Howdy,

I have been running true duals with stock cats since this winter. In April I had to replace the main cat with the o2 sensor. I started my truck up today and it sounds like the cat is failing again. Neither time, have I got a CEL, and i'm getting nervous. I talked to a couple muffler shops, and they all pretty much said that I need hi-flow cats to run true duals. They said I probably don't have any backpressure. Is this true? Anybody with 5.4L, true duals, and stock cats have the same problem? I am going to put a maggie on to replace the stock cat, but I'm nervous something else is wrong with the truck to be failing cats like that? Any advice/comments/suggestions? Thanks,

Mike

 

I don't see how having true duels will hurt the stock cats.

I have had true duels on mine for 1 1/2 years now with no problems.

 

You would have more back pressure with the stock cats and less with high flows!

Phil

 

Right!!!!

how does the exhaust shop know the cats are bad??

 

It's official... they were just trying to make a sale on some maggies. I just knocked on the Cat and didn't hear any rattling... then i fire up the truck and got back under with a mirror. I have a hole the size of a quarter on top of the pipe, right after the cat. It was shooting exhaust up into the heat shield. Unbelievable! I'm going to have a nice chat with management on Monday morning.

 

How did it get a big hole in the pipe?rusted?

 

Ya,that will definitely make it sound like somethings wrong!
Glad you found it.

 

bull****-4 years 78 k miles on my duals- no issues whatsoever-btw- i checked the pack pressure in my cats under load in 2nd gear at 5500 rpms 1.5 psi backpressure on each bank=[hardley anthing for stock cats]

 

You should try that test with some high flows and see what you get!
It just may be way LESS,,,,lol.

Phil

 

phil=i'm just healing from a motocross injury from mother's day-to the tune of over $150 k and counting- needless to say i gor brain contusions-i dug up all my vehicle notes- with the in cab test using a magna helic gauge:-it was a combined 1.5" back presuure- roughly .75 a side- hardly anything fo a daily street driving van but i will be going to magnaflow hi-flows for sound and will post results- my memeory still is in libo at times- sorry for typing wrong numbers-phil

 

i can't imagine waht a 6k lb supercrew runs like at 11.68-my 89 ta gn motor turbo v-6 runs 11.0@121 -would love to have that performance in a sreeet sleeper ford tuck