BOV- What's the point?

[NIZR34GTT]

I took my Turbosmart BOV of my R34 it ran like a vw.I could never adjust it to get the car to run right. I put the factory one back on and it runs like it should do.After market BOV are a waste of money as far as my car is concerned.

[TTT]

GTRman1992..

are you saying that you are running no bov at all, 20psi boost and you hear NO NOISE between gear changes?

[alstar]

ive been told you should not run an after market bov on skylines becouse it is not good for the engine, it requires the pump back system to run at full potential, unless you have done the work on the engine and the car has a new ecu to change fuel mapping, is this true.......

[Roy]

Stock or aftermarket, as long as you are runing one. GTRman1992 i hear what you are saying about not running a BOV, but dont agree.

Whats creates boost is the turbo spinning at rpm, and whilst not running a BOV will not stall the turbo, or force it to spin backwards, it will help slow the rpm. As the inlet tract is of fixed volume, the combination of dropping exhaust gasses and trying to pressurise a fixed volume, the turbine wheel will not have enough axial force to continue spining the compresor wheel whereby maintaining any positive pressure in the inlet tract.

After all the turbo does not represent an air tight seal so air can escape the'open' system back thru the airfilter.

BOVs by way of venting air either to atmosphere (my preference) or recycled back to the inlet tract, will lessen the rpm lost by the turbo, meaning when you crack the throttle and the exhasut gasses start to flow, there is less accelaration of the turbo required to get back to boost producing rpm.

I am at the minute not running a BOV because im redoing all my pipework, and i sure as hell notice poor response from the turbo after gear changes. (Its a fair whack bigger then std turbo) My new pipework is going to run 2xBOVs to ensure that they can vent the cfm that my turbo can produce.

Everyone has an opinion on BOVs

[DJ984]

Roy, will you be running a BOV on both the turbo and intake sides of the Intercooler?

[Skyrine-Dave]

just mount 2 of the suckers as close to the throttle body on the intake side of the intercooler... closer to the throttle body the better in my opinion

[Roy]

Placing one that will vent to atmosphere next to the throttle body, about 4" actually from the throttle body, and then the other is going after the turbo outlet (just before the pipe shoots thru the inner guard, and is being plumbed back to the inlet.

Im still umming and arrring over plumbing back the BOV on the turbo outlet, compressed air from the turbo will be hotter then inlet air thru the filter, and as it will not be passing thru the intercooler, will only be recirculated back to be compressed/heated again... i may just atmo vent both of them, as i dont want a return line running accross the rocker cover from the throttle body.

But then there is the whole stalling thing so will have to wait and see how it goes... may need to chase down a HKS EIS (piggyback idle thingy)...plans need to be flexible

[GTRman1992]

GTST - Yes I have no BOV at all. The factory ones are blocked off.

Roy. I agree when you say everyone has an opinion on the subject. BOV is almost like having a religeous discussion. Soon I will be setting up a pressure sensor with high speed logger in front of the turbo outlet. This will measure both the pressure wave some claim and the back on boost response time. I will do it on a GTR that have BOV's so we can shut them off and get a true final answer on the subject.

Roy, On your loss between gear changes, I think it is the bigger turbo. As I said earlier I spin the wheels from 1st to 2nd and 2nd to 3rd, so I cannot understand the powerloss arguement. Will see soon anyway.

[Gson]

well as far as the atmospheric and inlet venting models go which one is better!

i allways thought the plumb back was the better!.. Roy why is the atmospheric your preference?

[rev210]

The factory nissan BOV is very good. They leak a little insignificant amount of air back to allow for a nicer throttle response just off boost. You can easily block the bleed hole if this is a problem for you. It has no effect on performance at all.

For the most part people who claim that the factory ones leak are usually 'hearing' the leak and not seeing it on the boost guage. OR are blaming the BOV for boost drop caused by something else. If you do have a leaking factory BOV the replacement will cost you less than $50. These factory BOV's can be further modified to allow for operation at 40psi or so if you are concerned that there is some substance behind the myth that they don't work at higher boost pressures. And you can atmo vent them (provided you block off the other pipe no longer used) if you are concerned about a small amount of slightly warmer air.

[GTRman1992]

Gson plumb back are better as the air going into the engine is measured by the AFM's, so if you vent it to atmosphere your car will run rich on gear changes as the ECU thinks that air is still in the system. There are ways to fix this but its all too hard only for the swissssss noise that will get you a defect.

