Trackday add-on silencers (PAIR).
Trackdays are a great opportunity to enjoy your car's full potential - but the UK tracks are now the most noise-averse in the World. These add-on silencers slip-on to the tailpipes of the 2bular exhausts. They have the same bore as the tailpipes so no back-pressure is introduced - no loss of performance. I have seen some extremely dodgy designs which WILL damage your engine with the back-pressure they cause. If you can't drop a coin through the silencer from one end to the other - AVOID!
I build these add-ons to the same quality as the rest of the 2bular range. For lightness, I use 0.8mm Stainless silencers skins and (expensive!) Acoustafil ZT-1 for the packing materials. TIG-welded for integrity. I have long experience of SuperBike silencers and incorporate the same design features in these add-ons. They can be re-packed if necessary - but feedback suggests they are very reliable.
It is very important to point the noise down towards the tarmac! You keep them in this position for the static test. Each silencer can also be rotated on the tailpipe to point away from the microphone nearest the edge of the track. Distance reduces decibels - you need to use everything you can to beat the drive-by noise-meter.
Originally, I used a 250mm long silencer and these were good at Brands for 91dbs static and rotated away from the mic on the outside at Clearways, ran all day with no problems. Recently I built a new batch at 300mm long. Having been advised about Thruxton and their 90dbs(!) static test I will test some 350mm designs.
All circuits have reduced their decibel limits - my favourite track Oulton Park, has come down from 105dbs to 92dbs. But they are offering more 'Noisy' days (at extra expense - of course). I have many clients reporting to me all the time about their experiences at trackdays and NOISE is a big issue. For me, as an exhaust designer, it's becoming a lottery. The WEATHER plays a big part in drive-by noise measurement - and I don't want to be dependent on that!
These silencers are strictly for track use and are not road-legal.