Lower EGT after CAT is gone?

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As I noted on another post about lost cats, I very recently replaced my cat with the Mopar test pipe. Two things have changed considerably: 1. My EGT's under several different driving conditions have gone down between 50 and 100 degrees on average. 2. My probe is post turbo and the cool down time to 300 degrees after highway cruising takes less than half the time it did previously. I assume from this that the cat was clogged pretty bad. I only have a little over 55K on the truck. Anyone else notice this much effect without their cat?

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Ron

'96 Club Cab 2500 4x4, 4:10LS, Camper/Tow package, Auto, BD Pressure Loc, Mystery Switch, TST 230/605, Cummins Chrome, Mag-Hytec rear and trans covers, Boost, Pyro and trans gauges, Optima Red Tops, All black. Tow 14k HitchHiker triple glide 5th Wheel. Also use 9. 5' Lance camper. NRA Life Member.

 

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I had considerable amout of turbo lag and a lot of black smoke with a plugged cat. Didn't have gauges on at that time so I can't answer what happened to egt's. Without the kitty my mileage is 21 mpg and have more power than I can shake a stick at.
Were you ever at the the TDR meet in Rochester ? If so I had the silver truck with stacks. I had them taken off in May and went back too dual exhaust.

 

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Jeff -

Why did you tack off the stacks? Just curious.

 

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I gutted the cat at 200 miles, the second day I owned it. The honeycomb was clogged already. I have a VW TDI Jetta and I pulled off its cat and the honeycomb is much larger and will not ever clog like these on our trucks do. I put it back on the car and let it be. On our trucks it makes backpressure and heat increase. Diesels don't like either.

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Chris Timochko
1997 5sp 4X4, HX40, BD 4" Brake, Marine Compression, Custom Tuned Injection Pump, 370B Injection Nozzles, Delivery Valves, Governor & AFC Spring Kit, Psychotty Air, Water Injection, NOS Diesel Kit, 6" Chrome Exhaust System, No Smoke Valet Switch, McLeod Dual Disc Clutch, Mag-Hytec Rear Cover, Cummins Chrome Kit, Optima Red Tops, Hadley Bully Horns, Hurst Line Loc, Goodyear Wrangler AT/S 305/70/16s. Test mule for Auto Wurks Diesel race program

 

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Thanks for the replies. Looking into the cat the element looks to be as fine as window screen. If those are the size of the openings all the way through the cat it's no wonder they clog up. I too have seen the honeycomb on other cats (gas) and the openings are much larger. Jeff, I was not at Rochester.

 

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I too just lost the cat on my 97 that has 151,000 miles on it. It seemed at about 2200 rpm the truck ran into a wall. If I really pushed it hard, I didn't notice that wall. But now it is so smooth all the way thru the power band. .
But that 3" straight pipe doesn't hurt either. . LOL #ad
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Rick

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RICK
97 2500,CC,5 SPEED, 3. 54 Limited Slip,Psychotty System,K&N, ISSPRO 3" Pyrometer,Silencer Ring Removed
12,000 RBW 5th Wheel Hitch,25' Excel 5th Wheel,Rancho RSX17000 Shocks,Amsoil Dealer,Straight Piped

 

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An old friend of mine is a diesel mechcanic for a large So. CA bus company. He was telling me they have one series of bus with a cat equipped Detroit Diesel,since they can't gut or remove the cat legally they've put cat replacement on the maintenance schedule,every 10,000 miles. Doesn't take long for a bus to rack up those kind of miles. They recieve a 100% core return from DD(DC are you listening?). To me it just goes to show that a cat doesn't work on a diesel.

[This message has been edited by illflem (edited 11-16-2000). ]

 

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Hey KatDiesel
Why did I take the stacks off? Cause I'm stupid. #ad
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I could not drive it into the shed anymore with them on. Of course I knew that would happen before I put them on. They did not do such a hot job running the drivers side pipe. Sorta got the exhaust crunched. Also was running the exhaust over the fuel tank too close.
Then in May I turned up the power. Had to fix the cat since it was plugged. I saved the other cat back and put it back on. I can only imagine what it would sound like with the stacks with more power and a fixed cat.