I know what it is but I think a lot of people are confusing it with something else!

Please give your explanations/definitions of boost lag!

 

lag is the delay between a change in throttle and the production of noticeable boost when engine rpm is in a range in which intake pressures are above atmospheric pressure(boost)

 

Roughly speaking, turbo lag is the time from when the driver demands more power by depressing the accelerator to when a turbocharged engine actually makes the additional power. The major player here is the inertia of the turbine and compressor wheels inside the turbocharger. Turbos must turn at relatively high rpm before they make boost; the values vary depending on turbo and engine size but 40,000 to 80,000 turbo rpm is not unusual.

turbo rpm varies widely depending on the rpm and load on the engine. It is not at all uncommon for the turbo to stop, or to turn quite slowly when the engine is loafing along. This is typical of idling or low-speed operation at light throttle settings on secondary roads. It can even happen at slower cruise speeds on a freeway. But I dont think that happens to us.

If, during such light load operation, the driver then fully opens the throttle (or asks for maximum power on a diesel engine), it takes noticeable time for the engine to ingest more air, push it out the exhaust pipe and raise the exhaust gas temperature. When these things happen, the turbo turbine then accelerates to speeds where it makes boost on its compressor side and the driver feels a swelling of power as the turbo “spools up.”

In early applications decades ago, turbo lag was often pronounced and made pre-cision driving difficult. However, detail improvement of turbo turbine and nozzle shapes, moving “variable vane” turbines, and advanced engine-management techniques have greatly reduced lag. It appears only a matter of time before variable turbo inlets and vanes effectively banish turbo lag as a concern for all but the most exquisitely fine-tuned engines.

Is that right? hehe

 

dammit.. I forgot to say.. ART is not allowed to answer this question!!

 

a little simpler.

what drives the turbo? exhaust. you don't get more exhaust until you hit the throttle. and the lag is the time it takes for everything to circulate.

 

Simplified, lag means how long you have to wait to hit boost once you hit WOT.

 

thanks for the responses guys! Monday mornings SUCK!!