is 7" really better than 6" ?

[peter clarke]

On my 180 bhp K series use a 4-2-1 system with a 70 cm longTechcraft 6" exhaust with Acoustafil ( or a 4 to cat to Caterham 6" for the yearly test). They sound different but both loud. Have not checked the noise level but want a quieter exhaust. Looking at Raceco and Powerspeed.

Those of you who have swapped from 6" to 7", have you found a significant reduction, say 4-5db or is it only 1-2 db??

Before I invest would like to know if it is worth it!

[Stationary M25 Traveller]

Talk to the guys at PowerSpeed. Tell them what you want to achieve. They can engineer what you want.

[Mankee]

I have the VHPD/SLR 4-2-1 system with a 6" silencer. When I ran it as is with the full quantity of standard Caterham/Cheesman exhaust packing, it was rather loud. It passed the static test at Bedford but was a big problem on driveby at only 7000rpm or so. I seem to remember the static result was around 99db at 4800rpm.

 

I borrowed a 7" silencer from the race version of the exhaust from another club member, which was much quieter on the static test at around 94db at 5000rpm. It was bloody heavy weighing over 10kgs though!

 

I am now back to my 6" silencer but have modified it to be repackable and am using Acoustafil. The result is a silencer that is comparable in terms of noise with a standard 7" silencer but half the weight. The conversion cost me about £150 to have the new sleeve made up and for the new packing material.

 

It's not as nice as a shiny Raceco or Powerspeed but it does exactly what I want it to do for not much money.

[peter clarke]

Thanks a lot Mankee, just the kind of practical information I was after. Wait to see if any more replies but maybe I will stick with what I have, prices of the nice repack-able units are, to say the least, horribly expensive, especially if it does not bring much.