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Join Date: Jan 2004
Location: Sacramento
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BOV location and size?

Anyone seen any recommendations as to where the BOV should be located and how to properly size it?

If it is to small undue pressure might be put on the Turbo.

If it is to big and located before the intercooler might the pressure drop between shifts more than we want and add to lag.

Or maybe it dose not really matter.

Just wondering.
Old 01-20-2010, 06:16 AM
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Found this on the Getty site so maybe there is somthing here to think about:

" Blow-Off Valves

GReddy Blow Off Valves are easily adjustable to eliminate compressor surge and preventing premature boost leakage, while increasing boost response between shifts. Each valve is made of durable cast and billet aluminum frame and the valve to diaphragm ratio provides performance that cheap piston types cannot offer. The spring stiffness adjustment screw and the three different sizes give the GReddy user the option to match vehicles with mild upgrades to heavily tuned engines. There are many factors in matching a blow-off valve to an application, valve location, turbocharger size and pressure, but as a general rule of thumb, we recommend the Type RS for 100-400hp, Type R for 260-450hp and the Stiff Spring Type R for over 400hp applications. Also available in easy to install kit form for many turbocharged vehicles."
Old 01-20-2010, 06:27 AM
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I thought the "adjustable" part had to do with when the valve opens. Is it for setting how much the boost pressure is bled down to so there is less recovery needed between shifts?
Old 01-20-2010, 06:31 AM
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Found this on a Garret site:

"Blow-Off (Bypass) Valves
The Blow-Off valve (BOV) is a pressure relief device on the intake tract to prevent the turbo’s compressor from going into surge. The BOV should be installed between the compressor discharge and the throttle body, preferably downstream of the charge air cooler (if equipped). When the throttle is closed rapidly, the airflow is quickly reduced, causing flow instability and pressure fluctuations. These rapidly cycling pressure fluctuations are the audible evidence of surge. Surge can eventually lead to thrust bearing failure due to the high loads associated with it.

Blow-Off valves use a combination of manifold pressure signal and spring force to detect when the throttle is closed. When the throttle is closed rapidly, the BOV vents boost in the intake tract to atmosphere to relieve the pressure; helping to eliminate the phenomenon of surge."


Putting the BOV after the IC might increase its capacaty as the air will be denser there.
Old 01-20-2010, 06:36 AM
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I put mine between the compressor and the IC. Works great, fantastic in fact. If you've got room, put it between the IC and TB.
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'86 930
DTA P8Pro ECU - Synapse BOV - 60# Siemens inj - K27HF - Dual GHL - Kokeln IC - Elgin SC330 cams
http://www.flickr.com/photos/86_930/
Old 01-20-2010, 04:50 PM
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And I am kind of guessing bigger is better as the turbo would stay spinning faster with the least amount of resistance.

Norm,

What do you think about the Synapse BOV. I had my std BOV rigged to stay open at curse years ago and I think that is what the S-BOV dose???

Do you notice faster boost off idle and cruse?
Old 01-20-2010, 05:46 PM
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My turbo system flows almost 900 cubic ft/min. I really like the action of the Synapse and it fits better, because of its shape, in my application. There are two ports. One is for vacuum, the other for boost connection. The BOV reacts very fast off idle or cruise. I believe it is tunable but I am not sure how people have accomplished that.

My engine management system used to go into epileptic fits when the TB closed. My throttle response is totally improved now. The high flow turbo stays spooled. Transition between gears under boost is superb.
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'86 930
DTA P8Pro ECU - Synapse BOV - 60# Siemens inj - K27HF - Dual GHL - Kokeln IC - Elgin SC330 cams
http://www.flickr.com/photos/86_930/
Old 01-20-2010, 06:26 PM
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Do you have both ports hooked up?

Sounds like a monster. HP@Boost?
Old 01-20-2010, 07:41 PM
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