Entaran said:
define lag.
fullboost (x psi) at what rpm?
everyone's idea of lag is different.
dre's is wildly different to mine. I consider 2700 rpm laggy
TURBO LAG
Definition: Within a
turbocharger's operating range, lag is the delay between the instant a car's accelerator is depressed and the time the turbocharged engine develops a large fraction of the power available at that point in the engine's power curve.
Also:
Boost Threshold vs. Turbo Lag
Turbo responsiveness is usually measured in two ways. The first is boost threshold. Boost threshold is the engine rpm point where the turbo begins producing effective boost pressure, at full throttle. Below the boost threshold point, the engine will usually feel a little mushy and unresponsive. Once the boost threshold is reached, the boost will rise toward peak boost and the engine will begin producing significantly more torque. A well designed wastegated street turbo system designed for high power output may have a boost threshold of around 2,500 to 3,000 rpm. Peak boost will then be produced by around 3,500 to 4,000 rpm, and should hold all the way to redline.
Turbo lag is sometimes confused with boost threshold. While turbo lag is also rpm dependent, it is more of a direct measurement of turbocharger response, as opposed to engine response. Turbo lag is the time it takes for the turbo to spool up from the moment the throttle is pressed to the moment maximum torque at that particular rpm is developed. Obviously, turbo lag widely varies based on engine rpm. For example, if the boost threshold is 3,000 rpm, and you floor the throttle at 1,500 rpm in sixth gear, then turbo lag could be 20 seconds or more, as it will take a long time for the engine to accelerate, off boost, from 1,500 rpm to 3,000 rpm in sixth gear. Conversely, if the engine is at 5,000 rpm, and you floor the accelerator, it may only take .25 seconds for the turbo to spool up again. Perhaps the best way to quantify turbo lag is the slight delay in maximum power delivery that occurs in between full throttle shifts, or when you floor the accelerator to pass someone on the highway. A properly designed turbo system can be both responsive and produce high levels of power, though it is not easy to acheive the right balance.
There you go. :wink:
I should sticky this in a tech section too.....