We have a lot of new members, most looking for a good exhaust and come across the Invidia system. This one is highly recommended because it sounds great and also happens to be one of cheapest available. However this exhaust is notorious for triggering a CEL, so I'm going to dive into the root cause and go over a few options to make sure your install is trouble free. The issue highlighted below applies to the Invidia exhaust specifically, I haven't noticed similar issues with other exhaust options, so don't come at me with "my bazookarkhausnovel is fine" - cool story bro, I don't care.

Problem:
Invidia uses a full 3" flange at the front, which doesn't mate perfectly with the 2.5" recessed flange design of the stock manifolds and PPE headers. This is a flawed design decision, most likely to keep cost down. When an exhaust leak happens at this spot, the downstream O2 sensors will flag catalyst codes, typically P0420 or P0430. Leaks happen because there isn't a flat surface on both sides of the joint to create a problem free connection.

The system comes with several different sized gaskets: two 3" gaskets, two 2.75" gaskets, and two donut gaskets. A lot of times users will install the smaller 2.75" gaskets up front because they appear to fit the header side a little better. Or if they use the 3" gasket, it shifts during installation. In both cases, lack of a good seal causes leaks. I've also seen recommendations to use the OEM style ring crush gasket. Frankly that style can be even more problematic. Basically the outer diameter of the OEM gasket is barely larger than 3", so keeping the exhaust flange centered makes getting a good seal on that gasket nearly impossible considering any minor shift will open up a leak.

Essentially leaks come down to user error either with the install itself, or using the wrong part. Good thing both of these are easy things to correct!

Solutions:
1) Install gaskets correctly. The 3" 2-bolt gasket goes up front, the 2.75" 2-bolt gaskets go in the middle section near the x-pipe. Ensure the fire ring of the gaskets remain centered on the Invidia flange while tightening up the exhaust bolts. Yes it will move around, just be patient. If you use the 2.75" gasket here by mistake, the fire ring will collapse into the flange and eventually leak. This step is the easiest thing to do, and will work for almost everyone.

Invidia changes up their hardware, but in general the gaskets on new systems have a "fire ring" on them. If not a quality replacement is Vibrant 1458 3" gaskets.

2) Okay, so your installer didn't listen, you used OEM style gaskets, or you really tried to ensure gaskets were installed correctly, but either way something didn't go right and now you have a leak? Or maybe you want to be proactive and avoid the chance of a leak altogether. More options below.

2a) Use a multi-layer 3" gasket from Grimmspeed. These things are thick bois to avoid blow outs. You still need to install them correctly as outlined in solution #1, but will hold up quite a bit longer. Note: there's two versions, a 7-layer (recommended) and a "2x thick" one with 12-layers (may have issues crushing to seal).

2b) Stack gaskets. This one is generally frowned upon, but in the case of trying to mate two completely different flange styles and sizes, sometimes you have to get creative. Here we use an OEM "style" ring gasket to fill the recess on the header flange in order to give the fire ring a flat surface to seal to. Walker 31384 gasket will fit in the header flange, and at only 1/8" thick will fill the void without sticking out. With that gasket in place, install the 3" gasket as defined above (notice a theme here?).

3) Copper RTV. This one can technically be used in conjunction with all options above. Copper seals great in high heat situations, like exhaust applications.

Additional reading since this issue has come up numerous times in the past:
https://www.clublexus.com/forums/rc-...a-exhaust.html
https://www.clublexus.com/forums/rc-...ing-a-cel.html
https://www.clublexus.com/forums/rc-...ode-p0430.html
I posted this in the RCF Owners Group on FB, cross-posting here for posterity's sake.

Parts:
New flange hardware, good to replace to ensure nothing comes loose. OEM is locking.
9017710007 4 $ 0.97 NUT, LOCK
9010510590 4 $ 1.09 Exhaust Bolt

Gaskets -
Walker 31384 (small round to fill void in header)
Grimmspeed 3" 7-layer (or 2× 12-layer)
Vibrant 1458 3" flat
Cooper high heat RTV

Pictures:


Notice how much larger the Invidia flange is compared to both the exhaust piping itself as well as the header exit pipe size. Keeping a flat 2-piece gasket centered here is crucial to avoid leaks down the line.


OEM and PPE use the same flange here, a recessed 2.5" exit designed to use a round crush style gasket. Works for most exhausts, just not Invidia.


Vibrant 1458 is a quality 3" gasket.


Grimmspeed used multiple layers of steel to create a super thick gasket that can take a ton of abuse and remain sealed. Go with the regular 7-layer version as these 12-layer "2x thick" versions may actually be too thick for a good seal.


Stacked gasket option with a touch of copper RTV.


Walker 31384 is the thin gasket with 2.5" I.D. and 3.11" O.D. giving a better chance of a good seal.



Location of the three sizes/types of gaskets used with the Invidia exhaust.

 

Hi,
Great write up re the 3" Grimmspead with Walker ring used in conjunction with RTV copper. Any idea where I can get the 2.75" downstream cat gaskets. Mine just went out and gave P013C code. Validated further with smoke test at the connection...both sides have failed. My guess is use new 2.75" with copper RTV?

 

Vibrant 1465 is a 2.75" gasket.

However an exhaust leak passed the header flange wouldn't trigger a CEL though.

