skybus

I'm not getting a pressure drop, it's the fact I'm getting spiking of .8 bar - that's the problem! I can only put this down to a faulty HKS BOV (I've disassembled for inspection, and everything's in order as far as I can see) What I question with the HKS BOV is, if you have a look at the way the SSQV works, boost is always in the chamber of the BOV pushing the seat against the seal - it helps keep the valve shut (in theory you could block the vacuum line, and the piston will seal against the seat based on pre throttle body boost). Most BOV's (non-HKS!) I'm aware of use spring tension and boost found on the vacuum line to remain fully closed. When there is vacuum at the manifold, both manifold vacuum AND boost in the pre manifold piping are used to push the valve out / compress the spring, and vent the excess boost. What I don't understand with the HKS is, the vacuum release has to work against spring tension AND residual boost pressure to open! Well, to answer my own question (under "Product Detail") http://www.racinglab.com/mit3019turhk.html still not sure if I understand fully though... Also (for Simon-R32), the way the PFC boost controller works is, it comes with a MAP sensor that plugs into the PFC and uses the existing two wires to the stock boost control solenoid. Because the PFC uses this MAP sensor to display boost on the Commander and control boost, the Commander will never display vacuum (due to my MAP sensor being plumbed into turbo piping rather than post throttle body). Is this OK? Does the PFC need to know if there is vacuum? Before I had the work done, tuned etc., I had plumbed the MAP sensor into post throttle body... Thanks for all your input... Steve

It was still afternoon here in the UK, so the brain was (kinda) functioning I'm not feeling particularly clever today however... It appears the best route for me to take is get all the bits back for a recirc. Can this be done, even if my engine has been tuned for no recirc? Oh, and happy new year everyone! Steve

Hi guys I have been through almost every BOV topic / post / thread on this and the sylineowners.com forum ad infinitum, but still have not seen any discussion on the below: Here's a little background info: I have an R33 GTST with... 2835Pro S set to 1.1 Bar HKS induction Z32 AFM Apexi PFC / Boost control kit (and Datalogit on the way) ARC Frount Mount HKS SSQV BOV!! Plus other bits that are not really relevant to this discussion My tuner has plumbed the boost control kit into pre intercooler piping, basically just off the turbo (boost gauge on PFC commander never shows vacuum!), which I can understand the reasoning - you see actual boost pressure from the turbo, not post Intercooler / throttle body boost). Also, all recirc piping has been removed / blanked off, so I can't really head back down the recirc route. Because of this new "plumb boost feed directly off turbo" method, I now see massive spikes of 1.9 Bar plus massive flutter on gear change (you wouldn't normally see this when the boost controller is tee'd off the manifold). I'm guessing here that the BOV is not opening enough (it does open a little though). So, there are two things to note with this issue: 1. HKS SSQV. Now I don't want to go into recirc / atmo discussions (as we've all seen multiple different theories here ) so can anyone tell me if this BOV can discharge the excess boost (1.1 Bar) effeciently? One thing I've noted with this BOV as well, is that the pressure generated by the turbo pushes against the piston, keeping it closed. So in theory, wouldn't manifold vacuum have to be greater than the boost pressure to pull the piston out? 2. 1.9 Bar being measured at the turbo. Surely this is bad?! For the guys that do not run a BOV, when the throttle body is closed, this equates to (I assume that a closed throttle has an area of 25mm / 0.025m (radius) squared times pi = 0.001963m2): Pressure = Force x Area 1.9 x .98 (to get atmospheres) = Force x 0.001963 1.82 / 0.001963 = 927 N Force = Mass x Acceleration 927 = Mass x 9.8m/s/s (gravity) Therefore Mass = approx 100Kg?! So an instantaneous mass of 100Kg is either being applied to the throttle butterfly / throttle butterfly pin, or the turbo blades?!?! Even if my theory of obtaining a figure for mass is incorrect, there can be no argument that 927N of force is being applied to either / both these parts, instantaneously... Has anyone else measured boost spikes on the turbo side, or is there something completely wrong with my setup?? Thoughts / input on my force theory would be welcomed, as would an idea on an appropriate atmo BOV to vent the right amount of boost... Cheers Steve P.S. I have now changed into my flame-retardant suite - let the burring commence!