Have a muffler shop cut out the cat. converter?

[volvoidaho2343]

2000 V70 Glt Style SW, was wondering if i could just have a muffler shop cut out the converter and weld a piece of straight pipe inplace of it? My state dosen't have any emission laws. Will this effect the driviably of the car? Thanks in advance. Any advice about this subject would be greatly appreciated. The cost of a new converter is approx. $1100, and a piece of straight pipe is app. $35 to have put in.

[JDS60R]

If there is nothing wrong with the cat then leave it alone. If there is you will need to fix the cause of the converter failure and then have a magnaflow converter welded in. They run about $100.

If you pull the cat then you will get a code and the car will compensate by running rich to avoid future problems. You will loose power.

[igel513]

Get a universal cat. conv. from Amazon- Magnaflow 34105 for $57.89 + S/H. It is legal also for use in CA, I just bought one.
I read somewhere it's a Fed. offense to remove a cat.conv. from your car, is this true. True or not, I believe we have to have the cat in our cars to help save the environment.

[byeboy]

How does the ECU react with the Magnaflow cat?
Does that cat have provisions for the front and rear O2 sensors?
Anyone here been running one successfully?...and for how many miles?
Thanks!

[misha]

...If you pull the cat then you will get a code and the car will compensate by running rich to avoid future problems. You will loose power.

Why it will run rich with cat removed?
1st o2 sensor(which serves for proper air/fuel mixture) is before the cat and 2nd one cannot disturb the air/fuel mixture.2nd one is there just to monitor cat efficiency.

He will get the code for REAR 02 sensor because the cat isn't there and that would be all.Even IF the car will run rich,that would not be noticeable and will not produce problems in driveabillity & performance.

In fact...without the cat he will have about 10hp more than with the cat on the car.

[rspi]

I don't know about all that cat stuff but if the car doesn't have the proper back pressure on the exhaust it will cause the valves not to seat properly and cause burnt exhaust valves. Not sure if the muffler is enough to keep it right.

We do not have emissions either and a lot of people have cut the cat away. I like breathing fresh air but whatevery.

[jimmy57]

Misconception that second is for catalyst monitoring only, at least on Volvos with Mot 4.4 or later.
The front is still primary but the rear has an important role in fine tuning fuel trim so the catalyst efficiency is maximized.
The rear O2 sensor should have a stable voltage that is 0.65V +/- when load factor computed inside ECM is stable. At the same time frt O2 sensor will have oscillating voltage if binary sensor and oscillating current if wide band type sensor (most 99 and later are wide band front sensors).
Backpressure is not needed but can affect torque at low revs. If reduced backpressure also reduces swirl and turbulence in combustion chamber which is toughest to achieve at low revs, then torque will be less. Dual path intakes are one way this gets addressed so torque is better with freer exhaust for higher HP.
Exhaust valves will cool better when exhaust is evacuated. Years back, in the early days of no lead fuels, there was some cushioning affects of the exhaust gas pressure that helped reduce valve seat wear. This was a poor metallurgy problem and backpressure was a weak band-aid. This was also when EGR ruled and specific power was dismal. Backpressure It is not an altogether bad thing but it is not required unless you have an exhaust gas recirculation valve and it is needed in greater portions when the intake to exhaust pressure differential is not forcing the flow needed for emissions.

[keybuster324]

good luck

[QuirkySwede]

In fact...without the cat he will have about 10hp more than with the cat on the car.

This is as misleading as all that K&N horsepower @#$%^*!.

Like RSPI talked about, the exhaust is part of the tuning, and not just for #2 O2 plug feedback. Even "if" there's a 10hp, you can bet your power curve will suffer as a result -- it's called "narrow power band," which is fine if you're a drag racer who runs at WOT and only cares about the power between 7,000 and 7,750 RPM (relative) and rebuilds the entire engine every other race. Ever notice how horribly the open header motors idle?

Further, the car will be SLOWER because distance covered is shown by the area under the curve, NOT the "peak of the mountain." People who do not understand this (much less the difference between HP and torque) are easy prey for marketers.

Then there's that the richer mixture burn cooler and dirtier which means the motor...

[misha]

Have you EVER removed a cat from the car and drove the car without it only with welded straight pipe instead of the cat?I'm not talking about a results on paper...i'm talking from my experience and experience from lots of people.

The only side effect is that engine is louder than with a cat.It will not run richer than with it.You just have that feeling and richer smell because the cat isn't there anymore to clean those exhaust fumes.

There are some rumours that cars with two o2 sensors will not run properly with cat removed.Also there are rumours that they run normally except check engine light is ON all the time.Maybe somebody who have experience with this can verify those rumours.

There are many cars including some of these cars with only one O2 sensor(the front one) and there are many cars which run normally with cat removed a long time ago(a lot of countries don't have smog tests).

Personally...i don't like the sound of these cars when cat is removed.They sound a lot more smoother and quieter with a cat.