Shortly after purchasing my 2002 Subaru Impreza sti type UK one of the first mods I wanted to do was to fit a dump valve or BOV (blow off valve) as its sometimes known. Having heard other Impreza’s with them fitted I thought this was a must.
Having done some research I settled on the Turbosmart supersonic, fitting and setting up was a breeze. The sound was fantastic and it definitely turned some heads, but I couldn’t help but feeling the car wasn’t quite running as smoothly as it was before. Having looked on various Subaru forums I found that this could be due to the air already being metered even though it had been dumped to atmosphere.
I continued running the car with the dump valve fitted for around a year, constantly trying different settings to improve the running of the car. One day with an hour to kill I decided to remove and refit the standard Impreza recirculating valve to see if the car really was running better without it. The change was instantly noticeable, the car didn’t hesitate between gear changes and it generally felt smoother and quicker.
I have no doubt that my Impreza runs better with the standard Subaru unit fitted although the sound created was so good, it was almost worth putting up with. If anyone would like to purchase the dump valve please use the comments section or my contact form to make me an offer.