<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by JonB - PartsRack:
Just last week I talked 2 folks OUT of buying any hi-flow cat. It was wasted money, in an OEM exhaust setup.
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Hi Jon,
When you replaced stock cats with a straight pipes, did you see no increase in throttle response or power? That would be very unusual. Care to do a little dyno testing?
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Of course, removing the cats is not environmentally friendly and is really only legal for off road use, so lots of manufacturers make larger cats that flow better. There are converters out there that don't reduce the power on a Viper.
The stock cats are very restrictive (exhaust velocity is good, restriction is bad) and we've always seen improvements by eliminating them on otherwise stock cars in testing. I would not at all consider the improvements vs. cost (two high flow round cats with clamps and pipes costing about $250, total) to be a waste of money. If a customer pays too much from a vendor that has not negotiate a higher volume / lower price or has high overhead and a larger markup, I can see your point, $450 on up would make a little closer to a "waste of money".
I agree it is difficult to find that right mix of body size and internal substrate area, given the constraints of the side sill size. The fact that some aftermarket headers don't have flex pipes and if the collector comes into the side sill at an irregular angle (up or down) doesn't make it any easier to fit a larger body converter. Even I have one customer who is in the process of returning his cats because the Balenger headers he's using didn't have the collector pipe square in the side sill and the exhaust pipe was too high. We can't all hit the nail on the head 100% of the time
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As you said "all cats are not created equal". We certainly found that out during testing. It is very important to find a manufacturer that used techniques to retain the substrate in a fashion that would extend the converter life. In the Viper, the temperature and exhaust pulses can otherwise cause the substrate to move, fracture and eventually fail. Here's a picture of the ones we're using which shows the metallic O-Ring and retaining points in the body:
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Because I haven't seen which ones Part Rack is offering, can you put up a picture?