Is a car question OT?

Wasn't there a plan for roadside cameras for emissions testing ? Using IR/ UV spectrum analysis ?

Jeez, that's another car to avoid, wot a load of absolute bollocks.

Thanks for the heads-up.

Yeah, they've done it as the manifold+cat combined thing as usual but then decided that they need two of them. Ie one on cylinder 1+2 and then another on 3+4. Can't see the reasoning behind it at all :(

The Natural Philosopher submitted this idea :

I understand the 'poisoning' can be burnt off with a torch.

Smaller cats, closer to the cylinders, meaning they get up to operating temp faster.

Ok, I suppose that makes sense. Then I guess it's just another small step to 'as we have two cats we have to monitor them individually for better emission control'...

Lee

The ECU probably manages the fuelling for each pair of cylinders separately, too.

And the pre- and post-cat lambdas are so it knows/can tell you when one cat's dead.

I did wonder how that would work - what if you lived just round the corner from one and passed it every day just after setting off with a cold engine, high enrichment and a cold cat?

SteveW

In message , Nick Odell writes

Corsas (and Golfs) have a bit of a reputation for putting on the light for no good reason. I agree with the comments that it is most likely the sensor rather than the cat itself. All the light tells you is that the oxygen level is out of spec - too high or too low.

Probably to meet latest emission specs EU4?

Keep up, isn't the latest for cars EU5 from 2009. EU6 is due next year.

Nope. All the light tells you is that the ECU has logged a fault. It might be the lambda. It might not be.

Can't really see it making much if any difference when they fit the cat a couple of hand spans downstream of the exhaust valves rather than a few feet down the exhaust pipe as they used to.

It'll make a very big difference.

to temperatures at least.

And to how long it takes to get to 'operational' temperatures.

The standard way to start a car - full rich mix, retarded ignition, and cold exhaust pumps huge quantities of unburnt fuel soot and CO into the air.

For journeys under 10 miles a cat hardly is worth having in winter.

Anything you can do to preheat or shorten its heat up time is well worth it.

Maybe it was badly worded

For "when they fit the cat" substitute "when they all fit the cat"

There seems little point in keeping the exhaust streams separate and using two cats when lots of manufacturers seem to be able to easily meet the regs with a single cat, also very closely coupled to the cylinders.

Why increase the total external surface area of the cat housings, increasing heat losses, when one housing, with the equivalent catalysing surface area, does the job.

I can think of many reasons. All to do with trading efficiency for cost.

The engine management light specifically refer to emissions out of spec

- according to each handbook on my 3 vehicles.