Rasp...coming from what part of my 370Z's exhaust?

marcussoori · 11-04-2010, 03:14 PM

Hi all, I have Stillen G3 long tube intakes, stock headers, Berk HFCs, and the Stillen CBE.

When the car/engine is cold I have lots of rasp at low revs, which goes away after the car is warm.

When the car/engine is warm or cold, I have lots of rasp under heavy load from acceleration.

It's starting to get annoying, as the rasp wasn't there when the parts were first installed. Anyone know if the rasp is coming from the HFCs? Or is it coming from the CBE?

If the HFCs are the culprit, will I eliminate rasp by switching to test pipes? Will the exhaust get louder (remember, Berk HFCs currently, not stock cats), even at cruising speeds?

Finally, some with exhaust plus HFCs/test pipes say there's an "air fart" noise on overrun (letting off throttle after accelerating), would this be even louder with test pipes than HFCs?

Thanks in advance!

m4a1mustang · 11-04-2010, 03:17 PM

Test pipes would be even more raspy. Chances are the rasp will go away if you revert back to the stock cats.

However there's a chance you've developed a leak somewhere.

ProfessorDave · 11-04-2010, 03:27 PM

HFCs would be my bet

marcussoori · 11-04-2010, 05:51 PM

m4a1mustang, why would test pipes create more rasp?

Also, can anyone answer my other questions as well?

Thanks...

Osiris · 11-04-2010, 08:13 PM

i've had the Stillen CBE installed for a while now. Just installed the HFC and now i have a rasp. Although IMO it sounds great. So to answer your question, it's a very good bet it's your HFC.

Jordo! · 11-04-2010, 08:18 PM

Definitely the HFC's; test pipes will sound as bad or worse.

Options are to live with it, replace OEM cats, or get resonated test pipes/HFC's.

marcussoori · 11-06-2010, 01:58 PM

Could you explain why resonated test pipes will eliminate rasp? Is this their purpose? Do resonated test pipes work as well as resonated HFCs? What brands should I consider?

So to maximize power and minimize rasp, my order of preference should be:

1) Resonated test pipes (less rasp, more power?)
2) Resonated HFCs (less rasp, no difference in power?)
3) Different HFCs (maintain power, hope for less rasp)
4) OEM cats (least rasp/least power/quietest)
5) Test pipes (most power/most rasp/loudest)

?

I look forward to your advice! Thanks in advance...
Marcus

Jordo! · 11-06-2010, 03:53 PM

Shouldn't affect power, but the resonators are supposed to cancel out the vibrations making the rasp sound.

marcussoori · 11-07-2010, 08:34 AM

Bump for more opinions...

destinyZ · 11-07-2010, 08:44 AM

Quote:

Originally Posted by m4a1mustang

Test pipes would be even more raspy. Chances are the rasp will go away if you revert back to the stock cats.

However there's a chance you've developed a leak somewhere.

^^^ check all your flanges and your gaskets to be sure they're no broken welds or a bad seals. Another thing is make sure that your pipes are not rubbing up against anything (heat shields) this could be mistaken for rasp. use some exhaust crack joint and crack sealant. The gaskets that come with the exhaust are not very good, you should get them from napa/autozone along with grade A bolts, nuts and washers probably from home depot. if not a bad seal, broken weld or head shields touching your exhaust then you COULD have a faulty HFC. You can see if they will take it back and get another one. The HFC should create minimal rasp if any. I hope this help and GL

mjohn617 · 02-08-2011, 09:21 PM

I have been dealing with this issue for a while! I have had the rasp since I put test pipes on. I just recently put on the Stillen CBE and the rasp is crazy loud now. I did some throttle manipulation a couple months back to combat the back pressure, it worked great but my gas mileage went to **** and I was getting some weird side effects with throttle response and a lot of backfire.

I am really beginning to believe it is the resonators; not by their design but by the exhaust design. Your stock cats are doing a really good job at creating a "buffer" to a stable atmosphere. Removing them seems to be creating a high flow which in general is good. From the point at which the exhaust splits all the way back to the exhaust tips seems to be the issue...in this case pressure differences. Just like when you crack a window on the freeway and everyones ears explode, it seems the pipes are fighting each other. I have spent hours trying to figure this out, I am getting a clear sound coming straight from the resonators when I use a stethoscope...no where else!

I am really starting to believe '10Anamoly 's theory with using a pipe to bridge atmospheres...check it out if you already havent read it.

Fancy Tech: How to Get Rid of Exhaust Drone, works great!

Bottom line, this issue is driving me MAD!

theDreamer · 02-08-2011, 09:40 PM

Straighter the pipe the more rasp.
Also, it will depend on where your resonators, mufflers, and cats/hfc/TP are. Depending on where each is located and the distance & size will adjust if you have or increase rasp.

