13 replies to this topic

[majj2]

Hello

Ive been testing my mini's CO level with a gunson analyzer prior to its MOT. Ive calibrated it to 2.0%(in air) as instructed in the manual but when i start testing the CO level on the car it drops to 0.1%. I know this may sound good/daft but ive struggled with emissions on this car for the past 5 years because its a 92 plate so should have a cat(which it hasn't) and is fitted with a 12g295 head and twin carbs,so always sends emissions through the roof!!!

Any idea why????

Matt

P.S Ive tested the analyzer on my BMW Mini and it read what the MOT recorded so i know thats working ok.

[Shifty]

Have you balanced the carbs?

Using a gas analyzer to tune twin carbs is a nightmare. On my MG Midget I used a colourtune on cylinders 1 and 4, this meant the carbs were set up individually.

[majj2]

Have you balanced the carbs?

Using a gas analyzer to tune twin carbs is a nightmare. On my MG Midget I used a colourtune on cylinders 1 and 4, this meant the carbs were set up individually.

Hello Shifty
Ive balanced the carbs a while ago but what im trying to do is lower the emissions prior to the MOT because they are always high(None 92 spec) But for some reason the analyzer(Digital one) keeps goine from 0.1 to -0.5

[Shifty]

What do the plugs look like?

Don't forget you've got 2 carbs and you're trying to measure and adjust them at 1 end point. How do you know which carb to adjust to get the mixture correct?

With the exhaust analyzer you don't.

Use a colourtune on cylinders 1 and 4, the exhaust emissions can be checked with the analyzer.

Also have the carb needles been changed to suit the 998? If the carbs came from say a 1275 midget then they may be too rich.

[majj2]

What do the plugs look like?

Don't forget you've got 2 carbs and you're trying to measure and adjust them at 1 end point. How do you know which carb to adjust to get the mixture correct?

With the exhaust analyzer you don't.

Use a colourtune on cylinders 1 and 4, the exhaust emissions can be checked with the analyzer.

Also have the carb needles been changed to suit the 998? If the carbs came from say a 1275 midget then they may be too rich.

Haven't checked the plugs yet,will do tomorrow. When ive started to reduce the CO levels ive adjusted the jet on both carbs at the same time and marked and recorded the amount of turns/nut flats.I have the probe up the exhaust so it wont matter if i have 2 carbs or 20 the CO level will record whats been pumped from it's rear!!! The needles are from a 998 mini cooper

[Shifty]

I don't think I've explained my self very clearly here!!

If the co is high, then you'll adjust the mixture to compenstate. As you're measuring the combined input of the twin carbs you don't know that each carb is equally out of tune.

Say carb 1 is running rich and carb 2 is running too lean, out of the exhaust the gas may measure to rich, so doing it your way you'll adjust both carbs down. Now carb 1 may be ok but carb 2 is way lean. Hence you're just chasing your tail all the time.

I can only tell you how I've done it in the past, which in this case is with a colourtune. Once the carbs are set correctly(and balanced/linkages set) then you can check the output at the back.

Once set with the colourtune, take it for a spin and check the plug colour, fine tune the carb as required.

At this point it may be possible to lean each carb off a flat at a time to get the exhaust gas right, but assuming that the carbs/linkages/balance/needles/dashpot oil/vacuum hoses/breathers etc are all correct the chances are that it will be fine.

They can be tricky little suckers to get right, but rewarding when they do come good. Once set they should only need balancing.

[majj2]

I don't think I've explained my self very clearly here!!

If the co is high, then you'll adjust the mixture to compenstate. As you're measuring the combined input of the twin carbs you don't know that each carb is equally out of tune.

Say carb 1 is running rich and carb 2 is running too lean, out of the exhaust the gas may measure to rich, so doing it your way you'll adjust both carbs down. Now carb 1 may be ok but carb 2 is way lean. Hence you're just chasing your tail all the time.

I can only tell you how I've done it in the past, which in this case is with a colourtune. Once the carbs are set correctly(and balanced/linkages set) then you can check the output at the back.

Once set with the colourtune, take it for a spin and check the plug colour, fine tune the carb as required.

