NismoPick

Any stock bov from turbo cars will work. When I first built my turbo setup, I used a 1G DSM bov & recirc'd it... but it wasn't much of a performance part, plus I wanted the PHHHHH... Wooosh! sound, so I got a Turbo XS RFL bov.

Anyway, stock DSM & WRX bov's will work fine for recirc.

Safe boost... There's about 1 billion web pages that talk about "safe boost level" so I would suggest googling it. The gen rule of thumb is nothing more than 10 - 11psi w/o an intercooler. With an IC, but still stock engine, prolly not over 14psi. You can blow a stock headgasket real quick if you don't know what you're doing.

So use the internet & research it. www.google.com works wonders.

machsound

guys isn't this one of the biggest z31 forums out there how come no one can answer a question about putting a turbo on a car? And when you do don't tell them to google it there is alot of b/s information on the internet all of you should know that

What the guy said was pretty close to psi you can run i'd stick closer to 9 or so without a intercooler and no more than 15 with the stock engine is strong and can handle alot more psi than that but your fuel system is the big problem take a fuel pump out of a z32 twin turbo or w/e or find a good hi/flow one upgrade your lines and most defently your injectors they are way to small to run anything more than 15 psi on the car you will be running to lean and get pinging (so all together change your whole fuel delivery system) if you want more power.

Now for a bov (do you guys know what they actully do) they release extra presure on the intake side so that the turbo can actully spool faster you do not need a bov (no one contradict me my bro 87 conquest tsi did not have one and i think they knew what they were doing) now it is a good idea to put one in there just so you can get your turbo to spool faster.

I would tell you to actully use and intercooler on your car. I know how arizona heat is and if it is anything like texas it gets way to hott in the middle of summer. The intercooler will help with keeping everything a little cooler at least. You go no intercooler in the middle of summer with 10-11 psi of boost your going to seem a big jump on your temp gauge!

Make sure you get a 02 sensor in there also to tell if your running to lean or rich. To lean is bad pinging and stuff and to rich is bad also with detonation! if your going to do it do it right! thats all i got to say

And guys please help people out im sure there is people out there that know more than i do about this kinda stuff i have only had my z31 for 3 months come on!

NismoPick

uh hum... lets break this down here:

He wasn't asking about "putting a turbo on his car." That's why we're not talking about that.

Good... but not really what he's asking.


Yeah... so Subaru, Porsche, Nissan, Toyota, Mazda, etc... they're all wrong for putting BOV's on their turbo cars. Do YOU know what the purpose of the BOV is?

yep... but he said no intercooler


um... I think the Z31 has an O2 (not zero two) sensor already. He would benefit from an AIR FUEL METER.


So let's not serve BS to those that ask questions... ok?

jfairladyz

Also on the BOV, it's not only meant to help the turbo spool quicker. A more important function of the BOV is to protect the turbo from compressor surge. Compressor surge can ruin a turbo. It can destroy your thrust bearing and, if the turbo is spinning fast enough and pushing enough air, even damage the compressor wheel. I would recommend a BOV for any turbo charged car. Is it needed, no. But its a damn good idea.

entropy31

attack of the know it all noobs . i like the "oh, this guy i know has a conquest so i know what im talking about". haha. welcome to zdriver. it seems there are a few things you need to learn about how this place works. we will always suggest that people search for info first. get the info, then come here and ask for clarfication. this keeps us from answering the same questions over and over. stick around, we will be glad to help you with anything, and appreciate your input. but we ask that you help yourself before we help you.

ZenArcher

Pointedly ignoring most of that post.
How does a BOV help the turbo spool quicker? A BOV vents charged air to atmosphere when the throttle plate is closed during shifts. A recirc valve places the charge air back in the intake where it is used. And I've run 11 or 12 psi in Texas summers without an ic and had no overheating issues at all.
Now I remember why I stopped posting here

nismo619

u know machsounds does have a good idea.. maybe there is a few GROUCHY people in this wed site...

