Just removed my CAT

[MMamdouh]

Hi guys

Yesterday I was at the mechanic for a mid exhaust box replacement job... I was under the impression that their was some mid exhaust boxes available with longer front pipe that will bypass the CAT but when I went to buy the stuff I found out that the mid exhaust box is just like the OEM one and the pipe that is actually making this modification possible is the pipe coming from the exhaust manifold to the CAT including the flexible junction (down pipe??).

I didn't buy the damn thing simply because it was insanely pricy... the mid exhaust box cost 105 LE (17.5 USD) while that pipe cost 165 LE (27.5 USD), it is just a damn pipe with a flex junction so why cost that much??

anyways the guy at the shop told me if the piping on the old exhaust box is intact then I could cut it off and make a custom pipe that will bypass the CAT... sounded like a good idea to me.

I went to the mechanic with the new ex. box and I was looking for an old exhaust box to get the pipe from it (the pipe on one exhaust box is too short to make a full length replacement pipe) and I found a CAT that is empty from the inside... I asked him about that and he said that they emptied it for a bypass trial and it made the car a bit loud.

personally I don't mind the loudness in exchange of a free exhaust so I tried the empty CAT on the car, it is not that loud... it feels that the exhaust is running in to an empty resonator or something, pretty logical as it is actually running into the empty enclosure of the CAT.

as for power gains... I haven't had a chance to really test the car, I was running low on fuel and I didn't want to go that fast till I refill the car (fuel lamp already on).

Probably today I will test it after I finish work... it is going to be 12:00 AM or so and the streets will be empty and I got a full tank... testing will commence in some 3 hours from now. the only thing I felt was a better acceleration on third gear but that is not a real test yet I had better results when I removed my resonator so I will keep my patience till I really test it... also the exhaust smells different now and the car is a bit louder but I like its sound.

When the test is done I will post the results for you... BTW I drive a 1.5 8 valves SOHC and I had only one CAT on the exhaust.

MMamdouh

[MMamdouh]

OK the test is done and overwith....

the car feels more responsive but on high revs... at low revs you can't tell the difference, i went till 140 Km/h on 4th and it was easy... used to take much time before.

it felt different than removing the intake resonator, the resonator job made the car responsive at low revs... now i think i got better on both low and high revs but my exhaust is louder so does the intake.

MMamdouh

[kinkyllama]

How much louder is it? ... do you have a straight through muffler?

[MMamdouh]

not that loud... actually i like its sound now but i am not sure if dad will like it... he didn't drive the car yet.

as for my muffler: no i don't have one, my whole exhaust is OEM setup.

MMamdouh

[MickeyX]

If ur looking for a good performance muffler go with the magnaflow. I just put that in my car as a b-day present to myself and it sounds fuckn great.

[nefary]

what is CAT?

[KnightWalace]

Catalytic converter, i believe it burns up excess particles that the combustion chamber didn't, making it more "emission" friendly.

But more often than not, it just robs horsepower

[daewooluvr]

what is CAT?

haha

Magnaflow does make a pretty good muffler.

I am happy with my Borla XR1 but I want to get a high flow resonator. My exhaust is LOUD.

[delphis]

anyone know of a good muffler that will help decrease restriction but not be overly loud? I don't want my car so sound like it has a coffee can attached to it.

[MMamdouh]

what is CAT?

A CAT is an abriviation for a "Catalytic converter"... it is a device in your exhaust system that process the exhaust gases and reacts with harmful gases like carbon monoxide and nitrogen oxides and prevents them from exiting to the atmosphere and pollute the environment... so it is an imissions device.

this is how it looks...


a peak into a CAT...


as you can see it is formed from tiny holes allover the inside so it can react with all the exhaust gases passing through, those tiny holes is what makes a CAT restrictive.

in the mod i did i got a CAT that is empty from the inside (all the tiny holes and mesh fromation is removed) and i tried it for a week. i felt a better engine response at high RPM but also some exhaust noise... kinda like a fart in a tin can.

i didn't mine that sound at all... i drive with the windows up and the music loud so i never really notice it, on the contrary my dad did notice the sound and told me to do something about it as it is annoying as hell.

i got off my lazy ass and looked at spare parts shops and i found this...


it is a pipe that replaces the CAT... no strings attached the other pipe i was told about was the down pipe (comming from the exhaust manifold including a flex junction and goes all the way to the mid exhaust box) and i didn't need that as my pipe is in a pretty good shape plus it will cost me 4 times as much as this pipe.

i didn't install it yet as i still have the flew but most probably it will be on by the end of the week... more feedback will come when the installation is done.

MMamdouh

[MMamdouh]

the installation is done and overwith, the nasty sound went away, replaced a rear box gasket and by exhaust is problems free.

even the extra heat on the hand brake handle i used to feel was gone now... seems the heat insulation arround the CAT was not that good.

MMamdouh

[MMamdouh]

my down pipe is punctured now and i have to replace the damn thing.

now i have two options:

1- get a short down pipe just like the OEM one and keep my short pipe that replaced the CAT.

2- get the long down pipe that replaces the CAT and end up with an extra pipe.

i think the CAT replacment pipe is a bit narrow as you can see in the previous pic so i will be getting better flow with a long down pipe, the only drawback is that i won't be able to put my CAT back on if i wanted to.

the money is not an issue here... the short and long pipe got little price difference that can be covered if i sold the CAT swap pipe.

what do you think guys?? is the CAT swap pipe subistantially narrow? or should i get an OEM replacment downpipe and keep my "CAT reinstallation" option possible??

MMamdouh

[panther]

Did you notice any improvement in fuel economy with the cat removed? Here in the UK we pay the highest fuel price in Europe and it is steadily increasing at an alarming rate. If removing the cat will improve MPG I was thinking of getting an old cat from my local breakers and bashing the ceramic insides out to make it hollow.

[MMamdouh]

i never care about fuel economy... i only look at performance, practically both are two sides of one coin.

if you can do a mod. that makes the car faster then it will make it consume more fuel... on the other hand if you are a conservative driver then the same mod. will give you better fuel economy.

now back to my CAT, i only felt better engine response at high revs... some 4500 or 5000 i guess, the engine felt like breathing more freely, i think in your case (looking for fuel effecency) that would not help much... also doing this could make you lose some back pressure and your torque could suffer.

also getting an empty CAT is not a good idea... i tried that and the damn thing sounds like a fart can. it will simply sound like something is wrong with your exhaust and it will be horrable in a cold morning start.

better to get a pipe just like mine or have it custom made... the empty CAT is just too noisy to be practical.

MMamdouh

[panther]

Ok thanks for that. I mainly use the car for driving around town so I don't think I will benefit from removing the cat, and I don't fancy sounding like a fart can I noticed you mentioned that you gained better low revs response by removing the air resonator. I will give that a try.