are two cats needed to pass mot
 

hello can anyone please tell me do i need two cats on my 95 classic turbo impreza to pass mot it has front one on but has failed due to really high emmisions any help would be great thanks

depends mate some pass without any some fail with both it depends if theres any other problems with the car to be honest poor fuelling etc the downpipe cat is the most effective/restrictive so would have thought with that still in it would have passed-would also depend on mileage of the car/and mods if any to it (fuelling related)

had diagnositcs done today they said everything else ok but cat not working it only has front one on at the minute only had the car 2 months it has also had air filter changed and a formula one cat fitted think its a bit like a regulator i have just fitted today new middle cat do you think this will compensate if front one not working properly thanks cheers for ur help:thumb:

The centre one may be enough to pass, where are you?? i have another option....

Not an oxygen sensor problem then?

As long as O2 sensor is operating, centre cat is enough to pass test as long as it is thoroughly warmed up beforehand.

My car has just passed with only a centre cat in place, 1.003 lambda, 38 hydrocarbon and 0.01 CO, it will pass no probs but cat needs to be hot and your lambda sensor needs to be spot on..

My MY99 has just passed with just the centre cat (0.02% CO i had on idle)

PeteS(mapped by Bob)