A good few months ago now I had the "pleasure" of a C63 as a courtesy car. It happened to belong to Acid from MSL and was a Weistec Stage 3 modified one with a substantial amount more horses than it started life with.
The ride home was interesting though I didn't really get much chance to use it due to the traffic unfortunately. I do remember it being very loud and an extremely harsh ride though, due to the suspension he had fitted.
Anyway, I'm digressing. I put the C63 in my garage overnight and left it there till the morning when I went to start it. OK, it was loud, but probably not as loud as my M157 when that starts in the same place. Both cars had similar exhaust systems, his having headers, mine 3" downpipes from the turbo back. Neither car had cats or resonators.
I think with the M157, the cold start has more effect as the turbos are by-passed to heat the cats, with the car initially starting at around 1,400RPM before it decides a certain temperature has been set. Missing the turbos out obviously removes their silencing power so the noise is more pronounced.
This is my theory and, though it may be totally wrong, there's no denying the fact that mine is
very loud when starting from cold, as a few on here can testify.
Developer John posted something technical about how the cold start worked on the M157 but I can't find it and too tired to look now, but it was basically similar to my theory.
