CLK MOT pass with 2 cats removed

[LeighW]

What impact did the removal of the cats have on the exhaust note...?

It's made mine a little more raspy when accelerating whilst the engine is cold. It's not actually louder, but you can hear the exhaust gases as they pass through the empty cats. It's much less once the engine is warm, although now I know it's fine on emissions, I may get straight pipes welded in place of them.

It certainly revs more freely than before they were removed; although as my cats were broken, they could have been (and probably were) partially blocking the exhaust, so it's not a definitive comparison.

 

[e55]

This is a very good thread and hopefully will save me a few quid in the future.

I think new Cats on my car cost about £1500 per side ................so hopefully the above suggestion will work!

Thanks guys!

 

[television]

A big reason for failure is parking or driving through long grass. The outer casing cool down faster than the ceramic inserts,crushing them in the process .
I reversed into a farm track with a grass center to allow a tractor to pass, when I drove away tinkle tinkle and that was that,take them out or £1500 for new ones

 

[GrahamC230K]

Yes sudden cooling has always been a given reason for cat failure. I imagine a lot of drivers having problems after the widespread flooding this year.

 

[television]

Yes sudden cooling has always been a given reason for cat failure. I imagine a lot of drivers having problems after the widespread flooding this year.

Good point,one minute hot the next cold, in fact the cooling that takes place with flooding will be much more rapid than grass

 

[bouncer]

The car was supposed to have cats on it will be tested as if it had cats on regardless.
If your engine is efficient you may scrape through the emissions test. The two cat design is there to help with overall emissions not just at MOT time for a static test not under load.
The two cat design is there for a reason, it will help with the emissions when driving down motorways, under heavy load, urban driving or just blipping the throttle.
You have a your environment to consider. All the extra Nox (oxides of nitrogen) that your vehicle is pumping out stops the blood from absorbing oxygen and has even more health implication than just that.
Not preaching. . . . but they are there for a reason, and not just to make money.
And if a vehicle has duel fuel, it will only be tested on the fuel that it was presented for test with.

sTeVe

 

[bolide]

Just one more thing...

I think all petrol-engined cars now used a closed-loop Lambda system with Lambda probes before and after the catalyst. The ECU monitors the exhaust gases each side of the cat and changes the mixture, when cold, to heat up the cats quickly and, when warm, to reduce emissions

By removing the cat you effectively break that closed loop and the ECU won't be able to control the engine or emissions as closely

This is also a clue as to why some engines pass emissions test without cats - their basic burn, courtesy of the accurate stochiometric mixture, high CR, good knock sensors and good design, burns cleanly

Nick Froome
www.w124.co.uk

 

[LeighW]

Just one more thing...

I think all petrol-engined cars now used a closed-loop Lambda system with Lambda probes before and after the catalyst. The ECU monitors the exhaust gases each side of the cat and changes the mixture, when cold, to heat up the cats quickly and, when warm, to reduce emissions

By removing the cat you effectively break that closed loop and the ECU won't be able to control the engine or emissions as closely
www.w124.co.uk

My CLK has probes after the first cat, nothing after that, which is why it runs fine without the second cats, but probably wouldn't without the first.

 

[bouncer]

Just one more thing...

I think all petrol-engined cars now used a closed-loop Lambda system with Lambda probes before and after the catalyst. The ECU monitors the exhaust gases each side of the cat and changes the mixture, when cold, to heat up the cats quickly and, when warm, to reduce emissions

By removing the cat you effectively break that closed loop and the ECU won't be able to control the engine or emissions as closely

This is also a clue as to why some engines pass emissions test without cats - their basic burn, courtesy of the accurate stochiometric mixture, high CR, good knock sensors and good design, burns cleanly

Nick Froome
www.w124.co.uk

Yes, the first lambda sensor before the cat does all the hard work changing the ecu to lean up or richen the mixture. For vehicles equiped with a second lambda sensor after the cat (OBD) this second sensor is there to measure the efectiveness of the catalytic converter. its this sensor that puts on the MIL light on your dash. so dodgey emissions and no cat = light on. (code number i forget)= catalytic converter below threshold.

sTeVe

 

[kth286]

LeighW

I do not think you had 4 Kats on your car at all.

The first devices you think are Kats are probably devices that help keep the exhaust gasses up to heat between the engine and the real Kats at the cold stage before the engine has heated up to operating temperature. They help the real Kats get up to normal operating temperature as quickly as possible.

I am surprised you do not have before and after lambda probes, if you think your car is a later model. The later models do have before and after probes.

 

[rajinder_1]

this is very interseting, but i have had a situation when my c0 was high on a car we had and he increased the accelaration which bought it down and pass the test, is this right or am i mistaken?????

 

[Dieselman]

LeighW

I do not think you had 4 Kats on your car at all.

The first devices you think are Kats are probably devices that help keep the exhaust gasses up to heat between the engine and the real Kats at the cold stage before the engine has heated up to operating temperature. They help the real Kats get up to normal operating temperature as quickly as possible.

