Whats the difference between an NA and NB downpipe?
 

Other then the fact that the flange is different, anything else?

I just realized that the first downpipe I bought was not for a 1.6 like I thought, it is for an NB. How did I figure this out? It just hit me that the number written on the flange "61003" is a begi part number. Looked it up on the site and its for an NB.

DAMNIT.

I just spent the last hour filing out the flange holes to fit my cat, but now it may not work all together. Unless everything else compared to an NA is the same.

OK. I filed out the holes and it slides onto the catalytic perfectly. I mounted the downpipe to the turbo and put both halves together and it leaves about a 3 maybe 4 inch gap. So it basically doesnt reach the cat without me pulling on the whole exhaust a bit.

I also have a FM by Begi 1.8 set as well, and it requires me to do the same thing.

Is this normal? Do I have to pull on the stock exhaust a bit to mate it to the downpipe or is it supposed to reach all the way perfectly?

IIRC the 1.6 and 1.8 cats are a different length and the angle of the flange is different which is why the DPs are different.

He has a '96 IIRC, thus he has a 1.8, but apparently he has to shift the exhaust to get them to mate together. Seems like a long ways but maybe not.

and the difference between 1.8 NA and 1.8 NB?

I'm not sure there is but the difference might be around the fact that the NB has the cat in the midpipe.

I layed the assembled down pipe onto the factory manifold and it seems to match length wise and even the O2 hole matches.

So I think it might have to slightly tug on the rest of the exhaust. My other thought is to take the ring that mounts the factory exhaust to the transmission and re use it on the downpipe to strengthen it a bit.

The flange locations are different between a 1.8 NA and NB Miata. I'm not sure of the exact amount, but 4" sounds about right.