As already pointed out in this entry that the undersized and fast spinning supercharger is the real reason for the flagship not being able to last on the track, even during winter months. Here is more information on this subject and reality check involving this supercharger's efficiency.
Roots supercharger can indeed be a very efficient and responsive device, aiding in extracting more horsepower from ICE. But... this is only true only when the supercharger is used within its optimum use. For roots type supercharger, this optimum means relatively low speed and low boost pressure.
What happens when the supercharger spins too fast and generates too much boost in the process? The efficiency of the supercharger takes a big dive and instead of just simply compressing the air, the air heats up due to the loss in efficiency. To remedy this problem, the supercharger has to be increased in size, thus, reducing the speed needed to generate the wanted boost.
Here is how this efficiency works, in fact, under conditions set for this supercharger by Juechter's team, the supercharger becomes more efficient at being a HEAT PUMP than the intended supercharger. As already experienced by a few aftermarket tuners, reducing the supercharger pulley diameter results in no increase in boost, obviously the supercharger is already maxed out, explaining very well why it has such a lousy THERMAL efficiency. What was Tadge Juechter thinking here? Is this guy really that ignorant? No way that Eaton would be misleading GM, this seems like a truly stupid move by Juechter and GM.
The practical symptoms of this situation have already been noted by several press reviewers, the supercharger becomes noticeably hot to touch and the existing after cooling bricks are not even close to remedy this problem. In fact, it is impossible to expand the aftercooler sufficiently to eradicate this problem. Of course as already mentioned before, the hotter the air, the less density and oxygen content the air will have, thus, the anti knock sensors direct the fuel system to enrich the AFR to prevent engine detonation.
In spite of propagation of myths regarding overly conservative factory tuning, the tuning itself is considerably less conservative than the tuning that was found on the previous LS Corvette engine family. Furthermore, in spite of IAT being low, this is not is happening at all, with IAT being measured at the intercooler exit. Yes, it may be cold there but the supercharger itself is the point where the air heats up, setting off knock sensors as already pointed out.
Here is an example of LT4 factory tuning tables
And here is an example of previous generation. The previous generation is considerably more restrictive and conservative, ironically enough.
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