Tom2769

iTrader: (3)

I purchased my ISF with the ISS DES exhaust installed on stock exhaust manifolds. I installed PPE headers a few months after buying the car. Ever since I installed the headers, I'm getting a resonance at around 2,500 rpm that sounds like a vibration or buzzing. It's present a couple hundred rpm on either side of 2,500 and is more pronounced when cold, less so when warm, but still there. Outside of that narrow rpm range, the exhaust is perfect and sounds incredible. When the sound is present, It sounds to me like the exhaust pipes themselves are resonating or vibrating at this particular rpm range. This is NOT drone - I had that too, but quelled it with side branch resonators and the muffler tip silencer inserts that some of the Borla guys discovered. I've done the following to try to find the source: replaced gaskets between headers and exhaust, replaced gaskets at the x-pipe, removed under-car heat shields. My next step will be re-installing the stock exhaust (provided by the prior owner) to see if that solves it and confirm it's not something specific to the headers themselves. But before I do that I wanted to reach out and see if anyone with the PPE and ISS DES setup also experienced this resonance?

I've run into a similar resonance issue on a Tacoma pickup I had with headers and a specific brand of aftermarket exhaust. The resonance on the Tacoma was eventually solved by adding a certain type of resonator at a certain point in the exhaust. There was a lot of trial and error in that solution, and it was arrived at by several forum members each trying different solutions until the one that worked was found. I'm not inclined to try multiple potential solutions (adding resonators here, adding cats there) without some indication of success by someone else before me. If I can't solve this, I've considered switching to a Borla exhaust and calling it a day. Anyone else have experience with this on a PPE/ISS DES setup?

Meraki Autoworks

iTrader: (8)

Yes I had a similar issue. Ended up selling my QES exhaust. Sounded great though!

-Josh

Max16

You probably encounter a resonance frequency because of the X-Pipe in the ISS.
An X-pipe has benefits for performance but is more tricky when it comes to drones/resonance.

Tom2769

iTrader: (3)

Josh, what rpm were you getting your resonance at? Did you try anything to get rid of the resonance before swapping it out?

​​​​​​You probably encounter a resonance frequency because of the X-Pipe in the ISS.
An X-pipe has benefits for performance but is more tricky when it comes to drones/resonance.

^^You may be right about that. I wonder I replaced the X-pipe with a muffled X-Pipe - like the Magnaflow 11386 (essentially an x-pipe with a muffler body built around it) if that would kill the resonance. Anyone have experience running a muffled X-pipe?

Max16

I do
That's exactly what I had before. You will also loose sound, will be quieter. My drone was non existant with this muffled x-pipe and I was straight pipes after it (with sikky headers).
The fact is that I also have a custom exhaust with 0.065 wall. Majority of exhaust manufacturer use 0.049 wall to save weight (and cost). These thinner walls add another variable to the equation because they drone easier (easier to get in the resonance frequency of the exhaust).

Tom2769

iTrader: (3)

Yeah, I don't know what the ISS pipe thickness is, but it's probably relatively thin. Makes me wonder how common unwanted resonances are with many of the aftermarket exhausts out there. I didn't have the issue until the headers were installed, though, and there are a lot more ISFs out there with stock manifolds + aftermarket exhaust than cars with headers. I'm tempted to swap in a resonated X-pipe in place of the non-res X. Would just like some indication I'm moving in the right direction...

Max16

You will be. I had zero drones with this muffled x-pipe and that's the only thing I had in the entire exhaust system.
It's pretty efficient.

Richy21

What did you end up doing Tom?

Tom2769

iTrader: (3)

Not much, yet. It feels like 500 degrees in my garage right now (AZ summer), so the car work slows WAY down this time of year. I did look into the Magnaflow muffled X-pipe as Max suggested, but based on quick measurements of the ISS DES, it looks like my exhaust pipes are not the same distance apart as the Magnaflow inlet and outlet pipes, so installing one would require some additional mandrel work. Certainly possible, but I don't think I'm interested in modifying the ISS exhaust that much. Honestly, I'm leaning toward selling the ISS DES and going with a Borla. Before I pull the trigger, though, I really should swap the stock exhaust onto my headers just to make sure the resonance is not somehow originating from the headers themselves. I've also considered adding hi-flow cats to the ISS to see if that would tame the resonance, but I'm tiring of trial-and-error fixes, so likely won't do that. That's why I posted this thread - was hoping someone else had the same issue and found a solution, or at least could offer more data points for troubleshooting.

It's a shame, because the ISS sounded SO good when I was running it with stock exhaust manifolds, but I think the added velocity of the headers is causing it to resonate in that narrow rpm range. Tough decision to give up the thru-bumper ISS tips, but I've decided I really don't want to live with the current resonance long-term...

ultimase

Might be worth playing with helmhotz exhaust reasonators

Tom2769

iTrader: (3)

Yeah, I did play with that concept, and had some success. I used quarter-wave resonators, not true helmholtz resonators, but the basic concept of noise cancellation at a calculated frequency is the same. These resonators did help reduce a drone I was getting, but did not address the resonance I am talking about in this thread. This resonance is a metallic vibration - it sounds like the pipes themselves (rather than the sound wave traveling in the pipes) that are vibrating in this case. Here's a thread I posted a while ago about my quarter-wave (aka side-branch) resonators:

https://www.clublexus.com/forums/is-...s-results.html

Richy21

Hmm Tom what does your car idle at In park and in drive mode?

hamooduae

Hello
This happened to my friend after installing his ppe ~ am not sure .. but he had issue with the engine mounts . That was the reason , as per what the garage guy told him that the installation of the mount wasnt proper . Not sure if urs has same sound

Tom2769

iTrader: (3)

I'm traveling right now, so don't have access to the car to give you exact RPMs, but it's a normal low idle post warm-up. Why do you ask? Do you have the same exhaust issue?

Tom2769

iTrader: (3)

Interesting. I suppose if the engine mount was trashed it could allow a header to impact something and cause a rattle/vibration. It really sounds like mine's coming from further back, in approx +/- the x-pipe area..