost condition correct?
1. Approximately, yes
2. I'll let high boosters answer. I keep mine below 1 bar
3. Yes, line off the top of the WG is vent. Some aftermarket electronic boost controllers use a solenoid valve on the vent hose to hold the wastegate shut until a preset boost level
4. Pressure applied to the wastegate signal line should open the exhaust valve in the wastegate. You should not hear the air you're feeding into the WG escaping from the WG dump pipe. If you do this test with the engine running, you should feel engine exhaust coming out of the WG dump pipe.

Agree that air coming from the WG vent hose during this test is a sign of a failed diaphragm.

As to your overboost problem, it could be "boost creep" where your max boost is spiking above the desired level. Boost creep can occur if the wastegate circuit of the exhaust is not efficient. Keep in mind that the WG spring is calibrated to open at a specific air pressure, but when the wastegate opens it is not bleeding off manifold pressure, it's allowing some of the exhaust gases to bypass the turbine which in turn should reduce the air being pumped into the engine by the compressor. Bottom line is that a 1 bar spring might actually not control boost to that level depending on the efficiency of the wastegate circuit of the exhaust, the turbocharger setup, engine config, etc.
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Jacob
Current: 1983 911 GT4 Race Car / 1999 Spec Miata / 2000 MB SL500 / 1998 MB E300TD / 1998 BMW R1100RT / 2016 KTM Duke 690
Past: 2009 997 Turbo Cab / 1979 930
Old 10-16-2014, 04:50 PM
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