Can i use my stock cat and exhaust from an 89 n/a s5 on my 87 tii to smog in california? Everything else is stock except for the straight pipe. or is the s5 cat and exhaust different from an s4 tii?

 

The '86-'91 parts book that I found online has four different part numbers for main cats S4 n/a & Tii plus S5 n/a & Tii. That said, my '88 vert just passed easily with a cat from an '87 Tii. My guess is if your S5 n/a bolts up and connects to the split air pipe, you should be fine...assuming the rest of the emissions bits are there, working and properly adjusted.

Since the flow restriction may be different, you may want to adjust the idle and idle mixture per the FSM after you install the cat. Good luck!

 

Thanks for the info. I just wanted to make sure if they would bolt up to my t2 before I go pulling it off my s5. I dont wanna take it out and find out the hard way. So if anyone with experience did this before, please share and thanks!

 

You need a stock TII downpipe to the cat. Everything else will bolt up just fine.

 

Thank you

 

Yes, you need a Tii downpipe. I got lucky and found someone who sold me a really old tII racingbeat for $100 so I have a full tii exhaust. But if you just get the downpipe I think everything else should would together alright.