That 70% is still a product of the initial number.
175% (MORE) efficient, initial efficiency suggestion was 40%, = 40 (100%) + 30 (75%) = 70%
70% + 40% (the original number - the percentages are additive) = 110%.
Seeing as how one cannot generate more than is put into a system (power in = power out), the above numbers just do not work.
I would venture to say this system (may) improve efficience by a given amount, but any real numbers have yet to be determined/realized.