What is turbo lag?

[03cavyTT]

whats turbo lag and does a blow off valve get rid of it

[Neutrino]

again wrong forum...but anyway

under light load the turbo hardly puts out any boost...so if punch it all of a sudden it will take a while for the turbo to spool up

a BOV will not get rid of lag but it will help get rid of the presure between the turbo and a closed throtle...presure that can push back on the blades and slow it down...so basically it helps the turbo spin out longer

btw i would recomend putting those questions under the cars in general>forced induction forum...that is why its there

[MustangRoadRacer]

the blow off valve aslo relieves pressure on the intake.
otherwise the turbo would be pushing pressurized air towards the engine when the throttle is closed, pushing on the throttle body and if strong enough, the valves.
that was a problem in the early days of forced induction.

[Polygon]

Originally Posted by 03cavyTT

does a blow off valve get rid of turbo lag and what is turbo lag

No, it does not. A blow off valve is meant only to relive pressure on the compressor wheel when the throttle plate closes by venting the excess boost into the atmosphere. A diverter valve will divert that air back through the intake. So a diverter valve can improve response but will not completely eliminate turbo lag.

Turbos have two impellers or turbines. One is an exhaust impeller and one is a compressor impeller. The turbo uses exhaust gases to spin, which in turn spins the compressor, which is connected to it by a shaft. The turbo lag is produced by the fact that it takes a small amount of time for the exhaust to spool up the turbo and compress the air when you accelerate. Remember a turbo will only boost under load.

[justav6]

arent we in general discussion forced induction?
anyway... turbo lag is the time it takes for engine rpms to flow exaust out the headers to the turbo, spin the turbine which turns the compressor, then the compressed air to get to the combustion chambers.this all depends on a bunch of factors. most importantly, the volume of space in the headers, turbo, intercooler, combustion chamber, throttle body, turbo, and plumbing. that is why despite what some people think bigger is not always better. actually as far as turbo lag goes the opposite is true. bigger is better for pushing higher amounts of boost (less resistance). also back pressure after the turbo slightly effects lag, but mostly just higher boost levels. a blow of valve arguably slightly reduces turbo lag, but it mostly just increases the life of a turbo, sounds cool, and keeps the engine from stalling if you get off the throttle real quick after pushing high boost levels. this sometimes happens with out a bow off valve because the pressurized air in the intercooler and plumbing has no where to go, so it goes backwards which causes the turbo to spin backwards choking the engine.

[97Tsi]

Originally Posted by justav6

arent we in general discussion forced induction?
anyway...

The thread was probably moved by a moderator

[justav6]

oh
sorry new here ( :

[Hypsi87]

BOV's pervent compressor suge which pushes the shaft hard agenst the bearings in the center section. that is reallll bad on a small shaft turbo but, not a problem with a bigshaft. Not all turbo cars need a BOV.