 

Hi,
Yes i agree. At that point you could remove all exhause components and that wouldn't have any thing to do with the O2 sensors and the error message. Lexus wasn't clear in their description of the location of the leak. They also said that the seal that was in there was a "Rubber seal". Since I just bought the car about 2 months ago I'm going to assume either the dealer got the same error code and stuck whatever gasket they had lying around, replaced the ones leaking, or the person traing in the car did that, then sold it. I was just the unlucky one to inherit the problem as the engine light came on after about 1300 miles.
Lexus wanted almost $500 to relace the gaskets at the top of the header pipe (where the pipe bolts to the exhaust manifold) which this thread has described in excellent detail. So I ordered 4 of everything to do this myself. By the way the copper RTV is ony good to ~700 degrees F. The temp as the location where th eleak is runs around 1000+ degrees. But the sealant will help hold in the "O" type ring during reassembly.

Now last question...to replace the 3" gasket what's the process? CAn it be as easy as unscrweing the 2 bolts at the connection, adding the RTV, the O ring gasket, then the 3" gasket and then bolting the pipes back together? Can I do this using floor jack and jack stands in my garage or do I have to get the car up on a lift?

2019 RC F first impressions...I really injoy driving this car! Very responsive and quick. When you'r eon it, at 4000 RPM, it feels like there's booster in the rear and off you go. Pretty amazing car. I am dismayed at all the review by the so called experts who compare the RC F to the BMW. The big thing they're missing is German cars are shop queens, while Toyota/Lexus cars are road queens. I've owned them both and there's nothing that compares to dependability of Lexus cars.

 

What exhaust do you have on the car now? I ask because this thread really only covers the common issue with the Invidia exhaust. A factory exhaust and even most other aftermarket exhausts can just use the factory round gaskets at the header to exhaust flange.

If you do have an Invidia, then the process to replace gaskets is pretty simple, just take into account the issues I highlighted in post 1. I replaced my whole exhaust on jack stands, but as with most things under the car, a lift would've been easier. It's as simple as unbolt, replace gasket, tighten back up.

One other item, and this is not Invidia specific, is that with aftermarket exhausts I've seen guys get the O2 sensor wires pretty twisted. Then they will get those slow response error codes. Make sure your O2 wires aren't tightly twisted. If they are overly tight, then the wires can possibly be damaged.

 

Hello LoSt180,
I have th eInvidia system that cmae with the car. It's the Q300-H but the exhause tips are not blued so a slightly different version...and about $400 cheaper. Unfortunately the Lexus dealer had already started work o the car thi sam before reviewing my email to hold off till we talked. Oh well ther goes $600 for , what appears to be, a pretty simple job! Live and learn. They warranty the work fir a year, unlimited miles. I sent them your excellent post on the problem but they're too busy to undersatnd or take the time. I'll keep the parts and when it happens again I'l be all over it! I do have th epicrures they sent but have no idea how to get them posted but it's clear whoever attempted the repair had low mechanical IQ (had to erase what I really wanted to say there) and used thinner gasket along with a tube of RTV...my gues not the copper type.
Thnx for the help!
DR

 

LoSt180,
On the pictures looking up through the flange on the exhaust manifold, is that a stock exhaust manifold or after market?
Do you have the stcok exhause system lying around? If so what does the flange on tha tlook like? Is it the same look as on the flange on the exhaust manifold, i.e. does it have the recessed area?
Thnx in advance
DR

 

As I noted in the captions, these pics are of PPE headers, but the flanged is exactly the same as OEM. I even measured both with a digital caliper when I still had the stock manifolds on hand.

I do still have the stock exhaust in my garage. The flange on the exhaust side is flat with a small piece of pipe sticking out to help align it to the manifold. The stock round gasket sits in the recessed area on the header/manifold and the flat exhaust flange seals it up. You don't overly tighten that connection, it's pretty normal for there to appear to be a small gap. The Invidia is completely different with a large 3" opening only, so that's why it needs flat gaskets as described in the first post.

 

Oh. I didn't know what "PPE" were until now.
Too bad Invidia didn't tkae the time to make their flange compatable with the stock exhaust manifold.
Just got my RC F back from Lexus. They used a Lexus part...number 17451-0V040, which is a donut type gasket. This is the one, on a stock system at the last flange connection point, just in front of the stock muffler.
Any idea how long (time and miles) your fix has lasted?
Looking on Amazon it looks to be conical on one side and flat on the other. No idea the dimensions. But we'll see how they work as they're covered for 12 months.

 

So they used the cone shaped gasket at the header flange? That's actually pretty clever if it holds.

 

Yeah...I agree. However the flange, as you mentioned, on the stock header piper, as I call the pipe that connects to the exhaust manifold, has a piece of tubing that stickes into the exhaust manifold, is there to allow the gasket to have something to crush against as the flange is tightened.
I'm thinking of just having a flange made that mirrors the one on the stock header pipe on one side and mirrors the surface on the Invidia side. I think you menyioned that the stock exhaust outlet size is 2.75" and Invidia is 3". If so that's not much difference and it wouldn't take a CNC machine a few minutes to make the flanges.
If convenient I'd sur elike to see a picture of th estock header pipe at the flange area..
Now one thing we haven't discussed is the improved performance of your exhaust system. Have you evaluated that?

 

It's a 2.5" outlet trying to mate with a 3" Invidia inlet.

If you wanted to get froggy and make an "adapter" flange, then you'd just make a 2.5" flat flange. Use the stock style gasket on one side and then a 2-bolt 3" gasket on the other side for the Invidia. Or you can just follow the steps in post #1 and be done with it. You're starting to make this more complicated than it needs to be, lol. My headers were installed in late 2020 and the gaskets have held up just fine.

Performance of the exhaust is kind of off topic since there's plenty of other threads dedicated to that.

 

Okay. If yours has worked for serveral years, assuming your RC F isn't a "Garage Queen", then when/if mine fail I'll use your method.
Thanks for all your great help.

 

This is the route I am going to go.

 

Hey @dagored I think this was the thread you were looking for. Did that cone shape gasket not hold? Did they put it on both sides or just one originally?