In my MY89 JDM Forester Stb, I noticed the brass restrictor was present between the compressor and wastegate T piece. I'm sure I saw a website reccomendation for removing this restrictor (unless that was some other restrictor), so just for kicks I took it out and went for a run.
Suddenly my boost went from 10psi (12psi spike on gear change) to about 12psi with a spike to 14, as I drove a bit more, boost maxxed at 14psi and was spiking above that and causing a fuel cut on gear change!
Now I certainly did not expect all this boost increase, I got online and searched around and all i can read, says the restrictor with a smaller hole reduces the spike. But what about the huge raise in boost in the absence of the restrictor?
Im not sure yet of the restrictor bore size. At this point theres no way I can leave out the restrictor, but, surely I can make a few more restrictors and see which one gives about 12-13 psi and doesnt get any fuel cut on spike.
Soon enough i'll get myself a EBC, but can I play aroud with this safely until then?

 

better get a dawes and a knocklink mate. that way u can play around all day messing up your boost SAFELY.

 

The smaller the hole, the larger the spikes.
Are you sure you remembered to reconnect the pipe after removing the restrictor from it?

 

Huzzit Bruce from ZA...
Jusr to clear up - The bigger the diameter of the hole in the restrictor, the less boost your car will produce. Why ? Because more pressure is in the system and the wastegate will open sooner. If you had to close the hole totally OR remove the pipe to the wastegate, no pressure would be available to open the wastegate and you turbo would spin to infinity and beyond (read self destruction - usually of the engine before the turbo but the converse has been known to happen too).

 

Well, this is a weird issue, first off, I tried inserting another restrictor with a larger bore, and the boost was limited to about 7psi. So this rule about restrictor bore doesnt APPLY to not having any restrictor in at all (because with no restrictor its all up at 14psi and spiking over) . THats what I'm wondering about at this point.

 

My theory would be that your connecting "boost" pipe is either closing up the hole (folding on itself or leaking somewhere) when you have the restrictor out. It is the only logical solution. No pipe at all will give you max boost and the turbo will spin until destruction. If I remove the restrictor from my boost control pipe, I get about 8.5 PSI of boost (01 WRX PPP)

 

Hey, Murray, fancy meeting you here!
Didn't know you still had a scoob. Thought you traded it in on a RunX...? When do we see you on saiog again?

 

Join saiog ? Later rather than sooner ? If this fekking company keeps its head above water (and me employed), I'll be looking at buying an 02 STI Dec / Jan 04. Still got yours or have you upgraded to... what was it... a Clio ? 8-)