240zdan Posted May 24, 2009 Share Posted May 24, 2009 i am finishing up the engine bay of my rb26dett 240z and was wondering if anyone here has ever recirced their bov back into one turbo intake pipe only and have had the engine not run rich between shifts. recirculating back into one intake would be alot simpler for me. no need for y pipes etc. Quote Link to comment Share on other sites More sharing options...
Whittie Posted May 24, 2009 Share Posted May 24, 2009 Isn't the whole point of a BOV to release intake pressure.... Hence, wouldn't it make sense to dump it to the exhaust... Correct me if I'm wrong but i get the impression you want to plumb back into the cold air inlet to the turbo, Yes? If you did that, then you would have a closed loop pressure system and the pressurised air would vent out the air filter.... If you ran to the exhaust, after the turbo's exhaust lines connect into the main exhaust (Dump pipe???), then you would circumvent needing to run two lines. Or even easier than that, just let the thing vent to atmosphere and enjoy the sound Quote Link to comment Share on other sites More sharing options...
240zdan Posted May 24, 2009 Author Share Posted May 24, 2009 sigh... any educated replies? Quote Link to comment Share on other sites More sharing options...
Whittie Posted May 24, 2009 Share Posted May 24, 2009 Sigh... Any english speaking posters? Quote Link to comment Share on other sites More sharing options...
Whittie Posted May 24, 2009 Share Posted May 24, 2009 Quoting WizardBlack: "If you visualize the flow of air through your entire intake tract, you might get a bit of an understanding why MAF cars are usually sensitive to externally vented BOV's and why installing the BOV closest to the intake manifold yields the marginally best performance. A MAF meters the actual flow of air, therefore the BOV must be rerouted back into the intake (before the turbo, obviously) AFTER the MAF. If you install it before the MAF, the MAF will register the air flow that is continually circulating. This will make the car run rich when you shift, roll off the throttle, etc. When you roll off the throttle (or shift), the compressed air suddendly finds itself slamming against the closed throttle. Just like a traffic jam, the air piles up against this blockage and then a pressure wave bounces off the throttle and works it's way backwards (upstream) to the turbo. It hits the compressor wheel and reduces it's speed; sometimes even making it spin backwards momentarily. This is pretty hard on the compressor and shaft. Someone smarter than I can compare it to the effects of surge and what typically fails first. Regardless of this, it disturbs the rotational intertia of the turbo and delays respool for the next time you press the throttle. A BOV releases the pressure and allows the turbo to continue to spin and harmlessly vents the pressure until you want it again. Now if you're still with me, you can imagine that installing the BOV as close as you can to the blockage (throttle) allows the entire intake route to continue to flow air forwards. If you install the BOV, say, right at the turbo, the air will bounce off of the throttle and have to travel all the way back to the turbo to find release (so to speak). Installing the BOV at the very end of the intake allows as much of the intake tract to continue to flow forward during vent. The ideal setup would be to install the BOV as far downstrem as possible and vent it right into the inlet of the compressor so it is used to spin the compressor and maintain as much momentum as possible. Hope that helps. On the subject of where to tap for the BOV: The BOV has a piston which is operated by vacuum/pressure and a spring. Whatever line is used to feed the pressure signal to it will get some movement from the operation of the piston. This can cause small fluctuations or delays in the pressure signal. Theoretically it isn't good to tie this line in with the FPR or boost gauge. Likewise, the BOV could fail or leak and alter your fuel pressure. A BOV can even hang open in vacuum (not a problem for MAP cars) but can flutter open and closed, etc (definitely a problem for fuel pressure). Many people install a BOV and crank it down tight so it sounds 'cool'. Most people will agree that the FPR's vacuum line is a lifeline for your turbocharged engine and the boost gauge line is your only chance of knowing when something is going badly and stopping it in time. Anything else on those two signals is an unneccesary risk to them. I personally tie them together so I know if the FPR line is ripped by seeing the boost loss and therefore getting out of the throttle. I also have a wideband, but every bit helps." Then if you are using the stock ecu, you have to plum it back to the turbo intake. I still don't understand the principal of this from a fluid mechanics perspective, but it obviously works. Seeing as the BOV should be at the intake plenum then plumbing to one turbo or the other should have almost NO differance to the total air flow through the system at the engine as the whole intake line will be at the same pressure and so should not alter the air/fuel ratio during shifts. The turbo shaft that is having air to it MIGHT spin slightly faster than the other shaft, increasing the pressure it can output at when the throttle opens and exhaust flows to the turbos but i'm not too sure if this would be a problem. If you're not running the stock ecu, why not just plumb to the exhaust or vent to atmosphere? Much easier and less complications. http://forums.hybridz.org/attachment.php?attachmentid=14036&d=1242351415 That is a mates rbz plumbed back to one turbo so perhaps it's not a problem Quote Link to comment Share on other sites More sharing options...
Canadianz Posted May 24, 2009 Share Posted May 24, 2009 It shouldn't matter if you plumb it into both or just one. The re-circ valves/ blow off valves vent back into the intake AFTER the MAF on RB's so it doesn't matter really. I have mine on my RB25 venting to atmosphere and it does stumble the odd time when bov vents on the stock ecu. If you think about it there is no need for an bov Y pipe becasue just after the turbo's the compressed air on the RB26's joins again in the turbo Y pipe. Remeber that bov air is metered already so it doesn't need to go back through the MAF ... just back into the intake tract. Hope that helps Chris Quote Link to comment Share on other sites More sharing options...
240zdan Posted May 24, 2009 Author Share Posted May 24, 2009 one intake it is then... thanks for replies Quote Link to comment Share on other sites More sharing options...
Mike Rowe Posted May 25, 2009 Share Posted May 25, 2009 one intake it is then... thanks for replies Mine is circulated back to just the front turbo using the original turbo aluminium air intake on the second minor inlet (if you know what I mean) There is a photo of it on my website http://www.bluevista.net.au regards Quote Link to comment Share on other sites More sharing options...
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