S3 good 159 now
around 260hp V good
Join Date: Jan 2008
Location: United Kingdom
If you drill a larger hole then you will start to get noise from the exhaust especially when at speed as exhaust gas will escape through the larger hole and not flow past and go around the last baffle. The hole was made to remove the excess pressure pulse caused when you put your foot down which will push its way through the hole. A 14mm hole ( 9/16” in old money) could give a potential flow rate of around 65 cubic feet of air per min, at 4psi. But this will change with temperature and flow direction and of course pressure. I have not measured the pressure so the hole size is a guesstimate but it seems to work. Now there is a hole there, I could try and connect a pressure gauge and take an actual pressure and temperature measurement. I could then calculate the gas flow through rate being achieved, or I could go to the pub?
You could drill a bigger hole but I would not recommend it. 14mm seems enough.