Cool that sounds better the written word can be interpreted in many ways this thread is testament to that fact. Most on here refer to the stock valves as the stock BOV's which is slightly incorrect as you say but in general meaning correct as the stock valves even given they recirculate they still blow off but vent back into the intake. Even the plumback Turbosmart kits refer to the kit as a Plumback BOV kit. So glad the confusion is sorted take note thread starter. I would be interested to know more about your mates 400+ hp zed. What turbos etc is he running etc and what boost on the stock valves would love to see a dyno chart showing the boost curve etc. I have a number on file of all different setups with stock valves different brands of aftermarket valves etc and different turbo kits. They are quite handy for reference when people mod there cars. Cheers
Cool that sounds better the written word can be interpreted in many ways this thread is testament to that fact. Most on here refer to the stock valves as the stock BOV's which is slightly incorrect as you say but in general meaning correct as the stock valves even given they recirculate they still blow off but vent back into the intake. Even the plumback Turbosmart kits refer to the kit as a Plumback BOV kit. So glad the confusion is sorted take note thread starter. I would be interested to know more about your mates 400+ hp zed. What turbos etc is he running etc and what boost on the stock valves would love to see a dyno chart showing the boost curve etc. I have a number on file of all different setups with stock valves different brands of aftermarket valves etc and different turbo kits. They are quite handy for reference when people mod there cars. Cheers
By memory he was running twin GT725R ball bearing turbos but he was only running 12psi I think to make the power he was at the time. I dont remember the fuel mods, but for engine managment he was running a electromotive tec 3 ecu. I believe he imported it from Japan with alot of the mods already... I'll have to bug him and see if he has any recent dynocharts.
Nice turbos. Interested more so to see the boost bleed if evident (given low boost 12psi) Stock BOV's for that setup has stumped me running higher boost will limitthe efficiency of the whole setup but if he kept it at 12 its borderline and probably will hold a steady boost line on the dyno. Interested any way.
Yeah I only recently moved so I'm not in touch with alot of my old mates now but I will try and get something out of him... I do know he had alot of shit stripped from his car aswell such as the power steering, ac, unneeded electrical stuff, 3/4s of the interior and it's just barely road legal lol
I had mine off the car at the time, I hooked them up to a compressor and checked for leaks with both the vacuum line and and recirc intake hooked up, it would leak on pulling the vacuum line as expected, I had no way of applying suction so it wasn't tested fully but at least I know there were no leaks under normal operation. It'd be easier if you could plug the pcv hoses going to the intake cam covers and do a boost leak test at 15 or so psi.. I think that's all that's required to leak test at more than the usual 5 psi but you might wanna double check in case I'm forgetting something and you end up blowing your seals! If the recircs leak, I'd also check the vacuum lines to them, the butterflies will be closed so there maybe less pressure than normal going through them. (there must be some reason for people to think they leak at low boost!)
lies! stock recircs are used on Z's boosting 25+ psi and have been tested to over 40 psi off car. that doesn't mean a BOV isn't an improvement but they won't leak unless they're fuxored.
Not lies at all! Well, not totally... Maybe a brand new stock recirc valve can handle 40psi but my 14 year old ones leak at >12. Maybe lies that they were originally designed to open at a little over stock boost but I think most of the old ones getting around these days would not hold much boost.
how did you test this? I've got old turdy recircs and they held a gazillion psi. my theory (which could be bollox) is that you may not get equal pressure to the vacuum line side of the recirc like you would while boosting because they're hooked into the manifold and your butterflies are closed during a boost leak test. sure you still get enough air flow to be able to idle but pressure may be reduced enough to not hold the recircs closed.
Simple explanation. The theory is while boosting the pressure in the intake pipe (bov or recirc valves fitted after the turbo but before the throttle bodies) and plenum is supposed to be around the same boost pressure and cancel each other out. In reality it will be somewhat of a different story. The BOV port is a hell of a lot larger than the small vacuum line coming from the plenum and when talking pounds per square inch (psi) the pressure in the intake pipe at the BOV (recirc valve) while maybe being the same in theory will actual displace more force on the spring and cause it to open prematurely once the set spring tension is overcome even if the vacuum line is matching boost pressure its sheer volumetric pressure ratio is greater and will bleed boost. When shifting etc the opposite happens, The vacuum line goes into a vacuum and relieves opposing spring pressure and the valve vents very quickly due to the pressure difference between the plenum in vacuum and the intake pipes which are still boosting due to a spinning turbo. Hope this helps
erm, you say they leak and give theory as to why they might but what has convinced you that they do actually leak? I tested mine off the car to 15 psi and they held fine.. many others including Greg Dupree use them at much higher boost levels and I believe he was the one that tested them to 40+ psi off car as well. oh and what I posted above was actually my theory as to why people 'think' that they leak when they don't... unless they're broken.
Two word Dyno charts. My car held boost better and had a flatter curve after the Turbosmart Supersonic BOVs were fitted plus air flow dynamics is right up my alley being a mechanical engineer. Testing off car and what happens on is two totally different things and I dont pay too much attention to the US guys as a lot of if it is third/fourth hand info going around the grapevine. But hey if you want to believe it thats cool everyone is entitled to there opinion and choice. I have merely stated the facts of the matter for people to interpret in there own way. Cheers
My method of testing was fairly basic and on the car, not bench testing so I could well be wrong. On my boost controller I get about 12-13psi at around 50% duty cycle. With the recircs blocked off an increse to 55% duty cycle gives me about 14-15psi, 60% - 16-17psi. With the recircs hooked up 60% will initially give me 16psi but then quickly reduce to 12-13psi and hold there. I put this down to the recircs leaking. I currently have the recircs hooked up and duty set to 50% until I have $500 to throw at some BOVs. I would be happy to keep the stock recircs but mine just don't seem to hold higher boost.
That sounds more like wastegate creep. remember the Boost controller only controls the wastegates not the BOV's they are purely driven by manifold and intake pipe pressure and vacuum. Although somewhat related but actually quite different in function and run separate to each other. Its a fine line here and we are walking it now.
But with the recircs removed from the equation the problem disappears. Smaller changes to the duty cyle make a more noticable difference to boost levels and it holds whatever I set all the way to redline.
I don't take what the US guys say as gospel but considering many of them with big hp use and recommend recircs, I'm sure one of them would have noticed a problem by now. You said you merely stated the facts for people to interpret how they like.. The problem is you didn't really leave it up to interpretation by relating your experience or belief and lots of people could fork out lotsa $ without researching or doing their own testing first. I don't think they leak by design, you do.. so let's just say they MIGHT leak, so test your own bitches! Actually I'm gonna test mine further.. (on car to remove any doubt). I'll disconnect the recirc from the intake, place a small FM transmitter I recently picked up at the end of the hose and listen for leaks through my stereo as I'm boosting along at 15psi.
Strangely enough your car is slow once you've released all of the boost, you want to keep it! I've known of people that got a turbo car purely to make obnoxious sounds with it, and then they fall flat on their face when a real turbocharged monster goes heads up against them.
You could have a bad boost leak at higher pressures too. My car recently exhibited similar probs was holding boost okay at 14 or 15psi set point on EBC but go to 18 and it would hit 18 initially then bleed to around 13psi. I replaced the EBC with a new Turbosmart E Boost 2 same prob did a BLT last night and holy hell leaks everywhere, might pay to do a BLT on your car you may find boost leaks are the main cause. Something to think about anyway Cool you test your own and if you are happy using the 18 year old factory items thats fine good luck to you. The original thread asked for opinions on upgrading the BOV's and mine was given based on my own trials/findings and researched material
