having just been reading the MOT tester's manual...
it doesn't say anything about cats on compression ignition engines - the
vehicle has to pass the appropriate smoke test, is all.
new system put on the 300 TDi - both boxes are "straight-through" and as
such don't restrict flow.
Put a non-cat front pipe on, mainly 'cos it's about 250 quid cheaper... I
think it makes slightly more black smoke on fire-up, but overall, it's
running better and smoking less, if anything, than before. It's definitely
responding better, especially at low-medium revs. Next time it gets MOTed,
I'll see if I've got leeway to turn the pump up a bit more :-)
Someone mentioned a bit back that on a turbo engine, the silencer is almost
redundant, so in a spirit of scientific enquiry, after fitting the front
pipe but no silencers (and of course no cat) I fired the engine up and
revved it a bit. It *is* noisier than normal, but not much. Certainly
nowhere near as noisy as a normal CI engine with no silencer on it.
so I reckon if you wanted, you could just run a pipe out the side or back.
However, since the silencers supplied for the disco are non-restrictive (or
the ones I got are) there's not a lot of point.
Austin Shackles. www.ddol-las.net
my opinions are just that
"'Tis a mad world, my masters" John Taylor (1580-1633) Western Voyage, 1