How Hot Do They Get???????

[Don Hiltz]

When I replaced my OE cats with Roe high flow cats, I noticed that the heat shield beneath the passenger side door was burned and cracked. On Monday, I placed an adhesive backed aluminized heat barrier over the OE heat shield where it was damaged. According to the manufacturer, this product should reflect 2000 degrees and the adhesive is rated up to 300 degrees.

I cut it to size and installed 24" of it between the cat and the bulkhead. There was approximately 1" space between the cat and the shield.

Yesterday, the nauseating smell began as it became evident that the adhesive was "cooking" from the heat generated by the cat. While I'm hopeful that the heat will act as a catalyst and serve to cure the adhesive, I not really that sure.

My question for the experts: How hot do cats get?

Thanks.....

Don

 

[Janni]

Our experience in using the heat tape is that the adhesive is the limiting factor - 300 degrees isn't really anything and why rate the material for 2K if the dang thing has fallen off due to poor adhesive long before that. Something I never understood. We were consistently losing ours off our ball joint heat sheilds - finally giving up on the stuff.

 

[Sean Roe]

Minimum operating temperature is 750 F.

 

[Scott E. Smith]

Don, did you by any chance use thermotech in the 12x 24 sheets? I'm curious because my viper is in the body shop and I was going to install the same stuff in the side sills. also...has anyone used header wrap to wrap the exhaust behind the sills? my new paint is very custom and expesive....i want to protect it!

 

[Snake Bitten]

I used header wrap under the sills...works like a charm...

 

[Don Hiltz]

Scott,

Yes, that's exactly what I used. It's probably a little too early to pass judgement, so I'm still hopeful that the adhesive will fry and bond the new material to the OE shield.

A major problem is that the area cannot be visualized. To really see what's going on, I'll have to remove the sidesills again. I hate to do that because the sheet metal screws will only take so many times in and out before they'll lose their ability to get a purchase into the sill.

Janni, you're absolutely correct. My thinking, however, was that the material would reflect enough heat to eliminate the possibility of frying the adhesive.

I guess I'll have to come up with Plan B.

Thanks to all who answered...

Don

 

[95Viper]

Be careful, I read of a Viper owner whose car caught fire when this stuff melted and laid on the cat.

Keep an extinguisher with you just in case! At least while you are trying it out.

Also, use a low strength, high temp silicone on the screws when reattaching. You won't have to crank down on them so hard and strip the hole.

 

[Don Hiltz]

After reading the response describing a Viper which caught fire, I elected to remove the side sills again and eliminate the heat barrier ASAP. Well, my fears were not unfounded....the adhesive stuck to the damaged area of the OE heat shield. In removing the aftermarket heat barrier, I observed that some areas were denuded of aluminum. Now I was left with bare exposed fiberglas in 5 or 6 small areas.

My muffler guy thought about the situation and came up with a plan which I wanted to pass on. He went to his "reclamation bin" and brought out a catalytic converter shield from an old Ford. This is a semicircular, corrugated metal (type unknown) shield which he welded to the exhaust pipe about 10" in front and 5" behind the cat. We allowed approximately 1" of space between the shield and the cat. On the other side, another inch was allowed. Now, the shield touches neither the cat nor what's left of the OE heat shield.

It may be that another aftermarket heat barrier would have worked equally as well, but I found myself not having the luxury of being able to order the product and wait for delivery.

The nauseating stench of the burned adhesive has almost cleared and I now feel much better, given that I'm no longer worried about a fire.

Sorry to be so long winded, but I lost a lot of sleep over this one.

Don

 

[picflight]

Your post was very informative Don, I enjoyed reading it.

 

[Viper Specialty]

One word when it comes to Sill-Screws:

NUTSERT

 

[genXgts]

Dan, please elaborate guy!!!

Glad you fixed your problem Don, nothing worse than cruising in your car not knowing if it will erupt into flames, and surely thinking the smell is getting worse, what's going to happen feeling.

I'm going Gerald route and biting down some header wrap from the car on down the sides, although your method seems effective as well. My theory is to not allow the heat out of the pipe and just deflect it back in and out the back.

God knows we've seen the damage that headers can cause with stock heat shields, Jet Hot will take care of that!!

 

[Snake Bitten]

So said Tomcat1

Gerald, How did you put the header wrap in place under the sill?

I simply wrapped the exhaust pipe from the first hangar in front of the sills, to the back hangar right out of the sills...Wetting the header wrap in a bucket of water (so it stretches and tightens when it dries) and using a 50% overlapp, holding it all in place forever with stainless steel hose clamps...You can barely see where it enters and exits the side sill, so I am going to apply some POR-15 with a foam brush in these areas, as the header wrap I used is white, POR-15 is black. Motorheads have been using header wrap for years...works like a charm.

I did not wrap the high flow cats, I ended up modifying <font color="blue">THESE</font> to shield my high flow cats...My headers are 2000 deg Jet Hot coated...

You can't even melt ice on my side sills...

 

[Don Hiltz]

One final, and brief, note. I wrote to the manufacturer, recounted the whole scenario, and advised them of my dissatisfaction with their product. I'll let you know their response, if I get one.

