TiAL BOV - spring determination / resource

[krasuskyp]

My shop determined my TiAL BOV is opening @ idle and I need a stiffer spring.

They're in process of getting back to me on ID'ing what's in there - any suggestions on how to ID or will it be self-evident upon opening it up?

Any suggested resources for a stiffer spring? I do like a good stiff one ya know...

[krasuskyp]

here's what came out - no identifiers other than maybe some shinier black areas?:



bueller...

[lite75]

Looks like that's a .4 bar. What style of Tial are you running?

https://www.verociousmotorsports.com/Shop-by-Brand/TiAL-QRJ-Boost-Control-Valves-and-Accessories/TiAL-Blow-Off-Valve-Springs

[krasuskyp]

thanks for the response!

I'm not sure, I got it from the forum classifieds years ago lol

it's black anodized (not in front of me to get a pic at the moment unfort), looks like a typical Bosch 710N (like from a 996tt) but in aluminum and larger not plastic and smaller... three ports

[icemann427]

Originally Posted by krasuskyp

My shop determined my TiAL BOV is opening @ idle and I need a stiffer spring.

I can't even believe that Ronnie gave you a pass on that one!!

[908/930]

Opening at idle or just not able to close properly? Did the valve seat get deformed?

[Utopia]

Chinnese Tial, perhaps??

[xbmwguy]

Paulie glad to see you got that sorted out. Call Daren at race part solutions. He has every spring known to man. He sent me 4 different spring rates to try then sent the others back.

[krasuskyp]

FRANK!

Tx man, will do now!

that former white 930 Daren in FL right?

[908/930]

Just trying to figure out why your shop thinks it needs more spring to help keep the valve close at idle? Next post answered my question, thanks 76 911s.

['76 911S 3.0]

BOV springs are rated in negative pressure or inHg. The spring refers to the negative pressure required to overcome the spring pressure and open the valve. Based on this chart, not entirely sure which Tial you have, but the black spring will open at any negative pressure less than -6 or -7 psi (or -8 to -13 inHg). If you engine vacuum is less than -13 inHg (most street engines will be in the -15 to -22 inHg range) then your valve will be open at idle.



Pick a spring a is just below your idle vacuum value so as as soon as you snap the throttle shut, the BOV opens to relieve the excess intake pressure but then quickly closes when the engine returns to idle.

[xbmwguy]

Paulie yes that Daren. I had same problem even it really isn’t that big a deal except for tuning idle so it helps to have the system “ sealed” so to speak

[krasuskyp]

awesome thanks so much everyone!

FRANK! Tx for the Daren referral, he overnighted me some options yest - fingers crossed I'm almost there...

will report back via my other thread w/ update as incurred... tx again all, hugely appreciated as alwayz...

[993Speedster]

I had the same issue with the pre-fit spring in my eBay Tial knock-off. Stock cams idle smooth and pull enough vacuum to open the blow-off at an idle or on decel. Since most of us with EFI are speed density tuned and don't have a mass airflow sensor metering the air pre-turbo, it's not too much of a detriment. HOWEVER this is not the case with CIS and in addition, while it's hanging open and not ejecting air, it's actually ingesting unfiltered air into the engine.

[16Volt]

Do you not have a wideband in the car? Just curious as you would have seen it running lean at idle I would imagine.

[krasuskyp]

yeah Shannon I do but my sensor is on the fritz and it's on again / off again right now

but yeah, my idle AFR was always super lean (16-18) which I didn't mind but never really thought about why (d'oh)... I'm now 13's, annnnnnd relegated back to the 10-11mpg club 8-)

[16Volt]

Congrats man!