does your BOV open when you chuck a rev?
 

Some guy i know came to me the other day asking about his turbo set up. I dont know much about it, because he had it installed by someone else and even he doesnt know much about it. Anyway, when he is standing still and just chucks a rev, the BOV doesnt seem to open, or you cant hear it at least. I know i have heard cars just chuck revs and blow off. what do you think could be causing it?

He said the turbo is from a saab, which makes me think its probably a T3 or something. and its the stock Saab actuator (10 psi?) he lengthened the arm to reduce the boost. thats all i really know. what do you guys think?

Re:does your BOV open when you chuck a rev?
 

you have to get the car under load to put it in boost, and it blows off when it is in boost

Re:does your BOV open when you chuck a rev?
 

hahaha im really liking ur sig scott

like scott said only under load unless u got a tiny turbo

Re:does your BOV open when you chuck a rev?
 

mine is open at idle ???

Re:does your BOV open when you chuck a rev?
 

Some BOV's open a bit at idle. completely normal. What he's talking about is when your rev in idle, it doesn't make the *PSHSHSHSHSHshshofadshpoaisuydhflkhshshshsh sound when you drop the gas.

Re:does your BOV open when you chuck a rev?
 

yeah ive seen lots of cars thatll blow off right above idle...

Re:does your BOV open when you chuck a rev?
 

Well it all depends how small your turbo is.A t3 42/48 will not build boost unless its under load.Its just to big(on a d)to spool in neutral.Mine wont do it unless Im boosting under load.

Turbos like an rhb5,te04h,..I think even a t25 will do it in neutral with no load.That becouse thay are so small that they spool pretty much instantly.

Thats weird.All the Saab turbos Ive pulled(5) all came with adjustable wastegates.

Re:does your BOV open when you chuck a rev?
 

it all depends on the sizing and flow of the turbo vs. engine output...

sounds stupid but that's all; the bov will open (normally) if it sees vacuum from it's vacuum source, then it opens.

if you rev the crap out of the engine in neutral (fucktard)
and the bov doesn't swoosh then:

#1 you're a ------- idiot and should quit wasting your money.
#2 the turbo isn't building any boost in that short ascent to engine heaven.

I think people don't realize how much TIME plays a part in turbo theory...

Re:does your BOV open when you chuck a rev?
 

All depends on how big your engine is compared to your turbo. When I had a tdo4 on my f22 it would blow off when sitting there and when I swapped turbos and put the 14b on it no longer really went off at idle. All about turbo size and the engine.

Re:does your BOV open when you chuck a rev?
 

I can't wait to put my RHB5 on there then. I will blow off at anybody. ;D

Re:does your BOV open when you chuck a rev?
 

blow me off baby

Re:does your BOV open when you chuck a rev?
 

it also depends on your plumbing, if you have really long pipes routing across the entire front end of the car and through an intercooler you probably wont get any pressure.
but if you have one short pipe with no intercooler going straight to the throttle body you are sure to get better pressure and have less pressure drop. in turn this will make the pressure build up much easier under no load.
with longer pipes and biggar intercoolers, you need to really work the turbo to get pressure under no load.

Re:does your BOV open when you chuck a rev?
 

very true. Good point turbo-dan.

Re:does your BOV open when you chuck a rev?
 

I know you can hear a SRT-4s BOV very easily, all you have to do is rev it up to say 1500 and let off, PSSHHH/.

Re:does your BOV open when you chuck a rev?
 

just my 2 cents... i have a t3 from saab 9000 for now and if i rev to about 6k and hold about 1-1.5 secod then depress accelerator then i will hear PSHHH. =)

Re:does your BOV open when you chuck a rev?
 

My inlaw's STI having very short piping and a relatively small turbo for a 2.5 liter engine, will open up the HKS BOV in neutral if revved over 4k. In comparison, my civic with a FMIC, large T3/T4 and and a 1.8 liter won't produce boost if not under load.

Re:does your BOV open when you chuck a rev?
 

maybe the blow off valve is to strong and just isint opening and hes getting backspin on his turbo?

Re:does your BOV open when you chuck a rev?
 

it takes TIME to produce boost or a bov sound...example:

you quickly rev the engine in neutral and the bov does not sound; this is because the turbine in the turbo has to be sped up or accelerated via constant and increasing amounts of exhaust gas. This in turn spins the compressor which needs a certain amount of shaft speed to produce boost(duh). It also takes a few moments for the intercooler and charge piping to be filled with pressurized air once the compressor is rotating fast enough...

therefore, with the short amount of time that you stab the gas pedal, the amount of exhaust produced by the engine isn't enough to spin the turbine/compressor up to speed AND fill the charge pipes with compressed air... Other cars with larger engine/smaller turbo combinations DO produce enough exhaust to "spool" the turbo up with a quick rev. Get it?

So you (or your friend) need to figure out at what rpm the turbo starts making boost under load. Let's say it's 3k rpms. So in neutral, you want to HOLD the rpms at 3k for a couple seconds(count one mississippi, two missi...) then quickly stab the gas to about 5k rpms and completely let of the gas. Since the turbo was spooled up to begin with(via 3k rpms of exhaust flow) then when you stab the gas it will be able to spool faster and produce the sound you want...

there.. that's all there is to it... now let this topic die please.

Re:does your BOV open when you chuck a rev?
 

hahaha, not true buddy, even at idle you turbo is spinning right? so on some cars, with the right bov, you can get it go off by tapping the gas. I've seen this before.

Re:does your BOV open when you chuck a rev?
 

stfu