how do you connect a boost controller on a Subaru 05 wrx

u do NOT want to do that. see here: l am going to copy & paste this here. It is by EJ20Legacy on WRXFanatics.com. l think it is pretty well laid out & has some decent real life examples. Please read this if u have a WRX or STi & r thinking about these mods.

Quote:
Originally Posted by EJ20Legacy
Thinking about putting an intake, blow off valve, or boost controller on ur WRX? Before posting about it, check this out cuz the WRX is not every other car out there & a lot of the 'normal' mods do not work the same way on it.

Intakes: The Mass Air Flow sensor (measures the amount of air going into the engine) on the WRX is very sensitive. It is designed & calibrated for the diameter of the stock intake piping, the way it is mounted on the piping, & the distance it is from the turbo inlet. Many of the aftermarket intakes for the WRX did not take this into consideration. Some of them have diameters that differ enough from stock to cause serious problems.

Even the intakes designed properly for use on the WRX rarely cause gains in power. It is generally accepted that the stock intake does not start to become a restriction until 300 hp & l personally think it is higher than that. High enough that with the stock turbo it is impossible to make enough power for the intake to become a restriction. With the silencer removed, the intake is pretty darn similar to an open, short-ram style intake, & if u have a properly designed aftermarket intake the tubing is the exact same diameter as stock anyway. so where is the restriction coming from? Many intakes lean out the air/fuel mixture, which can be good for a couple ponies on a car with no tuning. Once tuned though for either the stocker or an aftermarket one, l do not think a difference would be seen.

The intake most well-known to cause problems is the AEM (short ram or CAI, does not matter). Not only does it cause the MAF reading to be off, but it causes irradic readings that make it IMPOSSIBLE to tune for. No tuner (Vishnu, Cobb, TurboXS, etc) will even touch a car with an AEM intake on it, period. Best bet? Put the money somewhere beneficial!

BOV's: The stock valve is a recirculation valve. All of the air it bypasses gets sent right back into the intake & then into the engine. The thing is that it gets sent back into the intake after the MAF sensor so it is not actually measured. The ECU just assumes that it is getting all of that air back into the engine. So when u swap on an aftermarket BOV that vents all of that air into the atmosphere, obviously none of it is going back. However, the ECU does not know this so it is still injecting fuel for all of that air. This causes a brief rich condition every time the BOV does its thing. It is not really a big deal, but these r the side effects:

-- slight hesitation while the car burns off that extra fuel. Most people can not even feel this & it depends a lot on ur driving style. Certain BOV is r worse than others in this regard, but even the worst one is not that bad so if u really, really need the psssshh sound u may want to just bit the bullet on this one.
-- Afterfiring. This one you're going to have if u get an atmospheric valve. That extra fuel is going to burn in ur exhaust, & it will cause a popping sound. If you're catless, it is gonna be fairly loud & might get annoying after a while. Some people like it, l found it annoying. If u have cats u may not really notice it, but that means the cats r destroying all of that extra fuel & r going to break down & need replacement sooner than they would otherwise.
-- Idle problems. This l do not really attribute with a general BOV problem, it is really a problem with a poorly-tuned BOV. However, lots & lots of people have problems with the car is idle when they put an aftermarket valve on so it is gotta be mentioned. Obviously if ur car does not idle right it is a big problem.

Bottom line is that the stock valve is, by far, the best. The car runs & performs the best with it. It is good up to 18 to 20 psi. If you're running less, u DO NOT need to replace it. Anybody that tells u a BOV is a performance mod on the WRX is wrong. 50/50 & adjustable valves cause less problems than totally atmospheric ones, but the stocker still wins out for performance. It is even semi-noisy if u remove the intake silencer & pop a nicer panel filter like an ITG in there. l can hear mine echo off walls & stuff.

