excessive carbon build up

pulled my engine for inspection and after taking the head off i noticed the pistons have lots of carbon build up on the top, could this be caused by running rich?

it was running 11-11,5:1 in boost and from 6000tpm tapering towards/over 10:1.
has only run for about 5000km's btw and it doesn't consume oil or anything.

http://i1230.photobucket.com/albums/...pt/foto1-1.jpg
http://i1230.photobucket.com/albums/...lpt/foto-2.jpg
http://i1230.photobucket.com/albums/...pt/foto3-1.jpg
http://i1230.photobucket.com/albums/...pt/foto2-1.jpg

Arthur that is pretty exsessive carbon build up for such a short period looks like it's quiet a few .mm's high so wouldn't that effect the compression a bit?? headgasket failure would remove all that:laugh: (Saying that I suppose a water injection kit bolted on purely just to clean your engine as you go along will remove / steam clean the engine as you drive).

I believe to rich a mixture will cause what you have, I think it supposed to be just a browning colour to the top of the piston's.

Think you need a proper map

If everything works out it'll be mapped by Henk in october.
Have a few more updates which i'll put online when i've made some progress.

I'm just curious what causes this as part of the learning process.