I know this topic has been discussed several times before. But, I was thinking about it last night and thought of a few questions that have not been totally addressed yet.

I get the normal resonance right around 2800 with my OBX headers. I saw in a post yesterday (I think from SilverKnight) where he reinstalled his OBX headers with the factory gaskets. He mentioned that the resonance disapeared after the reinstall.

My question is in regards to this. I have heard a few members mention they get this resonance with Comptechs, but I don't think they may be getting it to the same extent - otherwise we would hear more about it on this board. The resonance I get with my OBX headers around 2800 RPM is very distinct and extremely annoying - especially under hard acceleration in 3rd of 4th gear. So much so, that I have debated going back to the stock setup. The resonance does not seems to fade with time as some have mentioned (over 3 months now with OBX headers).

Here are three points/questions I would like to open for discussion:

1) Does this happen with Comptech headers? The resonance is very distinct, loud, and annoying. It occurs at 2800 RPM, and it can really ring loud for several seconds if your trying to pull hard in 4th gear through the 2800 rpm range.

2) Is it an exhaust leak? I don't believe so because many of us have reported the exact same thing. What are the odds of all of us having an exhaust leak? Plus, I would think an exhaust leak would only get louder as the RPMs increase.

3) Are the OBX gaskets the culprit? Stay with me on this one for a second. SilverKnight mentioned he reinstalled his OBX headers with the Stock gaskets and the resonance disapeared. I noticed the stock gasket are around 1/4 the thickness of the OBX Gaskets (the OBX gaskets seem to have a thicknes of aproximately 2 mm). Could it be that the extra thickness of the OBX gaskets create the right enviroment for this resonance? Think of blowing into a bottle to make it whistle (resonate). If you move the bottle just a little closer or further away from your mouth, the resonance stops. When SilverKnight reinstalled the OBX headers with the stock gaskets the distance of the headers from the engine block decreased and this may have cause the resonance to stop.

Of course if people get this same resonance with the stock gaskets (or with the comptech headers), then my theory is not correct. Please comment with your experiences to help me prove or disprove this theory.

The OBX headers have smaller openings than the stock/comptech headers. This may also be the culprit. Let's go back to the example of the bottle. If you blow across the top of the bottle to make it resonate, and then expand the diameter of the top of the bottle while keeping the position of your mouth static - the resonance will cease. I think this is a fair comparison between the stock/comptech headers and the OBX headers. The OBX headers, because of their shape, may just create the right conditions to get this resonance. Of course, they were not designed for the CL in the first place.

Let the discussion begin...

 

I agree,

I have the exact resonance sound at 2800 rpm.

Have you considered the flex section? the Comptech's suffered from vibration noise due to a stiff flex section.

Let us see for those who used the stock gaskets on OBX if they do or do not have the resonance sound.

Finally, the good thing is that this sound only happens around 2800 rpms. And do not pull up on the 4th use the 3rd

 

in all honesty, i think my OBX headers have gotten louder....the resonance appears to have stretched out in its RPM range and gotten slightly louder....im not going to mess around with it though, i dont have the time or tools to rip it apart and i dont have the money to pay someone to rip it all apart and put the OEM gaskets on...unless i discover a major problem or exhaust leak, im leaving it alone.

 

I have the same resonance sound... It can get very annoying at times, but I usually have the radio fairly loud where I don't hear it much. I would like to know what it is caused from, and it hasn't gotten better with time.

Not getting rid of them though. I love the power increase too much.

I have a feeling it comes from the flex section, because that is where it sounds like the sound is originating from

Honestly, I just try and avoid ~2600-2800 (around where the sound occurs)... I just either gun it (raise RPM) or let off the gas (lower RPM). Usually seems to help

 

I have CT Header, the only thing I noticed since I installed the header is that it makes my exhaust a bit noiser. I don't hear this so called "Resonance" from the CT header. BTW, I reused the stock gaskets I already had.

Does any one have a sound bit of this "Resonance" sound? I'm really interested in hearing what it sounds like.

 

I have three weeks off for Christmas, and may use a day to reinstall mine with the OEM gaskets. It should only take a few hours. That is if all the posts still support the gasket theory.

jim - My headers seem to have gotten louder with time too.

