Replacing my cats with test pipes & a tune gave me more H.P. than anything I could think off. Since I did it for power not sound, I'll just leave that subject to you guys/the experts....

what exactly are you talking about?

no one said test pipes didnt give you power

I kinda agreed with you. Test pipes benefits. :confused: Why the hostility?

Your statement is wrong.

the same exhaust heat is being thrown down the exhaust. it does not matter cats or not ... I shouldn't have added in my statement about heat because its wrong... because you cannot produce more heat after the combustion is done .... that 600F+ you are talking about is just at that location the heat will generally be (as per what you are saying) at 600F in the cats .. if you have a cats at the Y-pipe (xyz y-pipe) the heat will be less.. because its farther down the stream ....

That is correct but the test pipes at least get rid off the heated air much quicker. Imagine me helping him. :)

So I cant take the cats out without destroying my exisiting exhaust then!?

If I got a combo which included high flow cats that would stop my stock exhaust from being destroyed?

Are any long tube headers available with cats built in? Cant seem to find any.

Alternatively do many people make the section between the downpipes and the back box section as a stand alone part?

Yea its on here, A few below this one !! :)

can you explain why the inlet to a cat is always cooler than the outlet to the cat?

when testing cats using a temperature gun, the best way to know if a cat is functioning is to measure the inlet of the cat and measure the outlet, the outlet is almost always 100+ hotter than the inlet

that alone tells me EGTs are higher leaving cats than they are entering them

im not saying you're wrong, im just giving my observation from what i have learned taking the auto classes i have been taking so i can get my ASE certification

not being hostile, but more confused, i really dont understand what you were saying there

well oxidation is taking place in the cat and it's an exothermic reaction (more heat)

regardless cats are not going to be helping exhaust velocity.

cats don't heat up the exhaust to work; when they work they heat up the exhaust.

the engine advances timing to get exhaust gases hot enough for the cats to work.

both of you have valid point :tup:
so I will shut up ! ;) hehe

if we come back on topic about the oem muffler , it means it cannot support high revving of the engine for an extended period of time.... no matter with cats or test pipe... I just dont see why the muffler would start rattle with just the test pipe ,, i haven't really pushed the oem muffler with cats anyway...

but it was mentioned also by another guy having test pipe and going thru 2 oem muffler ... might be a coincidence ? or the inside baffles are just poorly designed.

I think its the increased flow test pipes provide over cats combined with poor baffles that causes the rattling. I have a nismo and my muffler is fine granted I only had test pipes on for about a month.

It could also be caused by backfire, I know on decel or when up shifting I hear burbles and pops come from my exhaust, which is normal for a car with no cats to do. Heck Zs with muffler deletes pop on occasion.