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Tial BOV spring?

Marvelous3

Who engineered this?
Joined
Nov 12, 2002
Location
Atlanta
Riddle me this...

The Tial BOV I have on the red car came stock with a plain spring which says it is 11* for 18-20" vacuum. The red car pulls like 9-10" of vacuum at idle so this spring was way too stiff and causing compressor surge. I ordered a 7* spring for 8-13" vacuum yet was still getting compressor surge. I cut the 7* spring shorter and shorter trying to get it to work right but I was still getting surge. I eventually cut it so short that it was working but the BOV would remain open all of the time. I then added some shims to so that the BOV would stay closed while driving but the compressor surge is back. wtf.

If I boost it and let off vacuum will spike to 20" so there should be plenty of vacuum to pull the valve open. I do only have a smaller vac line running to the bov so maybe when I let off the vacuum is collapsing the hose? It's the only thing I can think of at this point.
 
Is your hose made of regular rubber or silicone? The silicone ones tend to collapse more under negative pressure.
 
idk? In park it's 14-15" but in drive it's only 10".

I'm pulling 18-19" at idle with ym 16V head and regular cams once the motor is hot... I just checked and my Tial BOV vacuum hose is 1/4" but it is rather long cause it's running from behind the right side headlamp over the intercooler and connects under Nathan's made intake so like a least 4 feet.
 
My intake manifold only really has 2 ports for vacuum. One I have dedicated to the map sensor only. The other I have two plastic T's in that connect to the fpr, bov, boost gauge and stuff. I'll look at it when I get home. I can't remember what all is t'd into what.
 
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I have a tial knock off, I have one big vac line going to a t on the driver's side of the head and from there it references the for,wastegate,boost gauge, and the bov with no issues. Are you sure the diaphragm is in good shape and nothing is causing the piston to hang up?
 
I have the map sensor on it's own line to the intake manifold.

The BOV is T'd into the FPR, and boost gauge.

I have the boost controler beteen the line that goes from the wastegate and the turbo.

All of these lines are 3.5mm but the BOV line is supposed to be 1/4".
 
Would it be a bad idea to t into the brake booster line instead? It's certainly big enough. I'm trying to avoid drilling a new port into the intake manifold.
 
I would out the correct size hose in a see if it fixes the problem. Tial has a large piston and needs a lot of volume to to fill that chamber.
 
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