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Dirty Exhaust

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Posted 03 February 2005 - 09:22 AM


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Tell me honestly, if we took out the CC, I know it will give more power
but then again I thought it's only for a while as ECU will reset the
setting again after that.

My CC need to replace already and I wonder whether shall I replace new CC
or just do away with it.



Posted 03 February 2005 - 01:11 PM



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aisey man..sportier ke? hmmm...getting itchy hand oledi to change my cat.
since u say the air is cooler, think i just might change mine too!! i once
heard the beautiful sound of a merc 2.5 16v cosworth engine (the one azman
owned prior to the t5), that was really music to the ears..the way the car
sucks in the air and that unforgettable growl...yummy. womder if we can
produce that sound with our s70 eh?


whoa, not only do we pollute the air, u want to smell the exhaust fumes
somemore is it!!! hehehe..joking bro, i think i kinda like the smell of my
exhaust, esp in the morning during warm up!!


Posted 03 February 2005 - 04:34 PM


    Taxi Driver

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the hp in the engine remains the same but due to the constriction of
exhaust flow from the engine by the cat, you don't really get the full
number of ponies.

Literally, the CAT ate the ponies.....

Once the CAT is removed, all the ponies can now come out and play.


Posted 03 February 2005 - 04:37 PM



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its possible that removal of the CC will give more power and then drop
after a while. This is because when the CC is removed, the exhaust will
not be as clean and the o2 sensor will detect that and adjust the ecu to
burn a more lean mixture. then the lambda problems come in Smile

CC's are expensive because they use some exotic materials (platinum) to
get the job done. The hot exhaust air coming out when you have a CC in
place is because the CC needs to attain a certain (very high) temperature
before it actually starts to work. it will not be effective if the
exhaust air does not reach that temperature. It works by some sort of
chemical reaction with those exotic materials at a very high temperature.
It converts unburnt fuel and CO into CO2 and water. It also does other
things which i cant quite remember at the moment Smile. If i remember
correctly, under normal engine conditions, the cc should have about the
same lifespan as the car.


Posted 03 February 2005 - 06:51 PM


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The most motorist could not realize the normal engine condition and
coupled with bad maintenance practice, the engine becomes un-tuned.
If the engine is out-of-tune and not calibrated to OEM specs, the
catalytic converter's efficiency is greatly diminished and could lead to
a converter failure (premature damage).

The recommeded operating temperature of CC is 650 to 750 deg.C (tuned
engine), but some will operate higher at +/- 750 to 870 deg.C due to
performance modification and this still within design allowance of CC. AT
1000 deg. C the CC life reduced to only 50 hours.

A three way CC will convert UHC, CO into CO2 and H2O, while NOx converted
into N2 (this what concept can't remember ... I just remind).

Most O2 sensor is located before CC, if CC removed, the O2 sensor will
not detect the CC removal (No Adjustment From ECU), unless you got 2
oxygen sensors before and after CC (some cars model got) and High
Temperature Sensor located at CC, then ECU will detect that CC has been
removed, coz no signal emitted by temperature sensor and O2 sensor after
CC to ECU, accordingly ECU adjust to enrich the fuel to protect the
engine (running rich)... for OBD-II check engine "buka" ... he.he.he.


Posted 03 February 2005 - 07:34 PM


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Just sharing with you all, why CC fail !, this could change our driving
habits and maintenance practices as far as environment issue concern.

1. Engine Tune-Up Required
A number of problems could occur to the catalytic converter as the result
of an engine that is out of tune. Any time an engine is operating outside
proper specifications, unnecessary wear and damage may be caused to the
the catalytic converter as well as the engine itself. The damage is often
the result of an incorrect air/fuel mixture, incorrect timing, or
misfiring spark plugs. Any of these conditions could lead to a catalytic
converter failure or worse.

2. Excess Fuel Entering Exhaust
The fuel that powers your vehicle is meant to burn in the combustion
chamber only. Any fuel that leaves the combustion chamber unburned will
enter the exhaust system and light-off when it reaches the catalytic
converter. This can super-heat the converter far above normal operating
conditions and cause a Melt Down. Possible causes are an incorrect fuel
mixture, incorrect timing, corroded spark plugs, a faulty oxygen sensor,
sticking float, faulty fuel injector or a malfunctioning check valve.

