Blowoff Valve VS Wastegate

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ovcrash

Senior Member
What's the difference between a Blowoff valve and a Wastegate??
And to do a "rally alike" turbo setup, witch of the two to i return into the turbo and not into the atmosphere(outside)??

Is it good to do that?? Or i will just kill the hell out of my turbo??
 

reckedracing

TTIWWOP
VIP
a blow off valve bleeds excess air off the compressor side of the turbo system so it doesn;t get backed up and damage the turbo...

the wastegate lets excess exhaust gases bypass the turbo side of your turbo setup...

and loco honkey quote
And you will NEVER have a turbo last more than a few hundred miles. If you're going to use an anti- lag setup like rally cars, you vent the BOV air into the exhaust upstream of the turbo. Either way, expect to replace turbos with every tank of gas.
 
Last edited by a moderator:

Tonyd0821

Banned
uhh...dumb question.

does a wastegate make the famous "psssh" noise a bov does?

do people usually have both? or one or the other?

alls i had was a bov on the grEEdy kit i had on my ek

it didnt come with a wastegate
 

NoJokE

Senior Member
Tonyd, yes your kit DID have a wastegate. The wastegate is on the manifold, without it your turbo would keep boosting until x amount of psi and eventually blow your motor.
 

Tonyd0821

Banned
Originally posted by NoJokE@Apr 23 2004, 03:30 PM
Tonyd, yes your kit DID have a wastegate. The wastegate is on the manifold, without it your turbo would keep boosting until x amount of psi and eventually blow your motor.

now that i think of it...

yes, yes it did. lol. im used to seeing the other type of wastegates that DIY turbo kits use.....
 

reckedracing

TTIWWOP
VIP
there are internal wastegates that are built into the turbo and extrenal wastegates that are attached between the head and the turbo housing...

the blow off valve makes the ppppssssstttttt
and the wastegate can make noise as well
some wastegates dump into the exhaust at the same place as the turbo outlet, some dump into the exhaust but like 18 inches down stream, and others dump intot he atmosphere

the last one makes noise...
you'll hear a pppsssstttttt and a louder pppsssstttt straight pipe exhaust type sound when these cars shift...
 

SolReaver

Senior Member
Originally posted by Tonyd0821@Apr 23 2004, 03:00 PM
uhh...dumb question.

does a wastegate make the famous "psssh" noise a bov does?


if horsepower had a voice, it would be the sound of an open dump wastegate :)
 

Slammed90Lude

Senior Member
big difference- at low boost levels an internal wastegate will work just fine- it's found on most greddy kits and a few others- however internal wastegates may lead to boost creep at higher boost levels (boost creep is when the wastegate is overwhelmed by boost pressure and reacts too slow, causing a few scary moments where boost is higher than it should be)- THis is where the external gate is used, and in my experience, an open external wastegate dumping straight into the atmosphere does not make the same sound as a blow off valve, it's louder, raspier and less glamorous, unless you know what that sounds means
 

ovcrash

Senior Member
Originally posted by Slammed90Lude@Apr 23 2004, 06:52 PM
big difference- at low boost levels an internal wastegate will work just fine- it's found on most greddy kits and a few others- however internal wastegates may lead to boost creep at higher boost levels (boost creep is when the wastegate is overwhelmed by boost pressure and reacts too slow, causing a few scary moments where boost is higher than it should be)- THis is where the external gate is used, and in my experience, an open external wastegate dumping straight into the atmosphere does not make the same sound as a blow off valve, it's louder, raspier and less glamorous, unless you know what that sounds means

So i only need one of the two? or the wastegate and the BOV is needed in a turbo setup?

If i need the two, the both release the extra into the atmosphere, so both of them make a "sound" so i don't see why i have a choice??
 

IDMaxGuy

Senior Member
ok a wastegates regulates boost, when your turbine is spinning it reaches XX amount of boost when it does that, a little flapper door inside of your turbo opens up and releases that excess boost into the atmosphere or back into the turbo (however you have it setup). IF you have no wastegate, then the turbine will build as much boost as it wants... now a BOV protects your turbo from back pressure in the intake piping due to sudden downspool or release of the throttle. the BOV is closed when boost is on because there is no vacuum. but when you let off the gas and vacumm builds... the BOV opens and the excess air is pushed out resulting in a PSHHHHH... so you NEED both of them, unless you are the people from exvitermini.com and your quote is "wastegates are for pussys" :D
 

Slammed90Lude

Senior Member
Originally posted by IDMaxGuy
a little flapper door inside of your turbo opens up and releases that excess boost into the atmosphere or back into the turbo


such is only the case if you have an internal wastegate- there is no flapper door inside the turbo if you're running an external one- but other, :whathesaid:
 

Canuck 93 Civic Si

Senior Member
Originally posted by NotUrAverage_Si@Apr 23 2004, 07:49 PM
you need both the wastegate and the bov.

a bov makes a different sound from how a wastegate sounds when it is open.

You need a wastegate. Without one you will either;

a. overboost and blow you engine apart, or
b. overspool (provided the engine doesnt blow first) and grenade you turbo. It actually does sound like a grenade going off :eek: , kinda cool huh.

A blow off valve isnt needed, but is preferable to extend the life of your turbo. It has been explained how in an above post.

They both have totally different functions. Alot of people get confused and think they can use either to control the amount of boost their engine recieves. Dont get confused
 

MikeBergy

Blah blah blah....
Every turboed car has a wastegate, but not all have bovs. A lot of oldschool factory turbocharged cars did not come with bovs, mostly because they were not really running high enough boost pressures to necessitate a bov. My 84 turbo tbird did not have a bov. I don't remember it even having an intercooler. It only made like 123 hp stock out of the 2.3l I4.
 

posol

RETIRED
wastegate = controls/bleeds excess exhaust gasses BEFORE going into the turbine to keep from overboosting/keep a steady psi.

BOV = bleeds excess gas to the atmosphere AFTER the turbo, before the TB, when the throttle body is closed. when closed, the boosted air from the turbo up has no where to go, hits the closed TB wall, and goes back down the charge pipe, thus, causing the turbo to want to spin backwards. this is bad.
this is what bov's prevent. they bleed that air, so as to protect your turbo.
 

IDMaxGuy

Senior Member
just what i said, but question, since ext. wastegates have no flapper, how do they work? is it done by backpressure or something?
 

SolReaver

Senior Member
Originally posted by IDMaxGuy@Apr 24 2004, 03:38 PM
just what i said, but question, since ext. wastegates have no flapper, how do they work? is it done by backpressure or something?

when the boost signal to the wastegate is enough to overcome the spring, the diaphragm lifts and releases exhaust out the dump tube
 
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