Nashua - I normally don't accelerate in fourth, but when I am cruising on the highway and pass someone slowly, the car will stay in fourth causing the resonance to really ring.

I am curious if anyone installed the OBX headers with OEM gaskets??? What was the outcome?

 

The resonance is still there. It's a different type of noise, but not near as loud or annoying as before I replaced the gaskets. This noise defintely comes from under the car. This noise is the gases passing through the flex session. I have heard it on Maximas with ypipes as well. I had another noises which sounded similar from the engine bay itself. Found out later it was leaks. I could not see the leaks till I removed the gaskets. They had black all the way to the outer seal. I suggested anyways that everyone should use the stock gaskets. That is what Comptech recommends with there headers, so you should do the same.

But after replacing the gaskets, like I said, MOST of the noises are gone except a certain RPM, there is a small noise I hear..

 

Thats what happened to mine. My car got much louder after the track. I started it in the morning and heard alot of noises, then they went away after the car warmed up a bit. But driivng still had more noises than usual. Now after the OEM gaskets have been on, in the cold its quiet. No noises except the resonance at 2800~.
Jim, I bet $50 bucks you have a gasket leaking somewhere.

 

It took me 1 hour to undo and reinstall my OBX headers. What I did, was disconnected the O2, and disconnected the YPIPE from the headers and frame of car. Let it hang down with a block supporting it so it doesn't pull on the rear exhaust too much. I left the rear connected. And I just unbolted the front and rear, removed the gaskets, put the other ones on, put all the nuts on, connected it all, then went back and tightended everything back down. Was really easy this time. I did it by myself as well.

 

ill offer this comment i have comptechs...however i started getting a resonance that i determined to be the headers down pipe hanger braket...the arm on the headers was touching the bottom of the hanger (which is broken) and at certain RPMs would resonate badly...i removed the braket as a temporary fix and the problem is solved...i suggest you all look...you'll get under the car from in front of the front drivers side wheel (jacked up ofcourse)....THE BRACKET is shaped like this _/ \_ with a rubber exhaust type (similar but not the same) hanger acctually bonded to the metal bracket...it's worth a look...

 

Sorry i didn't have the same issues with the Comptechs.

 

broken hanger

 

eeeek, dont say that dude!! :P i really dont have the cash to pay someone to reinstall headers, here i thought i did a good thing and saved myself some cash by installing them with some freinds....but now its too cold to be installing shit in someones driveway. im gonna go take a good look at the thing tonight..but im not about to start ripping her apart..hopefully its just my imagination....you know the OEM gaskets are like PAPER-THIN metal and the OBX gaskets were much thicker by comparison and looked to be of nice quality, the OEM gaskets were thin and rusty and cheap looking, i dunno, why would the OBX gaskets be failing?? they get burned off?? the material gets burned?? i dunno.

 

SilverBullet - did you reuse the original OEM gaskets? Or just buy new ones?

 

I reused the original ones.

Jim, the OEM gaskets are used for a reason. They were made for the car. It may be metal, but the secret is it shrinks when smashed. It's like a spring kinda. You smash it down, it makes a good seal. The ones with the OBX headers looked good, but they obviously didn't perform well. But removing the gaskets and putting new ones on wasn't a big deal. I got it done real quick by myself. 30 min tops with 2 people. Find a garage to do it in, don't do it in the cold.

 

Just to add 1 more observation...

Fact: The resonance happens ONLY when the engine is under LOAD!!!

Put it in N and Rev it.. no noise...
Put it in D5 and slowly accelerate on flat road... no noise...

Accelerate climbing a hill... You got the resonance sound!!

I can now assume it is a mechanical resonance and not air-flow resonance..

 

I've had this resonance from day one. I don't drive my car much, but it does not seem to be getting worse. I really don't think it has anything to do with gaskets. I vote on it being the flex section. It does not bother me, but if I can easily fix it, I will.

juice

 

im glad that im not the only one experiencing this with the obx headers, but i didnt notice that much of a gain, i even reset the car over night, drove out of town the next day, and it doesnt seem to add as much as some describe.. anyone with similar mods wanna do a test run? i travel frequently, so if any of you are interested, maybe ill stop by and meet some fellow a-cl members

 

Amzaingly, I was not able to hear the resonance sound.... sure it sounded deeper sound... but no humming and tin can rattles...

