Boost spikes

[SxMachine]

I prob know the answer 2 this already, but i need 2 B 100% sure. I'll b swapping a Ca into my S13 (90) everything still stock temporarily on Ca and car including factory 240 cat-back. In order 2 prevent spikes i'm assuming boost will have to B set to the lowest possible setting. What are the chances of back pressure buildup and how long can i drive on the factory cat.

[r34 gtr]

im doing that right now, as i need to fix some problems so i can limp to a uffler shop to get a custom mid pipe made. it looks like the ca18det factory exhaust was the same size as the ka24e exhaust. at least, the downpipe is the same size as the cat, and they bolt right up. im assuming the exhaust is too. backpressure is pretty terrible, but im running stock boost and it seems to be ok. id say if you dont thrash it too much, drive on it until you feel like you can afford a new exhaust. good luck with the engine!tim

[chezina]

The stock CA cat is bigger(2.5inch) than the standard(about 2inch) downpipe or exhaust! U can push 15psi through the stock CA cat(i'm not saying it's safe, just possible!). so u should be ok as long as u keep boost down to the minimum.