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Restrictor pill question?

9K views 18 replies 2 participants last post by  07wrbsti 
#1 ·
ive been searching since january 2015.

Bought the 07 sti january of 2015, loved it since. The gauge it came with, has read max, 8-9lbs since day one, never worried about it to much until I did some research. had some sputter issues, thought it was a vacuum leak, better zip ties made it drivable again. Then more hard stutters, until boost seemed to have hit a fuel cut-off or something. Finally a CEL, misfire 303, changed plugs and coils, been fine since. Still hitting 8-9lbs on gauge. Ive read about the restrictor pill, felt for it, its not it there. The only mods that I know of are a blitz nur spec muffler, dont know if its just the muffler or turbo back or whatever? I am the 5th owner of the car, so I dont know what its been through or whats been done to, just a chance I took, Ive been doing cars for years, so when everything seems ok, I went with it, happy so far. Just wondering, if I buy new lines with the pill and put in, will i need a tune cause im doing something different? Or will it be fine and hopefully hit more boost better just by putting it in?
 
#2 ·
You need to figure out what mods are on the car and what tune it has first. You make it sound like it may or may not have a turbo back exhaust and that's no big deal.. when in all actuality, if it has a turbo back exhaust and no tune, then it's only a matter of time before the engine fails. Every time you boost would be doing irreversible damage to the engine. Fortunately, the ECU can go into limp mode if conditions are so bad (in an attempt to keep it from blowing up).. which would restrict boost to around 8psi.
 
#3 ·
oh great lol. good to know. I know of, pretty much anything you do, you need a tune and keep logs and track of everything, so this may have been a bad decision possibly?
Any easy way to tell whether its just a muffler or full exhaust?
Anyway to full reset back to oem ecu settings to see what happens?
AP will be coming soon, its not my daily, i have a beat up 300k mile camry for work and a bike for good days, it sits most of the time cause i dont want to abuse or tear up any worse if not needed. I mean it runs great, but i know something isnt right and all the searching is only leaving me wondersome lol
 
#4 ·
oh yeah, when i was having stutter issues first and checked all vacuum lines, something i checked and changed tightened up, made me boost up to 12-15lbs peak boost, it pulled like I have expected sti's to pull, but during that better pull, it missed and had weird sputter issues during. when i put coils and plugs in, I had the battery sitting on the passenger floor for two days while i put everything back together in my own time. Went for a drive, nothing, 9lbs max smooth as can be...
 
#5 ·
It may feel like it's running fine, but without looking at a data log of the ECU you can't really know.


As far as the downpipe (whether it has turboback or catback), you can tell by looking at it. The stock downpipe has heat shields attached that are rather obvious:

Automotive exhaust Auto part Catalytic converter




An aftermarket downpipe will be smooth, and probably bellmouth (or divorced.. although the HKS downpipe is 3" with a block off plate like OEM).

Automotive exhaust Auto part Pipe Muffler Exhaust system




Whatever the case, what you're describing sounds like it could be a serious issue, and I would recommend not driving the car until you have an idea of what's going on. The best advice I can give you is to look for a reputable Subaru performance shop near by to look over the car and tell you what's up with it. And chances are someone here knows of a good shop in your area.

Another thing you could do is post detailed photos of the engine, boost control, and exhaust on here and we can probably tell you most of the modifications that are on it, if any. If there are no mods, then I would suspect that there is probably a vacuum leak that's throwing things off.. but really it could be a ton of things.
 
