Exhaust side sill heat and my debate

**catwood** · 08-04-2018

I have to mitigate the heat in the side sills up by the cats. Removing the cats is not an options for me. My debate is headers with high flow cats or just try to add additional insulation. Some of the insulation products I've found are nearly as much as the headers. I also plan to keep the stock mufflers. decisions, decisions........

**13COBRA** · 08-04-2018

Why are you insistent on keeping the catalytic converters? Just curious.

I'd go with headers and high flows over just adding insulation.

**ViperRich** · 08-04-2018

I have a 14 Gts and I went with the Belanger high flow single cat that resides in the engine compartment. I kept the stock mufflers and heat wrapped the entire exhaust from the cat to the tip, it is a hair louder but less resonance and has killed a ton of heat. I am very happy with how it turned out.

**catwood** · 08-04-2018

smog and smell. I didn't mean to imply keeping the stock cats if it came across that way. If I change exhaust, I'll go high flow cats.

**catwood** · 08-04-2018

Originally Posted by ViperRich

I have a 14 Gts and I went with the Belanger high flow single cat that resides in the engine compartment. I kept the stock mufflers and heat wrapped the entire exhaust from the cat to the tip, it is a hair louder but less resonance and has killed a ton of heat. I am very happy with how it turned out.

no check engine lights? Metal or ceramic cat?

**ViperRich** · 08-04-2018

No check engine light no o2 spacers or anything im pretty sure they are ceramic type I orderd them from Jon B at Viper parts rack. Jon told me the metallic would be considerably louder than ceramic. In hindsight I'm sure I would have been ok with it a little louder without complaints. I just didn't want it to drone me into not enjoying the great sounding audio system.

**Special Ed** · 08-04-2018

I have the single high flow cat and Belanger muffler from JonB. I had them for almost two years. The heat on the sills has been reduced by more than 50%, discoloration of the sills has stopped. They are slightly louder, in a good way and don’t drone. They were installed without any additional heat wrap. I couldn’t be happier with the result.
There was a complete write up in the forums under something along the lines of “Stubbs Guy Exhaust.

**serpent** · 08-04-2018

I think this has been beaten to death and surprised you don’t know the answer to this catwood. There is no smell when you remove secondary cats. I removed mine as my first mod about 2 months in after ownership. Best mod to date because it removed heat. From what I’ve been told by dan cragin the sensor is after the first set of cats. Anything after that the sensor won’t detect and you should be able to pass smog. This is what dan told me per messages. I haven’t had to smog yet.

Again no smell, I drive with windows down in Nor cal, Bay Area. 2nd cats removed, pipe welded in place connected to ARH catback exhaust.

**SRT_BluByU** · 08-04-2018

Maybe just add a hear shield between pipes and sull

**catwood** · 08-04-2018

Originally Posted by serpent

I think this has been beaten to death and surprised you don’t know the answer to this catwood. There is no smell when you remove secondary cats. I removed mine as my first mod about 2 months in after ownership. Best mod to date because it removed heat. From what I’ve been told by dan cragin the sensor is after the first set of cats. Anything after that the sensor won’t detect and you should be able to pass smog. This is what dan told me per messages. I haven’t had to smog yet.

Again no smell, I drive with windows down in Nor cal, Bay Area. 2nd cats removed, pipe welded in place connected to ARH catback exhaust.

Yeah, you'd think. I'll go pull some stuff to see if I can find the secondary sensor. I will have to smog the car once at least. I could wait until after that for the mods but the car is white and the heat is an issue that's being noticed. I really didn't intend to mod this one at all or at least not much as I think each project begats another project. The primary goal is heat reduction to the side sill - hinge cover and cost with no CELs. Yesterday I was thinking headers and high flow cats. Then it evolved into which cats and now maybe I do even less like just one cat per side and keep the rest OEM. I spoke with Todd at A&C and Lou Belanger and each have different opinions that make sense in an by themselves. Most of my experience on the exhaust side of things has been with a Gen 2. Things were simplier back then.

**serpent** · 08-04-2018

Originally Posted by catwood

Yeah, you'd think. I'll go pull some stuff to see if I can find the secondary sensor. I will have to smog the car once at least. I could wait until after that for the mods but the car is white and the heat is an issue that's being noticed. I really didn't intend to mod this one at all or at least not much as I think each project begats another project. The primary goal is heat reduction to the side sill - hinge cover and cost with no CELs. Yesterday I was thinking headers and high flow cats. Then it evolved into which cats and now maybe I do even less like just one cat per side and keep the rest OEM. I spoke with Todd at A&C and Lou Belanger and each have different opinions that make sense in an by themselves. Most of my experience on the exhaust side of things has been with a Gen 2. Things were simplier back then.

I have never gotten CEL and have driven car aggressive at LS and didnt have issue.
There’s an instructor that isn’t a member on the forums but has a white TA. His sills are yellow because of the heat, still on stock exhaust. I told him he should remove the 2nd set of cats to alleviate heat.

Won’t pass smog with headers. Also need arrow engine controller with headers. Ur best bet is the route I went and just remove cats. The ARH cat back has drone, I think sticking with stock exhaust maybe be a better route just have good exhaust shop remove 2nd cats and weld pipe in place.
You’re in SoCal, I’d take it to A&C, probably a 1 hr or less job for them.