 

Well, I'll offer this advice to you CL-S guys who came along a few years after 6th gen Accord V6's introduction. I was one of the few "early" Accord V6 guys to install the Comptech headers. The "1st gen" v6 Comptech headers had a problem with the flex joint on the y-pipe. It wasn't that the flex joint was stiff. It was the metal baffles inside the flex joint hitting each other at specific resonance RPM. At first, Comptech didn't want to admit the problem and kept probing me about my catback exhaust at the time. Eventually, Comptech identified it as a real problem and started a "silent recall." I said silent recall because it was never really announced to those who installed the headers. I found out only because I spoke to Mike B. at Comptech. They called this the 2nd gen Comptech V6 headers. He was able to send me a fixed replacement and I've had this y-pipe ever since. When I had the problematic y-pipe on, the resonance would get really loud at times. Eventually, the extra vibration caused by the resonance shattered the rubber stablizer piece as shown by typeR. When this happened, a metal clanging sound came along because the anchor for the y-pipe was basically resting on the metal plate below the broken rubber stablizer piece.

On a side note, Comptech headers never came with any gaskets. My stock gaskets were never reused. My Honda dealer, who installed my headers purchased gaskets from local auto stores. Obviously, you see that the gasket is not the problem. SilverBullet noted that the resonance stayed with stock gaskets. You guys need to bug OBX and ask them to find out whether the flex joint is the problem. Because with my "updated y-pipe" from Comptech, there is zero resonance.

 

Just for the fun of it I took off my Dynomax mufflers and put the stock ones back on and it worked well, 50% of the noise is gone and is much more bearable now. The stainless steel Dynomax's were a homemade system that gave a nice sound and were flow thru too but when I added the OBX's plus the resonance it got to be too much. Hopefully I haven't lost any performance...I do not want to take off my CAI or headers, too much power and fun.

 

Nashua - I believe there would be more airflow/exhaust at a particular RPM under load vs. the same RPM with little load.

But you may be right about this being a mechanical resonance.

If this is a mechanical resonance originating at the flex joint, then it should be fairly easy to dampen this. I'm thinking about adding a few hose clamps around the flex portion of the headers. This may help to dampen the resonance (if it's mechanical). It should at least decrease it.

I am away from home right now visiting family, but I will test this out when I get back to Dallas.

 

Airflow is much greater under a load then in idle . When in idle the ecu knows it's in idle and only has to add a small amount of fuel to make it rev . However under a load , the fuel injectors must pump more fuel and air into the combustion chamber to get the engine to rev at the same rpm . I'm not saying that the problem is definitly mechanical or airflow , but just because you rev it in nuetral , doesn't mean anything . I think its from the thicker gaskets , thats why comptech says to reuse the old ones , the OBX gaskets are too big . The exhaust system is NOT a pressurized system like the coolant system . You don't need much of a gasket to seal it . In fact to large of a gasket would separat the two metals that are trying to be held together . We installed several Comptech headers at my dealer and every time we used Acura gaskets ( new , not re-used ) and never had a complaint . I suggest that before the install , get a new set of gaskets from the dealer . I don't think you will have a problem

 

i just found out that one of the lock nut on the back flange has backed out (almost completely)...I can turn it with my fingers!!! Anyways, I retightened it....good as new now.

 

I hope you don't plan to leave it off too long...

 

what do you think'll happen?

 

I did the same thing on my Bimmer and got lazy by not putting the hanger back (it was just a u clamp assembly that would make a little resonance at times with the headers. I decided I could leave it off and dropped an exhaust into the street (funny now ... not then).



My current view is: if it isn't needed, why did they put it there? (Especially considering how CHEAP automakers are).

Result: maybe nothing or perhaps you end up "trashing" the headers and/or exhaust with increased stress (at least it has a nice molded rubber piece to “damp” the transmitted vibrations in the exhaust system).