18 replies to this topic

[mini_mad69]

My car just failed the MOT on emmisions.


It's a 1380, 286 cam, hif44, ram air foam air filter, minisport alloy inlet, MG metro head, pressed rockers.


Now it's failed because it was way up on hydrocarbons.

I have no actual figures unfortunatly, and probably wouldn't understand them if I did.


From what I've been told, it may be burning a bit of oil, this is because im using cheap supermarket stuff. Im going to fix my oil leak (advisory) and then fill it with some good quality stuff, which might help a little bit.

I leaned it off, but it was still way over, and you could smell it, it clogged their machine at the garage aswell.


I've been told I can lean it off a bit more, and advance the ignition a bit aswell.





What else can I do, to try and get it through? This is the only thing stopping it from passing.

[Bungle]

after all the modifications was the engine set up properly on a rolling road ?

[mini_mad69]

after all the modifications was the engine set up properly on a rolling road ?

Nope, was set up using a lambda probe and fuel ratio gauge.

But i've been told that the cam shaft fitted will make the car fail emmisions when tuned for performance.

[Guess-Works.com]

Get it tuned on a rolling road with the target being getting the emissions within the necessary range.... tuning is not necessarily all about performance, it's also about what's best for the engine and economy

If it turns out that the engine is burning oil, then I wouldn't worry too much about the MOT, but rather the engine...

[mini_mad69]

Get it tuned on a rolling road with the target being getting the emissions within the necessary range.... tuning is not necessarily all about performance, it's also about what's best for the engine and economy

If it turns out that the engine is burning oil, then I wouldn't worry too much about the MOT, but rather the engine...

Well he did not say for definate that it was burning oil, he just said that because of the excess hydrocarbons.

He did not know of the cam fitted when he said this. The main problem I have now is that my MOT is about to run out and will not get a rolling road session in time before it expires.

I might try what he sudgested and try get it through, then take it to a rolling road.

[h4wx1e]

happened with mine and was told it was the stem seals or something but that could of been for the smoke
but i did as they said and leaned it off and messed with the timing. i was told mine was double the legal limit on emmisions but i evetually got it through, now i need another tune up. i think after a car fails you have about 12 days or so to get it sorted aswell but i would look into that.

Edited by h4wx1e, 30 January 2010 - 01:48 PM.

[mini_mad69]

happened with mine and was told it was the stem seals or something but that could of been for the smoke
but i did as they said and leaned it off and messed with the timing. i was told mine was double the legal limit on emmisions but i evetually got it through, now i need another tune up. i think after a car fails you have about 12 days or so to get it sorted aswell but i would look into that.

Yeah, I think it's the cam causing fault, theres no visable smoke at any time.

So will lean it right off and advance the timing and then get it retuned after.

[davejf]

after all the modifications was the engine set up properly on a rolling road ?

Nope, was set up using a lambda probe and fuel ratio gauge.

But i've been told that the cam shaft fitted will make the car fail emmisions when tuned for performance.

I've got a 286 in mine and it's tuned for performance. Been set up on a rolling road and it's fine.
Thankfully the car only needs a visual check for the MOT, but the MOT guy i go to has got to know my car and we put the probe in just to see what it doing last time, 18 months after the RR session and it was spot on and well within the limits.

Dave

[Rosslin Racing]

what are the figures for the test anyone know?
with that cam you will never test it here, also leaning off the carb is VERY dangerous for your engine you my well burn a hole in the piston should you drive it for a lenght of time.

[minisilverbullet]

what are the figures for the test anyone know?
with that cam you will never test it here, also leaning off the carb is VERY dangerous for your engine you my well burn a hole in the piston should you drive it for a lenght of time.

Thresholds Here (sweden)

CO (0,5)
CO 2500 (0,3)
HC (100)
Lambda (0,95 - 1,09)

gotta be similar in UK?

[bmcecosse]

If it's burning oil - visible blue smoke - it will never pass. Engine overhaul required - changing the oil won't help! You can try opening up the valve gaps to say 25 thou - for the test - and running it as weak as it will take! Do you have a crankcase breather connected directly to the side connection on the carb ?

[curly305]

You can try opening up the valve gaps to say 25 thou - for the test - and running it as weak as it will take!

thats is what i did to my 1380 with a 286 cam and stage 3 head. weakened it just round the coner for mot shop when it pass back round the coner and set it back how it was

Edited by curly305, 30 January 2010 - 05:32 PM.

[mini_mad69]

As I said earlier the bloke testing it assumed it was burning oil, due to the high hydrocarbons. Then when I explained about the cam he suggested leaning the carb and advancing the timing.

I've changed the oil too halfords classic now anyway, as I know the stuff I was using wasn't great anyway. (asda smart price)

And no the breathers arn't connected, they breath to atmosphere and the carb blocked off.


I've advanced the ignition and leaned the carb off some more.

I've found the figures for the MOT here.

Description: Limits: Actual value:

CO: <= 4.5% 2.479% Pass
HC: <= 1200ppm 1330 ppm Fail


It got these values after sitting at 3000rpm to get the car and exhaust hot.

Edited by mini_mad69, 30 January 2010 - 07:08 PM.

[Sprocket]

hydrocarbon is unburnt fuel. The CO is low and would give lower than measured HC

Things that could result in high HC

incorrect cam timing
incorrect valve clearance
Misfire
weak ignition

The other emissions results that the analyser will give will help narrow down wher the problem may lie. O2 and CO2 % would help

[bmcecosse]

You MUST connect the breather to the carb - that will reduce the amount of oil going up past the rings - and being burned. Yes - a little bit of fume will be burned- but that will be much less than whats pushing up past the rings. Opening up the valve gaps reduces the overlap at TDC - so should help.