When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
Idle your Disco at night in full darkness while parked and look from the ground up at each cat to see if either/both are slightly glowing purple or orange after a drive.
I just drove 1,500 miles and put my hand on my floor carpet & console tunnel thinking about you and both were cold. No heat coming in at highway speed.
Had the exhaust checked out today. I figured the muffler was bad. It turns out the muffler is still solid so it doesn’t need to be replaced. I did have him weld a hairline crack in it but other than that he said it was solid. Also had him remove the resonator.
So at this point my working theory is that the performance cam is causing things to run hot so I will just add some additional heat shielding from design engineering and see it that helps. Still planning on checking for glowing cats tonight but my O2 sensors are reading just fine so I don’t expect to see an issue there. Stay tuned!
Update - I crawled up under there again and @Extinct is right - the muffler is too far back. I traced up towards the front and found a spot around the driver CAT that seems like a heat shield is missing. Got a new Design Engineering heat shield coming from Amazon on Wednesday so I will slap that in there and see if that helps. Seems like there used to be something here as evident by the studs.
Update - I crawled up under there again and @Extinct is right - the muffler is too far back. I traced up towards the front and found a spot around the driver CAT that seems like a heat shield is missing. Got a new Design Engineering heat shield coming from Amazon on Wednesday so I will slap that in there and see if that helps. Seems like there used to be something here as evident by the studs.
Not a great pic angle but yeah, you could use a heat shield with an air gap around the top of your cats.
Even so, your muffler temp readings suggest a problem upstream of the muffler. Cats might hit 350 but your muffler shouldn't. Certainly not 405.
Heck, I'm rethinking. Now I'm wondering if that shiny surface is not just a wierd pic angle/lighting but some sort of heat wrap around the cat itself (a pure fire danger if someone did that).
My temp readings were from my 11 min drive home, not sure your temps are out of the normal range depending on the driving conditions before you took the temperatures. The discos come with an aluminum heat shield between the cat and the floor, most cars do. I also wrap my Disco's passenger side cat with a piece of aluminum duct from HD to reduce the driveshaft grease cooking. Aluminum has radiant reflectivity of 98% and a radiant emissivity of 2%. So with those combinations, only 2% of the cat heat is emitted toward the floor and 98% of that is reflected away. That lets .04% of the heat reach the floor.
My temp readings were from my 11 min drive home, not sure your temps are out of the normal range depending on the driving conditions before you took the temperatures. The discos come with an aluminum heat shield between the cat and the floor, most cars do. I also wrap my Disco's passenger side cat with a piece of aluminum duct from HD to reduce the driveshaft grease cooking. Aluminum has radiant reflectivity of 98% and a radiant emissivity of 2%. So with those combinations, only 2% of the cat heat is emitted toward the floor and 98% of that is reflected away. That lets .04% of the heat reach the floor.
What kind of duct material and fasteners are you using?
I mispoke - the driver side CAT has a heat shield in place but the spot above it in the picture does not have any shielding. It looks like there used to be something there and that is what I am going to replace.
I'll take a closer look at the CATs but wouldn't I be getting some sort of O2 sensor error if the CATs weren't working?
