I have searched the threads and have not found exactly the answers I am looking for on this. I have a Flowmaster exhaust system with a 40 series dual outlet muffler. It seems way too quiet for me and I was considering removing the cats as a sound increaser. Would removing the dual cats and adding a single high flow cat be as loud as no cats? Would there be any disadvantage performance-wise to removing the cats and just adding in a piece of straight pipe? Are there any sensors or anything that would be removed by cutting out the section from the rear cat to the front cat that would cause me problems? Finally, short of not running a muffler and spending a bunch of money I don't have on headers, is there any other way to getting my exhaust to get more of that "Flowmaster tone" that I love? Emmissions testing is not an issue. Thanks a lot for any help you can give.

 

I have considered doing the same thing.

I live in Jacksonville and the only thing I have done to my exhaust (all stock) is to remove the muffler, add a tee, and run duals to the outside of each rear tire.

The noise factor is not bad with the muffler off, but I want to just run straight pipe from the y to the tee in the rear. I am sure it will be slightly loud, but I do also wonder if this will pose a problem.

My O2 sensor is located in between the y right before the first converter. I don't think this will pose a problem with the operation of the vehicle if the ' straight ' pipe is used.

Just my thoughts, I hope this will help. I am interested to see if another user has more light to shed.

 

Is there also some kind of restriction in the Y-Pipe that would make it quieter?

 

There is no kind of restrictor in the Y pipe, and the O2 Sensor in that crossover pipe is not affected by anything downl the line from it. So in other words cutting out the cats won't give you any Check Engine Lights or anything. And I don't think that there is much of anything you can do upstream from the flowmaster to make it sound better. Your cat idea might help a little bit, but i don't think it will matter with a flowmaster.

 

Catalytic converters are not a sound deadening device at all and do little to nothing to restrict exhaust flow. The only advantage to removing it might be a greater flow IF you had a stock cat behind headers and the Flowmaster behind it. Basically leaving a stock converter in a system designed to flow greater volume naturally will flow less because its not designed to handle the same capacity. Other than that scenario, the presence or abscence of the cat is negligible.

 

Well, I was planning on adding a cheap set of headers until I could afford a good set. So, you think that with headers there may be a performance increase by removing the cats?

 

If there is, it will be slight to say the least. The idea here is basically that you try to keep all the components in the system capable of flowing the same volume of exhaust. So, the system is like a chain....only as strong as its weakest link or in this case, only capable of flowing the capacity of its most restrictive component.

 

To be honest I am more interested in that "flowmaster tone" then in trying to gain performance by just removing the cats. I hear plenty of trucks around town that sound better then mine and I can't understand why a 40 series muffler is so quiet when I have friends with smaller motors that are much louder.

 

greystreak is wrong the cats infact do deaden the sound removing them will make your bronc a little bit louder. what i recomend though insted of buying headers yet, why dont you go down to the exaust shop cut every thing off at the y where the two manifold pipes come together run three inch pipe into a single in- single out 40 series and turn it down before the axel that will give you the big buff fowbe sound you are lookin for. ive been installing performance exaust systems for ten years in california and thats what i do (only i have to keep 1 cat normaly a carsound high flow)

sean
81 eb
new 302 removed all smog crap (including the computer)

 

I just spent a bunch of money to get the exhaust done so I would rather not cut out anything I don't have to. You don't think I will be able to get the nice sound I am looking for with my 3" in, dual outlet 40 series that exits behind the tires on the sides?

 

yes you can

 

So what is the difference between what you described and my current setup? I am hoping the combination of headers and no cats would help the sound a lot.

 

btnbronc,

Say what you will but, Catalytic converters are not, nor have they ever been designed as sound deadening devices. Admittedly they may have some effect on tone due to the mild distortion of the exhaust flow through them. However, they are strictly superheating devices designed to burn off additional exhaust pollutants that are missed in the normal combustion cycle. If they did such a good job of killing sound, mufflers would not be necessary or manufacturers would have combined the two devices into one.

 

The tone is one of the main reasons that I was considering removing the cats in the first place. I really want to be able to have that distinguishable Flowmaster sound.

 

Cats do, muffle sound. A cat is simular to a muffler, but the have a honeycomb baffled structure that traps gasses and superheats it till it burns.

A muffler has baffels in it that guides sound and air to different parts to "muffle" the sound.

What happends when u speak, then put your hand over your mouth? Your hand is not a muffler, but yet a baffle.

Now, blow out air out your mouth, then put your hand in front, now it's a restrictor.

A cat baffles sound, and restricts air, u remove the restriction and baffle, u get better flow and sound.

Why do u think most ppl with mustangs buy the H or X pipes w/out cats, for better sound and performance.

Have u ever seen a NASCAR car with cats?!?

I went from having a full exhaust system, to, having two cats and no muffler, then to having one cat and no muffler. When I removed the muffler, my truck didn't get any louder, but when I removed the bigger second cat, there was a big difference in sound.

I now run a smog less, cat less system to true dual side pipes, best sound I've had yet on it. Not loud at idle, but a nice crackle at wide open.