They are all Cats. The first ones are close coupled to warm up more quickly from cold satrt, so become effective earlier.

 

[LeighW]

LeighW

I do not think you had 4 Kats on your car at all.

The first devices you think are Kats are probably devices that help keep the exhaust gasses up to heat between the engine and the real Kats at the cold stage before the engine has heated up to operating temperature. They help the real Kats get up to normal operating temperature as quickly as possible.

I am surprised you do not have before and after lambda probes, if you think your car is a later model. The later models do have before and after probes.

I can assure you they are cats, I have spoken to the head tech at my local MB dealer about it. Regarding the lambda probes, the first cats have them, the second ones don't. Regarding my car being a 'later' model, I mean it is a post facelift W208, the pre facelift model has rear cats only. I hope this clarifies.

This thread was intended to clarify that a car (MB of similar era to mine) was able to pass an MOT without the second (unnecessary in my view) cats. I thought it may help some members save cash when faced with the common occurence of cat failure.

With regard to others' comments made about responsibility to the environment, I am quite confident that the 6.5k miles I cover per year in my '2-cat' Merc is doing far less damage to the environment than a field full of flatulent cows, or a soot belching empty bus etc... But that's going off topic.
Bottom line; your car will pass your MOT with the rear cats removed. If you believe that cars are frying the planet, and that removing your cats will send you to hell, don't do it.

 

[Dieselman]

With regard to others' comments made about responsibility to the environment, I am quite confident that the 6.5k miles I cover per year in my '2-cat' Merc is doing far less damage to the environment than a field full of flatulent cows, or a soot belching empty bus etc... But that's going off topic.
Bottom line; your car will pass your MOT with the rear cats removed. If you believe that cars are frying the planet, and that removing your cats will send you to hell, don't do it.

Your knowledge of what catalytic converters do is flawed, they don't reduce Co2, they increase it.

I'm also pretty sure your car does a lot more damage to the environment then a cow or a (non) soot belching bus does as well, but that's a different debate.

And when was the last time you saw a soot belching bus anyway...???

 

[LeighW]

Your knowledge of what catalytic converters do is flawed, they don't reduce Co2, they increase it.

I'm also pretty sure your car does a lot more damage to the environment then a cow or a (non) soot belching bus does as well, but that's a different debate.

And when was the last time you saw a soot belching bus anyway...???

I'm well aware of what a catalytic convertor does, I'm also aware that the amount of methane emitted from cattle is considerable, and not overly helpful to the environment (it's not just CO2 that's warming the planet). I followed a T reg (1978) double decker bus this morning which was taking children to a school near to where I work, and it was belching huge clouds of soot every time it accelerated. I don't live in a city, and believe me, the buses used by the local companies are far from state of the art.

Anyhow, this thread was to offer help to anyone that wanted it, nothing more. I have no desire to argue about environmental problems or any other issues, I'm sorry if I have given this impression. Anyhow, back on topic...

 

[Dieselman]

I don't live in a city, and believe me, the buses used by the local companies are far from state of the art.

Surprised to hear that given the three companies that operate that area, their fleets are pretty new.

You should report the operator of the school bus to VOSA, they have a special phone number to report smokey vehicles on.
I note it isn't a service bus, but a private party one, though it still falls under the smoke test but not Coucil rules for age of vehicle.

Here you go:

Dirty Diesel Hotline - ring 0870 6060 440 (the Vehicle & Operator Services Agency) to report on any smokey diesel you see. Be ready to give location, vehicle registration number, vehicle type and distinguishing marks if possible.

BTW. It wasn't me that brought up the environmental issue, I was just correcting a misconception.

 

[LeighW]

BTW. It wasn't me that brought up the environmental issue, I was just correcting a misconception.

I know you were, but I maintain the cow argument.

 

[Dieselman]

Two points:

Humans also create methane, so what should be done about that?
And.
Do you know what plans are in place for farmyard methane.?

In addition we need livestock for food, not just meat but ALL dairy products, so I feel it would be fair to call them a necessity, whereas cars are a luxury and we have the technology to make cars less poluting so why not use it?

I like technology..

 

[television]

Two points:

Humans also create methane, so what should be done about that?
And.

Select the baked beans better, find the ones that cause the trouble and dont eat them

Do you know what plans are in place for farmyard methane.?

In Sweden the farms have been putting back into the system for years, and the farmers get a rebate, do bear in mind that in the winter in Sweden the animals are kept inside much longer than they are here, so easier to collect

 

[Dieselman]

Nice to see you're on the ball Tv. Bio-digesters will become big business in the Uk soon and the methane collected used to fuel generators to generate electricity.

Of course when the cost of fossil fuel is very high, nobody will be forcing the anti-greens to have the cheap electricity the cows methane is producing..

Hold on, I can see then next comment coming...There aren't enough cows....cant win..