Hi-Flow Cats too loud!

2fast4thelaw

Have any of you felt that when you install Hi-Flow cats that it makes the Z a little to loud? I have a Gen3 intake, Stillen HFC's, and a Stillen CB and it makes my car really loud when I tromp on it! I am almost considering putting the stock Cats back in to tone it down a little. I like the power gain and greatly improved throttle response and top-end but I am not sure I like the sound.

m4a1mustang

Fast Intentions makes resonated HFCs which would probably quiet it down a bit while keeping power gains.

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OVERZLUS

Do you have a video so we can hear what it sounds like? I'm thinking about getting HFC's too, but I'd like to hear others first.

Thanks

6MT

No!! That sound is wonderful!! Yes, it is louder than stock. And through some revs, the resonance is a real "drone", but I love it. As I mentioned in an earlier review, the 370 (with the Stillen exhaust mods) is not a car that you should try and have a conversation with someone who is hard of hearing...

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Andrew

2009 370Z Sport/Touring 6MT sold
2013 Honda Civic Si coupe D/D

2fast4thelaw

It sounds great at idle and start up but when you stomp on it, it really wails! Its really freeking loud when I floor it. It sounds like a crotch rocket!

The funny thing is its louder inside the car with the windows up. It drones a little with the windows up but not at all when they are down.

The Stillen CB sounds awesome with the stock cats so I am probably going to put them back in.

Hindsight, I wouldnt have bought the HFC's

My Stillen Cats may be up for sale.

6MT

Yeah.... isn't it great?

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Andrew

2009 370Z Sport/Touring 6MT sold
2013 Honda Civic Si coupe D/D

BerkTech

Before you start with the exhaust mods it's important to hear what the car will sound like with ALL the mods. For the OP it wouldn't be cost effective to swap exhausts with something that sounds better with HFC's so going back to the OEM cats would be your cheapest option to get the car to sound better.

Here's a quick clip of the Berk Technology exhaust on the DoubleDown Motorsports 370Z. Clip shows the car with our BERK HFC's.

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Brazilbro

If you pull them off let me know.. I got test pipes but want some HFC for Time attack

Shift_Xz

The Berk system sounds awesome! I can't wait to get a hold of my 370z... $$$

FricFrac

Opposite for me - idle is weak - way to quiet. Sounds fantastic under load. The drone is around 3-4K RPM and its because that's the resonant frequency of your cabin - open the windows and you change that resonant frequency (somewhat). It doesn't matter what exhaust you have you'll get that frequency where it "throbs" like that.

Just a question - if you don't like the exhaust note why did you get a loud exhaust system? The NISMO exhaust should give you better flow and its much quieter. IIRC someone is getting rid of their NISMO CBE because its too quiet.

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'09 370Z - '93 300ZX Vert - '83 280ZX - '83 280ZXT -'81 280ZXT stroker - '72 240Z - Stillen CBE, HFC, G3, Grounding Kit, Sways // Swift Spring // H&R 15mm // 5% Tint // Clear Bra //

john370z

I have the exact same setup and feel the exact same way! I have added much sound deadening material which has reduced the drone by 50% but it still had that sound that hurts my hears a bit between 3K and 4K rpm. I love the gains in power but do not like the loudness. I too have been thinking of putting the stock cats back on but have not done it yet. Mine are BERK....if someone in interested in buying it might push me over the edge and sell them. Let me know what you do?

john

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2009 370Z, Had Berk HFC and un-installed them cuz too noisy!, Stillen CBE, 10mm rear wheel spacer, K&N drop in filters. Blower to come...

BerkTech

Agree with you on that one. The Nismo exhaust is what I would describe as "the exhaust the Z should have gotten from the factory".

Nismo exhaust w/ Berk HFC's. Minicobra's car.

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Sonic370Z

That would be me!

370Z Nismo Catback Exhaust


Agreed, if you are happy with the HFC's and want to keep them, but looking for a quieter exhaust note, check out the Nismo. Guaranteed to be quieter than any aftermarket setup. I don't have videos of mine, but the user Minicobra1's YouTube videos are what convinced me to go with the HFC+Nismo combo. He has 2 vids on YouTube if you want to check it out.

In the end, it was still a little too tame for me. In fact, I took the Nismo muffler off and ran it for a few hours with only the resonators installed and it sounded FANTASTIC. But I like loud exhausts, haha. Anyhow, definately worth looking into if you want to retain the HFC's. And if you're interested in the Nismo, I know where you can get a like-new one for a good price.

2fast4thelaw

I loved the sound of the Stillen exhaust from the clips I heard. The HFC's radically change the exhaust note. I am not changing out my exhaust system, thats like throwing the baby out with the bath water. I am just not happy with the HFC's It makes the car sound ricy. Plus I doubt I will pass emissions when I have to test car in the next 3 years with the HFC's. Plus I dont like the hiss the HFC's make. It makes it sound like I have an exhaust leak. I think my HFC's need to go.

CrownR426

I wonder if cops look at these launches and try to find out where it is.
lol, hope none of us get caught!

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