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I'd say it's there to regulate the opening/closing speed of the wastegate, since the solenoid is an all-or-nothing device. This would make the boost more stable once the boost goal is met. Without it, it would probably flutter up and down a bit.

Factory electronics are programmed with the orifice in mind. If you use a manual boost control, chuck the orifice.
 

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R.I.P Dennis Jarvis
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I picked up my orifices at Autozone. Vacu-tite part number 47311
 

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Did you dig up every ancient post about the WG restrictor? Good work. There are 20 or 30 in every junkyard I've ever been to. I put a few in my pocket and I've never needed any more.
 

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makes sense.....what about the pressure drop? guess maybe this isnt an issue....

my car was running with a grainger valve and the stock orifice......i am ditching both once the TU 3bar cl arrives.
previous posts are correct, in the general idea that:
the restrictor acts to 'modulate' the WGA; but, its a little more complicated...

1st, the WGA has a Stiff spring, and a large diaphragm which the boost P acts upon;
this combination results in a defined response behavior for that design WGA,
including a particular resonant frequency...

2nd, WG hardware- flapper, WG hole size, flow of WG hole relative to main flow, etc - together, interact with the engine's exhaust flow, with a defined response behavior, with resonant freq

AND these 2 components interact each other, with a combined, predictable response, and combine resonant frequency(s)

WGA vac/boost "circuit" (solenoid, restrictor, even the length / ID of vac lines) can be tuned (designed) specifically to the 'mechanical' system which it is designed to control;
this vac/boost 'circuit' is the WGA's "controller"

this would be done primarily to eliminate resonant frequencies...
this design work is Control Systems Engineering
"In practically all such systems stability is important and control theory can help ensure stability is achieved."
from Control engineering - Wikipedia, the free encyclopedia

ever driven a MBC'd car that oscillated boost +/- ~1 psi, with a cycle of ~1 sec ? I have, many.
my cougar does that after I MBC'd it ; didnt before; only added 2 psi ..
 

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R.I.P Dennis Jarvis
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detobias, excelent write up!
 
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