Guest DATTO Posted April 4, 2003 Share Posted April 4, 2003 hey just wondering what you guys think about puttng the BOV before the throttle body or putting after the turbo. ive been told both ways are fine but after turbo works better...i dont know,,i guess shed some light for me so i can finish the car...hehe the intercooler pipes are now done, 2.5" mandrel pipes, 10psi boost car feels great for the old 71 240z. the spearco intercooler makes a pretty good diference when that thing starts to boost. now if i can just get a better clutch. if interested i have pics of the setup with the 300z maf and 300z ecu. runs great. i wonder if we put the timing back to stock from 18deg and run 91 gas, i wonder how it would feel..hehehe take it easy all. Quote Link to comment Share on other sites More sharing options...
Kennysgreen280zt Posted April 4, 2003 Share Posted April 4, 2003 The idea behind a BOV is to vent boost while you are in a high boost/closed throttle situation (ie when you are shifting) That being said the BOV should be placed post turbo and pre-throttlebody. Closer to the Throttle body is better. I have usually heard 6 inches is a good number to have. Since I assume you are running a MAF setup you will want to have the BOV "vent" back into the system after the MAF and before your turbo. the idea being you are feeding the turbo its own boost to keep it spooled for that split second you are shifting. If you vent it to the atmosphere you may experience some rich running condtions if the BOV opens any durring idle and while you are shifting.(mmm flames ) Hopefully this helps you out some. later! ~Kenny Quote Link to comment Share on other sites More sharing options...
SHANE Posted April 4, 2003 Share Posted April 4, 2003 hey just wondering what you guys think about puttng the BOV before the throttle body or putting after the turbo. Uhh after the turbo and before the TB are one in the same. i think you mean before or after the intercooler. Quote Link to comment Share on other sites More sharing options...
Guest DATTO Posted April 5, 2003 Share Posted April 5, 2003 hey kenny im going to do what yah said, reason why i was thinking right after the turbo is because of the backspin on shifiting, i was scared that the charged air in the cooler was gonna spin the turbo back but i dont think its gonna affect it much if i do it your way few inches after the TB. so i told my builder to put it after the TB, so far the car runs great at 10psi,,,pulls real well at 3rd gear. but dont think the clutch is holding well. we are thinking of put c16 gas and run 14-15 psi. the 300z system is running well too. i like the open MAF system. lost a bit of torque than the flapper door but not much to really cry about. imma try my scottie Downpipe and put the timing back to stock and run 10psi, the intake manifold is great, got flow tested and flows 14% more than a stock turbo intake manifold. its the older non-egr non webbed manifolds. and we put the 240sx TB, i like the setup...idles and feels good. so hopefully my other 2.9L nismo stroker turbo motor will run better than this setup. thanks again for some input, take it easy. mike Quote Link to comment Share on other sites More sharing options...
Guest livewire23 Posted April 5, 2003 Share Posted April 5, 2003 (mmm flames ) Hopefully this helps you out some. *drool*, there's nothin better. Seeing flames shooting out the exhaust as a BOV dumps to atmosphere will help me out anytime of the day, no matter what Im trying to do. As per the subject, what I've heard is right before the TB too. I think what he meant by after turbo or before TB is what it should be closer to... Would be funny to have a BOV before the turbo or after the TB. Sounds like something a ricer would do... Quote Link to comment Share on other sites More sharing options...
Lockjaw Posted April 5, 2003 Share Posted April 5, 2003 Put it after the intercooler before the TB, that way the air you vent is cool air verus the hot compressed air coming off the turbo. Not that it will make a huge diff, but you never know. Quote Link to comment Share on other sites More sharing options...
Roostmonkey Posted April 6, 2003 Share Posted April 6, 2003 The closer to the TB the better..as the TB closes, the air stacks up at the butterfly and the pressure builds up and will travel backwards to the source (turbo). This is because air is compressable, so relieving the pressure before it can back-up to the turbo is best.............. Quote Link to comment Share on other sites More sharing options...
Mudge Posted April 6, 2003 Share Posted April 6, 2003 Would be funny to have a BOV before the turbo or after the TB. After the TB? BOV in the intake manifold? Quote Link to comment Share on other sites More sharing options...
SleeperZ Posted April 6, 2003 Share Posted April 6, 2003 Put it after the intercooler before the TB' date=' that way the air you vent is cool air verus the hot compressed air coming off the turbo. Not that it will make a huge diff, but you never know.[/quote'] Just a random thought, but why not bypass before the intercooler? Aside from an elevated temperature through the BOV, it would keep your IC a little cooler... I'm not sure I buy the "stacked air" theory saying it's best to vent before the TB, as that's the source -- actually the source of the compression is at the turbo. The throttle plate is just causing the flow restriction that could cause the compressor to surge. Quote Link to comment Share on other sites More sharing options...
Roostmonkey Posted April 7, 2003 Share Posted April 7, 2003 I did say the turbo was the source.Again,because air is compressable the pressure will build at the resistance and as its compressed that pressure will travel backwards thru the I/C to the turbo (source).Putting the BOV as close to the TB also spares all the hose connections the spike in pressure. Quote Link to comment Share on other sites More sharing options...
SleeperZ Posted April 7, 2003 Share Posted April 7, 2003 Again,because air is compressable the pressure will build at the resistance and as its compressed that pressure will travel backwards thru the I/C to the turbo (source). That's what I'm not following. Yes, the air will back up behind the throttle, but that doesn't mean pressure is highest there. The pressure is generated at the turbo, and that is where I think the spike will be highest. If you are talking about a sonic shockwave back from the throttle body closure, I don't think we are talking on the same time scale or energy level. That type of standing wave effect would only be present for less than 5 milliseconds; I think we are talking on the scale of 200-500 milliseconds here. As the throttle closes, the air flow will drop - the turbo compressor is still spinning, and the boost pressure will climb momentarily. The pressure is still highest there at the turbo compressor outlet because you still have positive airflow into the engine, and the pressures will drop as you approach the TB. Personally, I don't think it matters much where the valve is, as long as it's between the turbo and the TB. Mine happens to be mounted right at the throttle, but only because that's because I just followed the herd without thinking about it. I'm interested in the discussion of the benefits/tradeoffs without the misleading or incorrect information, and at this point it seems to me there may be a slight advantage to having it at the turbo outlet. I continue to be open to hearing other ideas and factors I may not have considered. Quote Link to comment Share on other sites More sharing options...
yo2001 Posted April 7, 2003 Share Posted April 7, 2003 I got mine right before my TB. I guess it's got more to do with throtttle response because all the IC and plumbing can stay somewhat pressurize without any air slowing down the compressor. But who knows Quote Link to comment Share on other sites More sharing options...
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