1989toy4wd

Okay people lets get this straight once and for all. Backpressure, no matter what , is always bad and does not increase the power or torque on any engine. Ideally your engine would run with absolutely no backpressure at all. Backpressure is the residual pressure within the exhaust system that is higher than atmospheric pressure. What you need is called the scavenging effect. What the scavenging effect does, is allow the exhaust gases leaving the engine to travel faster to get out of the system. Sort of like drafting in nascar. Without the scavenging effect the exhaust would cool too fast and causing it to slow down and 'hang out' in the exhaust pipes to long, hurting performance. This is where people get confused...with the scavenging effect comes backpressure (in other words, you cant have the scavenging effect without backpressure) People that say " you need some backpressure to help your engine run better," are partly right, what you really need is "a condition that simultaniously creates backpressure in your exhaust system," its just not the backpressure part you are looking for!!!!!!!!

suprathepeg

You are absolutly right. The reason we don't all have 6" exhaust systems is that backpressure can be used to shape a useful powerband. Sure you may open up 5hp at peak RPM but you will loose the power where you want it. Pack pressure is very useful if you want low RPM power, again that can make for a less then ideal powerband.

AH64ID

10hp on a 22RE is almost 10%, your not going to get that by removing the cat. I have run header free-flow exhaust with and without cat. Without cat was worse. there was no noticible pwr/mpg.. and it STANK, i couldn't roll the back window of my runner down it was so bad.

Leave the cat in. Of course most people are going to tell you they got a performance increas from removing it, its human nature to embellish a little.

IIRC the fine for not running a cat on a vehicle required to have one is 25K in washington... it isn't worth the .2hp you get, if that much

And also, yes engines perform better with less backpresure, but it depends on what RPM range your looking for, with a 22RE if you put a 4" exhaust on it have fun trying to get going. When I put my header on I did it on a friday, and the exhaust shop didn't have a slot until wed, so I drove around open header for a while, it was a DOG... I was so pissed for putting the header on becuse I lost SOOO much power... Then when I put the muffler back it is was a rocket....

just my .02

CoedNaked

First off, what modifications do you currently have on your truck? Have you done an exhaust, headers, intake, etc. etc. ?

05prerunner

I punched out about a 1" diameter hole in my cat just to increase flow some without having the stinky smell and i couldnt really tell any major difference but did seem to run a little smoother and feel more free on the highway.

1989toy4wd

My truck had a gutted converter when I bought it, and i didnt know it. I bought a new converter because I thought that it was what was making my truck run bad, and it wasnt. But I put it on anyway because it was too late to return it. There was no noticable power difference at all. The exhaust was just louder with it gutted, that was it!!

MMA_Alex

It will get you more power, however it will be a tiny amount unless the cat is clogged. While there are plenty of states with no emission requirements for these trucks, most states do have a requirement that you leave the cat in place, and impose heavy fines for removing it. It should also be noted that some of us intend to live on the earth for a few more years, and would love if you would do your tiny part not to trash the place.

ironroad9c1

yup ,its just not worth the time to do it ,you get nothing from it and anyone that tells you otherwise is a lier
i tend to diagree on the whole larger pipe after the muffler thing , i have found its always better to go on size smaller after the muffler 21/2 in ,muffler,2 1/4 out to tailpipe.

these guys seem to agree with me.
http://www.pontiacstreetperformance....p/exhaust.html