Viera · 02-08-2011, 09:54 PM

I think it's definitely coming from you CBE. A friend of mine has the Agency Power CBE paired with the Berk HFCs and has ZERO rasp. It is a very deep tone.

mjohn617 · 02-09-2011, 11:39 PM

I put my cats back on today, sound is BEAUTIFUL! Looks like I have some Berk test pipes for sale...I don't think im going back until the turbo kit.

chops · 02-09-2011, 11:44 PM

Quote:

Originally Posted by mjohn617

I put my cats back on today, sound is BEAUTIFUL! Looks like I have some Berk test pipes for sale...I don't think im going back until the turbo kit.

i know what you mean...i have HFC's and sometimes contemplate putting the stock cats back on. i hate the rasp

11-04-2010, 03:14 PM	#1 (permalink)
marcussoori Enthusiast Member Join Date: Mar 2009 Location: USA Posts: 468 Drives: 09 370Z Red AT Sport Rep Power: 16	Rasp...coming from what part of my 370Z's exhaust? Hi all, I have Stillen G3 long tube intakes, stock headers, Berk HFCs, and the Stillen CBE. When the car/engine is cold I have lots of rasp at low revs, which goes away after the car is warm. When the car/engine is warm or cold, I have lots of rasp under heavy load from acceleration. It's starting to get annoying, as the rasp wasn't there when the parts were first installed. Anyone know if the rasp is coming from the HFCs? Or is it coming from the CBE? If the HFCs are the culprit, will I eliminate rasp by switching to test pipes? Will the exhaust get louder (remember, Berk HFCs currently, not stock cats), even at cruising speeds? Finally, some with exhaust plus HFCs/test pipes say there's an "air fart" noise on overrun (letting off throttle after accelerating), would this be even louder with test pipes than HFCs? Thanks in advance! __________________ Stillen CBE & G3 LTIs, Motordyne M370, Berk HFCs, H&R 15/20mm spacers, CiNcity headlights, yellow OEM strut brace, Password: JDM CF engine bay parts, EVO-R CF front bumper parts, CF "Z" badge, VIS CF hood, Fujimura CF "diffuser", Show-N-Go plate frame, Katzkin red interior, interior CF, Pioneer BT-90 full system, Viper SmartStart

11-04-2010, 03:17 PM	#2 (permalink)
m4a1mustang A True Z Fanatic Join Date: Feb 2009 Location: Northern VA Posts: 55,385 Drives: on two wheels Rep Power: 6962	Test pipes would be even more raspy. Chances are the rasp will go away if you revert back to the stock cats. However there's a chance you've developed a leak somewhere. __________________ - Steve Zs & Coffee - Saturdays at 10AM in Fairfax, VA and Columbia, MD (Click the banner!) LIKE us on Facebook!

11-04-2010, 03:27 PM	#3 (permalink)
ProfessorDave A True Z Fanatic Join Date: Jul 2010 Location: Scranton, PA Posts: 1,580 Drives: In the fairway Rep Power: 19	HFCs would be my bet __________________ Rain, snow, sleet, hail: 2009 Mazda 3 sGT HB Everything else: 2009 370z, PW Touring 6MT

11-04-2010, 05:51 PM	#4 (permalink)
marcussoori Enthusiast Member Join Date: Mar 2009 Location: USA Posts: 468 Drives: 09 370Z Red AT Sport Rep Power: 16	m4a1mustang, why would test pipes create more rasp? Also, can anyone answer my other questions as well? Thanks... __________________ Stillen CBE & G3 LTIs, Motordyne M370, Berk HFCs, H&R 15/20mm spacers, CiNcity headlights, yellow OEM strut brace, Password: JDM CF engine bay parts, EVO-R CF front bumper parts, CF "Z" badge, VIS CF hood, Fujimura CF "diffuser", Show-N-Go plate frame, Katzkin red interior, interior CF, Pioneer BT-90 full system, Viper SmartStart

11-04-2010, 08:13 PM	#5 (permalink)
Osiris A True Z Fanatic Join Date: Mar 2009 Location: http://www.cfzclub.com/ Posts: 1,524 Drives: Angry Rep Power: 19	i've had the Stillen CBE installed for a while now. Just installed the HFC and now i have a rasp. Although IMO it sounds great. So to answer your question, it's a very good bet it's your HFC. __________________ ^^^^^^^^^Like our Facebook!^^^^^^^^^

11-04-2010, 08:18 PM	#6 (permalink)
Jordo! A True Z Fanatic Join Date: May 2010 Location: nirvana Posts: 6,394 Drives: 2023 NATM Rep Power: 418	Definitely the HFC's; test pipes will sound as bad or worse. Options are to live with it, replace OEM cats, or get resonated test pipes/HFC's. __________________ Enjoy it. Destroy it.

