Decat Noises ??
 

OK I have finally DeCatted my Scoob MY00PPP with a open Neck H&S d/pipe. With the 1.3mm restrictor the car goes very well however I have a few questions for others who have gone the Decat route ;)

1) Having had the Decat it seems that the Turbo is very loud - I mean I can hear it spooling etc ? Apparently its not that loud from outside but from the cabin is very noticeable, loads of whistling etc. Its not lagged or anything and is this normal ??

2) I am now hearing different sounds coming from the car too. As you can imagine the exhaust note has changed (deeper) but I can now hear what can only be described as a stick being put into a spoked wheel sound when I accelerate and she comes on boost sort of metallic?? It seems to be noticeable at 3K rpm upwards but goes quieter with more acceleration. It sort of sounds like a Rasp ?? has anyone else had the same

I have performed the search for such experiences on here but there didn't appear to be any real conclusions. Can anyone give me their thoughts/experiences ?

Cheers

Nelson I also have an MY00 but no PPP and original centre section and my car makes both those noises you have described. I was worried about the stick in the spokes noise but nothing has blown up in the last 3 years since I decatted my DP so I am now not worried about it.

Hi Nelson

I've just decated my MY99PPP, also with an open Neck H&S d/pipe (H&S straight through centre and original PPP backbox). I did lag the d/p but the turbo noise is still much more noticeable than when catted. I notice it more around town when you can hear it whistling.

I'm not sure about the metallic noise you describe - I've not noticed it.

Also, I didn't need to change the restrictor since the boost seems very stable.

Dibs

Yep mine has the same sounds, add on the induction kit and you have a complete scale !!

MY99 full de-cat, K&N ind etc

the rattle could be the heat shield mine does now since the de-cat

hi. my my99 ppp had the downpipe changed for a tsl downepipe . i have noticed the same problem, but the vibration appears to come up my steering column
I belive it must be from the lower heatshield as it doesn't appear to be fixed very well
it only happens when the engines under extreme load (all the time)

Well earlier this evening I drove the Scoob through town and managed to find some narrow roads with walls either side....it is defintely a rattling metal sound I can here and yes it does sound like a heat shield or something similar. What heat shield could this be cos the Deact doesn't have a shield (only the turbo) ? I do have the PPP standard Decat centre pipe which I believe is the oem pipe with the cat removed.....and the 'cat' housing does scrape when I drive over speed bumps etc...I am however looking to replace the centre with a straight through piece instead.

So do you all just live with it or is there a way around these very annoying rattles ?

Shouldn't rattle. But whoever installed it should have trimmed the heatshield to accommodate the bigger pipework. Perhaps this hasn't been done very well. If you're worried about it, some people say just leave the heatshield off. Take it off and see if this is what's causing the noise.

I would say the chances are it's the heat shield around the turbo. probably the lower part of it.

Why not take it off and see if it still rattles? It's not a difficult job.

I've removed mine completely and wrapped the turbo/downpipe with heat wrap.

There's one other option gents:

when the downpipe was changed, the centre section is usually loosened also to allow better fitment. Sometimes when the exhaust is put back on, the centre pece may move position slightly and on accelaration and deceallaration rub against the drive shaft due to gases causing the whole exhaust to vibrate.

I noticed this after fitting a Ninja backbox and having to loosen the centre pipe, the noise resembled a few tin cans being dragged behind the car on wedding day.........!!!!

Also, don't forget that until the downpipe proper carbons up you'll hear alot of metallic sounds especially as it's right underneath you almost.

Just my 2p worth.

Skoosh - full decat uk wagon.

I think the ticking you can hear is a result of the decat. It may be the sound of the boost control solenoid and or wastgate opening/closing.

It will be more noticable at mid revs due to boost pressure not being high enough to hold the wastgate fully open. Hence it may open/close in line with the boost control solenoid duty cycle.

If you lag the pipe it should be less noticable. Although mine had become more noticable of late, since the lagging has gone hard and has started to stick to the pipe. Hence I think it sound absorbing properties have been reduced.

It's been on over a year, so I may change it soon. The lagging on the centre is still soft/normal tho' as this does not get so hot.

P.S you will probably find the stick in the spoke noise reduced as the pipe gets hot. Also lagging gets rid of the horrible tinnie rattle you get when the pipe is cold at approx 1,500 to 2,000rpm

Scott and the rest of you - thanks for your input most appreciated - the Boost solenoid is exactly what it sounds like actually just amplified ;) and yes the stick in the spoke sound did go the warmer the car got :)

The Turbo heatshield has been trimmed to fit the new Decat D/Pipe and is secured very well no movement at all :)

Helpful
 

Excellent thread, answered a few questions I was afraid to ask.. ;)
Cheers
John

Glad to be of help...;)

Guys i've been getting these very noises too, just decated two weeks ago with a magnex downpipe. the tinkling noise that you's are talking about, i also get, but its pinking, my car is running lean, found out last week on the rolling road. just thought i would make you's aware.

Paul

Keevster - sorry to hear about the pinking - can you tell us what spec your scoob is ?? The tinkling noise I hear is only at around 3-3.5K rpm it goes if I rev past this amount ?? was your doing it all the time ?

Mines not pinking as I have a Knocklink.
And I know this worksas the bottom 1 or 2 lights flash when I really rag it.

MY04 WRX, EU import. funny you say that mate, hearing this noise at 3/3.5k. I get the exact tinkling noise at 3000revs, and thats what i put down to pinking. The bloke that RR it stated he heard the pinking, and stated it was running lean, 12/1-14/1 at one point. i will be getting a second opinion next week on this.
as per usual i have heard so many stories, that a decat should not run lean, and stories telling me it will run lean. hopefully i will find out soon.

Paul

You need a knocklink if you decat a PPP'd car.
You are probably hearing resenance(sp?) from the downpipe, this will enhance the noise of your engine, my MY00 PPP'd scoob sounded much different after decatting, the power came in lower and there was a more promenant sound from the engine, thats why i had a knocklink, all was well though :D
I would say it is as good as my new scoob, alas nope..... :(

Tony:D