Exhaust noise - trackday limits etc.

[lockwood77]

Guys, I\'m looking for a bit of advice about exhaust volume on FDs - do any of you track-goers have problems with noise limits? I\'m interested to know what exhausts people going on track use.

At the moment, I have a huge backbox attached to mine (make unknown) and an aftermarket mid-pipe (de-cat), stock downpipe, ARC airbox (apparently a lot of noise comes from intakes on some cars, don\'t know if this applies to the FD). Not surprisingly by the size of the exhaust, it\'s loud!

I also have a 5Zigen backbox that I will try, although whether it\'s that much quieter or not, I\'m not sure (the missus has a 5Zigen on her Civic and it\'s pretty loud!)

I\'m booked on a day with Don Palmer at Bruntingthorpe in a couple of weeks and there is a 60mph drive-by limit of 87db at 20m from the car. Very much doubt I\'ll pass with the big backbox, no idea yet with the 5Zigen.

What would the implications be if I put a stock backbox on for the purposes of trackdays - (a) would it be quiet enough with the de-cat and (b) would the more restrictive nature have any negative impact on the engine (other than slight loss of power)?