catalytic converter problems?
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Senior User
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catalytic converter problems?
when i had my exhaust done i had the shop cut the pipe off just upstream of the muffler and they ran straight pipes back from there. i want it louder so i was wondering if anyone has had any driveability issues with the downstream cat cut off with the O2 sensor bungs installed. im wanting to cut both cats off, and run a flowmaster 49 SI/SI. thanks in advance for any feedback guys! oh yeah, its an 03 5.4
Posting Guru
Joined: Oct 2008
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From: Hernando Ms
Leave the cats and 02 sensors alone,they are there for a reason,and if you eliminate them you will GREATLY reduce the performance,and economy of the truck...not to mention itll likely cost you in the long run...my .02..oh yeah...and its not legal
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From: Iowa
It will be loud, it will cackle a lot.
You will probably get pestered by several forum members about how its illegal and you shouldnt do it, in this thread. Just letting you know.
Oh and you will probably loose some bottom end power. Might gain a few HP at the peak though.
You will probably get pestered by several forum members about how its illegal and you shouldnt do it, in this thread. Just letting you know.
Oh and you will probably loose some bottom end power. Might gain a few HP at the peak though.
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From: Hernando Ms
Postmaster
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How sure are you that your truck isn't already ultra loud. Ford has built a lot of sound deadening into their trucks, probably more than any other automaker. Even the steel they use deadens sound. I know you want to be able to hear it when you are driving, but remember that the stock sound deadening installed in the cab will make anything you do seem quieter that it really is.
I second the glasspacks idea. Leave the stock cats alone, modifying them is a last resort.
I second the glasspacks idea. Leave the stock cats alone, modifying them is a last resort.
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I guess I haven't looked that close at the exhaust near the cats. If you have the O2 sensor pre cats and you cut the cats off, the truck will still run fine. If there is an O2 sensor after the first cat, you had better leave it there or risk major driveability issue, unless you can get the computer reprogrammed to read the new O2 values.
I have found that fuel injected vehicles using O2 sensors to monitor and correct mixtures generally run very clean even without the cats in place. Illegal? Yes. Harmful? Not as much as some would like us to think.
I have found that fuel injected vehicles using O2 sensors to monitor and correct mixtures generally run very clean even without the cats in place. Illegal? Yes. Harmful? Not as much as some would like us to think.
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From: Pelahatchie, MS
On an OBDII system, there is an O2 sensor fore and aft of the lead cat on each bank. It uses the readings from the lead sensor to check a/f mixture and the readings from both to ensure that the catalyst is still doing its job. There should be 4 cats on the truck, 2 on each bank.
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from my understanding, cats are only used to burn up excess hydrocarbons, and oxides of nitrogen, and shouldnt affect the amount of oxygen (or lack of oxygen) in the system. the O2 sensors contain zirconium oxide which reacts with oxygen to produce a dc voltage usually between .1 and .9 volts. anyways, in theory the O2 sensors should operate the same with or without the cats installed. i was just trying to see if anyone actually had any problems with performance. i know it will be extremely loud without cats and will have a huge lack of back pressure which is why i still want to have a muffler. khan your right about the sound dampening. in 2003 ford went to the extra mile and reduced the interior noise substantially. however i have heard the exhaust from the outside and still am not pleased. i want it to sound raspy, but not like straight pipes. i think the muffler will cut down on alot of the popping and add enough back pressure to keep good low end torque.
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From: Michigan
I did what redwood said to do shorten the pipes to turn downs, except i put a flowmaster on without research and would have rather put something on there that is not notorious for rusting out. could have pipe cut to get muffler closer to cab but then you risk the fumes getting in.
Could add headers, short or long tube, to get more sound out of it too but that is obviously more money and a bigger pita.
Could add headers, short or long tube, to get more sound out of it too but that is obviously more money and a bigger pita.
Postmaster
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The cats consume the unused hydrocarbons and in the process produce heat. This causes the gases to expand and accelerate as they pass through the catalyst. This creates a positive induction that increases power output and fuel economy so long as the cat is working properly. Remove the catalyst, you loose bottom end torque, and your gas mileage may drop off.
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