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Discussion Starter #1
So, I (finally) got my de cat manifolds and equal length downpipes installed.

Question is: Do mine sound as yours ?
Mine develop a heavy rasp / resonating sound from about 2000 RPM upwards that seems to die off at about 4000 RPM.
Is that normal ?
I had thought that the rasp sound would not come on till say 3000 RPM.
 

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Sounds about right, if you don't want it like then there are various options that you can pursue to change it, Dan will explain that further.

One thing I've noticed about the noise since having my mapping sorted is that the noise has indeed changed, no way near as raspy as before and infact sounds more 'tuned' for the better word :)
 

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From the downpipes backwards, what are you using?
 

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Yep mine rasp :)
 

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Discussion Starter #5
From the downpipes backwards, what are you using?
I am just using the standard exhaust.

Dan is most welcome to say a few words, but I think he is hiding from me from that last email that made him go search part in a dirty parts bin :lol:
 

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My rattle in low revs actually went away when I changed back to standard exhaust which would be same set up
As yours, maybe check your exhaust shields. Downpipes also make a difference are you running aftermarket stainless steel?
 

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I have the rasp on mine and I believe it comes from the cat. Well I pin pointed it to around there. I also thought it could be the crap metal gaskets.
 

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I agree, I've long suspected the cats as being the source of the rattle too. It's there on OEM or wizard on my setup, doesn't matter. Cats are pretty old & knackered.
 

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Mine are full of oil :lol:
 

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I had this rasp when I had the standard centre cats too, then when I changed to the sports cat/silencer it cleared it up no end, but was still slightly raspy. This changed this weekend when I had the map done again and now I no longer have those nasty noises :)
 

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I like the rasp :confused:
 

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It's some times but can be a little annoying others. I want to get rid of it. Goin to replace it with sports cat and better gaskets.
 

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I also have the rasp, and it definitely sounds like it's from the centre cat (I'm sure it can't be good for it). It was really bad when I had a scorpion back box fitted - almost to the point of being embarrassing and with really bad cabin resonance between 1750 and 3500 rpm. I switched to an IMASAF backbox (copy of the original) and it really helped tone it down.

My current set up:

CF2 Manifolds -> Dan's front pipes -> standard centre cat -> Scorpion front silencer -> IMASAF backbox.

I had this rasp when I had the standard centre cats too, then when I changed to the sports cat/silencer it cleared it up no end, but was still slightly raspy. This changed this weekend when I had the map done again and now I no longer have those nasty noises :)
Where did you get a sports cat and map from?
 

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I also have the rasp, and it definitely sounds like it's from the centre cat (I'm sure it can't be good for it). It was really bad when I had a scorpion back box fitted - almost to the point of being embarrassing and with really bad cabin resonance between 1750 and 3500 rpm. I switched to an IMASAF backbox (copy of the original) and it really helped tone it down.

My current set up:

CF2 Manifolds -> Dan's front pipes -> standard centre cat -> Scorpion front silencer -> IMASAF backbox.



Where did you get a sports cat and map from?
The sports cat is a racing cat so bit more free flowing than a normal one, I got it from the wizard and the mapping was from Gus @ Alfatune. :)
 

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Hmm slightly worried as i have Scorpion cat back at mo and have just got some cf2 manifolds.
Although i will most likely be using Alfatune front pipes and std main cats and get Gus to map aswell.
 

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A catalytic converter is a device on an automobile that takes harmful gases produced by the internal combustion engine and converts them into CO2 and water vapor. There are two varieties of catalytic converter: one with a pelletized substrate (the material inside the converter is dozens of ball bearing sized ceramic pellets) and another with a monolithic substrate (the material is one large, honeycombed mass).

Are the Alfa ones honeycombed or the pellets?
 

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Discussion Starter #20
Will you not run into problems with emissions when running a sports cat ?
I have already removed the manifold cats, so the emissions will be higher already, and with a high flow sports cat it may make it even worse...
 
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