Terminology confusion???

[Bill]

Im getting a little confused with some terminology being used.

Can some one correct me here.

Wastegates - All turbos have them. Come in internal and exteral formats. External vent to outside, Internal feeds back into the intake or exhaust?

Blow off Valve - Vents excess pressure when you back off the accelerator like between gears.

Bleed Valve - Same as a Blowoff valve?

Where does a Blow off valve vent? Exhaust, Intake or just to outside?

[Gold Rays]

bleed valve - allows u to control ur boost

Blow off valves vent back into the intake (stock BOV)

or

vent outside (atmosphere)

or

vent both to the intake and atmosphere (aftermarket BOV)

Hope this helps

[GTS-t VSPEC]

You got the wastegates and Blow-off valve right.

Some blow-off valves will vent to atmosphere, others will recirculate back into the intake.

Bleed valve will increase the boost made, by bleeding the air to the wastegate line, hence making the wastegate open at a higher boost pressure.

[b2barker]

Wastegate - Controls howmuch exhaust gas goes through the turbo, and howmuch goes straight out, to control boost delivered by the turbo.

BOV - yep, back into the intake on stock 'lines and into the air for woosh sounds.

Bleed valve- No, it is a cheap addition that bleeds of some pressure on the line to the wastegate so it doesn't open so much, so more exhuast goes thru the turbo and you get more boost. Electronic Boost Control (EBC) is a more expensive way of controlling the wastegate and hence boost.

[Skyrine-Dave]

not entirely correct about the wastegates.

the internal wastegate just means that the waste gate is incorporated into the exhaust side of the turbo from the factory.

external wastegate is an aftermarket accessory used for more accurate boost control and can be fed back into the exhaust or to atmosphere.

[red900ss]

Originally posted by Bill

Im getting a little confused with some terminology being used.

Can some one correct me here.

Wastegates - All turbos have them. Come in internal and exteral formats. External vent to outside, Internal feeds back into the intake or exhaust?

Not all, but most. Vent to exhaust otherwise you'd have exhaust going into your intake.

Originally posted by Bill

Blow off Valve - Vents excess pressure when you back off the accelerator like between gears.

Yep, keeps the turbine spinning and reduces shockwaves travelling back to compressor.

Originally posted by Bill

Bleed Valve - Same as a Blowoff valve?

The source of the force that opens the wastegate in our cars is compressed air ("boost" air between compressor and engine). The more pressure in this line, the more/quicker the wastegate opens, therefore if you reduce this pressure the wastegate doesn't open as much/as quick/as early. Bleed valve is an easy way to do this.

Originally posted by Bill

Where does a Blow off valve vent? Exhaust, Intake or just to outside?

Never to exahust afaik, but to either of the others depending on the set up. Stock is back to intake.

[Duncan]

blow off valve - primarily used to make overly load noises on gearchange with little impact to no on performance, very good for increasing defectability speed though.

[WazR32GTSt]

although i'm sure some may have gotten those explanations i thought they were rather sketchy so i thought i would add:

blow off valve...

primarily used to prevent 'compressor surge', which is when the throttle body closes and the boosted air flows back through the intercooler and through the turbo which is spinning in the opposite direction. not good.

the bov opens up when the throttle body closes to direct boosted air out of the intake system. on a stock skyline it passes through a pipe and back into the intake so you don't waste the boosted air (and to cut down on noise)

wastegate...

when exhaust gasses exit the cylinders they flow towards the turbo. here they have 2 choices:

1) pass over the exhaust housing of the turbo, thus spooling up the turbo and compressig air in the intake. this is desirable if you are accelerating...

2) pass through the wastegate which is usually located right next to the turbo. remember back to physics and the exhaust gasses flow through the path of least resistance, thus pass through the wastegate and into the exhaust, thus bypassing the turbo and stopping/limiting the spool-up. This occurs when the turbo is at the desirable boost level. on some high-power cars this is not big enough to direct all the gasses around the turbo exhaust wheel, so they fit an externally-venting wastegate which generally flows more air. These are loud and pointless on a stock car.

bleed valve...

the wastegate needs to know when to open or close according to whether or not the turbo is boosting. a pipe runs from the turbo to the wastegate to tell it how much pressure the intake is being boosted to. the wastegate then opens or stays closed as required to keep the boost level even.

a bleed valve is a small (and cheap) valve that fits into this pipe and can 'bleed' (remove) some of this air. thus tricking the wastegate into thinking there is less boost than there actually is and make it stay closed for longer.

For those that know more than me (most of you), please correct any of this if its wrong.

Thought this may help bill.

Waz.

[Bill]

Thanks for clearing that up guys,most helpfull!

And thanks for the detailed explanation Waz.