DOUG @ ECS

This is a question that I am very frequently asked so I figured I would put up a thread regarding it to hopefully help some of you with your decision.


First thing to understand is that whatever spring pressure you use does not effect boost levels on a blow off valve. Only a waste gate is effected by spring rate as far as boost levels go.

Spring rate will effect noise level, the lower the spring rate, the lower the noise level will generally be due to the valve opening more/faster. So if your looking for the quieter set up then the 3# spring would be for you along with the QR BOV.

Downside to using the lower spring rate;
How the BOV works is when the engine reaches 3#'s of vacuum (with a 3# spring) the valve will open, where as a 10# spring will open at 10#'s. So during WOT shifts you will retain more boost, or all the boost on shifts if your fast enough, when using a higher spring rate.

We will usually use a 10# spring for cars with a stock or near stock cam shaft, but if you have a radical cam that barely makes 10#'s vacuum at idle, then you will need to go with a lower spring rate so the valve is open during idle conditions.

Downside to using a higher spring rate;
You will typically see slightly higher IAT temps with a higher spring rate due to the car going into boost earlier, but I have not seen enough of a downside on that end to over come the power difference.


I tried to make the post as basic as possible so it's easily understood, but if you wish to add to it, by all means go for it.

robert miller

Great info man. Robert

Mike04

Thanks for the info

ChargedGN

Good timing,

Recently got my car back from ECS and not really liking the amount of noise from the BOV, actually had a car infront of me start to pull of the road as they must have thought I had a siren or used the horn on them after a 1-2 shift

And if my guage is right I seem to hear it open at around 15-20#'s of vacume


Is there a significant noise difference between the 3 and 10# spring?

Are there quieter BOV's with a 10lb spring then the Tial?

Trying to get used to the noise but I like to fly under the radar when driving around

WayneCar

Great info from ECS. As usual.
Thanks
Wayne

rzmnco

Great thread and clears up a lot of confusion.

Z06supercharged

I have a 3# spring and its insanely loud at very little throttle. I couldn't imagine it being louder than it is with a 10# spring.

Here a video how loud it is shifting very little throttle at 2500 rpms. It can be hellish loud if I wanna scare the hell out of pedestrians walking anywhere nearby or even other cars if I time it just right with rpms and shift. I've even had some people swerve a lane over on freeway occasionally probably thinking a jet was about to land on them. Everyone says my car sounds like a jet coming down the road just cruising and the loud whoosh on top of it shifting makes it even more hellish sounding. Had many people tell me they can hear my BOV on the freeway going through the gears over 1/4 mile away not even in wot. WOT is insane sounding all around with the B&B Bullets and loud BOV.

https://www.youtube.com/watch?v=sMN1...e_gdata_player

Quickshift_C5

Anyone have a video of what these things sound like? I'm curious!

0Matt @ ECS

We do have a Tial Qr valve that is quieter than the Q's... If you want us to swap it please just shoot me a quick email (matt@eastcoastsupercharging.com) or a call, and we'll get you scheduled in. There will be NO charge to swap the BOV for you, we want everyone to be satisfied.

- Matt

0Matt @ ECS

It does sound really good though ! Yes with using a 2 or 3psi spring you effectively make it a bypass valve where the valve is consistently open during any off-boost throttle driving.

robert miller

Great shop to work with for sure.. Robert

Z06supercharged

Even with a 10# spring its a bypass valve off-boost cruising and light throttle.

5 Liter Eater

Sorry guys but I have to disagree with this. It's correct from a sound perspective but technically not correct. As mentioned if you put a 10# spring in it will not start to open until 10# or 20"hg of vacuum. The BOV should be open any time the blower wants to make boost and the engine is not able to injest it because the throttle is ~closed. So if you are cruising at ~2500 RPM the blower is flowing enough to be making some boost if you were WOT but since the throttle is relatively closed and the manifold is at say, 15"hg or 7# of vacuum, the BOV is closed and the air in-between the blower and throttle blade has no where to go except back through the blower which is exactly what the BOV is supposed to prevent.

The 10# spring is "quieter" because it's closed more often and really only opening in-between shifts, maybe at idle with a stock cam that idles @ ~20"hg. It's not blowing off while say driving through a parking lot.

From my understanding with a centri blower the BOV should be open until just before crossing over into atmospheric which the 3# or 6"hg spring accomplishes. This is certainly not the letter of the law and open to debate but I'd say bottom line is, if it's not open at idle then the spring is too strong.

DOUG @ ECS

The lower spring pressure opens the valve more and faster, where the additional noise comes from is when the valve is just cracked and the air flow is rushing threw a smaller opening. The 3# spring would have the valve completely opened way before that point lessoning the "whoosh".

So we will have to agree to dissagree.

MVP'S ZO6

I have a 6lb spring and it's crazy loud. Ordered right from ECS. Quick and easy!

http://www.youtube.com/watch?v=as6IE...e_gdata_player