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Originally Posted by Auto_newb
Hmm I didn't really know that a centrifugal s/c could have the same lag comparable to a turbo, but it can't really be compared to turbo lag, because turbo lag is load dependant or dependant on the amount of heat/exhaust being pushed out the engine, the S/C is RPM dependant, it really depends how fast you reach the 5000 RPMS or whatever.
BTW, if it takes that much RPMs maybe it's because it sucks?
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No, turbo lag IS ALSO RPM DEPENDANT!!! I really shouldn't be called turbo lag, it should be called boost lag, since that's really what it is, it's the lag until the onset of boost occurs.
First off, just cuz it takes longer "doesn't mean it sucks." Not all turbos are the same size. Bigger turbos like a full on race one can create much more power because they are bigger, allowing them to flow much more air. This bigger physical size, amoung other things, means it takes longer for the pressure (boost) to built up so that the extra power is felt.
It takes until a certain rpm for the exhaust gases to exit the motor and spin the compressor of the turbo fast enough towards the critical speed of the turbo that a strong boost onset occurs. The rpm this occurs at is dependant on many factors, compressor and exhuast housing size, the turbine size and design, etc. For example, in the smaller turbo in my first example above, the rpm at which the exhaust exiting the motor begins to spin the compressor fast enough that a strong boost onset occurs at around 2000-3000rpm. This is dependant on the RPM, not the heat of the exhaust. The rpm of the motor must be enough that the air exiting the motor spins the turbine fast enough that an onset of boost occurs.
This is same reason lag occurs in the cyntrifugal s/c, except with a cyntrifugal s/c the engine rpm must be fast enough that it spins the shaft fast enough so that the compressor can compressor enough air to cause a "strong onset of boost."
With a turbo, the engine rpm must be fast enough so that the exhaust exits the motor fast enough to spin the turbines fast enough so that the compressor can compressor enough air to cause a "strong onset of boost."
With both, the both a s/c and a turbo, this "boost lag" is rpm dependant. With a turbo, the lag depends on the turbos design. Turbos designed to produce 500HP will flow a lot more air than one than is designed to produce 300HP. Thisextra size and airflow required to make extra power also results in more boost lag however. It doesn't suck. It's just a trade off. That's why when you ask "what turbo should I get," people will always want to know what you are playing to use the car for after the turbo is installed, and what your power goal is.