The promise of a 0.2bar increase in boost (and thus performance!) 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.
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Once more it was back to the standard ABV and 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 old school looks and 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 now 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.