MoT- new emission tests

[l5foye]

In N. Ireland, new emission tests have been recently introduced. For diesel vehicles, these tests involve revving the vehicle up to its 'governed speed' and measuring emissions. These may involve doing this up to 6 times. For petrol vehicles, they are revved to 2500 rpm. Am I right in thinking that 'governed speed' means revving an engine flat out? There have been reports of engines being damaged during the MoT tests.
Are diesel vehicles tested this way in GB (England, Scotland and Wales)? Can anyone explain the logic behind the different ways of testing a petrol and a diesel engine?

 

[996jimbo]

For years test centres have had a sign on the wall warning that diesel engines will be revved to the limiter for emissions testing. Can't remember exactly how many years but it must be at least 10. Maybe for ever?

 

[Dieselman]

In mainland UK diesels are tested exactly as you describe, form idle to the red line a max of six times. The test is for three revs but the tester is allowed a maximum of six attempts.

Petrols are tested at idle and if they fail can be revved to 2500rpm to clear them out and to see if the oil smoke clears then they should be retested at idle.

The reason is that on the petrol there is mixture control throughout the rev range, whereas on a diesel there isn't, only at maximum load will the engine be fully fueled up.

As long as the engine is HOT there shouldn't be a problem. This test only wrecks engines that are about to go pop or have an over-life cambelt.

As a precaution drive the last two miles in low gear. I've been known to have a good blast in 1st just before the test. That way you read the actual engine reading not the soot buildup in the exhaust.

A sympatetic tester won't bother with continual revving if the car passes on the first rev. At 0.7 out of 3.0 they don't see the point of trying again.