boomer123

I have a procharger on my 05 gt....I LOVE this sequential blow off valve sound....but i need to figure out what bov this guy has on here or how he is making that sound when he lets off the gas. SO please let me know if you have any idea how to get that sound, thanks!

http://www.youtube.com/watch?v=OynGD...om=PL&index=41

mustang51js

i think you need more boost, my car never made any noise from the BOV untill i put a intercooler and smaller pulley,its still the stock BOV that comes from vortech.

FoxGT

That sound is caused from lack of a bypass/bov, one connected wrong or broken. If you hear it, it means something is wrong, or in this case, very wrong. You can usually tell when someone doesn't know much about what they're doing with forced induction if you hear that noise.

The sound is surge.
When the throttle plate is closed pressure ramps up between the impeller & throttle plate, since there is no exit for the air it goes back in the way it came. I'm sure you can imagine if you were running 10psi & the throttle plate slammed shut causing the pressure to ramp up to 60psi in an instant, it can be damaging. This causes belts to wear faster, stress on the bearings, & a risk of damaging the impeller/throttle body/intercooler.

On a setup with a small intake plumbing volume it's not so noticeable, so if you have large intake plumbing after the turbo & a decent sized intercooler, you'll notice it a lot more. The bigger the intake plumbing volume the more important it is to have a bypass or bov.

Fobra

haha - what an idiot (owner of that car)

mustang51js

so you think i need a new bov,like i said i just put the intercooler on and havent had it tuned yet, i will be getting it tuned next wensday, but if i hit the throttle you can hear it when i let off. Its still the stock one but now i should have more boost,should i change the bov.

boomer123

Thanks for the info FOX, but ive heard 2 different sides to this sound. A lot of people said the same things you said, but others said it is a sequential bov...meaning it shutters as to not let all the boost out of the system. So if your shifting from 2nd to 3rd and you put in the clutch and let off the gas...instead of going back down to 0 boost, it may only go down to 6 psi, which makes it more efficient in the fact that the supercharger doesnt have to build up the psi from 0, but rather 6. In a racing environment ive heard sequential bovs are more beneficial because it only lets out the back pressure necessary. Thats just what others have told me....im no expert on boost or forced induction lol

luckythirteen13

fox is right, that stuttering sound from the bov means its too small. sequencial blow off valves do not stutter like a retarded 3rd grader, they make one woosh sould like any other bov. any time i hear a stuttering bov i just laugh

FoxGT

Depends. It's not mandatory that you have a valve on at all, but it puts a lot of stress on parts. Ideally you want to aim for having no flutter at all. Having too small of a valve is a lot better than having none. Since you have a supercharger & boost is controlled by crankshaft speed there isn't a performance gain, it's all for durability. For turbo cars there is a performance gain as well as durability because the impeller loses speed very quickly without one, if it loses enough you will have to spool the turbo(s) again after every shift. Chances are you won't need to change it. There are still cheap options though even if it isn't big enough. I've built one setup using two 1st gen dsm valves because one wasn't big enough. Not bad for $10 a piece.

the sequential valves help combat surge more. Some standard valves do it at low boost because the pressure isn't enough to overcome the spring pressure so the pressure goes back towards the turbo, but they work well at moderate or high boost. Sequential valves are made to work in low or high boost situations with one chamber for low, one for high. Whether they're worth the cost is up to you, I've always favored single chamber ones primarily because I don't think the added cost is justified since at low boost parts aren't stressed very hard.

The fluttering sound is indeed an indicator that it's preventing the boost from escaping, what that means is that instead of the boost in the intake venting off to somewhere it's building up which causes a strain on the supercharger or turbo. In the case of a turbo that pressure build up is slowing the impeller because of the resistance whereas if it was escaping there would be no resistance and the impeller wouldn't slow down nearly as fast, which means the impeller is still at a decent speed to help build boost after you get in the next gear. With a supercharger it's belt driven so you will still have boost if crank rpm is still high (providing the belt isn't slipping). Ideally you want the pressure between the turbo & throttle body to be as low as possible when the throttle plate is closed.

mustang51js

[QUOTE=FoxGT;6635186]Depends. It's not mandatory that you have a valve on at all, but it puts a lot of stress on parts. Ideally you want to aim for having no flutter at all. Having too small of a valve is a lot better than having none. Since you have a supercharger & boost is controlled by crankshaft speed there isn't a performance gain, it's all for durability. For turbo cars there is a performance gain as well as durability because the impeller loses speed very quickly without one, if it loses enough you will have to spool the turbo(s) again after every shift. Chances are you won't need to change it. There are still cheap options though even if it isn't big enough. I've built one setup using two 1st gen dsm valves because one wasn't big enough. Not bad for $10 a piece.


So i have 2 stock vortech bov's,could i run one right after the other in line or am i better off getting a new one.Right now my car sounds like the one in the vid and my boost gauge jumps up and down,all this is below 3000rpms because i havent got a new tune yet, i go tomorrow for that but im still going to take it easy at first until i know im safe.

sadface

http://www.youtube.com/watch?v=VbNxugO-uf0

is what u need