Blow off valves and waste gates

[jc71corvette]

Hey im getting into the import stuff, and cars in general. I have a question about the two parts. Is the blow off valve part of the waste gate? Or are they two differnt things. From my understanding, the wast gate lets out any excess gases before it enters the turbine. Im really sorry, I should know this stuff already but I must have missed some things and details.

 

[GVR4592]

The wastegate vents exhaust gas to regulate boost, it can be vented pre turbo, or at the turbo itself. The blow off valve relieves intake pressure when the throttle closes, so the pressure doesn't get trapped and spin the turbo backwards.

 

[MyBeatGSX]

www.howstuffworks.com for the detailed answer

Quick answer...

The BOV opens to vent excess boost whenever you let off the throttle (makes that phssst noise). When you let off the gas the throttle closes and air backs up and if not vented it can hurt the turbo (called compressor surge, sounds like a chug when very bad and a flutter when mild). The BOV opens at this point and lets the boost vent out before it can damage the turbo. The BOV is usually located in the intercooler piping or on an intercooler end tank.


The wastegate controls boost pressure by bypassing exhaust around the turbine to slow it down. When the set boost is reached, it pushes the wastegate open which deverts the exhaust and keeps the turbo from spinning any faster and over boosting (when this doesn't work, we call it "boost creep", when it doesn't open in time we call it "boost spike"). The wastegate is located in the turbine (internal) or on the manifold (external).

 

[jc71corvette]

Ok, thanks. So from what you said, they wouldnt give any HP gain?
Now is it that BOV or the wastegate that gives you that fast "air" sounding noise?

 

[goalieman24]

Ok, thanks. So from what you said, they wouldnt give any HP gain?
Now is it that BOV or the wastegate that gives you that fast "air" sounding noise?

Although not much of a HP gain, an aftermarket bov is beneficial if you have the crappy stock 2g one which leaks with little boost.

The fast air noise is the blowoff valve

 

[jc71corvette]

ahh okay! u posted like right b4 i posted above, heh

BOV= gives that noise and releases the gases that is not currently needed now because you let down on the accelator

aight ty

 

[MyBeatGSX]

That's the BOV that makes the noise everyone likes.

The wastegate (when dumped outside the exhaust) makes a deafening and awful noise that no one likes.

No they won't give you a power gain. You can use a boost controller to change the signal to the wastegate and make it stay closed longer. That gives you more boost and more power.

 

[oldman]

Don't Vent That Bov!!!

 

[jc71corvette]

So thats all that boost controllers do, is regulate when to close and open your wastegate? Which in tern (if open) spins the turbine faster but you don't want to fast for the turbo.

 

[MyBeatGSX]

Other way around. Wastegate closed makes it spin faster. When its closed, all exhaust is powering the turbo. When its open, it lets much of the exhaust go past the turbo, thus slowing it down. Yes, too fast is not good. The faster it goes the most boost you get, too much boost = motor goes boom. WAY too fast makes the turbo go boom.

And yes, that is all boost controllers do. Very simple huh?

 

[jc71corvette]

Yeap heh. Im getting there. Heh

Do you have to leave your car ideling for 3 minutes or so when your done driving?

 

[MyBeatGSX]

Yes. How long is debatable. My turbo timer is set for 1 minute for regular driving, 3 minutes if I've been boosting or just came off the highway.

Use common sence. If you drove from your house to the store 2 miles away without hitting boost once, you probably don't need it at all (or like 30 seconds to be safe). If you just made a hard pull or just drove 10 miles on the highway, you better give it some time. Spare the aggrivation (sp?) and get a turbo timer as soon as possible. Most people don't have the dicipline to wait with car and the ones that do have to listen to their g/f's complaining about it.

btw, I'm sick so I'll be in all night. You can just IM me if you want and get all this answered alot faster. sn: "il capo di mafia"

 

[Jeremoose]

If you've been doing a lot of boosting it's a good idea to let it idle for a few minutes when your done driving to let the turbo cool itself down. Alternatively you can just purchase a turbo timer which does this for you

*EDIT* Damnit, sorry... You responded while I was reading through the posts

 

[MyBeatGSX]

That's why I suggested AIM, so we don't have 3 people writing redundant posts.