I've been going over ScootyPuffs last MOT, and I notice she just scraped by the emissions test. What can I do to reduce them back to a saner level? This is the first car I plan on servicing myself, so forgive me if this is a newbish question!
Give it a good service. The air filter will make a big difference if the old one is really dirty. Oil change, new spark plugs etc all help too. If you think there's a lot of unburnt carbon in the system, you can use an additive like redex, but you need to then go for a good run and get the revs up to help burn the carbon. A lot of people don't rate fuel additives, but it all depends on how bad it is, as to if you notice a difference or not. I used to get my old banger through the emissions test by pouring redex straight down the carb, going for a good run, making sure that I pushed the revs up, and then use a premium fuel for a few days. Fuel like optimax have additives in them so you don't get so much unburnt carbon. Always make sure your car is warmed up before you head into the garage for the MOT too, that makes a bit difference on the emissions reading too. If its still too high after that lot (though you'd prob only know by it failing the MOT), and the timing is okay, then you might have to look at one of the fairly new decarbon services at a decent garage/dealer. Hope that helps a bit. Sarah
if Sarah's suggestions don't do it then it may need a new catalytic converter, but fingers crossed it wont come to that
I'm not sure a new air filter would make much difference if any. Yes it good to not keep a filter for eons so it end ups blocking too much air. But with with the intelligent fuelling the system monitors oxygen in the exhaust. If this is zero, assuming O2 sensors and cat are working, the fuel injections should reduce the amount of fuel injected to compensate for the lack of air going in. Also, say with a MAF, that a Copen doesn't have, it monitors how much air is flowing in so it can do all the number crunching and keep the fuel:air ratio correct. If this is working then I don't see how the filter would be a main cause? If it does, putting a smaller air filter on that's new and clean, and restricts air flow should cause the same issues. Unless the dirt itself is the issue not the actual airflow? But the dirt shouldn't really be getting through, should it? You can add some methanol. Its doesn't burn with smoke. I've never tried it for an MOT.
I did say if the filter was really dirty though Variable injection systems do compensate as you say, lack of air flow will mean less oxygen and fuel in is reduced. But if the air flow is really bad its not going to be running right. Though I did assume that it was not just CO2 that was high, and running too rich or lean running can affect the lambda calculation too. Servicing the car is a good thing anyway, so it makes sense to do that, change the air filter etc and see if it works. It could be a whole host of things depending on the readings, but I'd try a service first before getting involved in cats, lambda sensors etc
talking about fuel what do you guys tend to normally use ? i personally use the tesco momentum 99 premium stuff
I guess if the filter is so blocked up the amount of air getting through could be too little for the fuel system to drop enough to keep the mixture right. But by then would you not notice a serious performance drop?