4evascoob

So rumble had well and truly gone and I have to fix it. Current is stainless rcm un equal headers invidia d/p standard centre and bb. Car is 2016 sti. It’s loud but raspy / horrible. Is there anything that could be done. I’m thinking q300 or r400 cat back but will this just make the rasp louder ? Any suggestions welcome.

JdmSti2006

Rumble comes from headers,looks like SS rcm unequal issue
turbo back exhaust just change a tone of it

1509joe

iTrader: (2)

RCM unequal headers still have individual runners instead of a single crossover pipe. As above.
Plus you'll need another resonator to take the rasp out of it.

4evascoob

So would a q300 or r400 help or make worse ? Think it’s more of a tuned sound with them ?

JdmSti2006

if rumble went with standard parts apart invidia downpipe then it's definitely due to headers, still unequal but they make them to flow better-less burble.
2.5l is known to have less burble than 2.0 and by error You made it even worse
if You will put invidia downpipe on oem headers it will give more burble
either way You go buying new parts it will cost a lot

4evascoob

To be honest it didn’t have much to begin with ! So do you think adding a cat back system would just make it sound louder but still bad ? Standard exhaust is of thought would struggle with the now performance of engine anyway ?

JdmSti2006

Yes thats what I think, is invidia downpipe de cat? if Yes it should give more burble than less, when I swapped to decat on my wrx it was louder with more burble plus something extra in a cab,noise like a Hammer hit a vice ,I loved it.
With burble You hear it more staying outside a car than inside ,my was on 3" full exhaust.
With new exhaust maybe it will be better a little but if You add silencers to drop a rasp it will quiten burble to.

4evascoob

so yea the invidia is full 3” decat , prior to turbo it is rcm unequal and Harvey u/p from invidia d/p it is standard exhaust. It sounds to me like the standard exhaust is just resonating with the upped power of that makes sense. For instance the piping to the rear boxes is tiny ! I would hope fitting a q300 or r 400 would take that away. It’s the resonance I don’t like.

JdmSti2006

Yeah it could be restricted but no more than with oem downpipe, now mainly in centre pipe as later You got big back box or 2 smaller with 2 pipes ,but oem burble should be there. Take off back boxes and centre pipe and try without , if You hear a burble buy Invidia than.

4evascoob

good idea I suppose I could just drop pipe off from centre to d/p , I’m sure it is the old exhaust not coping well with pressure as it steps down to smaller pipe. My last 2.0 sti had oe headers but ported and decat with prodrive centre and bb and it sounded awesome. Used to set car alarms off for fun ! The only way this would do it is if I drove into the other car !! Lol

1509joe

iTrader: (2)

As in post 3 single crossover pipe is what you need for burble. Not four individual runners.

4evascoob

which you won’t get with aftermarket ss headers ? The question is what will if anything improve it and take the resonance away if at all. I’m sure half the issue is the standard centre section and bb

1509joe

iTrader: (2)

Nothing to do with the centre section or back box as you haven't changed it. Try another resonator in the centre section otherwise get a set of standard ported headers. Think Alyn at ASPerformance does them.

JdmSti2006

mine 2.0l wrx was fitted 3" decat downpipe and invidia n1 race, never heard better noise and burbles on a scoob but i had a headache within half mile of driving
full rcm 3" decat on my jdm had no burble but sound was epic to
if You change headers You will need remap again i think -more costs

4evascoob

yes might have to stay as it is. Don’t think I could stomach any more cost as I’ve spent north of 9k as is ! See how it goes and maybe swap out another time. Exhaust is also 1.3 k on its own. I’ll load a clip later of the culprit !!

4evascoob

nobtrue I haven’t changed them but it’s made it worse if that makes sense. ? It wasn’t good to begin with running just decat and standard everything else.

1509joe

iTrader: (2)

I take it this is a UK car not a twin scroll JDM.

JdmSti2006

wow Sherlock ?

4evascoob

yes uk car ,
as said my thoughts are the exhaust ( standard centre & bb ) can’t cope or don’t like the now 500bhp obviously copes as it was mapped but it may not be happy hence the resonating noise.