Boost Controllers: Manual or electronic, both can cause serious problems. With the stock boost control system, the car only gives u full boost at full throttle (which is over like 76% or something. ish). With an aftermarket boost controller, u will get full boost whenever the turbo is capable of it, which includes partial throttle times from like 15% throttle on up. You do a lot of daily driving & highway driving in this range. The problem is with the ECU once again. At partial throttle the car usually sees 7 to 10 psi, or about wastegate pressure. It injects only enough fuel for 7-10 psi. When u pop a boost controller on there it just assumes you're still getting 7-10 psi, but you're getting full boost, which is probably 14.5 to 16.5 depending on where u set it. So you've got the fuel for 7-10 psi but 14.5-16.5 psi of boost! This causes an extremely lean condition because of all that extra air without any extra fuel, EGT is (exhaust gas temperatures) shoot through the roof, & soon a piston melts.

There r a couple ways around this problem. One is to drive ur car at under 10% throttle or at full throttle all the time & never drive anywhere in-between. There r plenty of people who do this, but that seems like a huge & annoying sacrifice. You could get a Vishnu EM l adapter (or similar product), which tricks the ECU & makes it safe to run full boost at partial throttle, but it makes the car a bit choppy as the transition between closed & open loop operation is not well defined. Or u could get a very fancy & expensive electronic boost controller that has throttle position input. Basically u tell it not to step in unless ur throttle position is over 80% or whatever number u choose. However, these r like $600+++

Now here is the kicker. For under $400 u can have ur ECU reflashed. This not only raises boost SAFELY but it changes ur ignition timing & fuel curves to fully take advantage of it. Less money, total safety, & more HP because of the additional tuning. Boost is not everything. Tuning for that boost will truly make ur car fly. If u need solid proof: my friend dyno'd his car with identical mods to mine, except he had a boost controller set at 16.5 psi on high setting & l have Cobb Stage 2 tuning. He put down 219 whp on the dyno, & l put down 237. l made 18 more hp at the wheels with slightly less boost & l am not going to melt a piston like he did after about 5 months of running the boost controller. And his had two settings. 90% of the time he was running it at 14.5 psi, which is stock boost. You do not have to crank it to melt a piston. On top of that, my curves were smoother & my A/F ratio was much, much better controlled.

Turbo Timers: They're cool but u do not technically need it on a WRX. On the rex the turbo is lubricated by the oil & cooled by the coolant. On a lot of cars the oil does both jobs, which is why u leave ur engine running afterwards--to keep the oil circulating. That could apply with coolant also, but Subaru actually did something cool here:

You know that coolant resevoir tank that is above the turbo up on the left (passenger) side of the engine? Well the coolant entry to the turbo is below it, & the coolant outlet comes off of the top of it & goes right to that resevoir. Basically, even after the engine is off, if the turbo is hot it will continue to circulate the coolant because the coolant inside of the turbo gets heated above the temp of the rest of the coolant & rises up into that resevoir. When that happens cooler coolant from below the turbo gets sucked up into it & it keeps cycling until the difference in the temperature of the turbo & the coolant is not very big.

If u take a hard drive & get the turbo really hot & do not drive gently for a couple minutes before parking just chill in the car for a minute & let it idle down. Never a bad idea to let it idle for a minute so some stuff can cool down & things can settle & whatnot, but 99% of the time there is no reason for the car to idle at all.

Not getting one will save u $120+. get intercooler hoses or put it towards a downpipe or something instead

BTW -- MisterX reminded me that installing a turbo timer will very likely cause ur dealer to void ur engine warranty if u go in with any sort of engine-related problem, or if they see it in ur car while you're at the dealership for something else. For a mod like this, it is definitely not worth the risk.

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Now just so u know, I've had an intake, I've tried three BOV's, have a turbo timer & I've run an expensive electronic boost controller in conjunction with a Vishnu EM l adapter for safety. The short ram intake l had was one of the properly designed ones. Going back & forth from that to the stocker l was able to tell no difference. Actually, at night when it was really, really cold l felt slightly better pull with the stocker pulling cold air out of the fender vs. the short ram taking warm air from the engine compartment. Normally this does not make a difference because the turbo heats up the air anyway, but when it was super cold out l could tell. l liked the sound of the BOV is of course but they were all obnoxious & it ran sooooo much better with the stocker l always went back to stock. l sold the boost controller & EM l adapter for much more than my current tuning cost. Not only does the car make a whole lot more power with the tuning, but it is smooooooth smooooooth smooooooth. It feels sooooo good. You can not touch that with a boost controller.

So there r the facts. Choose ur mods wisely.