de-cat c180

[ken crosley]

has anyone de-catted? a c180 and passed the m.o.t. with it. as im curious.?? have heared lots of conflicting stories. kc

 

[Dieselman]

A petrol car with no Cat isin't going to pass an emissions test. You could get the Co low enough but not the other gasses.

Just ask at your local test staion.

 

[tamrsoft]

How about de-CATing a common rail diesel, I heard you can still pass the current MOT emission test without one since the test figures are different for a diesel. Is this myth or fact ?

 

[MainMan]

Not only will petrol-engined cars not pass the MOT they won't run properly either. If it's got the "Closed-loop" cat system that most modern cars now have, the lambda sensor after the cat monitors the emissions and tells the engine management unit whether to make the engine rich or lean. It needs to alternate very rapidly between rich and lean to keep the CO down and provide the cat oxidation bed with enough air to turn the hydrocarbons to water and CO2. Mess with this system at your peril.

Diesels can get away without a cat as they don't have closed-loop systems. I'm not sure for how long though - there's new legislation coming in which tightens up emissions regulation for diesels - not before time either, I'm sick of having to turn the air to recirculate when I'm following one of the things.

I think it's sad that Mercedes (and other car firms) have decided to try and make a fat profit from selling cats. It's in the interests of the environment that all cars run with properly functioning emissions equipment. They should supply the stuff at cost. In the US it's legislated that emissions equipment is guaranteed for 8 years or 80k. Over here it's just a nice little earner for the manufacturers.

 

[ken crosley]

de-cat

many thanks for that. does any one know if a 1986 2.3 16v would have had a cat/(sold it now) as when i bought it .someone had welded a straight through piece of pipe . where a cat would have been (or did they just cut out the front box.?) only it passed the mot for 5 years (just curious). have a c180 1.8 now. (slow or what??)

 

[Dieselman]

many thanks for that. does any one know if a 1986 2.3 16v would have had a cat/(sold it now) as when i bought it .someone had welded a straight through piece of pipe . where a cat would have been (or did they just cut out the front box.?) only it passed the mot for 5 years (just curious). have a c180 1.8 now. (slow or what??)

A 1986 model is unlikely to have had a Cat.

 

[Dieselman]

Diesels can get away without a cat as they don't have closed-loop systems. I'm not sure for how long though - there's new legislation coming in which tightens up emissions regulation for diesels - not before time either, I'm sick of having to turn the air to recirculate when I'm following one of the things.

I think it's sad that Mercedes (and other car firms) have decided to try and make a fat profit from selling cats. It's in the interests of the environment that all cars run with properly functioning emissions equipment. They should supply the stuff at cost. In the US it's legislated that emissions equipment is guaranteed for 8 years or 80k. Over here it's just a nice little earner for the manufacturers.

A diesel with a Cat shouldn't smell other than a slight burnt smell.
The diesel cat is simpler than a petrol one as it is a 2 way device as opposed to a 3 way device. This generally makes it simpler and more robust.
A diesel can't run closed loop as it has no throttle so no mixture control.

Diesel Cat isn't needed for the MOT.

EuroIV spec requires a particulate filter so there should be no visble emissions from the exhaust.

 

[andy_cyp]

took the rear cat of my 32 and it passed its mot without a glitch, although there are still 2 cats on there aswell,it had 3 in all.

 

[big x]

Not only will petrol-engined cars not pass the MOT they won't run properly either. If it's got the "Closed-loop" cat system that most modern cars now have, the lambda sensor after the cat monitors the emissions and tells the engine management unit whether to make the engine rich or lean. It needs to alternate very rapidly between rich and lean to keep the CO down and provide the cat oxidation bed with enough air to turn the hydrocarbons to water and CO2. Mess with this system at your peril.

