HOW TO: Aftermarket STI Turbo Inlet on LGT

Stock turbo inlets suck, they are horrible for flow and tend to rip very easily causing vacuum leaks. Due to vacuum hose location I wouldn't suggest buying an STI inlet if you have a LGT version available, but with hard inlets you only have the STI's style available.

 

I personally got the Perrin STI/FXT/WRX2.0 inlet very cheap (had a tear that needed to be fixed), that's why I ended up using it. In the future I plan on making a custom LGT one though.

 

First remove the intake elbow

http://legacygt.com/forums/attachment.php?attachmentid=258324&stc=1&d=1510888312

 

Then unbolt and remove the MAP, WG solenoid, and unbolt the bracket. Shown is the WG solenoid and hose routing (will come in useful later).

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More vacuum hoses to remember, bottom most one is the EVAP canister one.

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Remove them all, Valve cover breather is the big 5/8" hose still attached

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Next unbolt the valve cover breather tube, removing the left heads hose helps you get it out of the way

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Unbolt the BPV recirculation hose, this will help a lot to remove it from inlet, and will help to reinstall.

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Remove PCV valve cover breather 5/8" hose

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Pull the wireloom back to expose the PCV "leak detector", this is the last vacuum hose on the stock inlet. It's a little tricky to remove the plastic PCV "leak detector", the pigtail is what locks the leak detector in place.

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This will expose the BPV clap, tricky one to remove. You will need to use pliers and pull on the hose to wiggle it out.

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Unbolt the inlet from the turbo and finally you can pull the stock inlet out.

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I dunno why people complain about room, plenty of room here for 3" pipe (I tested with a spare elbow I had)

http://legacygt.com/forums/attachment.php?attachmentid=258336&stc=1&d=1510888312

 

Stock vs STI Perrin, you can see the vacuum line difference. The tape you see on it is me fixing a rip from previous owner.

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Slip the new inlet in, not that difficult at all

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Stock sensor bracket will no longer fit, remove all of the sensors from it and put it in your left over Legacy parts bin.

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I had a hard time trying to attach the BPV hose back, turns out the fitting is bigger then stock so it requires some elbow grease to get it in. I found it easier to remove the inlet and insert the pipe into the BPV hose then insert it into the inlet.

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Continued to post 2

Another thing to note is, the STI inlet's entrance is slightly smaller then stock, you need to get it tightened well not to leak.

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STI inlet tends to rub against the PS pump too, need to put something there to prevent damage to the inlet.

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Time to put everything back together, this sensor was under the manifold on the bracket we discarded, just shove it back under the manifold.

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Now the fun begins with figuring out vacuum hoses. Since Perrin inlet, and just about all decent aftermarket ones don't have a PCV hose spot, you need to tee it into the valve cover breather hose. Now Perring suggests you tee it into the left head's breather, I wanted it to be closer to the manifold. I attached a 5/8" 90* premolded hose and ran it to the front and teed it into the valve cover breather hose.

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Used another 90* 5/8" premolded hose from my Nissan's, as for the 90* brass bard, I used a 1/2" to 3/4" PEX pipe barb. The EVAP hose (one connected straight into inlet without elbow) is a 1/2" to 3/8" barb adapter (they don't sell 90* elbows at Lowes/Home Depot sadly)

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Next you need to pull the metal plug out of the PCV "leak detector", and put it in the plug and tape it off. Alternatively you should be able to disable the CEL with a retune.

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Added some more clamps and ziptied the MAP senor to make sure it didn't dangle around. This is temporary for me, but will work good enough for a bit.

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Power wise the gains seem negligible and could be just typical in between day run difference, but seat of pants did feel the torque. But what you should pay attention to is the AFR's, with the inlet no longer having a vacuum leak AFR's dipped down to 10.5 on the graph. That's stupid rich!

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Do stock LGTs 2.5 dyno that low? Dynojet sim at that?

Do stock LGTs 2.5 dyno that low? Dynojet sim at that?

 

I've virtual dynoed two stock Legacies and they both made 187whp. Which is spot on with 25% drivetrain loss for 250bhp. My 04 FXT has similar numbers too (we all know Subaru underrated the FXT at 215bhp )

Thank you so much for this guide! I am far from a mechanic, but am mechanically inclined. This took me about 3 hours going slow and double checking everything. Dave @ Cryo is amazing too, helping with my tune and noting the vac leak. Ended up changing out the Inlet and Throttle Body hose that was beat and loose.

 

Also the PCV is prob due for a change. The Y-shaped venting pipe (whatever the actual name is) connected to the valve cover and the PCV filled with that lovely goo. I'll need to replace the hoses and the PCV I suspect, far easier than the Inlet I'm sure.

 

I did end up cutting the end off a CAT5 and threaded it through the Y-Pipe many times to get all that crap out. That's only part of it. Back to it.

 

THANKS AGAIN!! Great write up.

I'm going to be using this on my outback xt. I'm confused as to what the pcv leak detector is though. I can't seem to find much information on it.

Leak detector is supposed to throw a CEL when you have a leak between your turbo inlet and PCV valve. But in reality it's just a dumb connector that closes the loop in the wiring, so as long as the PCV plug is all the way in it reads as no leak, if it walks out enough it will register as having a leak.

Went with a Godspeed inlet: [ame=http://www.amazon.com/gp/product/B005EYSH3O/ref=oh_aui_detailpage_o05_s00?ie=UTF8&psc=1]Amazon.com: Godspeed 02-03-04 Subaru Wrx Sti Ej20 Ej25 Turbo Intake Inlet Silicone Black Color: Automotive[/ame]

 

I know it isn't close to Perrin in quality, but I really just need something that will do the job of the stocker well enough.

 

Managed to get it to work without splitting vacuum hoses either. I would definitely recommend removing the intake manifold to complete the job.