#6 ·
I understand. Ill take some pics of vacuum lines, turbo, exhaust and stuff, enginetc Bay and whatever, tomorrow with some sunlight. Another question off topic but... A couple months ago, my girl and I went to a monster truck jam about 2 hours away, got close to home and starting running hot sitting in traffic, ran fine and cool while moving, checked coolant when I got an exit, seemed ok besides what bubbled out the overflow from being hot. The next day, both main and sub fan fuses were blown, replaced and fans kicked on and ran fine, then a few weeks ago, started running hot in traffic again, pulled off after it cooled from moving, check fuses... still good. Got home, did some research and am hoping it's just air in the system and need to burp it, but it sits and haven't gotten serious about making everythingalls 100% yet until now cause it's getting nicer out. So I will try to burp it properly first and go from there. But as for the pics, I'll take pics tomorrow of everything and see what we can figure out. I appreciate the help, thank you very much.
I do know the vacuum lines aren't stock, they're some blue kind of different line, that is complete opposite of anything I can find, from all the stock vacuum line photos I've found.
 
#7 ·
And don't speak about head gasket, I've already thought and let anxiety kick my ass on this car lol. Still under my 3 year/35,000 mile warranty, so if worse comes to worse, I'm hoping some serious things can be taken care of. Wishing I could throw a rod through the hood scoop and get a full rebuild and start over from there. But in a perfect world.......
 
#8 ·
At work now, I'll get pics when I get home. Just wondering, if the previous owner decided he wanted the louder subie rumble, if he just put the muffler on, without a tune, would that make it run at 8lbs fine or would it have some missing issues or something without a tune?
 
#10 ·
I'm gonna put the restrictor pill and lines in, burp the system the right way, correct the boost gauge vacuum line, the right way, in the right spot then reset ecu and see what changes if anything and how it runs and reads after that. Thank you very much MainFrame, for giving helpful insight and pics and trying to help, I've gotten a lot of crap for writing so much and stuff, like this post. But please read this last long post and judge if you want, I won't lose any sleep lol. I just owe the bank money for this car, that my ocd has me checking every crevice and crease until it's perfect or what I've gotta do to get it close as i can get it to perfect. Thank you again MainFrame for being patient and trying very much!


Overheating, rarely in traffic, I pull off, cut it off, let the fans run till it's cooled down, check fluids and stuff, then get back on the road, doesn't run hot in traffic or anythinges the rest of the ride, runs normal. Makes me think I got air in the system, I did pull the rad cap off a few months ago checking ****, may have done it at the wrong time and got air in it, I'll bleed it this weekend to make sure there is no air.

Stutter happened once or twice during full boost, every other time or so, 5lbs or less ran smooth. Checked vacuum lines and snugged a couple up, ran good at first, then still had a miss. Finally, wouldn't go into boost at all, just bogged like fuel cut off, then finally threw a cel, misfire 303, changed plugs and coils, no miss at all, smooth from 0-100 everytime.

It's just the muffler, I have heat shieldsink and all, def looks stock from turbo back, besides the muffler.

Boost gauge vacuum line is plugged into a hose that looks like it goes somewhere under the right side of the tmic toward the back and is sealed of with lossely wound duct tape. So I will run it to the bpv with a t-fitting and have it sealed besides duct tape and maybe that'll give me a 14.7lbs or so reading on the gauge and I'll be fine. About the restrictor pill, if it's not in there, then that could be my main problem with this all right?

With the car off, the gauge reads a little to the left of 0 and at idle, reads between -20 and -24, depending on temperature. Don't know what they're supposed to be, but hoping it's the whacked vacuum line rigged job.

About the warranty, got it January 2015, with an extended warranty, with 85,000 miles, I was only ok for the gold package, one less than the best cause I had to many miles. I've put 15000 miles on it since then, always been at 8lbs on the gauge.

Trying to get the coolant burped right, boost vacuum line right and see where everything sits after that, then do timing belt and water pump. Would've already done it, but if Imy gonna have to have it torn down to rebuild stuff under warranty, then I'd rather have it all apart once, instead of me do timing belt and water stuff, then them go through and take everything apart to fix whatever may be wrong long as it's covered.