Don

 

[ruckdr]

Don,
Another thing that may help to reduce side sill temperature, is to install 'side sill vents'.
http://secureprocessing.net/PartsRack/WebShop/store/detail.tmpl?sku=80007&amp;category=Exterior&amp;cart=1046798539245641
Available from Parts Rack. I'm sure some can testify as to how much air is allowed to flow through the side sills using these.
Later,

 

[Don Hiltz]

Don,

Thanks for the input. I had thought of those vents too, but if yours is the same as mine the side sills are cool when you're in motion. It's only when you stop that the temperature begins to build up. Unfortunately, the vents would not address that problem.

Thanks for the thought. Not being the sharpest knife in the drawer, I'm always open for suggestions.

Don

 

[Ron]

The cats / side sills actually increase in temperature while running and cool a bit at idle. In fact, letting the engine idle for a minute or two to cool the cats before shut down is a way to protect your side sill paint from damage.

The worst thing you can do for your sills is to immediately shut down the engine after a high RPM run. Post shut down heat soak is when the sill temps reach their highest levels.

Simply, the more exhaust running through the cats, the hotter the cat gets. I made up a graph of sill temps under various scenarios a while back. Will try to find and re-post later.

 

[Steve-Indy]

The EXTERNAL temps of the STOCK cats on our stock 97 GTS with a CORSA 3" cat-back system on an 85 degree day with sidesills off run in the 525-560 F range, if that helps.

 

[Scott E. Smith]

has anyone used header wrap on the catalytic converter itself? my problem is I'm missing any form of heat shielding on the driver's side. and appearantly to get replacement...you have to purchase an entire sidesill assy.

 

[Ron]

Curious about the header wrap too. Wondering if it could overheat the cat.

Here's the graph. Temps taken on the top sill screw so it's indicative rather than representing absolute sill paint temp.

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[NCVCA]

I realize its not for everyone... but Random Tech makes ceramic and metallic high flow cats that from everyone I've heard from virtually eliminate side sill heat issues.

I have RT High Flow metallics going in my car in about 3 weeks.

The Cone's have lots of info about CATs and temps... Simplest guaranteed fix is to replace the CATs.

 

[genXgts]

dang, this thread is getting chock full of tech tidbits:

Gerald will you let us know why you did not wrap the cats, I planned on doing just that, from one end of the sill to the other. Not a good idea?

 

[Steve-Indy]

RON...don't tell'um what we're up to...

 

[Ron]

Steve,

Not a chance...

 

[Snake Bitten]

So said Ryan

Gerald, will you let us know why you did not wrap the cats, I planned on doing just that, from one end of the sill to the other. Not a good idea?

Here is the High Flow Cat I have...as you can see, it's configuration does not lend itself to header wrap, due to the sharp edge shown in picture...and there is actually another edge on the back side...I felt this would quickly damage the header wrap, so I opted to go with an aluminum heat shield...

You must be registered for see images

 

[GTS Bruce]

If you want cool side sills get rid of the cats. Bruce

 

[genXgts]

I would Bruce, but we are smog tested up here, which blows.

Thanks Gerald, think I can get away with wrapping my cats with the wrap!

 

[Motor City Mad Man]

Be careful, I read of a Viper owner whose car caught fire when this stuff melted and laid on the cat.

Keep an extinguisher with you just in case! At least while you are trying it out.

Also, use a low strength, high temp silicone on the screws when reattaching. You won't have to crank down on them so hard and strip the hole.

That Viper owner was me. I took my sidesills off a year or so ago after I noticed the sidesill had burned through the paint on the right side and has a nice brown spot. I took the sidesill off and noticed that the heat shield had disintegrated in the area right around the cat. So I bought some of that 2000 degree Thermtoc heat shielding that says it was specifically for catalytic convertors. Didn't want to buy the whole side sill for around $3,000 a piece just to get a new heat shield so I thought this thermo tec stuff for around $80 a sheet would do the trick. Did a nice neat job installing the shield on both side sills buy stapling it to the existing heat shield. Put the side sills back on and idled the car. Smoke immediately started billowing out from the side sills after they warmed up and I performed a world record removal on the side sill. Could have beat any indy car pit crew with my speed. Anyways, the heat shield was all charred and the smell made me wanna puke. I took them off needless to say.

As far as header wrap goes, I thought about using that but people say that it traps moisture and will eventually rust your exhaust system/headers.

Does anyone know if the heat shield that is near the rear exhaust tips on rear exhaust exit Vipers is the same material as the side sill heat shields? If I bought one of those I could cut it in half and put in near the cat on both sides of my Viper. Saw one for sale on E-bay a few weeks ago for around $50 but missed the end of the auction. There is a vendor on here that started selling a supposedly really good heat shield for the Viper side sills, engine compartment, etc but the price is way way more than I am willing to pay for heat shields. Still looking for a good, cheap solution while still keeping my cats. I have hi-flow cats and it still gets the side sills hot due to them being oval and almost touching the inside of the sidesill.

 

[Snake Bitten]

So said Motor City Mad Man

Didn't want to buy the whole side sill for around $3,000 a piece just to get a new heat shield so I thought this thermo tec stuff for around $80 a sheet would do the trick. Did a nice neat job installing the shield on both side sills buy stapling it to the existing heat shield. Put the side sills back on and idled the car. Smoke immediately started billowing out from the side sills after they warmed up and I performed a world record removal on the side sill. Could have beat any indy car pit crew with my speed. Anyways, the heat shield was all charred and the smell made me wanna puke.

Was this incident with your stock cats or with your high flow cats?

 

[Motor City Mad Man]

It was with my hi-flow cats.