What is the relationship between Audi and Porsche?

Question:

Answers:

They have separate research departments, separate assembly plants,
but do share parts, engines and cars (US VW Quantum == Audi) on occasion.
The original version of the Polo were actually made by Audi
called the Audi 50. The basic 1500/1600 now 1800 cc block is also
from the former Audi 80.
In Europe it is not uncommon to have both dealers that sell and
service both VWs and Audis (and sometimes also Porsches).
In North America the two (three) are usually separate.

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Regarding VW & Porsche (From Tom H.):
There are no ownership arrangements -- the two companies are essentially
separate. There is, however, a lot of co-operation, as Porsche does
consulting work for VW, and Porsche has some access to the VW parts bins.
VW has also built some 914s, 924s and 944s for Porsche, and Porsche is
to build the Audi 80 RS2 for VW.

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They are both German engineered. Porche designed a lot of engines for Audi/VW

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They are two different companies, but they're both German and they share certain parts and have collaborated/designed for each other on many models.

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Check the sources below... they should help answer your question.

What do the MOT centres do?

they are cars

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German cars.

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Their SUV's share the same platform...