On the W202 IL4's the lambda probe is in the manifold downpipe well before the cat IE.the cat plays no part in the measurement of the combustion process..On my BMW 740i they are on the front of the cat not behind.
My C-180 runs fine without the cat.Your oxygen reading will be a tad high to pass the emissions test without a cat and the co2 will be around 0.3% 0.1% over the limit.The C-180 is a clean running engine and in my view a cat is a complete waste of time on these unless running the stricter US west coast setups.With a nice hot engine running Shell optimax and the MOT tester in a good mood it may just pass without a cat however I understand in future these readouts will be linked to the DVLA computer so bungs won't work anymore.The testers doesn't look at the cat itself only the measured emissions.

adam

 

[Bazzle]

took the rear cat of my 32 and it passed its mot without a glitch, although there are still 2 cats on there aswell,it had 3 in all.

That made me take notice?? Never seen more than 2. Sure it wasnt a muffler?

Bazzle

 

[andy_cyp]

That made me take notice?? Never seen more than 2. Sure it wasnt a muffler?

Bazzle

It was that big box centred in the middle of the exhaust system.

Yankies call em resonators or something like that.

 

[Dieselman]

That would be the silencer.

The cats are close coupled up near the engine so they warm up quickly.

 

[MainMan]

On the W202 IL4's the lambda probe is in the manifold downpipe well before the cat IE.the cat plays no part in the measurement of the combustion process..On my BMW 740i they are on the front of the cat not behind.
adam

Don't know about the BMW but I'd be surprised if the W202 isn't running a closed-loop system, in which case it has lambda sensors both before AND after the cat, and they most certainly do feed back to the engine management unit. This is the only way they can meet hydrocarbon emission regulations.

I'm a bit confused by your statement that "oxygen reading will be a bit high". Oxygen isn't measured in the MOT test. I don't think the govt yet have a problem with oxygen emissions.

 

[big x]

Above picture shows the aftermarket cat I removed from my 1997 C-180 because it was noisy.I put the original back on after gutting.There is NO lambda (oxygen) probe in the exhaust.The exhaust is in 3 sections, the front section shown connects to the manifold down pipe,then the smaller centre silence and then the large rear muffler.
The system is called closed loop because the exhaust gas oxygen content is constantly monitored in the manifold down pipe and the ecu uses this signal and other parameters to adjust the inlet air-fuel mixture.What comes out of the cat plays no part at all in the process on this model or the W210's I've seen.
V6's and later W203 will no doubt be different as they where built to tighter emission standards.

adam

Don't know about the BMW but I'd be surprised if the W202 isn't running a closed-loop system, in which case it has lambda sensors both before AND after the cat, and they most certainly do feed back to the engine management unit. This is the only way they can meet hydrocarbon emission regulations.

I'm a bit confused by your statement that "oxygen reading will be a bit high". Oxygen isn't measured in the MOT test. I don't think the govt yet have a problem with oxygen emissions.

 

[big x]

And here is my BMW V8... If you click on the subgroups menu then click the small diagram you can see the cat has 2 oxygen probes both before the cat.Interestingly if you click on the other subgroups there is a deleted cat muffler shown,some markets must of not required the cat at all.

http://www.realoem.com/bmw/partgrp.do?model=GD42&mospid=47348&hg=18

adam

 

[Catman]

De-catted 1987 300SE

I have recently had the main cat and the precats in the downpipes removed, as they were breaking up. It was virtually impossible to get a catted replacement (unless I paid the exhorbitant stealer price). The car runs just as well, the mpg seems to have increased. The only down-side is that it is no longer a silent car, there is a sound as I accelerate - which I presume is because of the now empty cat box. The car passed it's MOT last week.

 

[Dieselman]

I have recently had the main cat and the precats in the downpipes removed, as they were breaking up. It was virtually impossible to get a catted replacement (unless I paid the exhorbitant stealer price). The car runs just as well, the mpg seems to have increased. The only down-side is that it is no longer a silent car, there is a sound as I accelerate - which I presume is because of the now empty cat box. The car passed it's MOT last week.

It would because there is no Cat requirement for this age of car so the emissions can be as high as about 4%Co. (IIRC)