Quote:
Originally Posted by Mystic
So this argument is basically a trade off of either:
keep the inlet pressurised but take a hit in turbine rpm - a la no DV
de pressurise inlet & maintain higher turbinerpm - a la DV
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Yes - but really there is no benefit from keeping pressure in the inlet. You risk damage to the turbo, and the very pressure you're trying to keep is working against you to slow the rotation of the compressor wheel.
Quote:
Originally Posted by Mystic
Would the individual turbo not also play a big part, larger slower spooling turbo would see more benefit to maintaining its rpm, compared to a turbo which can spool quickly & might lend itself more to maintaining pressure?
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Absolutely. That's a very good thought.
However, remember that the larger turbo has more mass in it's rotating assembly (compressor and turbine wheels), and therefore more inertia - so the "bad" pressure on throttle closure has less effect on stalling the compressor wheel. I think it would even out somewhat, but it's something I didn't think about actually!
Quote:
Originally Posted by Mystic
What about if you are at full boost/high rpm & just close the throttle to engine brake without a DV, surely that wouldn't be good?
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Yes - that's the worst case situation for the turbo - maximum boost pressure, maximum turbo rpm (perhaps 100,000 rpm+) and then TB closure. That would be the point where you'd have the most stress on the compressor wheel and front side bearing.