Venting/recircing BOV - how to tell?

[someonestolecc]

Gday,

I recently changed from a s15 stock re-circ to a professor sheepdog bov and I'd like to confirm it's blowing off.

The reason I ask is because today I took a ride in a mate rb20det with no BOV (stock) and it made a very similar noises to my car after a boost event... so I'm starting to think my BOV is infact too bloody tight and might not be venting at all. The only thing that goes contrary to that is that when I back off my car backfires as if it is running rich, which would suggest it is blowing off just fine.

Basically - I don't know if it's working or not.. other than a camera is there a way to confirm if it's venting before I plumb it back?

Also - what does the stock sr20/rb20/rb25 re-circ valves start to vent at? I'd like to use this as a yard stick.

Thanks.

[R31Nismoid]

you'll hear it if its atmo.

if you dont then its too tight

[someonestolecc]

Heh - thanks.

I'll try to rephrase what I probably didn't explain well enough in my initial post.

What I hear could be atmo BOV noise BUT it sounds very close to what my mate's non BOV rb20det sounds like when he takes his foot off the go-pedal.

So it could be the BOV or it could be pressure bouncing around my pipes.. I'm just not sure because I've never heard this brand of BOV before.

I was thinking of somehow strapping a party whistle to it... hehe... anyone have any more practical ideas?

[MANWHORE]

Hi cc

My car makes a very loud bov noise just using the stock nissan r33 recirc bov and a hks pod. So I guess, just because you can hear the woosh noise does not necessarily mean it's atmo.

In regards to tightness, I've been in a mates car with an aftermarket bov. I noticed that when he accelerated quickly and released the pedal quickly, the bov would sound. At lower boost levels and when releasing the accelerator slowly, he'd get a flutter noise. That means that the bov is not opening at that level.

So I guess what i'm trying to say is that you can tell if the bov is releasing pressure or not by listening out for the flutter v woosh.

[MANWHORE]

oh, I forgot to say.

In regards to telling if it's recirc or not. An atmo bov will usually have a trumpet on it or at least some vent.

I'll describe my stock bov for ya. Basically, it's on the back of the intake pipe, so that's one connection. Then there is the return line, which returns the air back to the intake system when the bov operates. there is also a small vacuum line to trigger the bov.

All the aftermarket bovs i've seen sit in the same place, but they do not have the return line. By me calling it a return line, it may be slightly confusing, because it's not really a small line. It's big. Perhaps 3-4 cm in diameter.

[LANFOH]

Open your bonnet when the car is running in neutral and get someone to rev the car on and off while you watch and listen from the front of the car. You should be able to see the BOV opening and clossing. If his car doesnt have a BOV at all then it may be his turbo just cavitating when the throttle shuts. Hope that helps

[someonestolecc]

Thanks guys.

Chris - Thanks for the reply, My BOV is atmo.... .. ...

LANFOH - Thanks for the reply also, free-revving the engine will only show me if it's opening and closing up until 0 pressure, as free-revving won't generate boost. I'd like to know when it's positive pressure (on boost).

I'm not having a go at anyone or am I unappreciative for the replies but none of them really address what I'm asking.. I'll rephrase again.

I don't know if my BOV is opening or closing when I'm on boost. The noise I hear could be flutter or the BOV blowing off.. I thought it was the BOV blowing off but I took a ride in a rb20det with no BOV and it sounded EXTREMELY similar. So I want to CONFIRM it's not flutter.

I think I might stick a party whistle on it so I can confirm it opens when I want to.. unless someone has a better idea..

[igor]

Maybe you can block the trumpet and see if the sound changes. If it doesn't then it means you are recirculating. Just a thought.

[someonestolecc]

That's a great idea - lol I hadn't thought of that at all

Whatta champ thanks! :uh-huh:

[TTT]

CC - if it is making the prrrrrrrrrr sound the RB20 non bov engine makes, then it is not venting.

sheepdog bov should make a single pssssshhhhhhhh sound.

when you have no bov, you also get some back fire.

or if your bov is too tight, you will get some back fire too.

loosen it up mate..

just a question.

did you put the vacuum line back on to the top of it?

[LANFOH]

Also check your vacuum hose on your BOV to see if its leaking and sometimes BOV sieze up with all that exhaust residue, this may be your prob if its not opening, just take it apart and scrape out some of the shit with some fine sand paper and put a tiny bit of grease along the sides inside. But if your BOV is opening in neutral this wont be your prob.

[someonestolecc]

Ahh thanks GTST that makes sense!! Then it's too tight!! I thought "Oh no it's backfiring I'd better tighten it".. NO WONDER !! Yeah the single sound only happens when boosting hard.. Also I thought maybe it's a special BOV cos it sounded different at high and low boost heh heh how wrong I've been!

The vacuum line is on it I'm not that silly Thanks for confirming what it's meant to sound like that's exactly what I needed to know!

Thanks LANFOH I will do that! Although it moves when in neutral and revving it's not stuck but I will clean it out tonight anyway when I re-adjust it.

Just a quick question. What should I clean it with? autosol shreds everything but I wouldn't use that because I don't imagine it's too good for the rubber (if it has any). Bit of damp rag be sufficient? Cos I'm just just trying to clean the buildup and not get it squeeky clean right?

[R34GTT-R]

Just stick your hand near it, rev the car by pulling the throttle cable.

[TTT]

CC - pull it apart, clean it all with degreaser and a rag.. then spray everything with WD40 and put it back together..

don't pipe the wd40 off.

[someonestolecc]

CC - pull it apart, clean it all with degreaser and a rag..  then spray everything with WD40 and put it back together..

don't pipe the wd40 off.

Gday - thanks for the tip. I cleaned it with metho all nice n nice. It was infact stuck as well. Now she slides real easy.

I'll give it a quick spray of WD40.

Now it's just strange. I've set it to the loosest possible setting, to the point where it's closest to opening but without being open at idle. Under .5-.7 bar it still flutters (depending on gear+load). Anything over .7bar it will blow off as per normal, but I think I still get a tiny bit of flutter.

Is it possible that it's just not up to the job?

As a final test I'm going to plumb it back at the softest setting and go for a drive. If there is no flutter at all I'll know the blow off noise is somewhat like flutter but not flutter itself.... if that makes sense