1980 rx-7 ls exhaust piping
 

I have a mostly stock 7 and am going to get new piping from the manni back and was wondering what the second small pipe is for and if it can be taken off or what i should do with it? Also was wondering if anyone had a recomendation on piping size i was thinking 2 1/2 or 2 1/4??

I would like to get it done today before they close if someone can reply quickly

The smaller pipe is for the air pump or smog related (not too sure, first thing to go on mine). Either way, if you redo the exhaust (I am assuming you will be getting rid of the cats) you can dump the air pump.

Also, 2 1/4 would be better for a stock port motor. Why just the manifold back? You should get a header first, then do your exhaust. No point in paying twice.

Good luck with passing emissions if you do not know anyone.

1980 stock exhaust components:

http://img.photobucket.com/albums/v2...27031dfc-1.jpg

If you are going to re-pipe a stock 80 any way other than stock, you need to start from a header and work back at least to the midpipe; the stock 80 manifold ( thermal reactor), the first pipe segment (air duct) and the heat exchanger are all coaxial (pipe within a pipe) and there's no good way to just bolt up pipe segments to them wihtout setting yourself up for an early manifold failure due to lack of cooling air flow through the outer jacket.

From the heat exchanger back, the midpipe and muffler (not pictured above) are conventional stuff.