Twin Turbo (CARB Legal) 2018 370z NISMO

filip00

There is a difference between turbo lag and turbo "hole".

Turbo hole is a rev range in which the turbo is useful, i.e. it's spooling to enough rotation that you can feel the boost build up. It's effectively the amount of gas coming out the exhaust that is building enough pressure to spool the turbo so that it spins high enough so that it can squeeze enough extra air into the engine so that you can feel it. On the above car's turbos it's very low, around 2000rpm which is incredibly cool and makes the car feel torquey. This also implies that the turbos are probably not huge. Generally, the larger the turbo, to higher this hole is, i.e. the more revs the engine needs to actually spool the turbo.

Turbo lag on the other hand is the time it takes for the turbo to spool from when you hit the accelerator. Let's say you're in the car above, that's now sitting at I dunno, 90mph, at around 4000rpm. It's in the power range, it will deliver a lot of power....however, if you completely let go off the gas, wait a second, and then you hit full gas, even if you're within the power range of the turbo (in the above case, above 2000rpm), it will still take A LITTLE time, just a tiny bit, maybe 0.2-0.4s until the turbo builds up boost. It's in the rev range, meaning the exhaust gasses will spool it up no problem, but that whole chain of events does take a tiny bit of time longer than it is for example in the N/A car. Rally cars for example have the misfiring system, or the antilag, which effectively doesn't allow the turbo to lose it's rotational speed, so that the hit on the accelerator gives immediate response.

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