Exhaust Replacement Advice

Someone has to have scrapped their cats before.. Apparently the Toyota cats use the most platinum so they're worth like $100+ each.. wondering if I can do that with all 4?

 

I'M preety sure the 4 cats are ODBII at least or higher for california, so it's the expensive ones.

Replace your headers by DT long tube or URD and add a set of URD O2 simulator on the second set of sensor. This set is monitoring the health of the cats. This way there will be no light in the dash and the 2 cats on the Ypipe can be easily seen from Under the truck

The first set is for the AFR reading used by the fuel injection loop.

 

UPDATE: just ordered the magnaflow manifolds (part # 49341 & 49342) and magnaflow off-road cat-back exhaust (part # 17115) through a local dealer. Manifolds were under $500 CAD per side and the exhaust was $325 CAD, no shipping charges. Just need to order the Doug Thorley pipe bomb and that'll complete the system. Will update in a few weeks when everything is installed.

 

There are four O2 sensors and four CATs on the 4.0L trucks. The order on both sides goes: manifold -> O2 sensor -> CAT -> O2 sensor -> CAT -> Y-pipe.

As was posted earlier, the first O2 sensor on each side is used to manage fuel trim and the second is used to monitor CAT health.

In this regard removing the second set of CATs from each side would have no repercussions that would be detectable through the computer system, but if the inspector is expecting to see four CATs and he can only find two... FAIL.

If the inspector doesn't care how many CATs there are as long as the electronic emissions equipment is functional and it passes a sniffer test you may pass without the rear CATs, but you also may not depending on what the standards are in your area.

I was getting a "catalyst efficiency below expected value" code for both sides on my '05, but it was only triggered under WOT (wide-open throttle).

I tested by clearing the codes and driving sensibly for several days with no check engine light/code triggered. Then I floored it for 5-10 seconds and the light came on immediately. To be sure I repeated the process three times with the same result. This ruled out any question of bad O2 sensors and hinted that there was likely some kind of deposit reducing efficiency at WOT.

I bought all four direct-fit CATs from Magnaflow and found that the header/front CAT and passenger-side rear CAT components fit perfectly, but the driver-side rear doesn't fit because the crossover pipe from the CAT to the Y-pipe collector is designed to route right through the area were the tailshaft and skid plate are located on the 4WD transmission.

I called Magnaflow and they were not aware of this. They also were not aware that the stock manifolds and the passenger-side rear CAT attach to the rest of the exhaust with studs that screw into the rear flanges of each component. All of the Magnaflow flanges have holes in the right locations, but they are not threaded and do not come with bolts, washers and locknuts. If you're replacing all four CATs with their system you will also need 8 bolts/washers/locknuts (make sure they are all metal locknuts, the kind with nylon inserts won't handle the exhaust heat) in addition to the components, gaskets and o-rings provided with the Magnaflow parts.

At this point I have to re-install my old rear CATs until I find out if I'm replacing or returning the new ones.

Here is a link to the CATs offered Magnaflow for 2nd Gen Tacomas:
https://www.magnaflow.com/02catalytic_converters/02product/shopdisplayproducts.asp

The header/front CAT components look like this:
https://www.magnaflow.com/02catalyt...rectfit01.asp?catalogid=47689&directfit=50848

This is the driver-side rear piece that doesn't fit 4WD trucks:
https://www.magnaflow.com/02catalyt...rectfit01.asp?catalogid=47685&directfit=93660