Hi-Flow Cats too loud!
 

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.

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

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:drool:

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... :icon17:

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.

Yeah.... isn't it great?:excited:

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.

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

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

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.

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

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.

That would be me! :tiphat:

http://www.the370z.com/parts-sale-pr...k-exhaust.html


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. ;) :p

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.

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

Yours and similar posts have pretty much convinced me to leave the CATS alone. I think the Stillen is a tad quiet, but is a comfortable system when traveling with no bad characteristics. I'd be kicking myself if I made the change and then did not like it...

"mattkim85" in CA already got pulled over for his being to loud. Check the classifieds.

What about stock exhaust en HFC's? That is the setup I am going for. From the video's DDM posted, it sounds good, not too loud and it should yield nice performance gains.

I must say by reading all the negative posts here, that I'm kind of disappointed. A lot of people (by far the majority) talk about "modding" their cars. With just a little (and I mean a small amount) of research, one can find out loads about what the different mods will accomplish.

I was the same way. Some pointed questions, a little research, and finally... the big decision was made.



Nah, I've decided not to continue. I'll get flamed too hard. :ugh2:

So people..... my experience was to do the Stillen HFC's, CBE, Gen II intake system, and sway bars. I was surprised with the sound's "loudness". Yes, it's not quiet. But the performance gained far out weighs the "inconvenience" of the sound. I really like it. For those of you who are having trouble with the authorities, all I can say is I feel for you. Where I live, there's no such bother when we've got Harley's and the like driving around with what sounds like no exhaust at all.... the 370 sounds as quiet as a Honda Fit.

The HFC's (and the whole exhaust system) "resonate" at different revs. Cold starts are LOUD. Some speeds (read: revs) are uncomfortable (read: droning). But, I took a four day trip with the car and was very surprised at the level of comfort (sound wise). The audio system would generally cover up any exhaust notes when I wanted it to. After that, the rolled-up windows did wonders.

:icon14:

I have the Stillen CBE, HFC, Headers, Gen 3 intake. car sounds like a Z. Cruising at 3000-3500 RPMS, sound is not harsh. Easy having conversations etc. In the hurry-up mode, it has a distinct throaty sound. Course this is comparing to just the Stillen exhaust since I had them install on day 3 of owning the car. Happy driver and local Law types have not stopped me. But this is Live Free or Die country. Or it could be I'm losing my hearing, but who cares.

Hope not :icon17: That was in a very deserted industrial business park on a Sunday, I looked for a place with no cross streets and on a cul-de-sac. Not saying that this is a safe thing to do on the street, but I did put some thought into it.
I've seen others shooting video, and it looks like there right in front of their house in a residential section :eek:
Try and be as safe as possible out there and use discretion. :tup:

I think the Berks sound great, probably not quite as loud as the Stillen/Berk combo.
I've got Nismo/Berk at the moment, and it's a little too mild for me. Sounds great when you get on it, but I don't want to have to drive my car fast all the time to get the enjoyment of the engine growl. On the other hand, I don't want something that is going to drone or attract too much negative attention. Hoping the Berks CBE will be the solution. :tup: I don't want to give up my Berk HFC's they have definitely made the biggest difference in performance gains so far.

I like the loudness under WOT that is why Im going to get Test Pipes when I get Exhaust

I loved the sound of my Borla With APS test pipes, Megan Racing Headers on my 06 350Z


DAN

I thought it was against federal law to removing functioning cats even if they were replaced with other cats.

Same for me... for now, anyways. I ordered the FI CBE with 18" resonators, which I'm thinking will be loud enough for me. If not, maybe I'll add HFCs... but only if I'm sure it won't be obnoxious.

HFC will not make it obnoxiously loud unless you are WOT all the time. If you drive normal speed limit and keep your revs under 3k it's not that loud.

The HFC definitly make the car sound modified and that is what I didnt really want. Its not a bad sound by any means, it just isnt refined like the exhaust note of like a Porche or something. It sounds like a tuner.

Now I would tell anyone who is considering test pipes it will border on the obnoxious loud side and will sound raspy. Even with the HFC's there is a little rasp at WOT but test pipes would amplify this.

OK OK OK.. I did it today! I took off the Berk HFC's!

Oh my God!

I love my car again!!!!!

It sounds about 75% less noisy.
100% less raspy!
100% less drone!
and still has a sporty sound at the upper rpm range.

To be honest, I drove home with a smile on my face the entire drive home from the exhaust shop, and that's the first time that's happened.

If anyone is one the fence on this one. I hope this pushes you in one way.

Good luck to all!

I havent pulled my cats yet and I may not. I just got my car back from the car audio shop and they put 120 sq ft of sound deadning in the car and it is sooo quiet inside. I can't hear the anoying drone anymore. Its a night and day difference not to mention hardly any road noise now.

I can live with HFC now. Without the sound deadning, I was ready to yank them like "John370z"

2Fast, not to get off thread but other than the doors, where did the shop install the material...I'm guessing dynamat??? Fixin to do mine

thanks

mac

Actually I used Rammat. Its not only cheaper but its better. I bought 2 rolls which are 62.5 sqft for about a $100.00 a roll. Plus I bought 6 yards of ensolite foam barrier that is glued to the Rammat.

RAAMaudio

I had it applied double layer in the trunk floor and wheel wells and yes, both doors. It was very well worth it as the car is amazingly quiet inside.

I had the entire interior of the car removed. I am adding pictures of the process on the Audio thread but there are a few there already.

Yep, it's also illegal to change out motorcycle exhausts,

Laws are made to be broken. :rolleyes:

That's kind of my point to a degree.

I'm thinking I'll swap cat-back first. If it's not loud enough, I'll get an HFC with resonators (both of them Fast Intentions)..

I do not want a drone/resonance in the cabin at any RPM. I just want it to sound as powerful as the engine is ;)