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In a very simple summary.... a cat filters and removes crap and harmful particles from your exhaust gas to keep emissions low and to protect the world from global warming 
A sports cat is a less-restrictive filter. It still does the job, but just with less restrictions. This will mean your emissions are higher, but most sports cats should still keep them low enough to pass an MOT or roadside check.
Think of the filter in a coffee machine... you want water and coffee to pass through, but you want to keep out the bigger bits that will turn your coffee into an nasty mess. You just want the good bits to escape.
Well, your filter is your cat. It lets through a certain amount and filters out the rest.
A sports cat would be like putting pin pricks into that filter. It will still filter out most of the bad stuff, but it lets through the good stuff quicker as there is less restriction.
A sports cat is a less-restrictive filter. It still does the job, but just with less restrictions. This will mean your emissions are higher, but most sports cats should still keep them low enough to pass an MOT or roadside check.
Think of the filter in a coffee machine... you want water and coffee to pass through, but you want to keep out the bigger bits that will turn your coffee into an nasty mess. You just want the good bits to escape.
Well, your filter is your cat. It lets through a certain amount and filters out the rest.
A sports cat would be like putting pin pricks into that filter. It will still filter out most of the bad stuff, but it lets through the good stuff quicker as there is less restriction.
Good explaination Rob!
A restrictive exhaust is more of an issue (compared to a naturally aspirated engine) for a turbo charged car that provides its own pressure to push the burnt exhaust gasses out - in a ideal world it would be a straight pipe with a big diameter to just behind a front wheel - i.e. shortest possible distance with least resistance.
A restrictive exhaust is more of an issue (compared to a naturally aspirated engine) for a turbo charged car that provides its own pressure to push the burnt exhaust gasses out - in a ideal world it would be a straight pipe with a big diameter to just behind a front wheel - i.e. shortest possible distance with least resistance.
thanks, great summary and can picture that. why are sports cat so expensive for such a little thing? gains are going to be little compared to a remap. is it actually worth it for normal road conditions?
i can see a straight through pipe would be good on the race track. but with it not legal on the road is a different story.
so how can something within MOT tolerance for emission be much of an improvement? if you know what i mean?
i can see a straight through pipe would be good on the race track. but with it not legal on the road is a different story.
so how can something within MOT tolerance for emission be much of an improvement? if you know what i mean?
I would personally put a sports cat way down the priority list, and would only consider it if I was going all-out for Stage 2. I would actually put a FMIC further up the priority list than a sports cat, despite the price difference.
Agree 100% with that. A cat is expensive full stop because of the precious metals it uses to remove the contaminents from the exhaust. Anything a bit specialised, and sold in low volumes is going to end up expensive.
I know some guys on here get on fine with a de-cat (pm Arosaracer), but I think there are plenty of better ways to waste your money first that won't give you potential grief with MOT's and the like. Don't forget, whilst its highly unlikely, it is possible (I have seen it being done) the Ministry of Transport use the police to set up road side emissions checks. If you are found to have de-catted your car (which you cannot legally do), there are big fines. As I say, very very unlikely, but possible.
I know some guys on here get on fine with a de-cat (pm Arosaracer), but I think there are plenty of better ways to waste your money first that won't give you potential grief with MOT's and the like. Don't forget, whilst its highly unlikely, it is possible (I have seen it being done) the Ministry of Transport use the police to set up road side emissions checks. If you are found to have de-catted your car (which you cannot legally do), there are big fines. As I say, very very unlikely, but possible.
This really varies from one region of the country to the next, but it's not that uncommon around my neck of the woods. VOSA are the people responsible for it, with Police backing and support. They basically perform a mini-MOT at the roadside, going over the more important items only. An emissions test can be, but is not always, a part of that.
It's all to do with making sure cars are safe 365 days of the year, not just on the one day you take it in for it's MOT.
At the end of the day it's the risk you take. I de-catted a Focus I had with good results, but sold it before MOT time so never had that hassle. But I was always wary of the fact that I could be pulled over at any time. Fortunately this was about 3.5 years ago before VOSA really came out in force around here, so I'm not sure I'd do it again.
