Rasp (very common I know), How to reduce it?
 

This issue had been discussed before but not in the direction (I dont think) I'm going to ask it.. I currently have the F.I 12" res system with their HFC's. I do not have any intakes on the car as I will be going FI in the next 6 months with the fast intentions kit.

As many of you know, when I let off the gas and let the car slow down on its own or coast, I hear a hissssssss that will last anywhere from about 3500 rpm down to about 2000 rpm. It is faily loud.. I want to try and keep the exhaust the way it sounds now, it has the perfect volumn for me. Would test pipes make it worse or better? should I put the stock cats back on? I dont want to lose any power if I dont have to but the hiss bothers me.. sounds like an exhaust leak but its not.

Any thoughts on this please?

Thanks in advance! :tiphat:

Test pipes will be worse, you need to go to stock cats for 0 hiss and 0 drone... You WILL lost HP.

(Yeah you can go Art test pipes or resonated HFCs, but you'll still have SOME hiss

i feel that if you are goin FI the turbos will act like a muffler and get rid of some of the hissing..

Resonated TP's won't hiss or rasp.

Generally, going to a wider diameter piping over stock seems to cause hissing -- especially changing the Y pipe.

That said, if you are definitely getting a turbo kit installed, I'd wait until that is done and tuned before changing anything else.

I have the hiss as well. Greddy 20G TT Kit w/ F.I. TT-TDX. It doesn't bother me much, but I keep thinking that I have an exhaust leak (then I laugh it off). I will be experimenting with a "custom" with F.I. first. If that doesn't work, I am going to try something off the wall w/ AAM. I really love the F.I. exhaust though. There is nothing out there that delivers the same performance AND sound.

Resonated test pipes sound like a great idea.
Will my exhaust be louder on the outside?? I don't really
Want it any louder. I would love to cut down on the drone
Too.

Thanks

You'll still have hiss with ART pipes/resonated test pipes. Depending on how the pipes behave with your other exhaust components, it should be lessened a bit.

I had a set of CNT resonated test pipes and there was zero hiss or rasp. Wasn't any louder, no drone.

EDIT: No louder compared to non-resonated TP's, but any TP's will be louder than HFC's or stock cats.

But... that was with Nismo S-tune Y pipe. I tried switching to OBX and it made an incredibly loud hiss -- went back to original Y pipe.

If you have the OEM Y pipe, resonated TP's may just do the trick.

Even resonated test pipes are loud with varied exhaust setups.
HFCs are probably your best choice. Less sound then Test pipes but you still get more HP over stock cats. & just a little less then test pipes.

Another option is to just add a set of resonators ($100) to get rid of your drone.

When I got my HFC's, I got non resonated ones. I'm wondering if resonated HFCs would be much better at rasp or drone? I think it would some but not much or enough.

How would I add resonators? Muffler shop or something? I really don't want to cut the exhaust at all.

Yes 100% test pipes will be louder over HFCs, but you'll also gain a few HP. FI HFCs you have everything running through a 300 cell cat...where with a test pipe, its running straiiiiight through. There's nothing resisting it at all.

Resonators have nothing to do with performance, only sound. They won't take away HP, but will help avoid rasp and drone.

You can order resonators online or just go to a decent shop to get them welded on your existing exhaust. It would make it more of a custom build but the resonators are only about 1 foot or 1 & 1/2.

But thats if you really want to get rid of the drone. If you decide that it still is bothering you, you might want to consider just some GTM Mat or something to insulate the inside of the car better. It works wonders...

We just finished up a GTM resonated test pipe and Berk tech catback set-up on a Nismo Stillen supercharged nismo. I havent noticed any hiss or rasp, it actually is the best sounding set-up I have heard to date.

Thanks,
Alex Goodwin
AlexG@motionlabtuning.com

That is because the BERK catback is quiet and sounds almost stock.

OP has the fast intentions 12" exhaust. Doubt he will shell out another $1k just for another exhaust.

Something must be wrong with mine if it was supposed to sound almost stock :icon17:

If the car is stock except for Berk.. its quiet. On a scale of 1-10.. its a 3/4.



Paired with ART test pipes, or HFCs is a little different story.

But coming from someone with short tails, BERK is weak lol.

The big questions is, will resonated test pipes lower the hiss? The drone would be a bonus but not the major issue.

Thanks for all the great feedback everyone.

For whatever it's worth, my ART Pipes connected to CNT catback had hiss. I like the sound, so it wasn't a big deal.

However, there was zero rasp and drone was only in the lower 2k range when lugging the engine (medium+ throttle under too low of a gear)

I have the F.I. resonated TP's and the F.I. 18" CBE. The hiss is definitely there just like you described it. When letting off the gas it hisses till just under 2000 RPM. TP's will not get rid of the hiss. Doesn't really bother me anymore since ive gotten used to it, and with the radio on at all i dont hear it, just the nice low growl from the F.I. setup. More than likely the TP's will make it worse then it is now.

FI non resonated and ART pipes major hiss and rasp on decel

Seems like j bends or those 90* pipes off of some part of the CBE are in your future.

Edit, branch resonators

did it sound good though otherwise? any videos?

I mean it is deep and loud. No sound clips yet and they don't do justice.

would you buy again or go with 12" res? i'm hoping it'll sound awesome. lol freeway drone doesn't give you a headache? dont have to yell over it?