Quote:
Originally Posted by hobieboy
other than increasing intake air temp, what more does it harm?
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I think Thierry was saying that if the hot side can't keep up, not only does it fail to rotate fast enough to keep up with the exhaust flow, but it also becomes a restriction in the exhaust flow.
For the cold side, my understanding is that if the cold side compressor is sized smaller then it is more efficient at lower RPM (boosts sooner) - but the trade-off (without variable-vane turbos) is that as it gets outside the efficiency map at higher RPM it can't flow as much air as needed/heats it more than a turbo better sized for that much airflow would.
Which is why there used to be a number of different K27 hybrid turbos - none of which were the same as a stock K27.
The K27/S was a quick-spooling turbo intended for CIS, ran out of flow at the top end. The K27/HF was a quicker-spooling (than stock) turbo that made more power at the top, and the K27/HFS is intended for use with EFI, because it needs so much fuel at the top.
In comparison to the K27/HF, the 3DLZ is just a boat anchor.