blow off valve / bov question

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MA70_Powa

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Jun 17, 2007
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well I'm pretty sure it is surge because I've listened to clips of it on the net and mine sounds just like it. If I ease of slowly I get a psssccch and then flutter, but if I take my foot off its much louder and sounds more like the 'tukey wobble' noise that people describe.
I'd record it myself but dont have a video camera :(

Also I called up turbosmart and they said the bov isnt supposed to flutter at all, and that I've probably exceeded the limits of that bov...

I noticed a bit lower vac reading at idle last night - 18-19 instead of 21 (along with a 450 rpm rough-ish idle) that wasnt there before I got my wastegate changed over so I'll check all my vac lines again and maybe put some bigger ones on in places.. see if it helps at all. But hopefully I'll get the knock-off ssqv on there soon.
 
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Poodles

Poodles

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Jul 22, 2006
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OK...

Gonna be a bit complicated, and I'm trying to keep it short.

- The BOV line is a dedicated line stock.
- Fuel pressure regulator should NEVER share a vacuum source.
- You're missing the warm start VSV
- You're missing EGR

Now, I dunno if you're supposed to have EGR as I'm unsure if the engine is original, ect... The engine's vacuum setup is far from ideal in it's current setup...
 
M

MA70_Powa

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I have a JDM engine so no EGR for me.

I'll try and fit that metal vac pipe thingy that usually goes to the vsvs and connect my vac hoses up to that... however wouldnt that be the same as having them Td into each other?

how am i supposed to get a dedicated line to the bov? Looking at the vac line diagram on cygnus I see no hose going to the vac tube the bov uses... I've tried looking at people's engine bay shots but can't see where the vac hose goes :(

I'll have a look in my parts boxes again to see if I have the vsv in there (ive got 4 to go thru :S)

Also is it normal to be able to hear the vacuum near the front of the intake manifold? it's quite loud from there so I just wanted to make sure its normal.

Thanks for the help so far!


EDIT: found this pic on cygnus of the bov vac routing: http://www.cygnusx1.net/Supra/Library/EPC/291420/catalog.aspx?F=2211&P=2

but where does the hose go from there?
 
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Poodles

Poodles

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Jul 22, 2006
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- Do you have a JDM ECU?

- No, as the BOV is dedicated to that one line on the front, and the FPR is connected to the port on top of the throttle body. Looks like you also have a charcoal canister so you're missing another port (need the right throttle body and it makes me think you should be running EGR as well)

- Shouldn't hear the vacuum, the line to the FPR is a much smaller line stock, so it's probably leaking. The line for the BOV goes from that port on the front, to the pipes under the intake manifold, to up through it, to the pipe on the 3000 pipe, over to the BOV.
 
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MA70_Powa

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well as far as I know, no aussie ones have egr (correct me if im wrong someone?). i do have a jdm ecu too and I have seen another jdm engine bay with the same TB as me.

I asked the guy I bought the engine off and he gave me everything he had in his car ( so I hope i do have the vsvs...) I didnt ask him about the charcoal canister though...Maybe the charcoal canister is there from my n/a motor and it didnt get taken out? I'll have to PM that guy again.

thanks for outlining the bov vac lines, I think I get the idea...

guess I'll have to buy some different sized vac hoses and start fixing things!
 
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MA70_Powa

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I'm awaitng replies and photos from people on the aus forums... in the meantime I also realised that my wastegate is hooked up to the intake manifold - which i gather is a bad thing... so thats another thing to fix!
 
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MA70_Powa

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Jun 17, 2007
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Ok, after getting some help on the aussie forums, this is my current setup. I'm bypassing that vsv which I don't have with a loop of vac hose for now. Just how important is that vsv?

p1152266_1.jpg



Comments?


My bov now has much stronger vac to it and my compressor surge has almost disappeared! yay! only thing is my boost stays at 6-8psi for a lot longer now before hitting 9psi :( lame.. do you think thatll go away when I fix the wastegate line?
 
M

MA70_Powa

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Jun 17, 2007
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OK an update for you. Got my wastegate vac line sorted - I got a bung welded on my IC pipe right after the compressor outlet on the turbo.
The vac line runs back to the firewall, across towards the engine then down to the wastegate to avoid being melted on the turbo or manifold - is this too long? I could *try* to make it shorter I'm just paranoid itll melt.

Also, my boost gauge shows 6psi when I hear my wastegate open (9psi spring)... does that mean I have a 3psi drop through my IC pipes? or does it just open earlier?

It seems a bit odd though because from 6 it goes up to 8 before peaking at 9psi eventually - and sicne I fixed my vac lines and everything my boost rpm range has risen - was 9psi by 3000 now its 9psi by like 3500 i think (maybe more ill have to pay closer attention).
 
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