Wrong! If he has it post cat it has nothing to do with the A/F mixture.

 

i was always told that the post controls the mix? if i am wrong thats fine, i learn something, but i have been told that from everyone from Dodge techs and the dealership, to like three guys on here...

 

The one before the cat (pre cat) is the one that controls that. The post cat just tells the pcm whether or not the cat is working properly.

 

A lot of guys will tell you the A/F ratio is controlled by both, or by the post, if either A. they don't know what they are talking about, and/or B. they don't want you to mess with anything to do with the catalytic converter (stealership).

Its a $10,000 Federal fine (last time I checked was a few years ago, may be more now), not to mention the individual state laws, for a shop to remove a catalytic converter without putting another right back on. A lot of shops won't even touch them.

Doesn't mean that you can't do it yourself though. I went the Magnaflow high-flow route, but to each their own.

 

i aswell have the magnaflow highflow... that way you know your legal, and still have a good cat

edit: and thanks guys for the knowledge, everyone has an opps sometimes.. lol

 

i punched out my cat after my truck died and wouldnt start now the truck runs great iwould try it

 

and granted you can do this... theres only one problem with that, these trucks relly alot on there back pressure to scanvaging rate, so by opening up the cat that much, it also opens up alot of scavaging, so.... you need back pressure to run right with more torque... it will work to let you know if thats the problem though...

but so will taking out the front o2 sensor, and letting it run for a few, you will hear alot of air pressure... liek a huge leak.... trust me, i filled my exhaust with mud one time... and it was the only way i could get my truck to run...

it will throw a check engine light when you do this, but it will go away when you put it back in, if not, bring it to autozone or advanced and they can clear it

 

No good. I work at Zone and we can't clear codes it's against the law as we are not a service shop blah blah.

Just go caveman and disconnect the battery for 5 mins

 

i just did it the other day... brought my buddies rustang in cause a check engine light, cleared ti no problems.. may just be there in ohio

 

Wrong, Wrong, Wrong. Backpressure is always bad. Scavenging is always good. No one seems to understand this. Scavenging is the exhaust causing vacuum on the back of the exhaust valves so that the exhaust gases get sucked out rather than pushed out. To get good scavenging at low RPM's you need small pipes because there isn' much flow so to create the vacuum you can't have to much cross sectional area. What I think people get confused about is that if you have small pipes causing good scavenging at low RPM's when the RPM's go up and more flow is created so the small pipes restrict the flow and backpressure is created. Exhaust systems are tuned for an RPM range. Bigger pipes scavenge at high RPM and high flow, small pipes scavenge at low RPM and low flow.

Sorry for the rant, its nothing personal. It just REALLY p*sses me off when I see people talking about exhaust when they don't understand. Scavenging and backpressure are one of the least understood topics Ive ever seen.