Yes, it does improve to a certain degree. However, not to a great extent. My 0-60 mph at 4000 feet DA, was 4.2 seconds. That translates to high-3s at sea level DA so that is a few tenths quicker. Majority of the gains are from 60+ mph onwards due to lack of torque below 3000 rpm. This is with intake/exhaust/RR racing tune and good PS4S XL tires. The issue I noticed is, the 60 foot that is very hard to bring down. It took my 30 tries and various methodologies to get it down to 2.09 seconds. The torque does not really come in until 3000+ rpm. We can only launch (2015 - 2019) from a max of 1500 rpm. When I brake release and then slam the throttle in, it usually is a bit of a bogging down and then suddenly the torque hits at 3000 rpm.

 

I've noticed that around 4000 rom it's like a rocket goes off in the rear and it really takes off. It's a kick to drive. Matter of fact we got on the new "Tron" ride in Magic Kingdom last week and the take off there, while I'm sure is a little quicker, feels identical. Still picking the bugs out of my teeth after that ride...grinning from ear to ear the entire 65 second ride.
DR4

 

We'll see how this lates fix holds re the CEL issue. The dealer used the 3" Grimms and the stock OEM cone gasket that connect the header pipe to the tail pipe. Althought Nigel mentioned that just the 3" gasket and the exhaust sealant works fine, my Lexus dealer went 1 step further. If it does fail it'll most likely be because the dealer used the OEM gasket with the Grimms 3". But if I do get another CEL then I'm ordering the header pipes and having a muggler shop adapt the Invidia tail pipe to the stock header pipes so I can keep the invidia tail pipe sections.
DR4

 

Good to hear, Invidia is a gem. I made a video last year and I still think it does not do the exhaust justice. The mic does not capture the subtleties like the exotic-quality of it.

 

Well mine sounds almost exactly like that. You can tell from the sounds you've souped yours up.
One thing I'm surprised by is the Car and Driver, et al, that keep saying the RC F isn't as "Good" as the BMW M series. I view the RC F as a compromise between performance and dependability. I've owned Lexuss', porsche's and mercedes for decades. By far Lexus has the dependability aspect nailed down. Once I get the CEL resolved I'll be golden.
BTW--nice car ya got there.
DR4

 

Those are subjective opinions and preferences. M is considered the benchmark by default. It was a pretty amazing accomplishment that even in the hands of a champion racing car driver on the same day, same conditions and same driver, RCF back in 2015 was only 3/10th slower than the M4 despite being 400 lbs. It really punches above its weight, so to speak.

 

Unfortunately, this thread is very relevant to my situation. I have an IS500, not a RC F, but had an Ark catback exhaust installed a couple months ago at Ark Performance. The other day I got a CEL for the first time so I had my car scanned at Firestone for free. P0420 $07E8 “Catalyst System Efficiency Below Threshold Bank 1.” My inclination and hope is that it’s a simple exhaust leak at the gasket, and so I intend to go back to Ark and have them take a look. I know stock IS500’s have had exhaust leaks (I’ve read the long thread on the sub-forum already), but my understanding is that’s error P013A and coupled with a false Parking Brake Malfunction. Mine doesn’t look like that. So…

1. What’s the chance it’s not actually an exhaust leak but actually a bad primary cat for example? The Ark exhaust uses a high flow secondary cat so is there any chance that exhaust blows back through the primary cats? Is that even physically possible?

2. From talking with Ark it seems like they used 2 gaskets at the downpipe/midpipe flange – their own gasket which I imagine looks similar to the Grimspeed one going through the bolts, AND the OEM gasket which has now been crushed repeatedly. Are they correct in using both? I assumed they knew what they were doing. Maybe the OEM gasket alone was too small? Anyways, I ordered a new pair of OEM gaskets (90917-06070) from ebay for them to install since my original ones have been taken on and off repeatedly (for the R&D of the exhaust). I assume there are only so many times the gasket can be “crushed” before it loses its effectiveness…?

3. How long can I drive with this particular CEL and code before my car goes into limp mode? By the time I get to Ark itll be about 150 miles

I hope these are not dumb questions but I value everyone’s experience and knowledge. TIA!

 

You can drive it indefinitely with that code without and real issue. Just will fail emissions checks until it's cleared.

I don't know what the front header flange looks like at all on the Ark, so there's no way to tell if it has the same design flaw as the Invidia. Generally, you are correct though, gaskets should be replaced after taking the exhaust apart. So pretty good chance yours have failed after repeated bolt/unbolt cycles.