NismoPick

Would that be nismo619 still being GROUCHY about what has happened in the past? I let that go 5 minutes after it happened.... have you?

nismo619

Nismopick i have let it go.. but on the good side of things nismo pick i have learned alot for your wrods of wizdon.. unlike other moderators lol its cool between me nad u nismopick.. no hard feelings..

jfairladyz

Well first off, I dont think Nismopick is a moderator

And to ZenArcher: Yes, a BOV DOES help the turbo spool faster between shifts. By venting the pressure to atmosphere instead of letting it slam back into the compressor wheel and slowing it or even stalling it. So by doing it that it allows the compressor wheel to continue to spin freely which keeps the wheel speed up which means the turbo is ready to go back on boost which translates to less lag between shifts

Is it more effective then a recirc. BOV? No. But it's still more effective then not having a BOV.

ZenArcher

"And to ZenArcher: Yes, a BOV DOES help the turbo spool faster between shifts. By venting the pressure to atmosphere instead of letting it slam back into the compressor wheel and slowing it or even stalling it. So by doing it that it allows the compressor wheel to continue to spin freely which keeps the wheel speed up which means the turbo is ready to go back on boost which translates to less lag between shifts"

That does not equate to spooling faster...

NismoPick

Did you know you can use [ QUOTE ][ / QUOTE ] to quote people?

Anyway... Whether you like it or not, a BOV keeps the compressor spinning faster between shifts & when letting off the throttle quickly.

On a side note, it doesn't make the turbo spool faster from a dead stop & idling... ONLY BETWEEN SHIFTS

ZenArcher

I doubt I'll be quoting people here in the future but thanks for the tip. A BOV does not make a turbo spool faster. If you guys want to think that it does that's fine by me but it still won't be true. If you go back and read my post carefully I explained exactly what a BOV/recirc valve does. Of course in the process of venting the charge air it prevents the charge air from going backwards and slowing the compressor wheel. That's it's primary function... Did I really need to explain that part to anyone? No, don't answer that. Anyways, some things that actually do make a turbo spool "faster":
A larger diameter exhaust
a smaller exhaust housing a/r
an external wastegate

NismoPick

So in your world of "I don't need to follow the laws of physics" you think that if there are two identical turbocharged cars, EXCEPT one has a BOV, and the other doesn't, there will be no difference in turbo lag / spool when driving? IS ANYONE ELSE READING THESE POSTS? I FEEL LIKE BANGING MY HEAD AGAINST THE WALL!

ZenArcher

Maybe banging your head against the wall would shake a few synapses loose and improve your reading and comprehension skills Sorry to barge in after all this time and inject some reality and precision into the place. Even zcar.com isn't this bad. I'll be off now. Carry on boys...

NismoPick

No, don't go.... I really want you to explain which law of physics allows the turbo to still lose the same spool when LESS pressure is forcing it to slow (by using a BOV).

jfairladyz

WOW Someone is REALLY lost arent they. I'd spell it out for you Zen, but I guess you're not coming back Oh well, you can remain lost in your own little world.

AZ-ZBum

I hate BOVs. I think they're ricer crap. Just my opinion. I personally prefer the full throttle shifts over obnoxious blow off valves.

BTW: A turbo will still lose a lot of it's RPM when shifting no matter what you do.

On the same engine, one with a BOV and one without, the turbo will still provide near enough the same boost levels by the time you start using the next gear.

Laws of physics still apply here people. What a BOV does is prevent compressor surge. But it does nothing for the turbine side. Don't forget, the turbine side is what drives the compressor side. And the exhaust is what drives the turbine. And the intake is what provides air for the exhaust. And if there is no air in the engine (you just slammed the throttle shut), you have no exhaust.

So.... If you no longer have RPMs in the engine, what is keeping the turbine side spooling?

Now, back to the original question:
I can't help you as I am against BOVs.This falls under stupid question number 25 on my list of commonly asked stupid questions. So, I'm guessing you're new to turbos and probably cars in general, right? Don't worry, you aren't the first to ask this question and you won't be the last. Now, the answer is...
Eleventy billion. Seriously. Depends on (but not limited to):
- engine condition - includes:
- - pistons
- - rods
- - valves
- - spark plugs
- - wires
- - fuel injectors
- - fuel pressure
- - fuel pump
- - etc
- octane fuel used
- air density
- temperature (air and engine)

Basically, you turn it up until you get detonation. Then, you either retard the timing a little or turn the boost down a PSI or two.

