Hey guys,

I just recently noticed that my LC starting making a flapping noise when I let off the gas. I did change the entire exhaust (header back) with an Armytrix Valvetronic system (a little less than a year ago), but the car never made that noise before. I'm curious to know if any of you had experienced this same noise (with or without the Armytrix), or if you'd happen to have an opinion on what it could be. For now, all I know is that I'm able to reproduce the flapping noise when letting off the gas and driving - I still haven't tried while on idle.

Note: I'll try to get a sound clip later today.

 

sounds like you might be tryin to get airborne...wow what a ride

 

I tried doing several videos, and between the wind, other cars, gravel on the road and not getting it to bounce off the surrounding walls was pretty hard to get the sound. I managed to catch it slightly on this video - pay close attention at 16 seconds. I realized after some time, that it could be that the Lexus dealership didn't install it back properly and there might be a small leak somewhere along the system. Reason I say this, is because I had some issues with my tail lights and they replaced both of them under warranty, which required them to remove the rear bumper (which involves a small portion of the exhaust).

 

Guys,

Looking for some opinions on what this could be. This is definitely coming from the exhaust, and the guys at Armytrix are being super helpful and cooperative. Just looking for some opinions on what this potentially could be. Sounds as if the air is getting disrupted when letting off the gas....

 

Just a wild guess but could it possibly be some issue with the internal baffles that have maybe worked loose in the mufflers? I definitely think it is an issue related to the Armytrix system.

You say they are being super helpful - - just curious in what way? Did they do the install??

 

I can definitely hear the noise you are describing. It may be worthwhile to remove the entire exhaust (with the exception of the headers) and check the gaskets for good seal, check for any areas of rubbing, etc. I had a noise that occurred during acceleration and it ended up being that the mid-pipe was rubbing against a heat shield.

 

I'm working with Armytrix closely, as they asked me to put her up on a lift and try out a number of tests, to isolate where it could be coming from. They've been quite cooperative and very good to work with. Hopefully, I'll be able to figure it out once I put it up on the lift. Keep you guys posted, and thanks for your input!

 

No they didn't do the install. But they're being helpful by being very responsive and working with me in trying to figure out where the issue is coming from - so that they can send over the components that would need to be replaced under warranty.

 

Any solution ??? Update??

 

None yet, as I've been out of town. I have an appointment next week with the shop that installed it for me to diagnose the issue.

I'll keep you guys posted.

 

So we did a follow up diagnostic on my LC to isolate where the noise was coming from. We isolated the mufflers - still noise; isolated the mid-pipe - still noise; isolated the entire cat back exhaust - still noise. Seems like the issue is actually coming from the catalytic converter or even further up. At this point, I'm actually bringing the vehicle to Lexus (appointment already booked), as it should be an issue that has to be dealt by them. I've attached video of the last isolation point (which is the entire exhaust), and you'll hear that the flapping noise is still coming out of the cats. Any ideas?

 

^^^^Where you able to isolate it to a side or was it coming out of both sides equally?

Lou

 

It seemed to be coming out of both sides equally - a little tough to hear when trying to listen directly from the cats though.

 

Wonder if it's something to do with the custom exhaust back pressure being less or more than standard and causing some kind of turbulence inside the cat? Of course i could be talking utter garbage here.

 

^^^^Not really. I have a full after market PPE exhaust system complete with headers. On previous cars, including my last ISF. I also had full header/exhaust systems and never had issues. guanche2k9 still has the sound when the exhaust system is completely disconnected, so no IMO, nothing to do with his exhaust.

Lou