So about a week ago i had my magnaflow cat back installed. Everything was fine, it was deeper and got rid of the rasp from the stock exhaust. Only problem was the fitment issue with the exhaust tip then later how low the mid pipe sits rattle on the support brace under the mid pipes but that wasn't to bad i just hid the brace bent and rattle was gone. Well, today i got my fi hfc installed man the whole exhaust system dropped lower and rattles like crazy now and the rasp is back. I thought all the rattle was comming from the same brace under the mid pipes so when i got home i took it off. It helped a little but there still something down there rattling and still raspy anyone have this problem after installin hfc's or with a magnaflow exhaust. This is very depressing all this rasp and rattle makes the car feel so cheap.

SOMEONE HELP!

 

hmm.... that was a given... HFC's tend to make exhausts a bit raspier than the OEM ones. as for the rattling problem, not sure...

 

Yea I had a feel it was gonna get raspier but this rattle sucks anyone else exhaust drop lower after adding hfc they said it was because there was no where to bolt the brace right under the cats cause the after market hfc doesn't have a hole for it

 

What HFC's and Test Pipes do, is amplify your exhaust note in some way, Magnaflow has a little rasp in it, yes its deep I agree, but some rasp is involved. When that note is amplified, the deepness AND the rasp are both amplified. If you're unhappy with the note, you can try header wrapping your HFC's otherwise just get another exhaust brand.

And don't take off the underbrace, just use some washers to space them out. I put two on each side back when I had the magnaflow

 

I was plan to get washers tomorrow because it was to late right now

 

Header wrapping exhaust the HFC i read somewhere was not exactly a good idea, as the pipe itself needs to be cooled by the ambient air around it. It does suck that your experiencing rasp though, but even a stock exhaust with the HFC will bring out rasp.

Is the slight performance increase worth having the HFC? maybe you can just do without it, and eliminate some of the raspy noise.

 

I have the EXACT same problem!!!! theirs a thred on it no real help.. Its the CATS something to do with airflow.. its not the EXHAUST.. I had NO noise till i put on CATS and no changing CATS will not help. Dealer and AAM could not find any solution. I think if we do HEADERS it may change airflow and help with noise... Does it happen when you downshift in 1st and 2nd gear???? thats the only time it happens to me i too bent brace no real help.. Keep me posted if you find out anything

 

it usually happens in low to mid rpms and when im comming to a stop. It gets pretty bad but after taking the brace off and driving it this morning there was still some rattle there then later most of it went away. There still is a little rattle more of a buzzing noise when comming to a stop or dropping to low rpms. I will probably get some washers to space the braces lower like sam said. Im thinking the exhaust needs more support to hold it up higher and firmer in place. I am goin to take it to a shop and have it lifted it up to see where there rattling comes from. I also might add some more support for the exhaust and maybe weld a piece of metal at the top and end of the mid pipes to hold it firmer in place. i am working the rest of this week but i will probably try this sometime early next week. i will let you know if there is any progress. also the rasp went down a little today so im feeling a little better i just wanna get rid of the rest of the rattling

 

Do FI HFC not have an "ear" type bracket on the cat to mount them securely?

Getting under your car with it on a lift and the engine running is the best way to see exactly where your rattle is coming from.

 

not sure didnt look like it

 

i've been looking around and i dont think FI have the "ear" type bracket but berks do

 

I would not header wrap the HFCs. I don't know the composition of the HFCs but header wraps will trap heat inside the cats like mikeyboy said, might not be a good idea, don't really know.

Since you don't want rasp, I'd get rid of the HFCs.
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wrap the hfc's. it will help your rasp and maybe rattling as well.

 

I've had this arguement on header wrap before, header wrap will decrease the life of your HFC's (due to the thermal stresses) to around 30 years so you should be fine

 

Weld a bracket on it like the Berk?