MOT time again

[hallii]

So I took my M/H in for an MOT, and as usual I found somewhere to watch and listen.

 

Am I the only one who finds the "flat out" revs for the emission test an abuse of the engine?

 

I never rev an engine like that, ever, the MOT man says. quite correctly, that that is how the test has to be done.

 

I suspect that the equipment to do "proper" particulate testing over the normal rev range is to expensive so they just use the flat out test.

 

Or maybe use a rolling road so the engine can be under load rather than free revving it.

 

I read the small print on the notice board, it says, basically, that if your engine blows up, cam belt snaps, piston lets go etc etc., it's not the garages problem it the owners problem.

 

Still, it passed, so that's it for another year.

 

H

 

 

 

 

[Guest 1footinthegrave]

Yes, it's absolutely bonkers, especially if taken in to the red zone. >:-(

[Dave Newell]

If the engine is in good order there should be no problem with revving it flat out. As a modern diesel it is rev limited by the engine management so can't over rev and it should be easily capable of handling its entire rev range.

 

D.

[hallii]

Dave Newell - 2013-02-16 7:09 AM

 

If the engine is in good order there should be no problem with revving it flat out. As a modern diesel it is rev limited by the engine management so can't over rev and it should be easily capable of handling its entire rev range.

 

D.

 

The fact that it (the engine ) survived the said test indicates that it is able to do so, the point I was making was that in normal operation my engine never revs flat out without any load and that wear and tear and posiibly hidden damage might be done to an engine so treated.

 

How about an engine that has done 250,000 miles, not uncommon for a commercial van, it could be servicable for many thousands of miles to come, but it could be destroyed in an instant if revved flat out.

 

Strange that no records are kept of engines that failed during this test.

 

H

[Dave Newell]

A healthy egine will not self destruct by hitting max revs with no load, in fact its more likely to go bang at max revs with full load on it as the pressures inside the engine are then at maximum levels. I have a 17 yearold MX5 with 113,000 on the clock and no indiction that its had any major work done, it will happily buzz round to 7,000 rpm and I have no particular worries about doing so but then I bought this car to go racing with. 30 seconds at max rpm (limited by the engine managment) with no load once a year is not going to harm a healthy engine.

 

D.

[bazooka]

The garage i use just leaves the engine ticking over from when i arrive till the test is finished, thats the reason i go there.

Baz

[747]

Quite a long time ago, VOSA recommended MOT Stations not to rev any diesel engine above 4,000 RPM.

 

I don't know if this guideline still applies.

[Derek Uzzell]

bazooka - 2013-02-17 6:53 PM

 

The garage i use just leaves the engine ticking over from when i arrive till the test is finished, thats the reason i go there.

Baz

 

In which case your garage is failing to comply with the MOT-test exhaust-emissions regulations that are described in detail here:

 

http://www.motuk.co.uk/manual_740.htm