Monday, November 28, 2005 - 11:01 pm, by: Mike Bradberry(Halflife)
I was told by the guy who did my 2 1/2" cat back that my cats had been done the cheap way for compliance. I didn' think to ask at the time what he meant. Could I expect to get a performance gain by buying high flow cats. I think there are 2 up front and maybe another after the join. (V8).Havn't seen under for some time.
Tuesday, November 29, 2005 - 12:19 am, by: Phil Gibson(Sciflyer)
After what ive seen with the V8 cats i would question the point of getting supposed 'high flow' ones to replace the standard items.
If you have a bodgy single-cat conversion then yes get that sorted to one-per-side as it was from the factory, but if you have the stock setup using two factory cats then i wouldnt waste money on getting different ones, the factory items appear to be every bit as good and are better built than most aftermarket cats...
Tuesday, November 29, 2005 - 09:05 am, by: Blaine Hanson(Blaine)
Phil - In WA all cats have been replaced for Aussie compliance. So I guess it all depends on your importer as to what the definition of "standard" replacement versions is. I think everyone who is interested in HP gains should do some research on the model of cats they are running and compare it to the available options. Based on cfm ratings. There are some articles on Autospeed. I personally believe if you help these motors breath better you will gain HP. I had two "standard" cats, then a 3" HF cat ( after I got headers ) and now I have the highest flowing 5" cat available at 1000+ cfm - why ? Each upgrade I gained HP. Is the HP gain worth the extra expense? Now that's another topic again and depends on one's budget.
Tuesday, November 29, 2005 - 12:33 pm, by: Blaine Hanson(Blaine)
I agree Phil, I have also seen inside the original factory cats, and I agree they appear as good if not better than what they are often replaced with. Another stupid compliance regulation.
Tuesday, November 29, 2005 - 01:40 pm, by: Phil Gibson(Sciflyer)
Yep my point is the standard factory cats are pretty damn good, you would need to do what you did and get some seriously high-spec cats to improve on them, and even then you'd probably only want to do it if youre upgrading the rest of the exhaust too.
The cats that were fitted to my car as part of compliance were the same ones that Peter uses here but i found them to be no better than the factory ones and were tinny and inferior build to boot.
After having some sealing problems with them i ended up getting a factory pair and putting them back on...
Tuesday, November 29, 2005 - 05:09 pm, by: Blaine Hanson(Blaine)
I don't blame you there. I think some of the compliance regulations are unjustified. I have seen Dave at Precision throw away many perfectly good factory cats after cutting the flanges off them for Aussie cats. The other thing some members forget is there are two cats in the stock V8 exhaust system. People swap these out and run one cat exhaust system.... hmmm and expect better flow / performance. So like I said above, for those considering a change, please do your research first on cfm flow rates before making any assumptions Don't believe all you read - " Hi flow " - compared to what ??