Boring information for you, that will be of no real use/value.

Im looking into Lambda sensors and the closed loop operating system, I found some information that goes someway to show that the catalytic converter is a con and not the great atmosphere saver we are led to believe by the govt/green peace/ general tree huggers...
therefore, fellow rogues/ all around not nice people, do not feel guilty for running the decat, also maybe use this to baffle the police should you be pulled for an emissions test.

For a cat to be effective it needs a precise mix of fuel/air, we use the lambda sensor for feedback on the mixture strength of gases leaving the exhaust and the ecu compensates on the basis of this (hence I guess failing lambda = incorrect fuelling and potential for pop).
However, the ecu doesnt try to find the correct mixture and hold it, it skates from rich to lean to acheive an average value that is acceptable for the cat.
(hence I guess disco lights at idle/cruise?)
It is only possible for the lambda to control the mixture in the closed loop mode.
closed loop being idle and light cruise.

as scooby drivers we spend a fair amount of time on the gas pedal, engine braking, generally hooning about.
NOT idle and light cruise.

Theres more to this and could bore you beyond tears, but the gist is that this info isnt available to the genral public or they'd all decat.

Andy

 

Oh yes....

fuelling is only corrected by the lambda at idle and cruise conditions

 

In a run to work I datalogged ages back, I was running closed loop or over-run about 95% of the time. A bit was warm up and the rest were a few accelerations.

Cats do work quite effectively with the mixture rocked about stoich. You will notice at cruise the rocking frequency is quite brisk, and the swing on a wideband is usually quite narrow.

The other question though is whether the energy used to process the precious metals is worth it, and also the need to run a richer mixture than might be ideal for economy so that emissions are lowest?

 

Then there's the length of time the gases spend in the cat. and whether the cat. reaches operating temperature.....

IMO they reduce polution in congested streets in urban areas. They probably do help reduce polution elsewhere but not nearly with the same effect.

I'll find out how mine's doing tomorrow in my MOT.

J.

 

John,
to make an engine more efficient, and hence more eco friendly wouldnt it be easier to adjust for a much weaker mixture within the ecu?
running richer might have the knock on of more pollutant emissions, no?
I am suprised about your 95% datalog, on my 60 mile commute I tend to find its a lot of point and squirt work that would put me outside of closed loop, I guess its just my thrill searching in an otherwise boring day .

Andy

 

Hi Andy,

its been well known for some time, that cats are only efficient when they achieve full operating temperature....

at temps below this, they are no better, possibly worse than having no cat at all

the daft part is on the average school run short hop to the shops and back, they churn out more noxious emmisions than non cat cars!!

but its a good money making excersise

all that lovely by product ,,,,, water, does wonders for zorsts

Mart

 

Ive read on a number of occasions that the pollution caused in the refining process for the elements used in a cat. far outweighs the damage done by the pollutants removed by a cat. in service. Now a catylist that converted Co2 to oxygen might be worthwhile.....

 

You could run leaner on cruise as long as the EGTs are OK.

You tend to remember the point and squirt stuff, but the monotonous bits that are spent (unless you are on back roads) you forget, whilst the ECU is happily running closed loop.

That was a sensible drive to work, that is why I manage to get 250+ miles to a 50 litre fill up, with a 2.5. In daily use I don't bother to redline it much (it is just too loud and fast for typical roads), just leave it in 5th or 6th and drive off the torque, at 3000 RPM the acceleration is similar to a standard UK STi wrung out.

 

"Stoichometry" That's quite a woody word, isn't it?

 

Stoichiometry is the branch of chemistry i will have you know but branch is wood

 

There is no reason you can't run the engine lean (lambda is over 1) and have the cat still work, and the output lambda to be 1.

This is what a lean burn engine does.

I have also heard that the refinement of the precious metals used in cats has a massive impact on the environment. However, in places like the US, cars burn a lot more petrol, journeys are longer and the overall effect is far different.

Also, many new cars now contain technology to speed up cat heating, including running rich on startup and adding auxillary air to the exhaust prior to the car, potential with it's own source of ignition, to actively heat the cat.

Paul

 

They used to do something similar on 1970s cars in the US before cats were mandatory - called a smog pump.

 

yes, but the point of it now is to give fresh air to burn the excess fuel with, the end result is the cat operates even in warm up conditions.