BOV sizes

[Draven]

prettiness of engine bay is not a priority, but nor do I want 3-4 stock BOVs cluttering everyhting up.
I'm hoping for as simple as possible... 1 turbo, throw out all the twins stuff. 1 bov would be nice

[30psi 4agte]

jsut to clarify a few things.

Draven dont go bosch --- I know you wouldmt any way but you should see what anything over 20 psi does to em. !!!

In the early dAys when i ran two of em i ended pushing the valvw through its seat and out the outlet pipe. If ya think that is amusing should have seen the look on the guys face when took it back for warranty !


secondly a blow off valve is best positioned as close as possible to the throttle body because:

When the throttle closes a large amount of pressurised rushing air is heading towards a dead end. This inturn causes a reversion pressure wave back in the oposite direction ( towards the turbo )
This pressure can cause the compressor to slow so rapidly that its fins can be bent !!
In extreme cases the wave has split intercoolers apart !! with the two waves colliding.

The blow off valve is positioned closest to the throttle so that the pressure wave has the shortest possible path to exit.

[Draven]

eh.
personally I'm dubious as to how bad that would be.. I tend to ascribe to norbie's camp of BOVs ... I'm actually putting the BOV in to quieten things down (no bov = BIG noise)

[30psi 4agte]

[QUOTE 30psi etc: How does the AVO one work? .[/QUOTE]


Yeah good : it is very similar in design to the Greedy type R but has a little different valve seat design.

It does have a huge diaghpram on it ( can prob see it from my avatar)which can be used to control boost also.
In short i am happy with it and have not had any probs with it and the boost i run.

[Norbie]

When the throttle closes a large amount of pressurised rushing air is heading towards a dead end. This inturn causes a reversion pressure wave back in the oposite direction ( towards the turbo )
This pressure can cause the compressor to slow so rapidly that its fins can be bent !!
In extreme cases the wave has split intercoolers apart !! with the two waves colliding.

This is one of the reasons people cite for using a BOV on a turbo engine, but the funny thing is you can't find anyone who's actually seen it happen. Keep in mind there are quite a lot of factory turbo engines with no BOV at all (1G-GTE, 3T-GTE, RB30ET) and they don't appear to suffer by its absence.

It's a fallacy. All that happens is compressor surge, and that does nothing except make a funny noise. Manufacturers install BOV's to get rid of that funny noise, nothing more.

[ganador]

This is one of the reasons people cite for using a BOV on a turbo engine, but the funny thing is you can't find anyone who's actually seen it happen. Keep in mind there are quite a lot of factory turbo engines with no BOV at all (1G-GTE, 3T-GTE, RB30ET) and they don't appear to suffer by its absence.

It's a fallacy. All that happens is compressor surge, and that does nothing except make a funny noise. Manufacturers install BOV's to get rid of that funny noise, nothing more.

how old are those engines though. that was in the day when they werent aware of those sorts of turbo problems

[Norbie]

Yes those engines are old, and notably there are still heaps of them driving around without turbo failure. I think this kinda proves the point.

[Mr Ed]

a reversion pressure wave back in the oposite direction ( towards the turbo )
This pressure can cause the compressor to slow so rapidly that its fins can be bent !!
In extreme cases the wave has split intercoolers apart !! with the two waves colliding.

Pft, you cant be serious?!? Are we talking about paper mache ICs here or what??

[ddeane]

Gidday

Maybe to to add a little to the debate. While a lot of early cars did not come with BOVs, I do not that most recent cars to seem to have them. I can't think of any noise that I can associate with not having a BOV when I was running the twin turbo 1ggte, even with 12-14 psi.

I have also heard the 'stories' about splitting intercoolers, and bending compressor blades. I thought that the main reason for our purposes was to stop the stalling of the turbine through back pressure when closing the throttle and having it have to spin up again when you get back on the throttle. In effect it is reducing lag.

Craig

[Norbie]

Maybe to to add a little to the debate. While a lot of early cars did not come with BOVs, I do not that most recent cars to seem to have them. I can't think of any noise that I can associate with not having a BOV when I was running the twin turbo 1ggte, even with 12-14 psi.

Obviously you've never driven a stock VL turbo. Modern cars running more boost and with an intercooler (more volume in the inlet system) would make even more noise without a BOV.

It's interesting to note that the 1G-GTE has a special mechanism to prevent the throttle plate snapping shut too fast, and this seems to be effective at reducing compressor surge.

[JustCallMeOrlando]

loud in what way

Loud in a charge air hitting the spinning compressor wheels way. It almost sounds like a venting BOV

[ganador]

Loud in a charge air hitting the spinning compressor wheels way. It almost sounds like a venting BOV

yeah as youve probly read that aint very turbo friendly haha, BOV a must

[JustCallMeOrlando]

Meh, all 1G's I've seen with a pod filter are similar, the turbos last forever. It's on the list of things to do, but I need to spend the $ to get a decent looking one and I don't have that coin to throw around atm.

[ndgcpr]

I am running some no name brand BOV on mine with about 5 holes around it. like the turbosmart type II. I really believe it has made a difference to my shifts as appose to not having one at all. It sits after the return pipe and slotted right in just above the aircon compressor so you can't even see it. I have also done it up pretty tight and it only opens when i am over 10PSI. So i get 0 flutter, and if i boost a little bit i get 0 noise. it is only if i am really up it, which is what i wanted because i would like to think my car is a bit of a sleeper

I think the 1G runs heaps rich on shifts when you add one though, i haven't really had any backfires though, so i am happy with the setup.

[Endless]

yeah as youve probly read that aint very turbo friendly haha, BOV a must

Did you even bother to read earlier posts!