jfairladyz

True the turbo will slow down when you let off the throttle no matter what. But what a BOV does is allow it slow down through it's own inertia. When that air slams off the closed throttle plate and proceeds to work it's way back to the compressor it's going to try to work it's way back through the compressor wheel. Thats going to try to put the compressor wheel into reverse. Of course there is not likely to be enough surge to put the wheel into reverse, but there is usually enough to atleast slow the wheel at an accelerated rate compared to losing it's natural momentum. And in some cases, with enough boost, the reverberation of air will stall the compressor wheel. By having a BOV that air that would've been causing surge is now being vented so it is not only no longer causing any damage, but it is now also not trying to work its way back through the compressor and slowing it. Like you said, without that exhaust flow to keep the wheels spinning that air flowing back to the compressor has less working against it so it's that much easier for it to slow or stall the compressor wheel. Now when you go to get back on the accelerator the turbo has regain all it's momentum: lag. With a BOV the compressor will be at a higher speed and so you won't have as much lag, thus with the turbo wheels having more momentum because nothing is working against them, the turbo will spool back up faster. This only works between shifts as the wheels must already have their momentum. A recirc. valve can be routed to actuall blow the recirc'd air straight through the front side of the compressor so as to give it a boost and keep it spinning faster. There are some top end turbo cars that have this feature. And that is the part of the laws of phisics that allow the BOV to improve spool and lessen lag: Momentum.

I'm a recirc. type of guy myself. I'm not a big fan of the whistling or chirping blow off valves that vent.

AZ-ZBum

and keeping the throttle open during shifts does much more by still keeping the turbo spinning even faster.

No, you no longer have a huge pressure on the compressor, but you do still have a huge vacuum on the turbine that will slow it down almost as fast.

So no matter what way you look at it, the turbo is still spinning much much slower than it was. How much of a difference? Not really enough to make a difference in respool time.

jfairladyz

True keeping on it is more effective. But it's still not always practical.

But again, when you make your point about the turbo slowing down you're still neglecting that the surge air just slows the compressor down more then it would be if that air wasn't returning to the comressor through the outlet. Sure letting off is going to slow the turbo. But letting that surge air hit the compressor wheel is just going to slow it even more. That is my point. By venting or recirculating that air you have fewer forces working to slow the wheel. Therefore the wheel speeds of the turbo will still be higher with a BOV then if you were running without one (and letting the throttle close between shifts).

AZ-ZBum

No, I'm not neglecting it. And I know it's called compressor stall for a reason. It's because it drops to near 0 before picking back up a little. But even with a BOV, it will still drop to less than probably 10,000 rpms. But in the grand scheme of things, when turbos spin at 100,000+ rpms, the difference with and without is virtually nil.

jfairladyz

Thats like saying the difference in your car getting to 100mph from a stop isn't going to be much different then getting there from 10mph. Again, it's all about momentum. It takes more effort to move an object at rest then it does to move an object that's already going. And recirculating just makes it that much more effective. And of course we'd all like our thrust bearings to last a really long time too. At stock boost levels it's not really that big of a deal. But when you start pushing more pressure then a BOV is a very good idea, especially if it's recirculated like it should be. The noise is ricey, but the part itself is far from it.

AZ-ZBum

Timewise, it won't. Very close, but think about it. Look at quarter mile times. Think about how long it takes you to get from 0 to 10 mph. 1/2 a second? little less? little more?Think about how fast a turbo spools. Think about the weight of the impellers. To go from 0 to 10,000 rpms on something that small and light is virtually instantaneous. That's why it is possible to go from 120,000 rpms to 0 in a split second.Yes. Very true. But a turbo's impeller weighs near nothing relative to the amount of air trying to move it.Where do you think the recirculated air actually goes? You think it's held in a state of limbo until it is called for again? In case you don't really know, it goes right back out the intake. So instead of dumping out raw, it vents back out through the filter.A good lubrication system is what helps here. Compressor surge has more of an effect on the actual vanes of the impeller.Everyone is entitled to their own opinions. I will admit a car running a lot of boost should have one to help people who can't WOT shift. But for anyone on a stock Z31 turbo, it's a waste of money.