Guest bastaad525 Posted October 6, 2004 Share Posted October 6, 2004 Just a couple questions about some odd turbo behavior, asked one of them before but dont recall there being a real answer, just suggestions for how to get around it. It's important to know I'm running a grainger ball valve style manual boost controller, currently getting it's boost signal from the intake manifold. Okay... two things I'm wondering about, hoping someone here can give a good explanation (or guess at one) for why these happen. I've already pretty much solved #2, but, I'm still very curious as to WHY these happen to begin with. #1 Different boost in different gears. The maximum boost reached will be higher in each higher gear. I get about 11psi in first, 12 in 2nd and 3rd, 13 in 4th, and 14 in 5th. Now, given the way the ball valve controller works, I can't for the life of me understand how this is possible. It's set to open at a given PSI, why does the turbo generate less boost in lower gears? #2 I originally had the boost signal to the grainger valve coming from the stock location, the two ports on the compressor housing. This worked fine before I got my intercooler installed. Boost would hold nice and steady from onset at 2500rpm all the way to redline (I don't recall if I had the problem described in #1 before installing the I/C). After installing the I/C, boost behaved totally differently. It would initially jump very high at onset (which occurs a bit later, about 3000rpm), say to 14psi, but then would slowly taper off, ~2psi for every 1000rpm, so that it'd be down to about 10psi by about 5500rpm, where I shift. I did solve this problem when I switched the boost signal from the compressor housing to the intake manifold. But... I'm still baffled, and really interested to know why it was happening to begin with. It just doesn't jive with the way the grainger valve works. Part of me still wants to actually take advantage of this odd behavior to exploit the ZX EFI's inherent fuel curve, which is to say, higher boost in the midrange, where the EFI runs really rich, and then boost falls off as RPMS increase and the fuel curve leans out. But, I'd really like to understand more about the cause. So... anyone have any ideas as to possible why's for these? Quote Link to comment Share on other sites More sharing options...
Brad-ManQ45 Posted October 6, 2004 Share Posted October 6, 2004 #1 is easy - boost is lower in lower gears because there isn't as much load. #2 I'm not sure of... Quote Link to comment Share on other sites More sharing options...
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