Saml01

iTrader: (9)

This is a begi old style bell mouth manifold. The turbo end is fine, but the other end that bolts up to the catalytic has a problem. The stud holes don't line up, the stock cat is just a bit to small and the downpipe holes aren't big enough.

The other problem is that it seems that the downpipe may not be long enough. I have to pull the exhaust by the cat to even get it close to the downpipe.

I don't know what to do, other then have the holes widened but could it be that its a 1.6 downpipe?

I cant believe I hit another snag :(. I was really hoping to get measurements for the intercooler pipes today and be done next weekend. double :(

04 Miata

The 1.6 and the 1.8 uses a different cat. The angle is different and the flange is different. I'm not sure about the length but it's possible you have the wrong DP based on your flange issue.

m2cupcar

iTrader: (5)

If it's not the wrong downpipe (meaning the flange angles match) then:

- I'd widen the flange holes with a file
- Cut the exhaust pipe on the back side of the cat and add a "parts store" exhaust sleeve and two clamps to extend the reach of the cat to meet the flange. The sleeve is essentially an exhaust adapter, same size both sides.

04 Miata

I just went to the garage and measured the holes on the DP flange. It's an old 1.6 BEGI DP and the holes look to be 3.25" center to center.

Saml01

iTrader: (9)

So you have the same one as mine and youre saying that it is an old begi 1.6 piece? Am I understanding you correctly?

04 Miata

My DP is from an old BEGI System IV kit and the flange holes are 3.25" on center. If you have those dimensions I guess you have a 1.6 pipe.

Saml01

iTrader: (9)

OOOOOOOOOOH.

OK, ill go measure in a couple of hours. Thanks a lot.

Trent

iTrader: (11)

Well, the 1.6 catalytic converter has a flange that is rotated about 30* off from the 1.8 flange. the bolt holes wouldn't line up at all if that were the case.

Saml01

iTrader: (9)

Then this is 100% a 1.6 downpipe because with the downpipe assembled the flange is off by about 30 degrees.

edit: or I could be wrong, maybe the angle is not off, but the fact that it doesnt reach the cat is 100% certainty.

Saml01

iTrader: (9)

My flange is 4.25 maybe 4.5 center to center of each hole. The factory flange is 3.5 center to center.

They are about 1/4 inch off from being able to mate up.

Heres a question.

Do the two pieces of the downpipe have to be completely inserted into each other and tightened down tightly. Because now that I think about it, if I was to not insert the two halves into each other completely it may be long enough.

Jefe

iTrader: (7)

Learn from your parents mistakes, wear a condom.

Joe Perez

iTrader: (8)

Putting aside the flanges, are the two pipes of the same diameter, that of the downpipe and that of the cat? The angles appear correct, but by appearance I'd wager that the DP is of a larger diameter pipe than the cat. Is not the Bell downpipe at least 2.5" in diameter, if not 2.75"? (That measurement alone the difference between a 1.6 and 1.8 downpipe will reveal, according to the info on Bell's website.) Such a discrepancy then I'd fully expect when attempting to mate with a stock catalytic converter.

A similar situation I also encountered as to the gap betwixt the two, with my 1.6 TurboTony downpipe and matching 2.5" cat. By way of a solution, I procured from a local exhaust shop two generic 2.5" steel flanges, each roughly 3/8" in thickness. Using them as spacers, one before the cat and the other aft, along with slightly longer-than-stock bolts was the system drawn properly together.

miataz

iTrader: (1)

Saml01

iTrader: (9)

The diameter of the downpipe is 2.5 inches.

But begi's downpipes despite being of a larger internal diameter are all designed to mate with the stock catalytic converter.

As for your solution in the second paragraph, that would not work because the gap is almost 5 inches.

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I sent this thread to stephanie and I hope she will be able to shed light on this. If it is in fact a 1.6 pipe, I have someone interested in it and I will order a new DP from Begi the same day.