back box performance info wanted

S

shabby.fx

Member
hi all, i just went to my local welding shop to get my back box changed, because i have a straight trough exhaust system. i bought a cheap back box the ones you find on a little corsa or similar. but when i told the guy to weld it on he told me my performance will decrease and i needed a bigger back box... i asked him why but he couldn't explain to me, so i got a bigger box and put it on.

i just wanted to know why this will decrease performance as it was the same as just having a straight pipe put on the back of it.

what does the back box do other then change the sound and what benefit can i get from it, also if you guys can find me some diagrams id be very grateful.
 
the cheap box what a single tube exhaust with a 2.5" in and 3" out but the cylinder around it is very slim, only about 1inch thicker then the inlet. and the one i have on is a cheap twin ext, with 2.5 in and two 2.5 out with a much larger surround.

i have an s13 on stock but with uprated intercooler and a rad
 
The size of the silencer around it makes cock all difference to performance. If the bloke you spoke to said that, he hasnt a clue what he on about.

Its the size of the pipe through it that matters. If its no smaller than the pipe it joined to before it, ie if the pipe before was 2.5in anyhow too, it will be no peoblem.
 
Yeah as above, as long as you don't go down in size to the original exhaust it'll be fine, you want to avoid causing any additional restriction on the flow of gas.

This is my Soarer exhaust, everyone keeps moaning that the pipes are to small, but they are the same diameter as the rest of the exhaust so it's not causing any restriction.

54f17649.jpg
 
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