 

As LoSt180 said in his post it's hard to offer a solution without know what your exhause manifold end (where you're connecting the Ark system) and the flange on e Arc system. So for simplicity I'd order the Grimm's 3" stainless stell layerd gaskets. Grimm's sells 2 trypes of these...one is

GrimmSpeed Downpipe to Catback 3" Gasket 2X THICK

and the other

GRIMMSPEED DOWNPIPE TO CATBACK 3" GASKET

They're layers of stainless steel the difference being the number of layers. I'd go with the thinner one and use the permatex exhaust sealant "The Right Stuff". Follow the directions on that sealant which says to spread layers on both side of the gasket then install it and lightly snug the bolts. Wait 90 minutes then torque them. The problem is the size of your exahaust manifold flange. If it's too small (<2.5") then this fix might not work. But my guess is Lexus thought about this when they designed the exhaust systems and made them the same so they could use their OEM gaskets on both the IS500 and RC F.
Not my most recent fix for the same problem on the RC F was the sealant, the 3" Grimms and then the dealer added the OEM cone shaped doughtnut gasket they use between the header and tail pipe connection. I've got 200 miles so far w/o a CEL. But Nigel (see the RC F CEL exhaust thread) says you don't need the cone type gasket.
I'll keep the forum up to date on how this fix is working as I drive more.
DR4

 

@LoSt180 Thanks for addressing my concern about limp mode. While I don’t plan to do WOT or anything crazy with a CEL, it’s nice to know I’ve got time to figure this out.

I called Ark and Grimspeed today and got some more information. Like the RC F, the IS500 downpipe diameter is 2.5." But unlike the Invidia exhaust, the Ark midpipe connects with 2.5" piping, so Grimmspeed’s 3" exhaust gasket won’t work. However Grimmspeed does sell a 2.5" gasket. Interestingly he also confirmed that people use their gasket + the OEM O-ring. The question is whether I really need them since I purchased new OEM gaskets. I'm waiting to see what Ark says about Grimmspeed...

According to Ark, the Ark midpipe’s flange actually was designed with a groove for the OEM O-ring. However, he said that it’s a really tight fit for the inset and so the gasket tends to get a bit mangled when you try to connect and tighten the pipes, so they added their own flat gasket for extra precaution. Combined with the fact that my original gasket had been re-installed so many times, he thinks a fresh OEM gasket could fix it.

The last thing on my mind is what if P0420 isn’t a leak at all? Should I lug my stock exhaust back to their shop just in case they can’t find leaks? That way they can return my car to stock and I could drop it off at the dealership on the way home and get this all fixed under warranty. Though this could save me some money, I'm sad just thinking about this...

 

As far as the CEL and codes...I think you can assume it's a result of the new exhaust system because you didn't have any CEL's before..right??
Well you got good news from Ark and Grimms. And just reducing the size of the Grimm's gasket should do the trick.
I'm attaching a picture of what's left of the OEM exhaust pipe to header gasket. There's a groove in the RC F's exhaust flange but not on Invidia's 3" flange. I'm not certain if the sealant I mentioned previously would solve the problem because the stock OEM shown is just slightly larger than the 3" invididia end...maybe 1/16'of an inch. You can see how mangled the OEM seal is. Tha tlasted less than 24 hours before the CEL came back.
But I think you're in the money because the flanges are the same size on the Ark and stock manifold.
DR4

 

Thanks for the information and photos! I have to admit though I'm not sure that I know what I'm looking at. Was this a brand new OEM gasket or was it mangled before you put it on (which is why it failed in <24hrs)? In the first photo, is the dark line at ~7 and 8 o clock where it was leaking? Also, is the entire gasket black because it was leaking and burnt, or is that just grease? Sorry...

BTW, Ark just said they don't think I need the Grimmspeed. I suppose I could see how long a fresh OEM gasket alone lasts, and come back to the GS gasket later if it happens again.

 

Yep...brand new OEM crush gasket the gooes between the Exhaust header flange (this has a groove in it for the gasket) and the flat part of the flange on the 3" Invidia. What happens without the gaske tsealant, the gasket shifts when the 2 pipes are tightened together. Because the Invidia 3" pipe is almost the same inner diameter as th eouter diameter of the OEM crush gasket, it partially fall sinside the 3" pipe and then there's no seal. The only reason this lasted 24 hours, instead of failing right away, was they (the dealer) put the sealant on th eflanges of the 2 pipes.
Hope this is a little clearer.
A side note -I almost bought a IS500 but thought about it a little longer and reconsidered. Our children are all grown up now and we live in a retirement community. Since there's no way in h_ll I'll ride with a senior driver out here (they drive crazy!), and they generally don't understaand/appreciate any type of "performance car", I went with the 2 door. How do yo ulike your IS?

 

Based on that description, I'd say new OEM gaskets is all you need. Basically ignore this entire thread since Ark doesn't have the same flange problem as Invidia.

P0420 & P0430 are purely emissions catalyst codes. The gasket leaking is the most common cause for those codes. That's because the gasket is after the cats, but before the sensor. The sensor picks up the extra fresh air and flags the code. Another possible cause is if the sensor wires got damaged from someone overly twisting them during installation of the exhaust, but those usually have other codes like "slow response" or similar.

You'd also get those codes if you installed headers that deleted the factory cats. So there's really no issue driving it hard.

 

Well if LoSt180 is correct, then it's an easy fix.