Bought a new exhaust flex pipe fo my 92 3.0 and noticed that the pipe diameter on the cat assy. is quite a bit larger than the new flex pipe diameter. When the 2 flanges are bolted together there will be a sudden reduction in exhaust flow right at the joint. Is this normal / correct?
Seems to me when there is a reduction in tube size it sould be a gradual taper, not an abrupt change like this?

 

As many have found out, the outlet on the cat is 2.25", while the pipes behind the cat are 2". However, it should not be an abrupt step-down transition; that will cause too much turbulence and back pressure. Maybe you need to get the 2.25" flex pipe, and allow the hard pipes to ramp down to 2" (or get a complete 2.25" cat-back system).

 

The stock flex pipe is 2". which is disturbingly smaller than the diameter of the converter pipe. However, the 3.0L does fine with 2" exhaust. I agree, the sudden step down is wrong.

If you bought your flex on eBay or from most online vendors, you will find most of them are the same cheap stuff. We sell our version on eBay as well, it is better built. It costs a little more too, but it takes more investment to use an OE type hanger, double braid flex pipe, and the proper flange. Most the other stuff uses a universal flange with the wrong sized opening, and a universal gasket to go with it. Our part uses a flange that is unique to the Aerostar and Windstar. It is not used on any other Ford model.

 

Thanks guys.
The flange on the cat pipe is damaged anyway so I think I will cut it off and put in a reducer / adapter to make the transition from 2.25" down to 2" more gradual (tapered) and hopefully reduce the turbulence and back pressure.

 

Finally got my mig welder back and was able to finish the exhaust last night... Smooth and quiet again. Now it's off to the emissions test, wish me luck.