1.6 FM Hybrid DP Question
 

Is FM assuming we're using the oem cat and exhaust? I don't understand the purpose of the hybrid DP. Can't you just use a high flow cat that's 2.5" instead of 2"?

From FM on their Hybrid DP:
"This special downpipe allows a 1.6 car to be fitted with a 1994-97 catalytic converter. Why? Because the 1.6 cat has a 2" flange on it that forms a big restriction. This hybrid pipe maintains the flange size and location of the 1994-97 cat so you can use any aftermarket or stock cat and remove that bottleneck. Exclusive to Flyin' Miata!"

http://www.flyinmiata.com/Store/images/22-40103.jpg

The inlet flange on the 1.6 cat is significantly smaller than that used on the 1.8, and you can't fit a 2.5" pipe in it. So if you want a cat that's truly 2.5", and not 2.5" with a 2.0" inlet, then you have to use the 1.8 flange.

That's why the downpipe exists.

http://www.flyinmiata.com/images/mis...s/IMG_9430.jpg