![]() ![]() BUT, that's the only thing good about it. It's actually a great feeling when boosting to redline, it almost feels like switching on nos, you get a great thump in the back as you suddenly get all this extra power from nowhere. VoD (Valley of Death) simply put, is the gap between primary and secondary. After you drive a TT for a few months, you'll notice this as the primary running out of "puff" in the moments before VOD (valley of death) and then secondary boost.įor more technical info and docs, I have a new thread up here with a bunch of technical info If you want to get technical, there's actually a phase between primary and secondary, the exhaust valve opens slightly to start spooling the secondary turbo, before opening fully, partially despooling primary, then spooling both at once. In the VF18/19's case, the compressors are identical, In some other configs the secondary is sliiiightly larger. And the turbo's are mostly the same size, or at least very similar. The main difference between turbo's is the primary is reversed to sit on the left side of the engine (the passenger side in rice hand drive), and the secondary doesn't have a wastegate (except A-rev). I guess this leads to some people thinking secondary is actually one big turbo, it's basically not. Both turbo's are about the same size! (more on that in a sec) - "secondary" is ambiguous, it will mean the second turbo, and also the phase where both turbo's are going at once i.e "I'm boosting on secondary" Which actually means you're boosting on both turbo's, or on the secondary phase. What's actually happening in the crossover period is the primary turbo despools, then both of them spool up in parallel. ![]() First myth: The first turbo is small, and spools early (true) and the second turbo (a bigger one) then takes over (false). That is, one turbo does the first bit then the second turbo kicks in after a certain rev range. Well, first off, as most of you know, both iterations of subaru's Twin Turbo (that is, the BD/BG Master-4's, and the BE/BH Phase-2's) are sequential setups. I thought i should spell out once and for all how the twin turbo's work, there's much misconception out there on the subject, as well as a bunch of myths. ![]()
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