Smoke/emissions testing for diesels

[tb2000]

Opening the throttle on a diesel engine only regulates how much fuel is injected , the only way to test it's emissions is to inject the maximum allowed into the engine & that is ONLY going to happen at full throttle hence a diesel smoke test has to be done at full throttle, Some basic checks are carried out before the test is done which include oil level, bringing the engine up to normal running temp but most importantly the cambelt history has to be taken into account, The presenter of any diesel car should be given a card at reception stating what happens during the smoke test & if there is any doubt or the presenter can't confirm the cambelt history the testing station can & will refuse to carry out the test.

For the record the engine is held on the governor for aprox 5 seconds , if the smoke reading is within the limits after this time the car passes & thats it, this is known as "Fast Pass" , If if fails then the test is carried out up to a maximum of 6 runs & a mean average is taken , more often than not the first test run can be quite high especially if the car only pootles around as there is a buildup of soot in the exhaust which needs to be cleared out.

I think it's probably a good idea to take the car out for a good blast before it's due to go in for the MOT, you can then at least be somewhere near sure that the things had a good clear out.

 

[The_Dark_Side]

Erm, What I actually said is there is no need to rev MY car higher than 3000rpm because its passed the point of maximum torque produced.

i've checked the thread and cannot see you mention maximum torque at all.
what you actually said was there was no need to rev beyond 3000 RPM in normal driving.i'd disagree with this strongly and would add that you could even be doing your engine more harm than good by doing this.
revving so low could promote soot build up over time.

My car is normally aspirated so nothing exciting is gonna happen however hard its revved.

this may come as a surprise but the MOT test isn't setup around your use of a vehicle.you may not rev your car more than 2krpm above idle but everyone else in the western hemisphere does and as such the emission test needs to pickup on this.

My point of comparing a Nova to a truck is that you can't generalise all diesel vehicles as being the same and having the same power bands.

we were talking about cars until you dropped HGV motors into the mix,why not throw in marine diesels for good measure?
all car turbo diesels will indeed develop boost at roughly the same point in their rev range so yes you can generalise.hgv's are different in that they have a much lower rev range to give prolonged engine life and of course when you have upwards of ten litres of capacity then your engine can easily make enough waste gas to spin the turbine below 1500 RPM.

 

[Lopéz]

40seconds on the limiter is hardly gonna knacker your engine unless is a bucket of bolts in that case get a new car

40 seconds on the limiter? No, no, no...... re-read my post. Diesels are taken to the limiter for a few seconds to get a reading, petrols need longer to get a reading (about 30/40 seconds) but this is done at a much lower engine speed.

 

[Sputnik II]

i've checked the thread and cannot see you mention maximum torque at all.
what you actually said was there was no need to rev beyond 3000 RPM in normal driving.

Yes, that is exactly what I said and for the reasons I later gave!

I'd disagree with this strongly and would add that you could even be doing your engine more harm than good by doing this.
revving so low could promote soot build up over time.

Oh right, I'll rev the heck outta my engine and reduce the fuel economy from now on just for you !

this may come as a surprise but the MOT test isn't setup around your use of a vehicle.

Oh, my really ?

you may not rev your car more than 2krpm above idle but everyone else in the western hemisphere does and as such the emission test needs to pickup on this.

I'd probably say 50% drive like me but, you tell me seeing as you seem to know everyone in the western hemisphere.

we were talking about cars until you dropped HGV motors into the mix,why not throw in marine diesels for good measure?

Because the last time I looked marine diesels didn't go along on a tarmac surface but, trucks do.

all car turbo diesels will indeed develop boost at roughly the same point in their rev range so yes you can generalise.hgv's are different in that they have a much lower rev range to give prolonged engine life and of course when you have upwards of ten litres of capacity then your engine can easily make enough waste gas to spin the turbine below 1500 RPM.

