Warming the Cat
Discussion
This week, I have taken both of my two son's little Rovers to my local MoT test station which I have used for close on twenty years.
The Rover 200vi for a full MoT, and my younger son's Rover 25 for an emissions test.
Both passed but there was a difference. Despite my taking the 200vi for a few miles blast to warm it up fully in these sub zero temperatures, the tester had to hold it around 3,000 rpm for several minutes before the Catylitic converter was warm enough to get all the three emissions to go green. It took so long that I was begining to think that an emissions fail was coming up. However, all was well.
Contrast that with the Rover 25 which I had replaced the cylinder head gasket on a few weeks ago. The car had passed the MoT in previous ownership less than three months ago but, I wanted to check the emissions as that MIL light has stayed illuminated since I got the car. Came on again after twice clearing the DTC fault code and I was concerned that maybe one of the sensors was damaged and so affecting emissions. The light has stayed off since replacing the Fuel Filter and clearing the MIL about 250 miles ago.
What a difference, as soon as the sensor was placed in the 25's exhaust pipe all three emissions came up bright red with levels well over the limits.......
After holding a brief fast idle around 3,000 for a few seconds, all three areas showed GREEN within less than ten seconds. On the way there, I had used lower gears to get the cat warmed with the extra engine revs and that appeared to do the trick. Makes a big difference in these cold temperatures.
..
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The Rover 200vi for a full MoT, and my younger son's Rover 25 for an emissions test.
Both passed but there was a difference. Despite my taking the 200vi for a few miles blast to warm it up fully in these sub zero temperatures, the tester had to hold it around 3,000 rpm for several minutes before the Catylitic converter was warm enough to get all the three emissions to go green. It took so long that I was begining to think that an emissions fail was coming up. However, all was well.
Contrast that with the Rover 25 which I had replaced the cylinder head gasket on a few weeks ago. The car had passed the MoT in previous ownership less than three months ago but, I wanted to check the emissions as that MIL light has stayed illuminated since I got the car. Came on again after twice clearing the DTC fault code and I was concerned that maybe one of the sensors was damaged and so affecting emissions. The light has stayed off since replacing the Fuel Filter and clearing the MIL about 250 miles ago.
What a difference, as soon as the sensor was placed in the 25's exhaust pipe all three emissions came up bright red with levels well over the limits.......
After holding a brief fast idle around 3,000 for a few seconds, all three areas showed GREEN within less than ten seconds. On the way there, I had used lower gears to get the cat warmed with the extra engine revs and that appeared to do the trick. Makes a big difference in these cold temperatures.
..
.
Max_Torque said:
200vvi has an "underfloor" catalyst whereas the 1.4 has a "close coupled" catalyst immediately after the exhaust manifold, hence the cat heats at a much lower exhaust mass flow
Yes, of course ~ well pointed out Max_T... Obvious when you think about it ... nearer the heat source, quicker warm up.Chapppers said:
A wickle blankie and a wuvvly wickle warm basket and some warm milky wilk... only the best for my princessy darling warling woo.
You should stop getting MOTs in winter maybe?
Pardon ... You should stop getting MOTs in winter maybe?
Much mirth Chappers ... 
You wont find those guidelines in your average Haynes manual.... There again, a car less MoT is usually more difficult to sell so needs must come rain, snow or shine.... or should that be an MoT-less car ...
Fleckers said:
And that explains why cars in hot places the CAT works better than in cold UK places especialy when the car in lots of cases has not got warm let alone the cat hot before it is shut off
Yes and these two outwardly similar cars support that statement. No doubt other vehicles much moreso.Fleckers said:
And that explains why cars in hot places the CAT works better than in cold UK places especialy when the car in lots of cases has not got warm let alone the cat hot before it is shut off
On any car that meets EU4 or later exhaust emissions (MY>2003), to pass the test the cat will have to be "lit off" within 10sec of engine starting!! Which is why all modern gasoline cars have close coupled catalysts!Gassing Station | General Gassing [Archive] | Top of Page | What's New | My Stuff