i was wondering what the bad side effects would b to me gutting out the cat

 

as far as i know the only bad side effects are only being able to pass most visual emissions tests and that it will make your car louder (which you may like). it'll increase flow a bit. 1/10 of a HP FTW!!!!! lol jk. i'm guessing you are thinking about this because it is clogged.

 

Well, let's see:

If you've an OBD2 equipped vehicle,

1) You'll forever have to contend with the CEL lamp glaring in your face when the secondary O2 sensor goes bug f**k.

2) You'll be presented with Increased Noise, which will beget increasing attention by the police which will bring forth such wondrous things like Notice of Demands; those pesky legal thingies which force you to fix the *&*^% thing.

3) IF you do make it to your next inspection cycle, they will reject you and demand it be replaced before you darken their door again.

Now, if you want to do it correctly, get a high-flow cat. Basically, it's a stock converter that's bigger, thus is can flow more.
You'll be happier, your neighbor will be happier and the police will go bother someone else.

Sounds like a win/win to me

P

 

+1 i forgot about obd2.

we're lucky to have you around here P!

 

don't forget it willll hurt your mpg ... and since f22/f23's are low compression motors ... sure suppose you get that .000005 hp in the high end but you will lose alot more low end torque

 

WHAT HE SAID BUT WHAT BOTHERS ME MOST IS THE CEL.
YOU DO GAIN A FEW THOUGH!

 

as far as the CEL ... some ppl have found that using a "Spark Plug Defouler" fixes that ... although i've yet to try it myself

https://honda-tech.com/forums/showth...light=defouler

 

really... how much do you lose in low end torque??

Gutting the cat will increase flow and increase gas milage. Not much of an increase unless you change out the muffler then you could obtain a 1/2 mpg increase.
*personally on my f23 i knocked out the honeycomb after the O2 sensor on my cat and not check engine light occured. cant remember if f22 has the same cat/

P_adams- you would hate to be my neighbor ~ my truck, car and bike are all unrestricted flow, haha.

 

gutting cat will increase flow but will not increase gas mileage ... i don't know where you heard that ... i couldn't say how much you lose because you would need to dyno test the same car with a working cat and a gutted cat and compare ... i just know when i gutted the cat on my f23 it felt like it lost some low end torque

 

Claims of horsepower gains from removing a Catalytic Converter I've always looked upon with a jaundiced eye. I've seen examples of recovering lost horsepower from defective (damaged) Converters, but I have yet to see any gains in Horsepower OR Fuel Economy without additional coordinated upgrades.

I think the perceptions of power gains lays with the increase in noise, not what you may feel thru the Dyno-Butt. The increased noise plays to the stereotypical male perception of louder is better / more powerful.

P

 

I stated not as much as an increase as changing out muffler as well.
Heres a good link for saving gas heres whats qouted out of the exhaust section, "virtually ending turbulent back pressure that can hold your vehicle much the way drag does. The average improvement to gas mileage is between 1 and 2 mpg, which varies by vehicle."
http://www.autoanything.com/ResearchGuides/Savegas/
first link after googling.
My f23 incresed by 2 mpg after complete exhaust and half gutted cat, checking mpg the correct way.

 

Don't forget the environment won't like you. That and the sweet smell of monoxide at stoplights.

 

I have visions of Al G'***** chasing him down the street, yelling something about "Carbon Credits"

P

 

no use in doing since accords are economy cars. just get an upgraded cat from magnaflow if you want the vehicle to breathe better. japanese vehicle have been made to perform better with them for 20+ years.

 

hahah

 

careful! dont want to make the creator of the internet mad P! he might take it away.... LOL!

 

You get increased gas mileage by increasing your hp output from the engine. If your engine is making more power all over the powerband, it has to do less work for a shorter amount of time to get you to the speed required. Think about it like lifting weights. If you can lift 20lbs. in 20 seconds, then work out for a month and can lift 20lbs. in 10 seconds, you do so because your muscles exert more strength after having been worked out for a month, resulting in less work for you and increased performance.

