DodgeIntrepid.Net Forums banner

1 - 20 of 29 Posts

·
Registered
Joined
·
346 Posts
Discussion Starter #1
I was talking with some friends last night, they were telling me that it is possible to remove the Catalytic Converters and have the mounts for the 02 sensors welded into the new pipe.
The only thing is they must be in the exact same positions. they also said that this would be a lot better as far as performance is concerned. Any thought or knowledge of this would be greatly appreciated
 

·
Registered
Joined
·
364 Posts
maybe from a performance standpoint it would be better....from a legal standpoint on getting plates....not so much....I had a 92 mustang GT and deleted the cats and ran headers to off-road X pipe to straight thru flowmasters and it was sweet.....everytime I needed plates, I had to re-install the cats to pass emmissions....if u don't have emmissions in your state, then its ok.....Indiana has em so I had to put them back on every other year...became a pain in the ass.....
 

·
Registered
Joined
·
346 Posts
Discussion Starter #3
That is good to know we don't have emissions here anymore. I am going to look into this further. what did you gain by doing that as far a performance or should I say what benefits could I expect?
 

·
get off my lawn
Joined
·
15,505 Posts
can always use O2 cheaters, and see what happens,, from a performance gain?? maybe a couple of horses,,
 

·
get off my lawn
Joined
·
15,505 Posts
the main problem is this,, on a OBDII car the front o2"s and the rear ones set the fuel trim,, so naturly, if it dont read a constant unison of the O2's , it goes full rich, or lean,, not a good thing, not only will it hurt performance,, it will cost you tons in fuel waste.
 

·
Registered
Joined
·
1,083 Posts
front O2's set the fuel trim, the second ones check the cat efficiency. removing the cats will give you a check engine light from the second O2's. as stated above, you might find some cheaters that will keep your cel/mil off.
advantage? pretty much nil on a stock engine, unless your cats are plugged.
most people are just too cheap to replace them if they don't have to in places without emission checks.

you can buy the bungs to mount O2 sensors in. drill a hole, weld them on.
 

·
Registered
Joined
·
364 Posts
ya not much real "seat of the pants" difference...perhaps a few HP due to air restriction on the factory cats.....if anything, I'd install "high-flow" cats and plug in your sensors and it'd probably net the same changes.....In my 92 Mustang GT there was only one computer and it was pretty basic...fuel, shift points, abs...not much going on there...our cars are a lot different...so u may run into troubles/codes cutting them out without "tricking" the computer into thinking the sensors are still there....
 

·
Registered
Joined
·
1,083 Posts
if anything, I'd install "high-flow" cats and plug in your sensors and it'd probably net the same changes.....
or better(cheaper) yet, remove the cats, replace them with straight pipe, and buy a small code reader to make sure it is only the missing cats that are setting the cel/mil.
if you don't have emissions to comply with, then it won't matter. if you want to keep the light off, them you'll need cheaters or try the spark plug anti-fouler method.
neither are guaranteed.

with the O2 sensors still in the pipe, i've seen some that set codes, and a few(rare) that don't without cats. i remove about a dozen a year, most not from a problem with the cat.
 

·
Registered
Joined
·
738 Posts
My friend hacks the cats off all his cars. The difference in performance after is very noticeable. A car that would lug like crazy will throw you into the seats when it lost the cat...

Dyno would show 1-5 HP difference. Like I've been told by guys who run performance shops with dyno's, it's free horse power and torque, so enjoy.

I've heard mixed stories for our cars. Some have done it, say it works good. Others with lots of experience say it would make our engines gutless from the lack of back pressure.

You can get kits, Vibrant makes one, it comes with an adapter and three sized holes. More or less you screw your down-stream sensor into this adapter, drop in the "proper" sized hole cup in, and install it to the exhaust.

More or less it simulates the pressure/air flow of the cat being in place, computer knows no different.
 

·
Registered
Joined
·
1,083 Posts
no offence, but, you think 1-5 horse will take you from lug to throw you back in your seat?
you driving a go cart?
you get more change in horsepower from barometric differences from day to day.
 

·
Registered
Joined
·
4,073 Posts
I have a year on my 3.5 with no cats, running fine. Car feels more lively, but I did swap from a 2.7 to a 3.5, so I am guessing I am feeling the power and torque difference from the engine swap.

Only reason I ditched my cats was we were unable to get the engine to line up with the mounts and the cats, so the cats had to go!
 

·
Registered
Joined
·
738 Posts
Haha, man you read into things far to literal...

