Romanteni

iTrader: (10)

Ok so I just bought a used HKS exhaust off a fella on here. Installed it, but noticed something pretty much right away. Yes its HELLA loud, and deep, when on cold start. But as soon as it starts warming up and RPM dropping just a little while idling - it starts making LOUD noise like there's shitload of little rocks inside exhaust, or sand, not rocks I guess.

We put the car up on a lift, and started the car, and while revving the engine up, when rpm drops you can hear that "sand" or w/e u want to call it right around resonators area.

I'm not huge exhaust pro, but can the stuff inside resonators get busted and make that noise? It's really loud when idling, when accelerating you can't hear it cuz the exhaust tone overtakes it, but as soon as you drop gas, you can hear it really loud again... The guy that sold it doesn't want to admit anything....

I got no cats, got test pipes and full HKS catback now.

Romanteni

iTrader: (10)

Sorry if wrong section, and flame if you want. Maybe someone seen similar issue, just wondering what the best thing would be. I'm assuming just cutting resonators out would make the exhaust sound horrible?

Romanteni

iTrader: (10)

Also, while standing under the car and the car just idling, I was listening close, and sounds like there's crapload of sand right on bottom of the resonators, and its making the sound just from the tiny vibration. Went listening along all the other pipes, and seems like its doing that only inside the resonators.

Hydrazine

iTrader: (53)

It sounds like you should be contacting the seller about this.

Romanteni

iTrader: (10)

Yep I did, as well as I was trying to read all posts on this forum/google regarding resonator noise.

Shipping back to seller would prob cost me a shitload, thats why I'm trying to think maybe fixing and just having him pay couple hundred would be more time/money effective? But I'm trying to think of possibilities to fix it first :/

davidv

iTrader: (2)

Material inside the exhaust may make noise. Sometimes you can shake the exhaust. Other times it may produce a loud rattle.

Romanteni

iTrader: (10)

thats the thing, its not really a rattle like rocks or rubbing, its a like a tiss sound... hard to explain. kind of like when you use a wood saw the "hiss" sound it makes when you turn it off and it drops in rpm. But when standing under the car, you can hear the "hissing" coming from under resonators, kinda like if you have sand collected on lower resonator part and its making that sound but its LOUD lol...

Few people suggested its test pipes, I'll try throwing cats on to see if that fixes it:/

R350Zz33

iTrader: (4)

is it raspy ?

blue350zed

iTrader: (14)

+1. Maybe try taking one off and shaking it around to see if something really is loose in there. If not, I would say it's just a bad case of the rasp.

terrasmak

iTrader: (8)

Non resonated test pipes can easily cause that sound

Romanteni

iTrader: (10)

Yeah it is raspy, but that isn't the problem, its the loud hissing when idling/dropping rpm i mean you can hear it from across parking lot that something's wrong lol...

I love working on cars, problem is its lowered and nearest place that can take a low car is like 50 miles away, so i cant be driving back and forth, thats why I wana research before I go there so i can check as many things in 1 trip as possible. Thanks guys

Romanteni

iTrader: (10)

hmmm weird tho, they're none resonated, but with stock exhaust there as no sort of noise like this... I guess we'll see once I put cats on if that fixes it.

terrasmak

iTrader: (8)

HKS is an open exhaust without chambered mufflers, you will hear everything.

Romanteni

iTrader: (10)

I see, but yeah I've heard HKS before, haha didn't hear this ****.

SQBassHead

iTrader: (37)

I say when you go to the shop,

1. Take off the canisters an shake them to see if any noise
2. If one don't work, put stock cats on and see how it sounds
3. Keep in touch with the seller, I hope you used paypal

Also, you never heard this with the stok exhaust because the stock muffler is completely diff from the mufflers on the hks,
If it does end up being the canister, this is what I would do
1.purchase a resonated x-pipe from magnaflow
2. Cut off the canisters, close the connection between the exhaust, and re-weld back on bc the canister look FKN sweet lol

that way it will still look like a hks and not a regular exhaust

SuperBlack350z

iTrader: (59)

it's the test pipes, not the exhaust.

Hydrazine

iTrader: (53)

You might want to look down inside the pipe to make sure one of the side branch pipes isn't protruding into the main flow stream.

Romanteni

iTrader: (10)

Dude guys you're the bomb, thanks for help. Driving to the shop today to try these things out, so I'll post on here what happens. If its test pipes, I'll be bummed, I hate the thought of putting cats back on, its just soo.... green and ****. Plus, thats like telling the CA police department that they're right... makes me sick.

ap2_S2Kyle

iTrader: (2)

its the test pipes. 350'z have a decel hiss when the rpm drops when you rev it..just the way it is

Romanteni

iTrader: (10)

Hmm how do the guys with test pipes do it then? Would putting resonated test pipes fix it, or is just of the way airflow is in HKS that it makes the hiss so dam loud? I though resonators on the exhaust would you know, fix the sound,. Well we'll see today if that fixes it, if it is infact test pipes, any suggestions on which ones I can get that would work, I mean I see lots of people here with test pipes or high flow cats...