I know it's long and forums hate this stuff, but I used to be a honda guy, rebuilt a few of my motors, pulled engines out to clean or paint Bay or just cause I was bored and wanted to drink beer and do something with my cars lol.
Subies and the temperamental things I've read about, make me feel like I'm doing brain surgery on a fish, if I'm not careful, but then when you do something, it isn't as bad as it sounded. I've been searching and reading and searching and finally keep coming across the same pages and haven't found any specifics, just things to try and this long post gives me the insight and helps to decide what I need to do to decide whether I need a good shop asap or just me over thinking. I am very ocd.
Thank you very much if you made it this far lol.
 
#11 ·
Stock exhaust from header back, just a muffler to make a rumble.

Don't know if the pics will work or not, but I have no restrictor pill. The hose connected to the right of the bcs, goes to the wastegate actuator, the hose to the left of the bcs, connects to the turbo. My buddy gave me his hoses with his pill in and all. He replaced his stuff with better stuff, he has a 2016 wrx. Imy thinking his hoses and T fitting will still work fine on mine, if not, then I'll buy stuff that's in my cart. He gave me he's bcs as well. Haven't looked yet, but seems like it should still work on mine, I'll know when I check, just wondering if you knew if 2016 bcs would fit on my 07 sti?
Also, if I take the two hoses off and have the restrictor pill in and that connects the two hoses and go into the left side of the bcs, then where is the hose coming out of the left side of the bcs supposed to connect?
 

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#14 ·
Yea, I've seen that pic alot lol. So I'm starting from scratch and put it where it's supposed to be with the restrictor pill cause who knows why they put the lines where they did without the pill, just cause they have some perrin pipe thing in there.
So, as what it looks like, when I put the pill and run the lines the right way, it should be ok.
If it's been running like this for let's say, 3 years, then there should be no damage, just been over taken care of only running 8lbs right?
 
#15 ·
People will usually remove the restrictor pill when installing aftermarket boost control. I see you got the line with the pill off of a 2016.. have you verified that it uses the same pill as your 07? Subaru uses different restrictor pills with different interior diameter for different models, so I would make sure it's the right size pill for your car before installing it.

I haven't looked at your data logs or learning view, so it's hard to say if it has been causing damage to the engine or not. For all we know it has been damaged a little more every day for the last three years and it will finally give out the next time you start the engine.. or it has done no damage and will run fine for another 100,000 miles. At this point it's anyone's guess. Hopefully once you fix the lines it will sort itself out.
 
#16 ·
Yea, I know what you're saying. It's either been non abused and babied for years or its wanting to shoot a rod whenever it wants lol.

Haven't been able to find anything on the pill size online. I was thinking just putting it all together and see what happens or just wait and order the pill and hoses for my car. So either throw this on and see what happens or play the waiting game some more lol. We'll see how I feel this weekend.
 
#17 ·
Put new hoses and restrictor pill in today. Just went for a drive. Hits 14.7lbs, in 2nd 3rd and 4th, but soon as it hits at WOT, it seems to cut back to like 12-13ish? Driving down the highway in 6th 5th or 6th gear, WOT, starts building boost and wants to jump to like 20lbs everytime on the gauge, soon as I see it start to go past 14.7, I let off quickly.
 
#18 ·
Boost tapers off in higher RPM, so that's perfectly normal. If max boost for your car you will typically only see that number for an instant in 3rd, 4th, and 5th gear before it starts dropping off.. lower gears won't produce as much boost.

As far as 6th gear, you shouldn't really be going WOT in 6th gear on public roads. It's extremely hard on the engine to floor the car in a high gear at low RPM. 4th, 5th, 6th gear should already be revved up to 4000rpm or more before you floor it.. so WOT in 6th means you're already going like 120mph, which is not safe on public roads.
 
#19 ·
Lo . No, not racing through all the gears, by any means. Just 2nd and 3rd gear pulls feel great and boost taper off, is normal so that's fine. But if I'm cruising down the highway in 5th or 6th, just WOT, to pick up speed, it seems to keep building boost, soon as it gets to 14.7, I let off, right away, seems to keep building boost.
 
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