No i haven not tested it on my truck first hand, but i will be VERY shortly. Since im redoing my exhaust, and Honestly what are your disagreeing with? The only thing you said was that a "unknown truck" (no specs listed) decided to do duel 3in. Was that true duel? Did it have an X or H pipe? Was the motor stock? Putting DUEL 3in on ANY motor thats not Turbo/Supercharged is going to take away some power due to the exhaust not being able to flow in those huge pipes. Duel 2.5s is what is recommended with a N/A Motor, or a Single 3in. You should of told your customer this.

and if your telling me a cat free system doesn't flow better then a cat system you are completely wrong. You can actually look up specs of the SAME cars on the net, overseas producing more power and mpg, but when the emissions crap is added (cats, ect) in the US the cars mpg is almost cut in-half and performance is dropped. Deleting the a cat on a stock Motor with increase performance and probably increase MPG a bit. they put cats on these vechiles without even thinking about BP they do it to make the world clean not to give your truck enough BP.. thats what the muffler and y pipe are for..

but after what you just said, "One guy had his own programmer and actually noticed a huge difference after removing it" so really you are agreeing with me. You don't need a programmer to make it work either.


see statement above about why cats are on vehicles, has nothing to do with performance in mind. Only the air. Which isnt bad, but if you want the little extra perf. Go cat free, but if you want to keep the air clean stick a high flo.


Velocity NOT Back pressure... thank you.

 

and you all say that the frame rail zip tie trick works? wouldn't that cause the O2 sensor to read very oxygenated and thus change the fuel curve?

 

WOW,thats a lot of quotes.Excuse me but I dont know how to do that so i'll just answer one at a time.

A cat not having anything to do with how a vehicle runs in completely incorrect.As you have said,you HAVE NOT tested your THEORY so you cannot make an educated statement on what is better.Sorry.

On the other hand,a few have posted here that HAVE done this and HAVE LOST POWER AND LOW END.Are they imagining it? They have FIRST HAND EXPERIENCE with what it did to their vehicles and have stated that they regret it.

As for my examples,I guess you missed that I said I did it both ways.Meaning I have done exhaust on truck and cars where the guys have eliminated their cats and then come back into my shop to have a high flow installed because they lost their low end! And I have Also done vehicles with TOO BIG of an exhaust and they then changed it.That was examples of both situations my friend.

Thats what im dis-agreeing with you on.

I've bben in the industry for over 23yrs man and with Meineke for over 18yrs and am only stating what I have experienced from my customers.Hey if you're happy with no cat,then more power to you.Your choice.Just when you finally do test your theory by installing a high flow cat and find that you really do have more off the line power,please post up on it.

Oh yeah and what do you think causes VELOCITY? Making the exhaust bigger????Not at all.The more back pressure from a smaller pathway,is what causes this velocity.Like I said,if you have lets say 10 gallons of water flowing per minute out of a 10 inch pipe,what happens to the flow of water if you reduce the pipe to 5 inches?? The "VELOCITY" increases.It doesn't decrease.Same as in a pressure washer,it reduces the pathway of the water being sent out and guess what....IT'S HIGH PRESSURE WATER VELOCITY.Thats what creates velocity man,not just making a bigger exit.

Thank you.

 

Oh and user,I am in no way trying to be dis-respectful.I am just agreeing with you on something that you admit you have not tested.I have so I state what I have experienced.Nothing worse than having a customer come back un-happy after doing a job,so I have learned what works and what doesn't.

Sure many have eliminated their cats and are happy and thats cool.But for those that have and have actually tested it,i.e.raced it,drove it with a programmer,etc,have always went back to either installing a cat,or a smaller exhaust tubing size in the other examples I gave.

Please don't take my comments in a dis-respecting way.This is your house and im just visiting.

 

MEINEKEMAN1, i appreciate your input as a technician. i have a feeling i will go dual 2 1/2 with an H-pipe and no cats to start, but if it becomes an issue of losing low end i think i will go to a small street converter because then i will bypass the lack of low end, and i'll have a converter .

besides, by the time i dump the cash into 2 cats, i almost have a converter anyway. and it sounds meaner that way too. nuts to emissions. global warming is going to be my kids problem, but lets face it, if i'm having kids, we have bigger problems.

 

Ok we are getting off track. The topic at hand was about "Backpressure" and "Low End Loss"

I said the cat has nothing to do with Performance/back pressure in mind from factory. It does effect the vehicle.. i would be dumb to say it doesn't.

From factory the Cats are put on the vehicle to help with pollution. They are NOT on there to help with Back pressure or performance, the company's are required to install them for environmental purposes! Thats what i was trying to say.

As for my theory, you can Google info, on why a Toyota Yaris can get 50+Mpg and more HP overseas then here in the U.S (reason because we have to install these environmental safe exhaust systems, that go by the U.S laws. Including "Cats")

Removing the cat may or may not decrease your low end. Depending on Motor Type, Mods, ect. BUT with the magnums the motor at hand in the topic GAIN an increase in power rather then losse low end. Even the 4.7s have noticed a gain and better ETs.

a few sites you can do searches on about this and find quotes from users saying it helps.

dfwdakotas.com
dakota-durango.com
dakotartclub.com
dephi.com

all Dakota/Durango sites, built around the 5.9, 5.2, 4.7 motors, lost of info at all the sites, along with this one.

 

The REAR o2s do not read Air to Fuel Ratios, thats the Bank1 o2s Job. The Rear o2s are ONLY there to tell your PCM that your cat is working, as long as the rear o2s are reading something different then the front o2s you will be fine. It wont dump more fuel or anything like that.

 

Again,I am only speaking form the experience I have had with my and my customers vehicles.

As for a Toyota Yaris getting more gas mileage without a cat,I can't comment on because,I have never tested one with a nd without a cat..,2-You're comparing a Toyota to a Dodge 360? and 3..Were talking about losing low end power,not gaining mpg.

The whole topic is about high flow cats...yes or no,and I and others have explained why they felt it was better to go with a HF vs no cat.

If you look,most of the times that anyone has claimed gains by removing their cat was only after the "CLOGGED" cat was removed.Their vehicles were bogging down or losing power,or poor gas mileage,etc,so they decided to gut or remove the cat and poof,their problems were gone.So that must have been the magic solution..removing the cat.The ones that have just removed their cats because thats what they heard would be better,have regretted it and later re-installed them or want to in my experience.Like I said,I have many times done performance exhaust systems where guys that race almost daily(street and/or track) and have removed their cats only to come into to my saying how it was a mistake and I have then installed performance converters and they have since told me that it was a big improvement.

But like I said,it's all irrelevant,each individual will do what he/she wants anyway so it really doesn't matter what anyone else says.Whatever makes you happy,is what it's about.

 

I was not comparing. I was using the Yaris as an Example of what the U.S Emissions can do to your vehicle. less POWER and less MPG. Same on our trucks also. It was an example.

I choose no cat. Everyone that i know that races, or has had cat less exhaust have been fine and still don't have cats, also i dont see built drag motors with HFC on them, i see longtube headers with straight pipe and maybe a single chamber muffler.. no HFC.

So far everyone i know has not regretted it.. so maybe its something in the air...

Amen.

 

LOL.

When you finally do test your "THEORY" post up the results.