The promise of a 0.2bar increase in boost had begun with the purchase of an N1 ECU. Successfully fitting the HKS EVC had been another big step towards that promised increase, and purchasing a suitable Blow Off Valve to replace the standard 0.9bar-capped EVC would be the final piece of the puzzle.
Research into JDM-style BOVs gave me a few different options – the HKS SSQV with it’s unique sound and the very JDM Take-Off Pushunn R to name just a couple – but I settled on a subtle-looking ARC BOV which I’d seen on a few Cappuccinos on Minkara. I managed to source a good example via Jesse Streeter & Yahoo Auctions Japan and when it arrived I quickly made up a simple adaptor to mate it to the ABV flange.
Unfortunately, despite it’s subtle looks (which I liked a lot), the more I drove around with the ARC the more I felt the noise it produced wasn’t to my taste at all and so it had to go; once more it was back to the standard ABV.
I was struggling a little as to where to go and what to buy next until my friend Chris offered up his vintage Collins Performance BOV for a trial. It had sounded brilliant on his old Turbo Technics Sierra XR4x4 and we both figured it was worth purchasing a flange adaptor and a bit of silicone piping to give it a go on the Cappuccino. We were not wrong! From the first trial run it was clear that the Collins was going to be on a long-term loan – not only did it sound great on the Capp but with its old school looks and some standard-looking black piping it looked nicely at home in the engine bay as well.
With the choice of BOV now finalised (at least until Chris buys another turbo’d car!) I could also finish off the routing of the extra vacuum/boost feeds needed for the boost gauge, HKS EVC, and now the Collins. This turned out to be the hardest part of all – there are lots of options as far as vacuum/boost sources go but I found particular outlets (and even the order of the feeds from the outlets) could cause problems such as high/unpredictable idling or slightly skewed readings on the boost gauge & EVC. The original EVC feed was the strangest of all, giving vacuum to both the ARC & Collins BOVs in a very artificial way, causing both late opening & very early closure. (After finding that out I plugged the feed and never used it again!).
After a lot of testing I arrived at the feed layout below, designed to eliminate all the oddities mentioned above as well as keeping the engine bay uncluttered – looping the EVC feed underneath the intercooler/intake pipes (and teeing off from this tucked-away location to supply the BOV) as well as moving the boost gauge’s flow controller into the cabin were all done to keep things looking as standard as possible.