Catalytic converter

[steve_spackman]

Does a Catalytic converter have an impact on fuel economy? :confused:

[chuck34]

Does a Catalytic converter have an impact on fuel economy? :confused:

Good question. My first thought is that it would have to as it adds restriction to the exhaust flow. It also needs to be heated up (by the exhaust gast) to work properly, so it may rob at bit of power that way?

That being said, I would think that the "modern" ones would have little impact if any. But I really don't know.

So I guess I shouldn't have posted anything. :-)

[chuck34]

Went and looked it up on Wiki. I know not the best source, but probably right on this?

http://en.wikipedia.org/wiki/Catalytic_converter#Negative_aspects

"Catalytic converters have proven to be reliable and effective in reducing noxious tailpipe emissions. However, they may have some adverse environmental impacts in use:

The requirement for a rich burn engine to run at the stoichiometric point means it uses more fuel than a "lean burn" engine running at a mixture of 20:1 or less. This increases the amount of fossil fuel consumed and the carbon dioxide emissions of the vehicle. However, NOx control on lean burn engines is problematic and difficult.
Although catalytic converters are effective at removing hydrocarbons and other harmful emissions, most of exhaust gas leaving the engine through a catalytic converter is carbon dioxide (CO2),[11] one of the greenhouse gases indicated by the Intergovernmental Panel on Climate Change (IPCC) to be a "most likely" cause of global warming.[12] Additionally, the U.S. Environmental Protection Agency (EPA) has stated catalytic converters are a significant and growing cause of global warming, due to their release of nitrous oxide (N2O), a greenhouse gas over 300 times more potent than carbon dioxide.[13]
Catalytic converter production requires palladium and/or platinum; part of the world supply of these precious metals is produced near the Russian city of Norilsk, where the industry (among others) has caused Norilsk to be added to Time Magazine's list of most polluted places.[14] "

Looks like they are a bit nasty. But since I think the stuff they remove is more harmeful than the CO2 they don't, they might be a good thing on balance. But I wouldn't argue the point too hard either way.

[Sonic]

Does a Catalytic converter have an impact on fuel economy? :confused:

Short answer - yes.

[Daniel]

Modern cats aren't that bad with regards to fuel economy like earlier ones.

[Rollo]

Before we condemn the answer, I'd like to throw a spanner in the works.

The mufflers and the cat converters are both restricting factors on the ability of the engine to breathe. Of course if they were not there then then engine would probably produce more power; more power equates to more fuel generally.

Now my question is: is the amount of fuel that is presumably spent to run the cat converter (through restrictive airflow) greater or less than the amount of fuel that would otherwise be burnt with the corresponding increase in power if it wasn't in place?
Can someone direct me to an SAE report or similar?

[Mark]

So I guess another question is, does it reduce the engines power?

[edv]

My catalytic convertor also uses an air pump (sometimes called the 'smog pump') which is belt driven off the engine, which pumps additional air into the CC at low RPMs, ie when at idle. This has a direct effect on mileage.

[MrJan]

As someone who has just changed from a cat and standardish exhaust to decat and sportyish exhaust it's fairly obvious that I'm using more fuel. Yet to work it out as not filled up yet but it's probably dropped by about 2mpg. Of course the increased rightfootedness of this week :cheese:

[Daniel]

But that may have a lot to do with the fact that your car will have an o2 sensor after the cat and without the cat the fuelling may be a little messed up.

[MrJan]

Lambda is before the cat :)

[Daniel]

Lambda is before the cat :)
I meant to say "may have an o2 sensor afte the cat" :p

You sure it's not just your lead foot? :p

[MrJan]

It's mix of both :D Sadly it sounds so good that I keep having to put my foot down but even then the fuel guage is falling a lot quicker than it used to when I booted it :) Worth it though, appeals to my inner chav :burnout:

[Daniel]

It's mix of both :D Sadly it sounds so good that I keep having to put my foot down but even then the fuel guage is falling a lot quicker than it used to when I booted it :) Worth it though, appeals to my inner chav :burnout:
:D

At least it improves performance :up:

There's some idiot on a Fiat forum putting quad pipes on a 1.2 500 :facepalm:

[JSH]

Lambda is before the cat :)

Many vehicles now have pre and post cat O2 sensors.