Miata Mailing List: May 1997, Message #78
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From: 	Lester Seal <apex@miata.net>

Subject: Re: exhaust diameters

Date: 	Thu, 1 May 1997 11:33:55 -0500



At 10:00 AM 5/1/97 -0500, you wrote:

>On Thu, 1 May 1997, Frank Mowry wrote:

>> Could someone run down the definate list of cat-back diameters?  As I'll be

>> turbo charging in the future, I want to find the largest diameter pipe from

>> the cat back.  The exhaust's I'm interested in:

>> 

>I once measured the inner diameter of the exhaust pipe on my '94.

>It was about 1.75 inches I.D. The Jackson catback measured about 

>2.0 inches I.D. The outlet flange on the converter had an I.D. of 2.50

>inches. I wonder what the manufacturers use as the driving decision

>for the exhaust pipe diameter. Is it the extra costs to buy and

>bend the bigger pipe, or is there a tradeoff between back-pressure

>and low-end torque on non-turbo, non-SC cars? I suppose it's the

>bean counters who decide.

>

>Harry Sue

>Chicagoland



The I.D. of a stock cat (inlet and outlet) is approx 2".



Lester Seal

Mass Miata

Team APEX 508-229-0090