testing for restricted cat/exhaust

Does anyone know how to test for a "restricted" exhaust or catalytic converted?

All comments, wise-ass ones included, are welcome!

I have seen exhaust guys bang on the cats and listen for a rattle. One way they go bad is to break up into pieces and start rattling.

On an Audi we used to have the cats went bad and never rattled, they just clogged. Lost power progressively until I replaced the cats. Couldn't pull up hills without flooring it.

HTH

You can do it with a vacuum gauge. I found a plugged cat on a friends 4Runner this way. Check out Jack Conrad's article here : http://www.ih8mud.com/tech/vacuum.php Any engine will have low vacuum at wide open throttle but you should be able to get 10"HG at mid throttle. If the vac dwindles as the rpm is raised and doesn't recover when holding a constant rpm ( @2000-2500 rpm) then you likely have a restriction. We were able to test the 4Runner with the exhaust intact and with the cat unbolted. You could see a huge change in the manifold vacuum.

BTW the stock 60 cat is a pellet type that allows the pellets to move around a bit. As they get older, some of the pellets disintegrate and allow the rest to move around more. This type of cat is harder to plug up than the newer honeycomb style. A rattle really won't tell you much of anything.

Cut it out and throw it away... no more restriction.

The cat really heats up if it's working. The inlet temp should be noticeably lower than the outlet. Laser thermometer works great, but you need one that reads to 1,000 degrees F.

An easy way to check the CAT is to go down to your local driving range and purchace a bucket of golf balls take them home and remove the section of your exhaust with the CAT. Then cram all the golf balls you can and then when you can not fit another ball, take a hammer and apply forcefull preasure. Oh hell just smack the crap out of it.. If the golf balls come out the other end with some black honey comb looking stuff, it was restricted. No need to replace the CAT, because you now have just remove the CATS insides and you should have a straight flowing exhaust..

Now for the muffler, cut the section of pipe right before the muffler and now you have a unrestricted exhaust..

I will warn you, using the golf ball method really works!!! I have used this technique in several of my cars. Well I dont have to pass a smog check for inspection. The guy just simply looks under the car to see if the CATS are there, and to him they are..