I wanted to measure the diameter of each exhaust pipe (final section only). I chose the pictures shown below with the idea of comparing it to the rear light, so the pictures are chosen to be taken from a largish distance to minimize perpective effects. Then I counted pixels for the diameter of the pipe and between the top two shiny spots in the rear light (are they bolts?) and compared. Wit three pictures per engine, the internal variation is in the order of 5%.

What I got:

In the Mercedes, the pipe is 1.368 times larger than the reference.

In the Ferrari, the pipe is 1.740 times larger than the reference (Might be a tad bigger than that, the second picture, where the ratio came a bit smaller, is the one taken from the shortest distance).

In the Renault, the pipe is 1.316 times larger than the reference.

Now I have a lot of questions:

How long is this bolt-to-bolt distance?

I got 3 pics from Mercedes, three from Ferrari and then 2 from Red Bull and one from Toro Rosso? Can we assume that for the same engine the teams will also have the same final diameter? Or can they be different? The Toro Rosso came a bit larger than the two Bull's pics, but the variation wasn't larger than Ferrari to Ferrari...

What real life effects does this have? I can imagine that a smaller pipe will mean larger back pressure and a faster flow. What else? Any large effects on engine power? Cooling?

I would like to see a paleontologist.