tial q bov on ecs kit open or closed at idle?

[malscott]

fired the car up last night, (finally) after checking and rechecking everything and i noticed that at idle the bov is fully open and letting air push out, i did some google searching and there is a lot of varying opinions on this some say should be open at idle and fully closed as you stay in the throttle and some say should be closed all the time and only open when you come off the throttle and the forced air is pushed out the charge pipes. I know i can just change the spring but upon further research i see some people saying that the weaker spring is better for the centri and a heavier spring is only used for a turbo. I did blip the throttle for just a second, the bov remains open and only closes when the rpm's drop but it opens back as the rpm's levels off, is this normal?

[Unreal]

Thats exactly what it should do. It needs to act as a bypass to let the air go somewhere when not going into the motor.

[RealQuick]

BOV

Idle - open
WOT - closed
Let off the gas after WOT - open

[Unreal]

On a blower it acts like a bypass valve. Turbo is load dependent and slows down so it barely moves any air, so it can be closed at idle with at turbo since the load is so low. Blower still moves a lot of air at idle, and it has to go somewhere. If you have it closed, it just rams into the shut TB, and you get reversion across the maf, and drive-ability issues.

[malscott]

Originally Posted by Unreal

On a blower it acts like a bypass valve. Turbo is load dependent and slows down so it barely moves any air, so it can be closed at idle with at turbo since the load is so low. Blower still moves a lot of air at idle, and it has to go somewhere. If you have it closed, it just rams into the shut TB, and you get reversion across the maf, and drive-ability issues.

Thanks bro for clearing that up for me, i was reading so many different opinions last night that i got a confusion headache-lol now that you explained it that way that makes perfect sense, i kinda had that idea in my head but wasnt sure, i know that pd blowers have a bypass valve for that reason so the air has somewhere to go at idle/not in boost i really appreciate that

[SSE 4 2SS]

Nice explanation Nick...

To add to that from the other side... Blowers slow with engine RPM's where as turbos have substantial inertia with no braking action other than air resistance..

In a turbo application, suddenly shutting the throttle leaves a huge amount of air pressure energy with nowhere to go... Hence the big Psssshhhhh, when lifting suddenly...

As an aside, as you pulley down in the future the air escaping will increase... There's a vette in our shop with a pretty big centri blower with a substantially over driven blower... Sounds like a huge air leak at idle...

[malscott]

understood, thats exactly the sound im hearing....like an air leak, i never thought of a bov in terms of operating like a bypass valve but, then again this is my first centri install.

[Unreal]

Which is also why big blower cars, and cars pullied way down have 2-3 BOVs. I run twin tials and may add a 3rd.

[malscott]

gotcha...i have heard of people running two bov's on big centris and never understood why, matter of fact my friend with a cobra had a d1 and kept talking about adding another one but sold the car before he did

[SSE 4 2SS]

Originally Posted by Unreal

Which is also why big blower cars, and cars pullied way down have 2-3 BOVs. I run twin tials and may add a 3rd.

That's what we refer to as overachieving...

[malscott]

wait a minute, i just saw a couple of camaros on youtube with centri blowers and it looks like the bov is closed at idle....what up wit that?? Also if the vacuum holds the bov open at idle, why doesnt a turbo car do the same thing, is it just because of a different (stronger) spring in a turbo application?

[malscott]

or is it that a vacuum connection is not used on a turbo application?

[Unreal]

Stronger spring, and people with it closed at idle are just doing it wrong, or sacrificing blower life/idle/driveability so it doesn't make a hissing noise at idle.

[malscott]

Originally Posted by Unreal

Stronger spring, and people with it closed at idle are just doing it wrong, or sacrificing blower life/idle/driveability so it doesn't make a hissing noise at idle.

gotcha bro, one more question so i assume ecs already installed the correct spring for my application or should i measure the vacuum and check the spring myself?