I don't have pics handy, though I'm sure I took one during the last engine swap on the '06.
But, basically (please forgive me in advance as I do not intend this to be condescending):
1. Exhaust comes out of the engine, into the exhaust manifold and a tee to the wastegate and turbo (turbine / "hot side"). I use the word "tee" loosely, since the actual routing is in the turbo housing.
2. At low(ish) exhaust pressure (gas volume and velocity), the wastegate stays closed, so all of the exhaust gases go into the turbo, spin the turbine, which spins the impeller in the compressor housing, which creates boost.
3. When exhaust pressure hits a certain point, the wastegate opens up a bit, allowing some of the exhaust to bypass the turbo. That gas can be vented to atmosphere or, in this case, shunted back into the exhaust after the turbo. That limits the turbine speed, which limits boost, which keeps your engine from exploding due to extreme pressure, predetonation, etc.
4. The wastegate can be a mechanical device - basically, a spring-loaded plate blocking a valve, which exits to the exhaust - or an electronically controlled valve. Mechanical wastegates are the norm.
In the downpipe shown in the pictures, the "extra pipe" is the route by which the "extra" exhaust gases bypass the turbo. If it wasn't there, they'd have to either go through the turbo ("boom" at high RPM + throttle) or into the air.
So, the wastegate basically bleeds off exhaust gases to limit turbine velocity, and the extra pipe lets you stuff that back into the exhaust so you don't get hypoxia and Mr. Emissions Inspector doesn't get annoyed.
The blow off valve (or bypass solenoid on a stock GXP) does something related, but different. When you let off of the throttle under high boost, the butterfly plate in the throttle nearly closes. All of that high-pressure, very-compressed air in the intake tract (turbo compressor to intercooler to throttle body) will try and force its way past that valve, and also backwards into the turbo compressor. Then, the compressor blades are trying to spin one way, which I shall label "clockwise", but the force of the compressed air in the intake tract, which has nowhere to go due to the closed throttle and is, therefore, trying to push its way backwards into the turbo, are trying to spin it the opposite direction (which I shall label, quite without purpose, "counter-clockwise").
That will happily knock blades off of the compressor, lock the engine, or other Very Bad Things. If you're very lucky, you'll just destroy a hose coupler or your intercooler.
The blow off valve is a pressure release valve that lets the compressed air exit the system somewhere between the throttle body and the turbo, to avoid damage to either. It becomes the path of least resistance for the compressed air, so the turbo and throttle can keep doing their thing.
A lot of people think that the BOV should be open at idle. They are wrong. Due to the Venturi effect, an open BOV will be a source of unmetered air if open under vacuum.
Not sure if I've answered your question or provided anything useful, but:
1. Wastegate - pressure relief valve on the exhaust side that keeps the turbo from spinning too fast (engine goes BOOM), lets some exhaust gas bypass the turbo when necessary.
2. Blow-off Valve (BOV) - pressure relief valve on the intake side that keeps compressed (boosted) air from damaging the turbo, intercooler and potentially the engine. (Compressed air + insufficient fuel after lifting throttle == BOOM)
Blue-ish 2006 2.4, Werks stage 1 turbo, Borla cat-back, DDM braces, Spec aluminum flywheel, Spec stage 2 clutch, Werks aluminum radiator, some gauges, RKSport hood, Morimoto FX-Rs, GReddy Profec, Norm's fenders
'07 GXP, RPM Stage 2, Solocatless downpipe, TCE Wilwood 6 piston front brakes, 4-piston rears , Stainless brake lines, slotted/drilled rotors, BC Racing BR coilovers, Performance Autowerks intercooler, DDMWorks CAI, charge pipes and braces
Last edited by raygun; 01-24-2019 at 04:50 PM.