3. Oil or Antifreeze or unburnt leaded fuel Entering Exhaust
Oil or Antifreeze entering the exhaust system can block the air passages
by creating a heavy carbon soot that coats the ceramic catalyst. These
heavy Carbon Deposits create two problems. First, the carbon deposits
prevent the catalytic converter from reducing harmful emission in the
exhaust flow. And second, the carbon deposits clog the pores in the
ceramic catalyst and block exhaust flow, increasing backpressure and
causing heat and exhaust to back up into the engine compartment. Your
engine may actually draw burnt exhaust gasses back into the combustion
chamber and dilute the efficiency of the next burn cycle. The result is a
loss of power and overheated engine components. Possible causes are worn
piston rings, faulty valve seals, failed gaskets or warped engine

4. Deteriorated Spark Plug or Spark Plug Wires
Spark plugs that don't fire or misfire cause unburned fuel to enter the
exhaust system. The unburned fuel ignites inside the converter and could
result in a partial or complete melt down of the ceramic catalyst. Spark
plugs and spark plug wires should be checked regularly and replaced if
damaged or if wires are worn or cracked.

5. Oxygen Sensor Not Functioning Properly
An oxygen sensor failure can lead to incorrect readings of exhaust
gasses. The faulty sensor can cause a too rich or too lean condition. Too
rich and the catalyst can melt down. Too lean and the converter is unable
to convert the hydrocarbons into safe elements and may not pass a state

6. Road Damage or Broken Hangers
The ceramic catalyst inside a catalytic converter is made from a
lightweight, thin-walled, fragile material. It is protected by a dense,
insulating mat. This mat holds the catalyst in place and provides
moderate protection against damage. However, rock or road debris s
triking the converter or improper or broken exhaust system support can
cause a Catalyst Fracture. Once the ceramic catalyst is fractured, the
broken pieces become loose and rattle around and break up into smaller
pieces. Flow is interrupted and backpressure in the exhaust system
increases. This leads to heat build up and loss of power. Possible causes
of a catalyst fracture are road debris striking the converter, loose or
broken hangers, potholes or off-road driving.


Volvo For Life ..... Aware to Future Life with Fresh Air.......


Posted 04 February 2005 - 09:37 AM


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I think my problem lies with no 6. I heard rattling sound. When my lambda
sign come out for the first time, I did send my car for check and they
suspect my CC is the culprit.

Do you recommend me to replace the CC or just do away with it?



Posted 04 February 2005 - 12:39 PM


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Bro...there is a dilemma :

- If cost is not a factor, it is wise to replace the CC.

- When cost is a major consideration, it is better you remove the CC and
replace with silencer or just straight pipe, coz risk will go to no.3.
This will safe your engine (tuned condition)and minimize toxic exhaust
gas compared running with CC damage.

BTW, did you check your Oxygen Sensor ???.

Actually, there is another factor that cause fail the CC (which is no.
7) : THERMAL SHOCK, When CC is in operating condition and suddently
emerge in the flooding road, cause the ceramic cracking (fracture
damage), then back to problem no.6.

Also be carefull when washing underbody, don`t wash underbody when hot.


Posted 04 February 2005 - 01:02 PM



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Iz: Does your lambda light still comes up?

Kenari1: After you removed your Cat, does your lambda light come up all the
time? Or did you disabled it? After 4 days, my lambda light lit. Ding. Is
it OK? Or am I in trouble? Is it going to screw up the engine?

When I have the $$ I will fit a Cat back in... First got to fix the
driveshaft head after CNY... RM500 - RM600 ... ouch!Blackeye


Posted 04 February 2005 - 03:40 PM


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i haven't removed my cat yet, but if your lambda warning lights up then
you've got a faulty sensor on your hands.
The lambda lights up because there is a difference between the sensors. on
an original layout, there is one sensor before the cat and one after the
cat. once you remove the cat, there is nothing between the two sensors so
in theory, both sensors should report back the same values to the ECU. If
there is a noticable difference between the two sensors then the ECU will
turn on the Lambda warning. In your case, I would suspect a faulty sensor.

i have read in the foreign forums that you can actually remove the sensor
and clean it up, if you've got the right tools but i've no details on this
but it was stated that the sensor is also quite fragile. so, don't break it
if you decide to take it out.