Questions: 1. Is the stock wastegate actuated by vacuum or pressure 2. Is it normally close ? 3. The T connection (before the WG) goes to a valve right ? 4. So the valve controls the actuator if its on/off ? 5. When the WG moves does it push or pulls ? are there aftermarket WG that bolts right onto the stock turbo and no modification to pipes ?
here's what i believe (correct me if im wrong so i can delete erroneous information) pressure yes not sure what valve ur talkin about... boost control solenoid? hmmm... not sure not to my knowledge
yes the valve im callin is the boost solenoid I assume it controls the WG by purging the system (when its open). IS it a control valve (control=regulate) or is it on/off function
the wastegate is controlled... when u tune, u can set wastegate duty cycle which i assume means how much it is open (im used to digital systems in which duty cycle is (time on per cycle)/(time off per cycle)) come on guys... i know there are tons of u out there who can answer these better than me
Sorry, just saw this... The actuator won't be on/off, it'll be a gradual opening of the wastegate. There's a spring inside the actuator that tries to hold the WG shut (pulling the arm you see going to the WG linkage); boost pressure coming in from the other side overcomes the spring at some point and allows the wastegate to start opening. I don't know if the solenoid on a stock WRX is pulsing/cycling or if it's setup differently.
I believe that larger turbos have bigger or longer wastegate cycles so, the wastegate noises you hear would sound like a single hands clap (in the repetitions) whereas with a smaller turbo it would sound more like several sets of hands clapping.... as in much faster repetitions. What I do know is that the wastegate door begins to open several PSI before the compressor reaches the optimal level, wasting valuable energy in the process and that is a big part of why it got the name wastegate.
I do not believe that it's the wastegate itself cycling, but rather the solenoid that controls the opening of the gate. As for the name, close; the name comes from 'wasting' exhaust that could potentially be turned into energy. It doesn't necessarily open early (though I gather our stock Suby ones do), but at some point it has to open (ideally after the compressor reaches its optimal level) and 'waste' the potential energy created.
That's probably correct moose. It makes more sense that you hear the actuator which is pretty much out in the open, over the wastegate door which is concealed in cast iron. I've just noticed on larger turbo applications I've heard some long and loud ticks as opposed to the small quick ones we hear with our TD04's. I do however believe the wastegate has to open early in order to prevent compressor surge.
That's actually the job of the bypass valve / blow off valve. Opening early isn't a good thing and a reason people go with aftermarket boost solenoids which don't 'bleed' and let the WG open prematurely.
Make your left hand into a gun. (Pointer finger out, thumb up, other 3 fingers curled) Point it to the right, that's your turbo. Your 3 curled fingers are the inlet, your pointer finger is the compressor discharge pipe (to the intercooler), your thumb is the wastegate actuator. If you were to hook a vacuum line straight from the compressor discharge (also known as boost source) to the wastegate actuator, as soon as the turbo spools it blows open the wastegate. Whatever spring is in the wastegate, that's how much boost it makes. If you poke a big hole in the line, all the boost blows out, nothing opens the wastegate and you run "infini-boost." So you T the line. The T goes to the boost solenoid. The solenoid is a "variable leak." It can go from locked closed, through "fluttering" open at a duty cycle, to wide open. When the desired boost is high, and the actual boost is low, the solenoid is wide open. All the boost goes out, nothing opens the wastegate, boost comes up. When actual boost approaches desired boost, the solenoid closes down and blows open the wastegate, preventing over-boost. Hope this helps... SS
Well, the bypass or blowoff valve can protect the compressor from a sort of backlash of boost that occurs when the throttle body door is suddenly slammed closed. And since it operates when that sudden rise in boost pressure is detected it probably could protect from a surge that is similar in size, or pressure, to the one caused by lifting off the throttle. But I don't think it can be set to work on smaller or lesser pressure settings, such as a few PSI which could be dangerous in terms of a lean condition. Which is what I understand to be the reason for the wastegates premature opening, which is necessary in order to regulate boost, in order to never let the compressor produce more boost than the fuel can "handle". Edit: SS it took me a while to write that last one. Thanks for your analogy.
I've honestly never heard of the wastegate opening prematurely being a design goal as much as a design flaw, but SS can probably chip in on that one.