[Ska]

GTRman1992 - If the psshht noise is a defect, how come I hear so many cars with them, the dep of trans and police would be instantly attracted to them?!? I can only see how a BOV would change emmission levels, but that's the only thing I could possible see that would make it a defect, and even then it would be hard to prove, right? Please be gentle, I am a noob to this :-)

I just have bought a stock R33 and want to have that beautiful sound, and after reading up and talking to several different mechanics about BOV's I have decided to get one, but not if it'll get me defected here in QLD, that's just a waste of money!

Ska

[DJ984]

Yeah, atmo venting BOV's are defectable because of the change to emissions etc....

The only reason you hear so many is because they havn't been caught yet... there are tricks to driving to make your BOV quieter when needed....

EG:

* Slowly back off the accelorator for gear changes instead of just lifting your foot off

* Tune the BOV so it "flutters" under certain RPM

*Drive around cops with low or no boost so that the BOV doesn't go off...

etc etc....

Then the only thing you have to worry about is getting pulled over for an RBT and getting defected....

[JimX]

I have been pulled over for many RBT's and not once have the cops asked to pop my bonnet. I could have been lucky all this time, but I'm just saying it's not a 100% dead certainty that you will get defected just because you are at an RBT. They have a drink-driving quota to fill while there, so they are more interested in getting you in and out as quickly as possible.

If the cops *did* pop my bonnet, they would most likely not find my bov anyway. It is pretty well hidden and you'd need some tools to disassemble bits of the engine bay to find it

[TTT]

guys...

I think that atmo venting bovs in QLD are LEGAL.

I suggest you call your RTA or EPA in qld to find out more, but I don't think that a bov is defectable for sound OR emmisions in QLD.

[Ska]

Interesting, I am contacting QLD transport to try to get clarification on this matter with them, it would be so good it they aren't. But I really do not see why they should be, the emission from them is only compressed air right, so it's not like they are adding any pollution and hang on a sec bov's would have to be legal, because my stock 93 R33 has a bov right? If so then it would have had to pass when it got the compliance plate when it was imported, and it did pass the roadworthy before I bought it?

I am looking forward to seeing what QLD Transport have to say!

[TTT]

your skyline has a bov that vents back to the air inlet, therefore keeping the air:fuel mixtures right.

vent externally on the standard AFM system and during the gear shift or back off from throttle, your car over fuels causing your car to run rich during that time, causing richer exhaust fumes...

THAT is one defect, the other here in NSW (depending on if the cop wants to be a jerk) is NOISE.

It is apparently UNDUE noise pollution.

[Jay95R33]

Interesting, I am contacting QLD transport to try to get clarification on this matter with them, it would be so good it they aren't.  But I really do not see why they should be, the emission from them is only compressed air right, so it's not like they are adding any pollution and hang on a sec bov's would have to be legal, because my stock 93 R33 has a bov right? If so then it would have had to pass when it got the compliance plate when it was imported, and it did pass the roadworthy before I bought it?

I am looking forward to seeing what QLD Transport have to say!

It's not the the fact that compressed air is venting that is the issue. But the fact that on AFM equiped cars with venting BOV the A/F mixtures go very rich while the BOV is venting air. This is where some people have problems with back firing and stalling.

So it's not the air that's coming out of the BOV that is of concern, but the super rich exhaust fumes.

J

[Ska]

So it's not the air that's coming out of the BOV that is of concern, but the super rich exhaust fumes.

OH ok now I get it, bugger still it will be very interesting to see what responce I get, I have already contacted them re air pods, because I saw some not too happy ppl in NSW posting that it is illegal for them to have air pods, and QLD Transport said:

Generally, the fitting and use of vehicle accessories (air pod) do not

require specific approval from Queensland Transport. As such, Queensland

Transport does not approve or disapprove the use of vehicle accessories.

However, Queensland Transport requires that vehicles continue to comply

with the standards set from when the vehicle is first supplied to the

market. Accordingly, the use of any aftermarket devices must not result in

deterioration of vehicle compliance with the applicable Australian Design

Rules.

The only regulation relating to air filters is contained in Queensland

Transport's Approved Inspection Station (AIS) Code Of Practice which states

that, "air cleaners must be fitted".

It is the responsibility of the driver of the vehicle to ensure that

emmisions levels are maintained.

It may be necessary to supply proof that the vehicle maintains the original

emmision levels.

So I guess that answers the BOV question too, fitting an aftermarket BOV would most probably change the emmision level's because of the motor running rich during release of the air.

Still I'll wait to see what they say specifically about BOV's and hope :Bang:

[paulr33]

In vic you are only allowed one air intake modified

modifications are: intercooler, pod filter

So you can only have one or the other, however most skylines (if not all) come stock with an intercooler, so any skyline with a pod is defectable (in vic), however Ive been pulled over before, they ask if you have any mods, i say yes, an aftermarket air filter, they pop the bonnet look around and go your free to drive off