godlameroso wrote: ↑
Fri Oct 23, 2020 1:40 am
PlatinumZealot wrote: ↑
Thu Oct 22, 2020 10:03 pm
stevesingo wrote: ↑
Thu Oct 22, 2020 8:42 am
Quite correct, my mistake.
But, AIUI the concept was widely used in Grp A Rally.
Keep in the mind those Porsche plenums are likely for the NA engines. The expansion cooling is proportional to the adiabatic pressure drop as per the gas law. The expansion will only take place if the gas cannot fill the chamber fast enough... sort of unlikely with a highly boosted engine. Otherwise that compressor will cram as much air as it can into the space, and the pressure drop would actually be minimal.
GT2 RS is turbocharged.
Yes i know porsche Gt2 is turbocharged. Didnt even read your wall to be honest. Haha.
Ok i have seen this before but forgot about it.
I still know there might be a catch from what I remembered....
OK rewatched it.
I see what you are explaining now. I thought you were saying the bulk volume would be cooled. That would be difficult without a throttling device of some sort.
So just regurgitating here; Porsche is pulse tuning such that the expansion in the wave takes place when the intake valves is open. So that the cooler part of the pulse gets pushed in. This effect they say happens only at high enough rpm. It essenially neutralizes the compressive pulse effect then reverses it.
Normally pulse tuning is done on the compression part of the wave such that the air is pushed in harder.
So porsche is trading some extra mass flow for lower temps. Ok. No magic there.
Alright.. So not a whole sale temprature drop, but localised. Still useful.
Cooler temps resulting in less chance for knock and thus cooler combustion. As seen in the video he showed a lower cylinder head temp by 20 degrees C. Fine.
Sure this "inverse pulse tuning" effect is more useful for hotter temperature charges such as in turbocharging.
I don't think this the same as throttling like in say an expansion valve, but according to them it make a cooler charge. cooler than the compressive pulse tuning.
Yes, prefectly reasonable to think F1 teams could be using this effect since they mostly operate at high rpms and high loads.
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