diff exhaust pipe sizes..

[FireStorm]

ok.. i was curious.. i know if you go from larger diameter pipe to a smaller pipe, it creates backpressure... as in.. a 3" pipe going into a 2.5" pipe...

thats obvious..

here is my situation... i had a stock exhaust.. replaced it with a flowmaster cat back which i believe is 2.5"

i want to get a high flow cat.. but in the future i plan on upgrading my exhaust all the way to 3" ..one step at a time and i cant a new cat back right now

my question is, would putting a 3" cat between the stock y pipe and the flowmaster 2.5" catback be worse than the way it is now? would it cause problems?

i wouldnt think going from a 3" cat to a 2.5" catback would be worse than having the smaller stock cat go to the cat-back... would it?

thanks for the help

[majeskyb]

If it helps, the stock piping is 2.25", and the stock cat is 3". so I'm sure replacing the stock cat with a high-flow cat would help it breath better, but until you replace everything with the same diameter piping, there's going to be bottlenecks.

[BLLDOGG]

2.25" stock piping and the inlet of the cat is 3" and the out is 2.25". since you have a 2000, you will have to get a after cat o2 simulator cause you will throw a code otherwise.

[memphis_raines]

I don't know where you get that idea. I put on a 3" in, 3" out cat, then later added a 3" catback, and then a month or so later added a 3" s-pipe and never saw a code.

[HAZ-Matt]

It's hit or miss. I think one of the largest problems is actually an O2 code for improper sensor temperature, which you will throw if you locate the sensor incorrectly (farther upstream or downstream in the exhaust) after installing the new cat.