Quote:
Originally Posted by Mitchocalypse
Hmm. I've often thought about this exact concept and would have applied it exactly the same as you have but the more and more I thought about it, the more i found things that might throw off the approximation so I pretty much just dismissed the idea.
Have you tested how accurate this is? Maybe it's just the way i'm looking at it but it almost seems over simplistic. I'm sure it gives a reasonable approximation - but how accurate is my question?
The two biggest things for me are intake air temp and volumetric efficiency. Obviously i don't need to explain the fundamental gas law, but I was also under the impression that at higher rpms, internal combustion engines (n/a) could reach greater than 100% volumetric efficiency so the absolute pressure in the manifold (or combustion chamber) could be greater than 1 bar absolute.
The way I'm looking at it (and I know I'm missing some things) is that doubling the absolute pressure wouldn't actually double the power.
Sure it's a good approximation, but how good?
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It's 100%
So long as you have the compressor map width and turbine to match i.e. BIGGER TURBO *to match your pressure ratio target, thus power target* (efficiency) and charge cooler big enough for the extra heat rejection. I have proven it in my own testing and that with rotary turbo drag cars I consult on. And its been proven over and over in many piston turbo examples most notable F1 1000bhp era.
Volumetric efficiency of stock ports is around 85%
My Street Ports around 105%
Bridge and Peripheral (many variations!) but say 110% (as used in turbo applications).
NOTE: Power differences are not just a function of this but where the power is made
The match between turbine to compressor (again I test this and have posted up many graphs
not Howard Coleman like conjecture and personal theory) is so long as relationships are maintained PORTS are not the restriction never ever have been to ultimate power, all they define is where it is made due to charging efficiency at higher engine speeds.
(Turbo's are simple as stated. And ancillaries as well, if you are reading this thread and comprehend it so far you will be all over these basics too.)
The formula and how it works is proven 