Quote:
Originally Posted by MartinClan
Boost ratio is only 1.9:1. Mind you if you used that AND the Metro servo that would give you (where's my calculator) 3.04:1 - still not great compared to the BM's 6:1.
Robin
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Rob
I have investigated this a bit, and am left wondering if a servo offers a constant boost, not a multiplier of foot pressure. The boost comes from the negative pressure generated by the vacuum of the inlet manifold over the surface area of the diaphram. Therefore the maximum boost is a constant (for a given vacuum): I assume the amount of that maximum boost available is controlled by the distance travelled by the push rod, otherwise the moment the brake pedal is touched the full boost will be applied?
If this is true, then the boost from a servo is directly proportional to the square of its radius. (surface area =pye x r squared). And if it has a dual diaphram then it will offer twice the boost of a single.
By this calculation a dual 7" has the same surface area as a 10" single.
Out of interest, what size is the standard BMW servo, or the Sierra servo?