There are a few reasons why you think you might have lost torque. There's a lot going on when you change your exhaust. If you go with something radical enough, you'll be changing your intake, tune, etc. etc. to compensate for the loss in back pressure or increase in gas scavenging, which is higher exhaust gas velocity. Exhaust setups that are too large will result in more cooling of the exhaust gases which leads to lower exhaust gas velocity (because cool air is denser than hot air). To make up for this, you'll need more air entering the engine to create more hot exhaust gases to keep velocity up. This is also why exhaust wrap can sometimes help on a larger exhaust, by increasing the amount of exhaust flow by providing insulation so as to keep up exhaust gas velocity.

When you bring in more air, you'll need more fuel, which means another tune so that you don't encounter a lean condition. Exhaust setups that are too small will lead to excessive back pressure and loss of torque/hp all over the powerband due to the engine not being able to push out all of the exhaust gas from the cylinder. In this case the charge of air coming in is heated by the left over exhaust gas and you could encounter a rich condition, though unlikely as your stock tune is set for your stock exhaust, which should be the most restrictive exhaust you ever use.

There's more to it than that, like dealing with exhaust pulses, but that's a dark art that I really don't know much about, and something you probably shouldn't really be concerned with unless you're trying to squeeze out every single ounce of power possible.

 

well that's all very interesting but in my overall experience ... it made my mpg drop and made my car feel gutless at lower rpm ... i have a cold air intake ... 4-2-1 header ... full catback exhaust ... and of course the gutted cat ... i'm sure a tune would help but i still think that the gutted cat is the real problem ...

anyone else with a 6th gen f23 gut their cat?

 

Why do you think the gutted cat would be the real problem? Why would that change your torque or hp numbers?

 

i wish i knew, all i know is ever since i had to gut my cat i've had problems

 

Without going into accepted principles of Fluid Dynamics, Pulse Wave Theory and the Conservation of Energy; I'm going to try to keep this simple.

There is a consideration which almost always gets forgotten in these discussions; this being Scavenging. This is a phenomenon utilized by engineers to improve the volumetric efficiencies of automotive power plants through the application of Fluid Dynamics and Newton's Law whereas a "mass in motion stays in motion".

In effect, the exhaust gasses traveling thru the exhaust system generates a vacuum behind the exhaust valve when it closes. When the exhaust valve next opens, this vacuum is instrumental in drawing spent combustion gasses out of the combustion chamber and conversely pulling a fresh charge into the cylinder. (That's why there is always some "Overlap" where both the intake and exhaust valves are open ....)

The exhaust system is designed to facilitate this exhaust velocity by the careful selection of not only the length of the system but also (wait for it) the pipe diameter as well.

What happens when you enlarge the exhaust pipe's diameter? The velocity of the exhaust gasses DROPS; it moves more slowly through the pipe. Why?
You're now pumping the same mass of gasses thru a larger area, thus it slows down. What does this do (You ask)??? It decreases the vacuum effect behind the exhaust valve thus decreasing the scavenging effect. Less scavenging effect, less air/fuel through the engine and ultimately less power.

True, there are advantages to large(er) diameter pipes, but that is more for systems which are boosted and operate at positive atmospheric pressures. In this case, you're literally pushing the gasses thru.

This all raises some serious questions. Why go to all the expense of a larger set of pipes / muffle if you're still dealing with restrictions upstream? Even with headers, you're still dealing with a 2" collector (They do hook up to stock systems, RIGHT).

P

 

Look 4 posts up, or better yet, read through the entire thread next time.

 

i have a straight pipe on mine.. i lost my bottom end torque and instead of buying a test pipe my whole exhaust is welded 2 1/4 piping.. i got a ticket so i bought a used cat for 10bux now im gonna put my DC headers on thats been sitting

 

...Haha. I respect you. You have knowledge but I must differ with you on this. When you remove the cat you do gain Horses and thats not a misconception or false assumption due to sound. The exhaust is no longer resticted by the convert process which allows less restricted flow and less back pressure. Everyone knows more flow, more go(which is not always true but in this case it is). Bad for he birdies thgh

Through certain ranges you may loose Tq and HP but ultimately your HP increases through out the entire RPM range mostly

 

I have a 91 honda D16A6 five speed does the same principle apply to an older engine such as this? I know they made the same engine without a cat it was the D16A7 and it has 7 more horsepower.

Thanks