As the title, is engine performance (bhp and torque etc) better or worse with a Vent To Air - VTA - Dumpvalve or BOV - Blow Off Valve - fitted???

M.

 

They don't affect bhp/lb ft - just the way the turbo responds after reapplying the throttle after a gearchange when accelerating (to a lesser or greater degree). If anything, then if they are s h i t e quality/badly made, they could lose! you performance through such foibles as remaining partially open when on boost etc, etc.That's why the OEM recirc is considered the best one to have, as it's been developed by Subaru to work best and has been accounted for by the ECU, etc.

Don't waste cash on an aftermarket whooshy VTA DV - get a decat downpipe instead. That WILL give you the max amount of bhp for a single bolt-on mod (aside from a turbo change) - although you would need to get it mapped to release the c.30-40 bhp that it would give (with upped boost)...

 

Eeee's reet tha noze



An uprated rear ARB gives significantly more benefit for very little money But I'm a firm believer in handling over power

 

Yes, forget engine mods until you upgrade the braking system (decent pads at the very least!). Then move on to uprated suspension - once again, at the very least, Whiteline's stiffer 22m rear ARB and their solid drop links too, plus, importantly, a full geometry laser alignment session.

Mods like the above will make you quicker as the car will stop better and handle better, which boosts your confidence. Confidence in the car beneath you i.e. it's predictability, accounts for so much IMHO...

 

My recent experience of Performance Friction pads in an otherwise standard STi Brembo set-up was outstanding. Of course, I always advocate learning to drive without the brakes anyway (Roadcraft).

The 22mm bar is good, but if you're a very smooth driver, able to keep the car settled and planted then the 24, or even 27 may suit. Hooligans whom get the @rse out all the time need not apply.

 

a vta can also cause idleing issues when coming to juctions etc.

can also cause the car to be a bit jerky on throttle lift off.