But a sports cat should be a much safer option as it goes a long way to ensuring the emissions are safe.... especially if you get the car nice and hot before any tests!
i'm thinking of new:
dv
intake
exhaust
so last breathing changes are:
sports cat
FMIC
upgrade hoses
before I think of remap, as quite happy with performance at the mo from the 225 (as will change later on when i start to get bored)
will only do the other breathing mods, if i got them used and alot cheaper than rrp. more likely for hoses and sports cat as FMIC is bit too much more labour intensive
would a stage2 remap be best when it came to it, once the above are done?
dv
intake
exhaust
so last breathing changes are:
sports cat
FMIC
upgrade hoses
before I think of remap, as quite happy with performance at the mo from the 225 (as will change later on when i start to get bored)
will only do the other breathing mods, if i got them used and alot cheaper than rrp. more likely for hoses and sports cat as FMIC is bit too much more labour intensive
would a stage2 remap be best when it came to it, once the above are done?
For stage 2 you will need everything from stage 1, as well as a turbo back exhaust (including down pipe and sports cat), a new filter (panel or induction) and a 4bar FPR. An FMIC is advised but is not essential, but you can be sure you wont get the full benefits from stage 2 without one.
Luckily in terms of the map Stage 2 is only a fairly cheap upgrade from Stage 1, so there is no harm in getting Stage 1 remapped and adding the other mod's needed as you go. If you decide you're happy and don't bother with the rest, you'll still have a great performing car. If you decide to go on and get the other bits, just get Revo to upgrade you to Stage 2
Luckily in terms of the map Stage 2 is only a fairly cheap upgrade from Stage 1, so there is no harm in getting Stage 1 remapped and adding the other mod's needed as you go. If you decide you're happy and don't bother with the rest, you'll still have a great performing car. If you decide to go on and get the other bits, just get Revo to upgrade you to Stage 2
i'm thinking of helping on breathing as main thing is lower cost, helps performance (a little i guess, if not similar to OEM), but main thing is a little noise and to have a bit more individual characteristic noise. as it's a little flat coming from a celica gen7 with intake and zorst upgrade, as you might know
p1tse wrote
what does a cat do?
A catalyst increases the rate at which a chemical reaction take place without actually being involved in the reaction.
In a petrol car, the catalyst promotes the decomposition of three pollutants:
http://auto.howstuffworks.com/question66.htm
http://www.answers.com/topic/catalytic-converter
http://www.eurocats.co.uk/technical.php
The catalyst does not filter out particles. If it did, it would soon clog up and stop your engine from running.
Diesels produce less pollutant gases, as the engine cycle is more efficient and diesels are almost always running lean, so there is plenty of oxygen present to ensure complete combustion. To meet emission reglations, diesels use a simpler two-way oxidation catalyst which doesn't affect NOx. NOx is controlled in the TDI engine by EGR.
what does a sports cat do over OEM?
The exhaust gas must be exposed to the catalyst over a large surface area to do its job. Typically the catalyst (metallic platinum, rhodium and palladium) is coated onto a ceramic honeycomb fitted into a bulge in the exhaust pipe that looks like another silencer. Well, it is a silencer too, but that isn't its main job.
http://www.eurocats.co.uk/images/eec-information.pdf
Just like a silencer, this restricts the exhaust flow. A Sports Cat is made to be less restrictive while still (in most cases) keeping emissions within legal limits. They do this by having bigger holes in the honeycomb, i.e. less cells per square inch.
http://www.millteksport.com/hiflow.sports.cats.cfm
So a 200-cell cat has 200 cells per square inch and a 100-cell only 100 (so each cell is bigger). OEM cats have more, smaller cells and this restricts the exhaust more.
are these ok for MOT etc.?
Usually (there isn't much point if they aren't) but check first - some are made for track work only, although I'm not sure how many classes of racing require catalysts to be fitted.
I think they are closer to the edge of legal, and need to be looked after more carefully - no driving through deep water (the cat gets hot, cold water will crack it open) no push or tow starts (too much unburnt fuel can damage the cat). A remap will adjust the engine parameters to make best use of the free-er flow and keep the emissions under best control.
pro's and con's?
(of sports cat's)
Pro - performance increase. Different exhaust sound.
Con - should be fitted as part of a high-performance replacement exhaust system - no good fitting a high-flow cat if your silencer is too restrictive. Cost - maybe £400 for just the cat. May fail MOT if mistreated. Need a remap to be fully effective.
