I know there has been a lot of talk about BOV's lately but I am a little confused as to when they should release the pressure. At what psi should the pressure be released?

 

I fitted some this morning before breakfast which was a nice and easy job, took it out, revs were fine etc

 

I am running about 14 psi but the bov's vent to atmosphere around 9psi. I know I can cut down the spring etc .. but my question is what is the ideal pressure that they should vent? Is it just positive boost? I don't want to damage the tubs with the air going back to them .. Compressor surge.

 

Should I just set them to vent at a stupid psi, like 3 or 4?

 

Can anyone let me know? I thank you .. :-)

ideally they should vent at anything over 0psi boost pressure

cheers Yas ... Guess I will have a play with them then.

 

So they must be set to vent to atmosphere at any postive boost, otherwise you can cause compressor surge that will bugger the turbos eventually?

cheers Yas ... Guess I will have a play with them then.

 

So they must be set to vent to atmosphere at any postive boost, otherwise you can cause compressor surge that will bugger the turbos eventually?

exactly

Right then ... off to the garage I go ... :-)

Right then ... off to the garage I go ... :-)

try and get them to go off at about 5000rpm when you rev in neutral

Well I have had loads of fun today!!

 

Got the BOV's to go off at about 5,000 revs. Not so much of a whoosh, sound like a whip cracking. Love the sound though.

 

I may plumb them back so they act as recircs again though.

 

They actually sound really nice ... will have to wait and see.

this is interesting...so by either adjusting the BOV or cutting the spring, you can set at what psi the BOV's release pressure ?

 

I was always put of BOV's becuase I was under the impression that they would go off even when making slight positive boost, giving the impression to outsiders that you were giving the car some stick when your not...but thats not the case. Cool :D

this is interesting...so by either adjusting the BOV or cutting the spring, you can set at what psi the BOV's release pressure ?

 

I was always put of BOV's becuase I was under the impression that they would go off even when making slight positive boost, giving the impression to outsiders that you were giving the car some stick when your not...but thats not the case. Cool :D

 

Hi mate, you can adjust when the BOV'S release the pressure however you must be careful that you dont go to far. I believe each different brand BOV is set to go off at a certain PSI however if you cut the spring too much the compression will reduce and not close the valve correctly and this will cause idling problems when coming to a stop or on hard braking. I have tested mine out thoroughly and I don't get that problem.

 

I think Lymon installed some this weekend and set his to go off at .7 bar

The ideal point is always a bit of a compromise:

ideally you want it to open at any positive pressure, but it should also be able to hold the maximum boost you want to run and it's near impossible to have both with a spring loaded blow off valve

 

Anyway, what I normally do with the cheaper model blowoffs is cut the springs 1 winding at the time until it starts to make a fluttering sound at stock boost or approx. 2/3 of the maximum boost you want to run (for a car with stock turbos this is at approx 0.6-0.7 bar) and then cut 1 more winding.

 

Also make a few longer testruns at stock and max. boost

I've noticed the cheaper valves sometimes may act/sound different once warmed up a little

So check if the car doesn't start to make the fluttering noise again or starts getting idling or max. boost problems. (fluttering sound: spring is loaded too hard, rough idle or max. boost problems: spring is too soft.)

 

-Eric

cheers Eric, given me some good advice there. Will have to experiment with them some more.