Wrap the Cat?

[spedrcr]

I have an early/v1.0 Fabspeed sport cat and am considering wrapping it with DEI header wrap. I recall reading somewhere here that I shouldn't wrap the cat "bulge" as there was concern of burning up the cat cells. I'm unable to find that discussion so I wanted to ask again for input. Any concern wrapping the cat? I'm fully aware of the potential downside to wrapping the pipe itself so just looking for input on the kitty cat question.

[wjdunham]

What are the downsides of wrapping the pipe? I've done some reading and corrosion due to water retention seem to be the only major concern?

[spedrcr]

Corrosion due to water retention and cracking but that seems to be more material specific rather than ALL stainless steel.

[Mixed76]

The catalytic elements may reach 2000F, which even stainless won't tolerate indefinitely. The stainless survives because the exterior side can dump heat to atmosphere and normally the catalytic elements don't touch the walls directly, there's a thin layer of insulation or inactive ceramic. If you wrap it, the stainless wall temp will be a lot higher, outside the acceptable region.


I'm not a metallurgist so don't know the failure mechanism; creep, cracking or corrosion I guess.

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[EC900]

Wrapping headers for appearance in a custom look is a method used in stopping radiant heat. But the Cat is restrictive and trapping more heat within could lead to problems with emissions and corrosion limited to what residual moisture the wrap may hold when pipe is cools down, doubt that the material is absorbent.
The heat coming off any Cat especially right next to an already hot engine, is what we hope to keep at minimum. And the heat shield is there for that reason - to deflect and should be used with even the FAB cat or any other cat. If I didn’t need emissions test, I’d ditch Cat altogether and go w/headers...no wrap.

[spedrcr]

Although emissions is no longer required for my car, I prefer to run a cat. Far less stinky. The OE heat shield does shield heat from the LR shock and wheel/tire but does not shield cat converter heat from the valvetrain.
Leaning towards wrapping all the exhaust in the area while leaving the cat bulge exposed. Would still like to hear what others think.

[PeteKz]

My opinion: Wrap the exhaust pipes, but do not wrap the cat, for the reasons mentioned above. The cat gets hotter than the exhaust pipe, becuase it is actually generating heat by reacting the unburned parts of the exhaust. It must be open to air. Use SS heat shields to protect the other parts of the car. I also think you should put heat shield on the bottom of the cat, to help prevent starting a fire under your car if you park over dry grass or something like that.

[porschedude996]

Originally Posted by spedrcr

I have an early/v1.0 Fabspeed sport cat and am considering wrapping it with DEI header wrap. I recall reading somewhere here that I shouldn't wrap the cat "bulge" as there was concern of burning up the cat cells. I'm unable to find that discussion so I wanted to ask again for input. Any concern wrapping the cat? I'm fully aware of the potential downside to wrapping the pipe itself so just looking for input on the kitty cat question.

What is your concern with wrapping the exhaust?

[spedrcr]

No concern over wrapping the exhaust. Was looking for input on wrapping the cat bulge specifically.

[stownsen914]

What benefit are you looking to achieve by wrapping the cat?

What is Fabspeed's position on the topic?

[porschedude996]

Not to pry, but I’m wondering what drove you to ask the community. Are you confirming someone else’s suggestion? Are you thinking the cat would run hotter to reduce emissions?

I see no benefit to wrap. In my case, totally stock 911SC, there is sufficient area around the exhaust tubing to keep things cool. The only time would consider wrapping is when you have a turbocharger to maintain the heat in the pipe “to” the turbo, and not after. The wrapping would keep the heat in the pipe to get the benefit to spin the turbine wheel.

I have in the past wrapped exhaust tubing on a high performance highly modified car with a steering shaft universal joint. The universal joint had bearings and grease inside. Thus keeping the grease on the inside.

[spedrcr]

As I mentioned previously, I recall reading somewhere on here a concern of wrapping the cat could result in burning up the cat. Just looking to confirm others would have the same concern. So in the end, I'm not looking to wrap the cat.

Originally Posted by stownsen914

What benefit are you looking to achieve by wrapping the cat?

What is Fabspeed's position on the topic?

Haven't asked Fabspeed. Good idea though.

[spedrcr]

The goal of wrapping the pipe, but not the cat, is to reduce the transfer of radiant heat to the nearby valvetrain, LR shock and wheel/tire and in-turn keeping the heat in the exhaust pipe moving the exhaust gases through the exhaust pipe faster.

Originally Posted by porschedude996

Not to pry, but I’m wondering what drove you to ask the community. Are you confirming someone else’s suggestion? Are you thinking the cat would run hotter to reduce emissions?

I see no benefit to wrap. In my case, totally stock 911SC, there is sufficient area around the exhaust tubing to keep things cool. The only time would consider wrapping is when you have a turbocharger to maintain the heat in the pipe “to” the turbo, and not after. The wrapping would keep the heat in the pipe to get the benefit to spin the turbine wheel.

I have in the past wrapped exhaust tubing on a high performance highly modified car with a steering shaft universal joint. The universal joint had bearings and grease inside. Thus keeping the grease on the inside.

[porschedude996]

Ahh, I can see your points, but consider this. The valve train is cooled by the engine oil and goes out the coolers, and the buttress/fins of the cover cool as well. The shock and the tire are moving in clear air and I would imagine the benefit would be little. If the shield on the cat is inplace, I would think that is sufficient. I guess you could test using a thermal gun (laser type) and look at the differences left to right after a spirited dive. The tire pressure needs to be somewhat equal so the drive/road heating the in same configuration.

I have some experience with wrapping a air cooled VW and the small leaks and valve cover removal for valve adjustment contaminated the wrap. Even the best wrapping techniques it still unraveled. Total mess. I even covered the J pipes with aluminum foil during servicing and it helped. I do the same without wrap. Seems me, in my head, that the benefits are little or non-existent. Just my opinion and everyone is entitled to one.

[stownsen914]

Keeping heat off the engine is a worthwhile goal. Consider using a heat shield as an alternative to wrapping. There are a few ways to do it. You can fab a metal shield to sit between the exhaust and the engine, and attach it somewhere convenient (ideally not the engine). There are also kits that allow you to attach a flexible composite shield close to the exhaust (not quite touching it), to shield items that sit close to the exhaust. I used a kit similar to the below on a racecar that had an exhaust running close to fiberglass bodywork. Seems to work well.

https://www.summitracing.com/parts/dei-010454

[spedrcr]

porschedude996 and stowensen914 Thank you for your thoughts. I appreciate it.

[porschedude996]

Your very welcome. Love the sharing of thoughts and help both give and take.

[spedrcr]

Chose to wrap the sport pipe but left the cat bulge open. So far I'm pleased.

[dw1]

Looks good.

I agree with not wrapping the cat, and I have enough knowledge of ferrous metal alloys (I'm not a metallurgist, but an engineer with lots of metals education & experience) to know that it is a bad idea due to heat retention both inside & out.

However, if you want to run a euro premuffler in place of the cat, then wrapping is fine - even advisable. Here's how wrapping the Fabspeed premuffler with the DEI kit on my '87 3.2 turned out: