Hey Community! New guy here! I tried searching the forums and on the internet and I still can't figure out the answer to my question. I noticed that a lot of WRX, STi's have Blow off Valves (that vent to the atmostphere) that are running Front Mounted Intercoolers.

I always thought that the WRX Turbo (2008-2013) requires that you run a Bypass Valve (that recirculates). My question is, does having a FMIC allow you to run a BOV (that vents to the atmosphere)?

 

Ah good question.

If you are running a front mount chances are you are tuned for it. During the tuning process it is possible to tune for a vta blow off valve.

Personally I am running a front mount but I got a turbo smart recuirculating. I wanted my car to be quiet and stealthy.

 

Both wrx and sti require bypass valve to be efficient, the setup isn't designed for blow off valve, older subies are a little more adaptable for blow off valves,they don't hinder their performance like the late models. The issue is that the computer reads the boost returning back to the turbo with bypass valve, when switching to blow off, the computer still thinks the boost is returning, and the problem that occurs is richness in between shifts and the annoying backfire. But here's what you can do, you can tune for the blow off valve so that the computer isn't expecting the boost to return, and then everything is good and you don't have to worry about it. My personal opinion is bypass out beats blow off just because our cars were designed for it, and I do believe and can't remember at the moment but I think bybass valves when returning the boost to the intake it actually helps keep the turbo spooled up between shifts for quicker boost response that's what the design was made for, so going block would actually hinder performance a little bit, I ran 50/50 blow off valve on my 2011 wrx and it was fine for a bit but still didn't have what I could with full recirc. But now I star bypass on my 2010 sti and still get a whooshing sound in the intake both turbo spool and recirc boost. Now to answer the Q, I can't answer with certainty but I think you can both bybass and blow off valve you just have to tune it out so the computer isn't registering something that's not actually happening. Anyone is welcome to correct me if I'm wrong on any of this.

 

The only way to run a VTA Bov correctly is through a Blow thru setup or being tuned for speed density where the MAF is eliminated completely.

 

^^ What he said.