11-06-2010, 01:58 PM	#7 (permalink)
marcussoori Enthusiast Member Join Date: Mar 2009 Location: USA Posts: 468 Drives: 09 370Z Red AT Sport Rep Power: 16	Could you explain why resonated test pipes will eliminate rasp? Is this their purpose? Do resonated test pipes work as well as resonated HFCs? What brands should I consider? So to maximize power and minimize rasp, my order of preference should be: 1) Resonated test pipes (less rasp, more power?) 2) Resonated HFCs (less rasp, no difference in power?) 3) Different HFCs (maintain power, hope for less rasp) 4) OEM cats (least rasp/least power/quietest) 5) Test pipes (most power/most rasp/loudest) ? I look forward to your advice! Thanks in advance... Marcus __________________ Stillen CBE & G3 LTIs, Motordyne M370, Berk HFCs, H&R 15/20mm spacers, CiNcity headlights, yellow OEM strut brace, Password: JDM CF engine bay parts, EVO-R CF front bumper parts, CF "Z" badge, VIS CF hood, Fujimura CF "diffuser", Show-N-Go plate frame, Katzkin red interior, interior CF, Pioneer BT-90 full system, Viper SmartStart

11-06-2010, 03:53 PM	#8 (permalink)
Jordo! A True Z Fanatic Join Date: May 2010 Location: nirvana Posts: 6,394 Drives: 2023 NATM Rep Power: 418	Shouldn't affect power, but the resonators are supposed to cancel out the vibrations making the rasp sound. __________________ Enjoy it. Destroy it.

11-07-2010, 08:34 AM	#9 (permalink)
marcussoori Enthusiast Member Join Date: Mar 2009 Location: USA Posts: 468 Drives: 09 370Z Red AT Sport Rep Power: 16	Bump for more opinions... __________________ Stillen CBE & G3 LTIs, Motordyne M370, Berk HFCs, H&R 15/20mm spacers, CiNcity headlights, yellow OEM strut brace, Password: JDM CF engine bay parts, EVO-R CF front bumper parts, CF "Z" badge, VIS CF hood, Fujimura CF "diffuser", Show-N-Go plate frame, Katzkin red interior, interior CF, Pioneer BT-90 full system, Viper SmartStart

02-08-2011, 09:21 PM	#11 (permalink)
mjohn617 Base Member Join Date: Jun 2010 Location: California Posts: 132 Drives: 2014 Lexus ES350UL Rep Power: 416	I have been dealing with this issue for a while! I have had the rasp since I put test pipes on. I just recently put on the Stillen CBE and the rasp is crazy loud now. I did some throttle manipulation a couple months back to combat the back pressure, it worked great but my gas mileage went to **** and I was getting some weird side effects with throttle response and a lot of backfire. I am really beginning to believe it is the resonators; not by their design but by the exhaust design. Your stock cats are doing a really good job at creating a "buffer" to a stable atmosphere. Removing them seems to be creating a high flow which in general is good. From the point at which the exhaust splits all the way back to the exhaust tips seems to be the issue...in this case pressure differences. Just like when you crack a window on the freeway and everyones ears explode, it seems the pipes are fighting each other. I have spent hours trying to figure this out, I am getting a clear sound coming straight from the resonators when I use a stethoscope...no where else! I am really starting to believe '10Anamoly 's theory with using a pipe to bridge atmospheres...check it out if you already havent read it. Fancy Tech: How to Get Rid of Exhaust Drone, works great! Bottom line, this issue is driving me MAD!

02-08-2011, 09:40 PM	#12 (permalink)
theDreamer A True Z Fanatic Join Date: Feb 2009 Location: Texas Posts: 30,879 Drives: 370z Rep Power: 4210	Straighter the pipe the more rasp. Also, it will depend on where your resonators, mufflers, and cats/hfc/TP are. Depending on where each is located and the distance & size will adjust if you have or increase rasp. __________________ theDreamer's Z // Fast Intentions // Uprev // GTM // HKS // TEIN theDreamer's Silvia // URAS // GREDDY Houston Zs // Facebook // Twitter // Instagram

02-08-2011, 09:54 PM	#13 (permalink)
Viera Track Member Join Date: Feb 2009 Location: Atlanta, GA Posts: 897 Drives: '09 M.Blue 370Z 6MT Rep Power: 264	I think it's definitely coming from you CBE. A friend of mine has the Agency Power CBE paired with the Berk HFCs and has ZERO rasp. It is a very deep tone.

02-09-2011, 11:39 PM	#14 (permalink)
mjohn617 Base Member Join Date: Jun 2010 Location: California Posts: 132 Drives: 2014 Lexus ES350UL Rep Power: 416	I put my cats back on today, sound is BEAUTIFUL! Looks like I have some Berk test pipes for sale...I don't think im going back until the turbo kit.

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