**ForTehNguyen** · 08-04-2018

get belanger exhaust with HF cats like I did. No CEL, no gas smell, pass OBD2 readiness fine, not using O2 spacers, not using any insulation product. Drone is a lot less now than factory, much less heat from side sills, and exhaust tips flush with the bezel are a real nice touch. No more drooly exhaust grime. I still have primary cats since I have stock headers. You can still get headers + exhaust with HFs since you wanted to go full aftermarket exhaust.

**Jack B** · 08-04-2018

Originally Posted by catwood

I have to mitigate the heat in the side sills up by the cats. Removing the cats is not an options for me. My debate is headers with high flow cats or just try to add additional insulation. Some of the insulation products I've found are nearly as much as the headers. I also plan to keep the stock mufflers. decisions, decisions........

The problem you have is, there is no air space in the sills, the insulation, exhaust system and the sills are contacting each other. You can do everything you want, but, it is no where near as effective as removing the cats. When you remove the sills, you will see where the exhaust has burned though the insulation in some of the contact areas.

**catwood** · 08-04-2018

Yes, I think I agree with you Jack. I know on the other ones (G2)I was able to isolate the heat back to the exhaust pipe and cat (HF metal ones) I never had an issue with smog and it was easier to switch back and forth from a straight pipe to the cat pipe. in the searches I found that some got it fixed under warranty. I'm going to go visit my viper friendly dealer on Monday and have them look. I'm probably also going to order an extra set of hinge covers for the future.

sharmut · 08-04-2018

Tried wrapping the 2nd stock cat with heat shield on the passenger side (protection film was melting) as experiment. Didn't work, after the first session on track, the film continue to show more portions of the film melting. As Jack pointed out, it's the lack of air flow.

Ordered hi-flow cats from JonB, hope they will arrive next week. Originally wanted the metal substrate for it's durability but was told it was only available in ceramic for the Gen V. Hopefully this will end the sill heat issue and cross fingers with the CEL. Ordered O2 spacers in case.

**Steve M** · 08-04-2018

Originally Posted by sharmut

Tried wrapping the 2nd stock cat with heat shield on the passenger side (protection film was melting) as experiment. Didn't work, after the first session on track, the film continue to show more portions of the film melting. As Jack pointed out, it's the lack of air flow.

Ordered hi-flow cats from JonB, hope they will arrive next week. Originally wanted the metal substrate for it's durability but was told it was only available in ceramic for the Gen V. Hopefully this will end the sill heat issue and cross fingers with the CEL. Ordered O2 spacers in case.

If they are only available in ceramic for the Gen V, it is probably because the higher flowing metal substrate cats were throwing codes (they did on my Gen 4). I have a sneaking suspicion that they aren't as "high flow" as their name might imply, so hopefully they at least reduce your heat problems.

**Jack B** · 08-04-2018

Originally Posted by Steve M

If they are only available in ceramic for the Gen V, it is probably because the higher flowing metal substrate cats were throwing codes (they did on my Gen 4). I have a sneaking suspicion that they aren't as "high flow" as their name might imply, so hopefully they at least reduce your heat problems.

Like Steve said, HiFlo cats are all over the place. Go back to the thread from Prefix about his testing of the cats, it is eye opening.

**catwood** · 08-04-2018

Originally Posted by Jack B

Like Steve said, HiFlo cats are all over the place. Go back to the thread from Prefix about his testing of the cats, it is eye opening.

Yeah...I read that and the loss of 20 HP compared to the better flowing ones. Of course that isn't a comparison to stock.

**Topplayer** · 08-05-2018

Originally Posted by Jack B

Like Steve said, HiFlo cats are all over the place. Go back to the thread from Prefix about his testing of the cats, it is eye opening.

can you link this thread? I am having trouble finding it

**Special Ed** · 08-05-2018

Originally Posted by sharmut

Tried wrapping the 2nd stock cat with heat shield on the passenger side (protection film was melting) as experiment. Didn't work, after the first session on track, the film continue to show more portions of the film melting. As Jack pointed out, it's the lack of air flow.

Ordered hi-flow cats from JonB, hope they will arrive next week. Originally wanted the metal substrate for it's durability but was told it was only available in ceramic for the Gen V. Hopefully this will end the sill heat issue and cross fingers with the CEL. Ordered O2 spacers in case.

I have these hi-flow cats from JonB. I track my car a fair amount and have used them for about 1 1/2 to 2 years. Heat cut about 50% no CEL, everything about them is positive. I do have the arrow pcm, do not know if that makes a difference on the CEL's.

**ForTehNguyen** · 08-05-2018

there isnt a sensor downstream of the secondary cat so the car would have no way to know if it was there or not. Stock or Arrow wouldnt matter. Arrow disables rear O2 sensing anyways for people who run catless. Running stock PCM here with HF mains and no seconds, no CEL.

**Exhlr8n** · 08-05-2018

I put on Jon B's Hi-Flow Cats (Bellanger) on my ACR-E, stock cat back, like the others sill heat cut 50%, its so much better now. Sounds better too. I used O2 spacers. No CEL.
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**Martin** · 08-05-2018

I'm in the same debate mode. Anyone who lives in California and has had to get tested recently knows that the smog check techs are looking out for modifications of any kind. I never had these kinds of problems before, but now, they will go as far as to crawl under the car and look for CARB numbers on anything that doesn't look "right". I got failed recently for a K&N filter that didn't show up in their computer as an approved modification. At another supposedly sympathetic smog station, I got flagged and sent to a referee station because the car "sounded loud" and the tech couldn't visually see the exhaust system without taking the sills off - so instant fail. The CA smog NAZI patrol is in full force these days. I might just keep my second cat, but gut it out and see what happens.