First off, yeah, yeah, fix it by buying Comptech. Good one guys.

Seriously though, I have heard several complaints about the resonance problem at 2500-2600rpm range with the OBX headers. I have the resonance too. I have heard some people say that using the stock gaskets instead of the OBX fixes the problem. Is this a fact? Has anyone discovered any other way to solve the problem? Wrapping the headers? Maybe something as drastic as welding a piece of metal to the tubes to tie them together? I love the headers but the resonance is annoying. Just figured I'd ask. Maybe someone out there has solved this problem? I mailed OBX about it and they never replied. (suprise suprise)

 

One thing I have never been able to figure out is why my OBX headers resonate at 1900 RPM, when everyone elses resonate higher in the band.

At any rate, I am not sure how long you have had your headers, but I stopped noticing the resonating sound after about a month. Its really not that noticable to me.

 

What about one of the people that had the Comptechs AND OBX for comparision?????

The 1st get Comptech headers had vibration (yes/no?)

Has anyone looked at the flex coupling (they used to mention the "loosen the braid trick" as a possible fix at Comptech...)

 

This is my advice.. I am pretty sure now that the resonance sound are from:

1) Unmatched ports. ( maybe a less important cause)
2) Knife Sharp edges inside the primaries ( most probable cause ).

It is easy to remove the front header, just try to do corret 1) and 2) above.

 

Nashua, I don't understand why that would be the reason. If the resonance was constant and just got louder and softer depending on rpm then I could understand it but why JUST at that one rpm range? The stock headers are not port matched, right? And they don't resonate...at least not at the connecting pipe. So we can assume that it is the front or rear headers resonating since the stock headers are iron and probably impossible to get to resonate? If it is the connecting pipe, maybe the "loosen the braid" trick might help. Although for the life of me I am not sure how to loosen the braid.

I can't imagine that OBX is ignorant about the resonance problem. If they DO know about it, it doesn't seem like a big deal to grind the edges down in the primaries and fix the problem, if in fact that is a contributing factor. Not necessarily create a 2nd generation of headers but just add a step before shipping! Does anyone know if the V6 Accords have the same problem? they have basically the same engine, right? It could be something as simple as the place that the connecting pipe is held down.

 

I'll mention this one more time. Comptech gen1 headers had a probelm with the metal pieces inside the flex joint touching each other, causing the resonance and noise. That might be a place to check.

 

Before I purchased the Comptechs, I asked about the "early resonance problem" and was told a "procedure" for "tinkering" with the flex coupling. I think I got a "... it worked for some ... " comment (YMMV):

Take a pick/awl and "poke" into the weave to try and loosen-up the strands (like releasing some stress). The closest I got to the concept was to "pick at" the weave. I don't know if the headers would need to be ON or OFF the car to flex the joint in conjunction with this operation.

(CAUTION: Please don't wreck your headers on my account)

Has anyone taken a cheap-o stethoscope to the car to see where the resonance is coming from?

 

Thanks for the input guys. Sounds like the flex joint might be the most likely culprit. If the Comptech gen1 design had the same problem, maybe someone at the Acura dealership that I deal with will have some ideas. They offered to install my OBX headers way back when I was getting springs and sways put on so maybe they have some input into the OBX ones too.

Don't worry EricL, I won't be attacking my headers with anything pointy anytime soon. I'll leave that to someone who knows what they are doing...which is most certainly not me.

Thanks again.

 

I DON"T think it's the flex joint. I placed a hose clamp on the wire mesh - a little around half way, and tightened it pretty good. There was absolutely no difference.

Also - I did not really check after the install, but I don't think OBX made the flex joint right. Mine does not flex at all. If you look at the stock headers, the flex portion moves quite a bit. My OBX headers do not move at all. I think OBX cut corners and did not make the joint correctly.

But, I don't think the flex joint is the problem. The flex joint is made more for when the engine physically shifts under sudden revving - the engine will wiggle a little bit.

I tend to agree with Nashua. Between Comptech, Stone, and the OBX headers the only major delta is the ports that connect to the block. They are smaller. The OBX are the only headers that resonate.

In a few weeks I plan to take my OBX headers off and bore out the ports. I'll respond with the result.

 

Well, you looked at them, so that gives you more time then me (ZERO).

Your "does not flex at all" comment is interesting...

The CLS DOES have some pretty serious motor mounts and a V6 60-degree engine does have out-of-balance forces working all the time. They put some pretty nasty (advanced) motor mounts on the car to reduce vibrations into the passenger compartiment (as to the #1 reason -- this could be argued until Honda came by)

Guess: I would think that putting the hose over the coupling would just tighten it up (stiffer).

You did mention that the stock flex coupling is looser...

That coupling is an isolator that is working at a range of motions and frequencies (higher frequencies == smaller, yet faster movements) -- yes/no?