At this point it may be possible to lean each carb off a flat at a time to get the exhaust gas right, but assuming that the carbs/linkages/balance/needles/dashpot oil/vacuum hoses/breathers etc are all correct the chances are that it will be fine.

They can be tricky little suckers to get right, but rewarding when they do come good. Once set they should only need balancing.

I agree with what your saying and your method is quite right.
But my problem is not whether the carbs are balanced,linkages ok,breathers ok or have no dash pot oil as this has all been checked.
What im trying to do is CHEAT the MOT into thinking my emissions are fine then turn the things back up and set them up correctly even if it means one carb is slightly lean than the other to help this...
The problem is ive checked the emissions a couple of times in the past few weeks and the CO level is way to high.But when i checked it yesterday the emission level dropped to 0.1% without adjusting anything,and this happened everytime i checked it.....How's that possible??
Youve got to remember the Emission levels changed in 1992 from 3.5% CO to 0.5% CO (Which is my Problem) and im running my engine with parts that where fitted to mini's 30 or so years ago. The emission testing then was rev the engine to check the smoke level from the exhaust.

[lrostoke]

I understand what your saying..

Shifty is right in his method for setting them, but thats not your problem. You are saying that for some weird reason your gas analyser is showing very very low emmisions , probably lower than is possible and it still be running considering there's no CAT fitted.

Have you tried testing the analyser on an older car such as an older mini, may be it is faulty and struggling with higher readings. OK it passed on the new mini comparison but those emmisions would have been very low anyway.

Any chance its developed an air leak which could be diluting the CO2 levels ??

Are the pipes connected correctly on the analyser, also I've found how far you insert the probe can make a big difference to the readings.
I had mine checked at a garage then inserted probe so it read same and marked position with some tape.

Edited by lrostoke, 10 June 2010 - 12:04 PM.

[Shifty]

I think I get what he's saying, basically he's trying to get the emission down to the level required for a CAT equipped car. I can see why you have problems with this especially with twin carbs.

Am I right?

Was the car actually ever equipped with a CAT?

Even some '92's didn't have CATs

[turbozutek]

I thought CATs only became mandatory in law in 1993?

[lrostoke]

He's also saying he is getting a really low emmisions reading without doing anything, 0.1% see his comment below. I think its that reading he his struggling understand. On a twin carb no cat engine that reading seems way off.

Ive calibrated it to 2.0%(in air) as instructed in the manual but when i start testing the CO level on the car it drops to 0.1%

[Shifty]

He's also saying he is getting a really low emmisions reading without doing anything, 0.1% see his comment below. I think its that reading he his struggling understand. On a twin carb no cat engine that reading seems way off.

Ive calibrated it to 2.0%(in air) as instructed in the manual but when i start testing the CO level on the car it drops to 0.1%

I see what you're saying and I may have misunderstood his question?

I'd be pulling the plugs out and seeing what they look like

[me madjoe 90]

If you are trying to CHEAT the Gas analyis machine just stand on the pipe from the exhaust that goes into the machine a bit that sometines works.


"I love working in a dodgy garage"

or like i belive has aready been said just shove the pipe in some other car while noones looking sorted

I mean its not like your doing any worse blaging the machine this way. Than if you do it the way your doing now and then set it back to how you had it before once you have tested it. Your just making more hastel for yourself messing with the ajustments.

Edited by me madjoe 90, 10 June 2010 - 02:38 PM.

[majj2]

I think I get what he's saying, basically he's trying to get the emission down to the level required for a CAT equipped car. I can see why you have problems with this especially with twin carbs.

Am I right?

Was the car actually ever equipped with a CAT?

Even some '92's didn't have CATs

Hello Shifty
Your reply is exactly what im trying to acheive. Ive since pulled the plugs and they where carboned up. As regards to the CAT it should have been fitted with one but when i bought the car it just had a standard one fitted.

Ive took another set of readings tonight and it's now showing a more realistic 1.7% CO on tick over,however the CO level does go through the roof when the rev's are raised. I think my analyzer is a bit tempramental.

Will defo try a colour tune when/if it gets through an MOT,sounds like a better way of tuning them.


Cheers
Matt