The Cat Is Commin Off! need sizes tho...

[lametec]

The 2.25" dp's are only 2.25" for the first few (like 5) inches. After that, they're 2.5" to the cat.

[89daytonaTII]

Quote:

Originally posted by lametec The 2.25" dp's are only 2.25" for the first few (like 5) inches. After that, they're 2.5" to the cat.

hmm i guess I've learnt 2 things today, i should get underneath an 88 and see what's up.

[vcrpro3]

Quote:

Originally Posted by crazymadbastard How about if you just "hollow out" the cat. I have seen people take pipes to smash the stuff out.

Tell me if i am wrong, which i probably am...straight pipe would be better in place of hollowed out cat,there might be some restriction created from turbulance inside the cat housing even though the honeycomb has been removed.

[moparzrule]

Lametec is 100% correct, I've been telling people this for years. People that want to upgrade to 2.5'' exhaust and everyone tells them they need a new downpipe because they have 2.25''. But you've got a perfectly good 2.5'' pipe to start with if you chop it off right before the CAT. Changing out that first few inches of 2.25'' pipe is pointless unless you are changing to a 2.5'' swingvalve or atleast porting the 2.25''.
The stock exhaust works like this on 84-88 turbo cars....2.25'' swingvalve, first 6'' or so is 2.25'' on the downpipe then flares to 2.5'', CAT, 2.25'' out of the CAT, steps down to 1 7/8'' right before the over the axle pipe, muffler.

[moparzrule]

Quote:

Originally Posted by vcrpro3 Tell me if i am wrong, which i probably am...straight pipe would be better in place of hollowed out cat,there might be some restriction created from turbulance inside the cat housing even though the honeycomb has been removed.

You are mostly correct. Is does create some turbulence, but not so much. The real problem with just gutting a cat is exhaust resonance, it's so loud inside the car it's extremely annoying. It's worse the larger pipe you go. I hollowed out a 3'' cat, only to take it off a couple weeks later and shove a pipe through it to give it the ''visual'' appearance of a cat to pass inspection.

[envyyourethics]

Not wanting to hijack...but

how strict is PA's emissions check

need to get inspected in a month..

i hollowed out the cat....do you think it will pass???

[moparzrule]

Yes. PA's test is only a visual on 95-older cars. As long as it's there, no problem. It doesn't even need to work. It's extremely stupid. Like for example on the extreme stupidity, say a car has a smog pump....doesn't need to work just needs to be there.