RobM wrote
Think of the filter in a coffee machine... you want water and coffee to pass through, but you want to keep out the bigger bits that will turn your coffee into an nasty mess. You just want the good bits to escape.
Well, your filter is your cat. It lets through a certain amount and filters out the rest.
A sports cat would be like putting pin pricks into that filter. It will still filter out most of the bad stuff, but it lets through the good stuff quicker as there is less restriction.
A coffee filter keeps back all the solid bits and only lets dissolved coffee through - no particles. And a catalyst is not a filter.
what does a cat do?
A catalyst increases the rate at which a chemical reaction take place without actually being involved in the reaction.
In a petrol car, the catalyst promotes the decomposition of three pollutants:
- Hydrocarbons (HC) i.e. unburnt fuel. Become water (H20) and carbon dioxide (CO2)
- Carbon monoxide (CO) from incomplete combustion. Becomes carbon dioxide.
- Nitrous oxides (NOx) produced at high combustion temperatures. Becomes nitrogen (N2) and Oxygen (O2)
http://auto.howstuffworks.com/question66.htm
http://www.answers.com/topic/catalytic-converter
http://www.eurocats.co.uk/technical.php
The catalyst does not filter out particles. If it did, it would soon clog up and stop your engine from running.
Diesels produce less pollutant gases, as the engine cycle is more efficient and diesels are almost always running lean, so there is plenty of oxygen present to ensure complete combustion. To meet emission reglations, diesels use a simpler two-way oxidation catalyst which doesn't affect NOx. NOx is controlled in the TDI engine by EGR.
what does a sports cat do over OEM?
The exhaust gas must be exposed to the catalyst over a large surface area to do its job. Typically the catalyst (metallic platinum, rhodium and palladium) is coated onto a ceramic honeycomb fitted into a bulge in the exhaust pipe that looks like another silencer. Well, it is a silencer too, but that isn't its main job.
http://www.eurocats.co.uk/images/eec-information.pdf
Just like a silencer, this restricts the exhaust flow. A Sports Cat is made to be less restrictive while still (in most cases) keeping emissions within legal limits. They do this by having bigger holes in the honeycomb, i.e. less cells per square inch.
http://www.millteksport.com/hiflow.sports.cats.cfm
So a 200-cell cat has 200 cells per square inch and a 100-cell only 100 (so each cell is bigger). OEM cats have more, smaller cells and this restricts the exhaust more.
are these ok for MOT etc.?
Usually (there isn't much point if they aren't) but check first - some are made for track work only, although I'm not sure how many classes of racing require catalysts to be fitted.
I think they are closer to the edge of legal, and need to be looked after more carefully - no driving through deep water (the cat gets hot, cold water will crack it open) no push or tow starts (too much unburnt fuel can damage the cat). A remap will adjust the engine parameters to make best use of the free-er flow and keep the emissions under best control.
pro's and con's?
(of sports cat's)
Pro - performance increase. Different exhaust sound.
Con - should be fitted as part of a high-performance replacement exhaust system - no good fitting a high-flow cat if your silencer is too restrictive. Cost - maybe £400 for just the cat. May fail MOT if mistreated. Need a remap to be fully effective.
RobM wrote
Think of the filter in a coffee machine... you want water and coffee to pass through, but you want to keep out the bigger bits that will turn your coffee into an nasty mess. You just want the good bits to escape.
Well, your filter is your cat. It lets through a certain amount and filters out the rest.
A sports cat would be like putting pin pricks into that filter. It will still filter out most of the bad stuff, but it lets through the good stuff quicker as there is less restriction.
A coffee filter keeps back all the solid bits and only lets dissolved coffee through - no particles. And a catalyst is not a filter.
You must have heard of these?
A push start is where you can't start your car (battery might be dead for example?) so you get some people to push you along, then pop the clutch out in gear and see if it starts. Also known as bump start.
Tow start is same principle except you get towed instead of pushed.
Yes, they will be more fragile. They can't be serviced, and no they won't last as long as OE.
A push start is where you can't start your car (battery might be dead for example?) so you get some people to push you along, then pop the clutch out in gear and see if it starts. Also known as bump start.
Tow start is same principle except you get towed instead of pushed.
Yes, they will be more fragile. They can't be serviced, and no they won't last as long as OE.
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