Actually some of the new variable boost turbo diesels get the turbo spinning at low engine rpm's

 

[Sputnik II]

Opening the throttle on a diesel engine only regulates how much fuel is injected , the only way to test it's emissions is to inject the maximum allowed into the engine & that is ONLY going to happen at full throttle hence a diesel smoke test has to be done at full throttle, Some basic checks are carried out before the test is done which include oil level, bringing the engine up to normal running temp but most importantly the cambelt history has to be taken into account, The presenter of any diesel car should be given a card at reception stating what happens during the smoke test & if there is any doubt or the presenter can't confirm the cambelt history the testing station can & will refuse to carry out the test.

For the record the engine is held on the governor for aprox 5 seconds , if the smoke reading is within the limits after this time the car passes & thats it, this is known as "Fast Pass" , If if fails then the test is carried out up to a maximum of 6 runs & a mean average is taken , more often than not the first test run can be quite high especially if the car only pootles around as there is a buildup of soot in the exhaust which needs to be cleared out.

Thanks for that, thats pretty much what I wanted to know.

 

[The_Dark_Side]

Yes, that is exactly what I said and for the reasons I later gave!

later gave,as in after i'd replied to the point in question.
i have many talents,telepathy is not one of them.

Oh right, I'll rev the heck outta my engine and reduce the fuel economy from now on just for you !

1.last time i checked,"revving the heck out of my engine" wasn't the next notch past 3000 RPM.there is a world inbetween.
as i stated earlier a driving style such as yours,namely minimal revs for the majority of the time will be detrimental to your engine.
2.gearing has as much to do with economy as your engine speed.

Oh, my really ?

yes,really.
you didn't realise this?

I'd probably say 50% drive like me but, you tell me seeing as you seem to know everyone in the western hemisphere.

i don't think it's an unreasonable claim,after all,you've just stated that you're speaking for 50% of them

Because the last time I looked marine diesels didn't go along on a tarmac surface but, trucks do.

and the last time i checked,the damage that may or may not be incurred by your engine when revving hard has nothing to do with the surface underneath your vehicle,be it land,tarmac or water.

Actually some of the new variable boost turbo diesels get the turbo spinning at low engine rpm's

can you give some examples of these vehicles and the respective points that they start to develop boost?

 

[numnutz]

Diesel engines are tested at full throttle. This is the only way of getting the correct reading. If you don't like it then buy a petrol, they are tested at idle and then for approx 40 seconds at 3-3500 rpm.

Why does a petrol need to be tested at 3 - 3500rpm, surely it will be producing more emmisions when it gets more fuel into the engine like a diesel?

This is purely a question, dont flame me!

Thanks

 

[#Chri5#]

in a Turbo Diesel the turbo won't come on song until approximately 2500RPM.
obviously the engine needs to be tested to see what emmisions are like at the higher end of the rev range.

Peak torque on my PD130 lump arrives at 1900rpm

 

[siztenboots]

Why does a petrol need to be tested at 3 - 3500rpm, surely it will be producing more emmisions when it gets more fuel into the engine like a diesel?

This is purely a question, dont flame me!

Thanks

Some petrol have secondaries that open around 3.5 ~ 3.75 Krpm , when they come on-cam, presumably the additional air needs correspondingly more fuel to maintain the stoic mix ratio.

Ninja edit, thinking about this, vtec is probably outside of the testing range

 

[siztenboots]

Peak torque on my PD130 lump arrives at 1900rpm

Duratorq TDCi 2.0-litre engine achieves a peak torque output of 310 Nm at 1800 rpm

 

[The_Dark_Side]

Peak torque on my PD130 lump arrives at 1900rpm

Duratorq TDCi 2.0-litre engine achieves a peak torque output of 310 Nm at 1800 rpm

the more modern common rail diesels allow torque figures like this whereas the older type of mechanically injected diesels need more rev's.
as a sidenote even with power coming in as low as this,it still undermines the OP's point that there is no need to rev beyond 3000 RPM as you would only be holding each gear for just over 1000 RPM before shifting up.

btw at what part of the rev range does power start to drop off?