I was explaining the sensation experienced before and after. OBVIOUSLY exaggerated. Anyone willing to interpret that as a car that won't barely idle let alone move the car will be a rubber melting twin turbo Lamborghini after removing the cat converter is a) a fool, b) has no business being around a car and, c) modifying it.

Rephrased, it'll take a car with little pep, to being very peppy! Gutless, to being more punchy! Look at it like the difference you'll get swapping final drive gears in our cars. Little more reserved and factual for your taste?

It's as simple as not having a plugged nose. You breath better otherwise correct? Same applies to engines intake and exhaust. The only time this isn't the case is when you dramatically effect back pressure requirements. Hence my conflicting statement above, explaining others opinions on the matter. That removal of the cats, in a sense makes our engines gutless due to the loss of so much back pressure.

That said, these cars I'm speaking of that have had this done, might as well be Go-Karts. Stupid, gutless four banger pop cans. Ricers. Rice Burners. Junk.
 

·
Registered
Joined
·
1,083 Posts
i wasn't reading anything too literal. you said 1-5 hp, which is a difference gained even from a low pressure day to a high pressure day. cats included or not.
i do these things for a living, so understand the actual gains/losses made from some components.
newer style cats, as used since probably the early 90's, will make little to no difference if removed unless they are plugged.
 

·
Registered
Joined
·
738 Posts
Ok, so why are you being entirely hostile? Nothing I've said is incorrect. I work at a performance shop and we dyno and road tune cars everyday that sometimes cost more than the dyno itself...

I've driven these particular cars many opportunities, before and after cat removal. The result was a VERY much more lively vehicle that had some seat sinking kick or acceleration it did not have before. Age of the vehicle is irrelevant here, we're talking about doing this to a nine plus year old vehicle with lots of mileage, and the vehicles which received these modifications in my experiences mentioned here were of the same variables. Some not even worth the $500 Dyno session. Not to a brand new car, this isn't a LX form.

Yes, day to day weather changes, seasonal changes included can effect engine performance. Hence why in the mornings that Turbo car has a nice snap sucking cool air and later in the evening when it's humid as hell it lacks that sharp zing.

Yes, 1-5HP is a pretty miserable gain. Bare in mind that is with a BRAND new car, tested back to back on a dyno within a controlled environment for optimal consistent results with and without a converter. That said, for argument purposes, 25HP can be considered negligible if it's only on the top of your power band. If I'm trying to get off the line faster, 25HP at 6500RPM is essentially useless to the goal. A higher flowing exhaust benefits the entire power band, hence why many people experience acceleration gains and the car seems more "peppy" - breaths easier.

The only reason removing them can be bad is if the rest of the exhaust isn't designed for back pressure, and you in short, take that naturally aspirated engine out of spec. More or less, loosing more than what you had before.

I'm sticking with what I've said, and what first hand experience has given me. Remove the cats on a older or higher mileage vehicle and you gain some pep and acceleration. Horse power wise, it still remains negligible, as we both agree the worse condition they are the better you'll do. Common sense.
 

·
Registered
Joined
·
1,083 Posts
i'm not being hostile. just making a point. 1-5HP is a difference that can be seen from just day to day weather conditions, that's all.
although i'm at a loss as to a "peppier" car with no gains in power. you have just described the placebo effect.

and i stand by what i've said, that it won't give you gains, especially in our cars, unless plugged.
for better power and mileage, cats in the last 25 or so years have been quite free flowing. they are not the cats of the 70's and early 80's. those could unlock substantial differences if removed.

but i digress. the question was posed about OUR cars, the lh platform. and, unless plugged, there is negligible gains to be had. you would see more gain from a cold high pressure day.
but if it is plugged or defective, then remove/replace as necessary.
 

·
Premium Member
Joined
·
16,626 Posts
...A higher flowing exhaust benefits the entire power band, hence why many people experience acceleration gains and the car seems more "peppy" - breaths easier.

The only reason removing them can be bad is if the rest of the exhaust isn't designed for back pressure,...
On the surface, that sounds contradictory. I'm trying to understand why no back pressure from the rest of the exhaust if the cat is removed reduces power, and back pressure from the presence of the cat also reduces power. If that is true, then the only thing I can figure is that there is a sweet spot - a perfect amount of back pressure - anything less (remove cat, remaining exhaust has no back pressure) reduces power, anything more (non-free-flowing cat) reduces power. *Or* is there a resonant tuning effect that comes into play? I don't know the answers - just thinking out loud.
 
1 - 20 of 29 Posts
Top