After checking the cost of new tailpipes I\'ve decided to get the internals of my JASMA exhaust rebuilt by a mate who runs a precision welding company.
We opened it up a few days ago and found what was left of the internal perferated pipe was about an inch in diameter, despite the pipes to and from the silencer being about 3 inches. Is it this small to reduce noise, or is the outside 3 inches because it helps sell the exhaust?
I\'ve searched around but can\'t really find anything specific on building a silencer for a rotary engine. I understand they get very hot and it\'s hard to make them quiet.
Current plan is to stick in a 3inch diameter perforated stainless pipe and pack it with stainless wool.
Anyone any advice?
Thanks!
Difficult I know but try and get hold of some better known makes and cut them open, racing beat, hks, apexi etc.
The only fairly quiet backbox I\'ve seen for an FD that hasn\'t used the make it as small as possible approach is the Racing Beat one.
Talk to Carl (Hayward Rotarys) as he will be able to sell you a very good quiet cat back.
QuoteOriginally posted by clive
Talk to Carl (Hayward Rotarys) as he will be able to sell you a very good quiet cat back.
Sorry Clive, but Carls cat back does not even approach my definition of quiet - I have it and one of his silenced midpipes (which is very quiet by itself) and it\'s still far too loud to take the car anywhere near most track days.
I do plan to test it back to back with a couple of other cat backs for noise and bhp when I get my car back.
Definetly want to go down the route of getting mine rebuilt. We can open it up and experiment with different ideas if necessary. It needs to be quiet enough for Goodwood, which is very strict. If it\'s successful then we may be looking at building them from scratch.
Out of interest, why do some of the Jap exhausts cost upward of £500 for just a tailpipe? I know the quality is good, but it still seems outrageous.
Cheers
If anyone\'s got any silencers (other than standard) that are ready for the bin, give me a shout!
Why not take a good look at a standard one ... Mazda will have spent way more than anyone else on making a quiet exhaust so why not rip one appart and take a look at what they did.
You\'ve got a good point there. I don\'t know what the rx-7 standard exhaust is like, but a lot of after market exhausts for other cars claim an extra 5-10% power. They don\'t tell you they often lose 5-10% torque. I\'m currently running a standard one while I get the other rebuilt. Problem is, that one\'s also falling apart inside and generating loads of back pressure on the second turbo. I can\'t open it until I\'ve something else to go on the car.
Anyone got any old tailpipes (including standard ones!) ready for the bin?
QuoteOriginally posted by Robertio
Sorry Clive, but Carls cat back does not even approach my definition of quiet - I have it and one of his silenced midpipes (which is very quiet by itself) and it\'s still far too loud to take the car anywhere near most track days.
I do plan to test it back to back with a couple of other cat backs for noise and bhp when I get my car back.
Hi robbie
Are you going to give it back to me or buy the one I supplied to you from me?The design you have is not the right one for really quiet use,I have a different one for really quiet use.
Listen to my RX3 at Rotorstock to see the difference.
Kind regards
Carl
I\'ll keep an ear out for the new quieter design at Rotorstock :)
As agreed I\'ll pay for the cat back once it fits, the car has been off the road since our last e-mails in February where you said it could not be fitted properly without having the car as well as the exhaust, so my hands have been tied. Hopefully I will get the car back in the next few weeks and will take it along to my local exhaust specialists to see if they can alter it to make it fit and if so pop a cheque in the post to you. If not then I\'ll have to arrange to drive down and get it sorted - giving it back is not an option as the midpipe rubs if it is used with a stock cat back, and I\'ve had it for that long I don\'t feel it would be fair on yourself.