Quote:
Originally Posted by lucid
I don't understand how you end up with 2.5 times the thickness when the required volume increase for equavilant heat capacity is 84% for the SGL rotor with 800 J/kgK, or with 1.5 times the thickness when the required volume increase for equavilant heat capacity is 13% for the SGL rotor with 1350 J/kgK.
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Ahhh, no... 2.5" thick as compared to 1.34", not 2.5 times as thick (with my 1/6th correction factor)! I thought that would be clear with the other numbers I was quoting like 22/19 (which were without units but obviously in inches). Also using your 66% volume correction (1/3 rd reduction) I can not get a reasonable ID and 18kg weight savings for the GT2 system. I think 5/6th is better for that particular rotor (likely wider vanes in the angular direction meaning less air *******.
Of course I agree just by a visual examination that 66% is a better estimate for many systems.
Quote:
Originally Posted by lucid
Anyway, if we take 500C as the max operational temperature, then the situation is clearly even worse for the Scuderia with the cast iron rotors in the comparison even if you pull the initial T down as the Scuderia with CSiC rotors will keep on performing.
Nope. The two Scuderia's in my analysis with the largest CSiC and iron rotors currently sold operate with very similar temperature rises.
....
Now, maybe the real question is this: is there a need for higher total heat capacity than what can already be achieved with a cast iron 380x35mm rotor? If there is, for whom? I surely do not have that need on the street or the track.
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You are following my reasoning. My point was both that 450 C initial temp is unrealistic because we know the rotor in your example is more than adequate to be almost fade proof in a Scuderia. It seems you chose that value quite arbitrarily to exceed the working temp range/limit of cast iron. As well, the CSiC system still shows a higher single stop delta T, combine that with the lower conductivity and you will definitely have a significantly higher T initial for that rotor. I agree with your point, you can find a CSiC system that will outperform a cast iron one - there is no doubt there. It is just this analysis is quite a bit on the optimisitic side in favor of the CSiC. My analysis was quite unbiased and used two real systems available on a real car
Overall I think we are both just about on the same page, which is encouraging. Cheers.