View Full Version : catylictic converter modification

01-31-2009, 04:34 PM
when i did the dyno for car craft the first graph was way pointy up and down and the dyno tech said it was probably adding fuel to cool the cat i dynoed about 230hp i thought it was because my exhaust was contacting the body causing false knock i returned the next day bone stock and dynoed 250.8 or something close to that a huge difference. i guess what im getting at is how to keep that cat cool in case that was the problem and although i dont plan on doing any mods to it quite yet i was wondering if it would help to move it downstream a little to keep it cooler? or will it be too cool and not function properly?

you dont have to be an expert just leave a comment speculation or

Nacho SS
01-31-2009, 08:19 PM
Gut the cat?

cherry gxp
02-03-2009, 03:11 PM
The chemistry of the cat only works when it is SUPER hot, the dual cores that turn the carbon molecules to CO2 and H20 coated with palladium/platinum and palladium/I forget? only catalyze the reaction when they're superheated. Therefore moving it downstream would actually take away from the actual purpose of the cat and still cause backpressure from it being there. If you're worried about it. Just buy a catless downpipe and call it a day. Or spend the extra dough and get the magnaflow hi-flow catted downpipe. Moving the stock cat around is going to keep the exhaust just as restricted but take away from the function of the thing. Hopefully this helps a little :)

Nacho - You could gut the cat, the only problem with such an action would be the irregular airflow created by that open space the exhaust gas is flowing through. I think physics would say that the gas would flow into the open portion and swirl back towards the front when it hits the narrowing end, therefore creating turbulence and also reducing airflow. However, if you were a pimp and wanted to cut out the cat and weld a piece of new tubing to your stock downpipe that just might work. I'm not sure but that seems like a poor man's way of de-catting your car ;)

02-03-2009, 03:34 PM
Don't waste your money on the catted down pipe, damn thing throws a code. Since a code is going to be thrown anyways just buy the catless one and save some money!

02-03-2009, 04:16 PM
Just so you know, the cat really only works correctly at 14.7:1 AFR and when you go wide open you are much richer than that, within a few seconds of WOT the cat temperatures will actually cool off and you can get an accurate WB02 reading after the cat then as well for WOT.

The power diff explains that you had some major issues developed by that cobbled down pipe you had on there or something. For you to pick up that much power, it was overly rich (SES LIGHT ON??) or was down on timing has been my findings with tuning stuff on the dyno.

cherry gxp
02-04-2009, 06:33 AM
^^^Nice explanation man^^^

02-08-2009, 03:28 PM
i remember that the first run i did have the maf screen removed would that be why?

02-08-2009, 03:39 PM
i remember that the first run i did have the maf screen removed would that be why?

Well if the fuel trims were all apeshit because of it, its possbile.