Nothing wrong with the question, and I misspoke, actually. All air entering the compressor, and fuel exiting the injectors, must exit through the exhaust pipe. So there's nothing regulating valve overlap effects, and conceivably you could dump charge air directly into the exhaust. No photographic evidence of pipework to support this ever being done.Big Tea wrote: ↑Mon Jul 09, 2018 11:43 pmAs I feared, I look a dik now LOL I'm used to it.roon wrote: ↑Mon Jul 09, 2018 11:30 pmMr. Tea:
All compressor charge air must be used for combustion within the engine, by regulation. Off throttle gas flow can be increased/energized via late ignition, avoiding piston power while maintaining turbine power somewhat. I don't know how commonly that is done, if at all.
If for instance there was sufficient valve overlap, would that not allow (relatively) cooler air into the hot exhaust. Would this be enough?
So long as the charge air is sufficiently heated by the ICE, there will be enough energy available in the exhaust stream to power the turbine and sustain the compressor. If there is too much dilution (too much charge air) then turbine power alone won't be able to sustain the compressor power requirements, and the H will have to consume electricity to make up for the difference.
In these engines compressor work and intercooling might be the main limiting factor for air:fuel ratios, in-cylinder dilution, and any valve-overlap/out-cylinder dilution.
I had a go at a similar idea here:
viewtopic.php?f=4&t=18874&p=736875&hili ... ap#p736875
With enough overlap there would be the opportunity to energize gas flow destined for the turbine under any regime. Ignition is limited to five sparks per cycle, but there are no limits to injection events, only fuel mass flow.