69 replies to this topic

[kingbarley]

what if i want to put three blowoff valves in my automatic n/a 850 volvo? will that make the girls panties fly off?

[...]

it just might

[Snabb T5M]

So how does one choose what size BOV to get? I'm looking at a Turbosmart recirculating BOV and they come in 32mm and 38mm outlet sizes? What size outlet do you get?

[ozzimark]

Needs to be big enough to flow enough air to keep the compressor to the right of the surge line when the throttle is closed suddenly. If in doubt and you're not up on your fluid dynamics, go with the bigger one.

But basically, figure out what your compressor wheel speed is when WOT, worst case. Then figure out where that wheel speed meets the surge line, then you know how much flow at a given pressure drop the thing has to be able to do, assuming you know what else the air is flowing through to get there (before or after IC, how many bends, what ID tubing, etc..) If you know the valve diameter and Cv, you can do some ballpark estimates on whether or not it'll flow enough.

[850wagonT5]

leroystew, on 18 April 2011 - 03:28 PM, said:

So how does one choose what size BOV to get? I'm looking at a Turbosmart recirculating BOV and they come in 32mm and 38mm outlet sizes? What size outlet do you get?

On a small turbo like a TD04-18T, it doesn't really matter. However, 38mm seems to be the most common size.

That said, I use an eBay GReddy ripoff on my car. 38mm as well.

[Snabb T5M]

Well I got the spring assortment for my Forge CBV so will see if I can dial in the CBV a lil better. Thanks for the feedback on choosing a BOV.

850wagonT5, on 26 April 2011 - 06:07 PM, said:

On a small turbo like a TD04-18T, it doesn't really matter. However, 38mm seems to be the most common size.

That said, I use an eBay GReddy ripoff on my car. 38mm as well.

[ndst5993]

Sorry if I'm mistaken here, but in my 87 745T, (and my saab 9K aero), the cbv offers bypassed air back into the intake tract, right before the TB. Isn't that to reduce spool time in situations where its opened quickly? (like between shifts)? Whereas a BOV just dumps that air back to atmosphere?

[T5Hammy]

ndst5993, on 18 June 2011 - 05:04 AM, said:

Sorry if I'm mistaken here, but in my 87 745T, (and my saab 9K aero), the cbv offers bypassed air back into the intake tract, right before the TB. Isn't that to reduce spool time in situations where its opened quickly? (like between shifts)? Whereas a BOV just dumps that air back to atmosphere?

I'm no expert but it should recirculate air from between the turbo and TB to between the MAF and turbo, in other words since the MAF has accounted for the air already this keeps its calculations correct and therefore prevents improper AFR's. If you dump the air via BOV that has been measured already the MAF has no way to recognize this, but if the car had a MAP sensor instead a BOV causes no problems since the sensor will register the drop in pressure. As for spool I don't believe its really effected, but it may make a small difference. If i'm completely wrong someone please correct me.

[ozzimark]

Pretty much spot on. Spool won't matter unless it's leaking; the CBV/BOV should be closed when you're on the throttle.

[JN2k108]

STiKiller04R, on 12 May 2010 - 10:18 PM, said:

is there a place to get the blocking plate for a k24 P2 R and a y pipe for the bov? if so could you please pm me por fav or

Viva should have it