SOD* emissions tips ?

It won't damage it but unless it's overfuelling because there's no compression then it won't help.

CHeck the boost pressure,

or

1st Do not adjust the fuelling of the pump by breaking the seal or adjusting the diaphragm spring tension on the boost valve where the air pressure pipe connects to the pump. If you want to reduce the fuel rate simply and reversibly without touching any of the pump settings then :- Disconnect the boost pressure pipe that goes to the fuel pump from the turbo and pop into it a small plug such as a small length of round steel bar. Slip another length of matching hose over the other end of the plug, fix securely with a couple of clips so it just looks like a pipe joiner and connect back to the pump. Now the boost pressure will never reach the pump so the pump will not attempt to up the fuel metering rate to match the extra air the engine is being supplied with via the turbo as the revs increase, so reduced smoke. The performance will be way down as you drive the car on the road but the tester who only starts and drives the car a short distance in the garage, the temp lost performance will not show up. Once test over remove plug and reconnect the boost pile as original.

Adjusting the cable will do little as the tester will often operate the pump by hand so will push the arm all the way to the stop.

Having said that, are you sure the smoke the tester saw was not just carbon particles that had been sitting in the exhaust pipe due to town driving ? I take it it had a good run before you took it for the test ? I know from experience a few full bore blasts in the test bay do not clear all loose particles.

Gio

Thanks muchly, I'll report back when the debacle is over :)

Just rev the knackers off it on the way to the MOT station. Full throttle on the redline in 1st, 2nd and third. Smoke will soon clear. Also make sure the engine is as warm as possible before the MOT test - more often than not they just wait til the oil temp is at 80 deg and do the test, if you can get the engine thoroughly warmed up it'll probably stand a much better chance of passing.

report ? :)

Oooops, sorry 'bout that :)

After a good service, blat etc. it was still over the 3.0 limit. I adjusted the throttle stop to stop it opening quite as much, until it just scraped through the test. I was gonna put it back to how it was, but there seems to be no loss of power or anything, just less smoke.

I'm of the opinion that a previous owner had been messing...

It's still a s**te, smokey old diesel though :)

Old diesels eh :)

I always see this puff of black smoke when a diesel car is accelerating. Also in new, "modern", expensive diesel cars, e.g. top range mercedes.

Basically a result of manurfacturers trying to reduce NOx by using inefficiently large amounts of EGR.

The very latest cars you wont see with this problem as their DPF's will be filtering the soot out, only to be pulled up in the highstreet at the kerb afew miles on when the DPF is blocked solid..!

Tim..

Lots do, a great many, but not all. They'll produce a small sooty cloud when the turbocharger(s) is (are) spooling up.

It's gone through now, so no need to worry about what I'm about to write... but as well as the Italian tuning technique, I'd also suggest running injector cleaner in the tank before you fill, before MOT. Don't take the car for the MOT with injector cleaner in it if you think it'll be close to failing, as this is still removing crud and converting it into soot.

I found that running one of the premium diesels containing GTLs (BP Ultimate, Shell V-Power, Total Excellium Diesel are the three I used) noticeably reduced the visible smoke out of the back. Plus they didn't taste like proper mineral diesel either. Oh and they're very expensive.