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TR6 PI MOT Emission Results


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Just a question from my MOT pass yesterday regarding the certificate. (1974 TR6 Injection)

Under heading ....................."Non - Catalyst Equipped Vehicle" its says:

Limits:                                    Actual Value:

Max 4.5%                               2.23%                       PASS

Max 1200 ppm                     481 ppm                  PASS

Do we know what these gases are, 

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1 minute ago, c.hydes said:

Just a question from my MOT pass yesterday regarding the certificate. (1974 TR6 Injection)

Under heading ....................."Non - Catalyst Equipped Vehicle" its says:

Limits:                                    Actual Value:

Max 4.5%                               2.23%                       PASS

Max 1200 ppm                     481 ppm                  PASS

Do we know what these gases are, 

Also does it tell me anything about the state of my engine ie rich, lean, good, bad etc?

Regards, Colin.

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I would assume its 2.23% of CO and 481ppm of Hydrocarbons. 

A good result, neither too rich or lean at idle.

I thought historic cars didn't need an emission test, only no visible smoke.

Edited by DRD
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Thanks guys, yes they have never measured the exhaust gases before, but I paid £45 and apparently that includes the cost of an emission test eg a modern car, so asked the engineer to give me a print out for interest. He did say they were much higher when started, but soon came down to these values above.

If the results indicate a generally healthy car (at idle) then that's good. Guess it may not be so healthy at higher rpm`s though.?

Cheers, Colin.

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Just looked at some past postings on this topic that seem to indicate 2.23% CO at idle is a bit lean and going to say 4% could stop the dreaded "pinking" which I seem to have.

So as a experiment how do I increase it a bit, metering unit tweek, advance/retard timing form 8°BTDC etc

Colin.

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Agree it is a bit lean. My car car failed its French MOT the other day with 8.5%!! (but it ran really well)

My "Man who does" got it down by adjusting the advance/retard on the distributor and the air - screw on the manifold. Went back for retest and it was still 5.9%, very friendly helpful French MOT man then waited for 40 minutes while minor adjustments made till eventually a reading of 3.5% and a karate kick to the machine to save the data got the result we needed (it is also "under 4.5%" in France)

I think that now I have my new MOT valid for5 years it may need tweaking up a little.

kc

(PS we decided not to fiddle with the MU)

Edited by kcsun
added the PS
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Hi,

I was reading your topic, are you sure that the MOT gives you the 'raw' CO value? ... Because there's also sth called the corrected CO value, CO C on the picture attached, which takes into account the CO2 value. The formula should be : CO C = CO * (15/(CO+CO2)). If you make the calculation with my values, you will indeed find 4.82 for CO C. The picture is from my PI car, but a long time ago. From what I understand, it takes into account the possible air dilution in the exhaust line (e.g. a hole in the line).

Thanks for your feedback ! 

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12 hours ago, c.hydes said:

Just looked at some past postings on this topic that seem to indicate 2.23% CO at idle is a bit lean and going to say 4% could stop the dreaded "pinking" which I seem to have.

So as a experiment how do I increase it a bit, metering unit tweek, advance/retard timing form 8°BTDC etc

Colin.

If its pinking then maybe the timing needs retarding a bit. What petrol are you using?

But PI does need to run slightly richer to compensate for transient leaning of the mixture when the throttle opens quickly. Not sure what that translates to at idle though. If you do a search here surely something from one of the gurus on here will come up.

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From my old Autodata manual %co at an idle of 750-800rpm is 2.5 to 3.5, as a comparison the TR7 is 2.0-4.5.

 

                                  Harvey S. Maitland

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Thanks for the input. To answer some of your questions:

The MOT printout  results do not give any other explanations other than what I highlighted in my first post.

I have retarded the timing from 11°BTDC to 8° and my advance is approx. 26 - 28 max at the crankshaft. I use standard supermarket petrol 95 RON, and have a fast road camshaft with a stage 2 conversion, as was a US 125 bhp but converted to 150 with higher compression . Tappets are 14 and 18 thou, vacuum at idle is 9/10" Hg, all BP6ES plugs are light brown, but still get pinking or what I believe is pinking.

My thoughts are:

  • Try 99 RON? 
  • Retard ignition further?
  • Tweek the MU to add a bit more richness?

Cheers, Colin.

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Sounds like it retarded enough, you could try Shell V Power and see if that helps.

Your engine is a similar spec to mine and because its non standard I got it setup on a rolling road. Tbh the CO at idle is fairly meaningless in that case.

Mine runs OK at 11 BTDC but I do user super unleaded and an octane booster. Also I've found cooler iridium plugs better as well. They cured my running on problem. 

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14 hours ago, TR6_PI_1969 said:

Better with the picture! 

Screenshot_20200712-001621.png

Normally in France you are only obliged to pass a pollution test in a petrol car if it was registered after the first of octobe 1972

Peu importe le carburant consommé, le contrôle anti-pollution concerne :

Les voitures à essence mises en circulation à partir du 01/10/1972,

Les véhicules diesel mis en circulation à partir du 01/01/80.

cheers

Alan

Edited by Kiwifrog
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4 hours ago, Kiwifrog said:

Normally in France you are only obliged to pass a pollution test in a petrol car if it was registered after the first of octobe 1972

Peu importe le carburant consommé, le contrôle anti-pollution concerne :

Les voitures à essence mises en circulation à partir du 01/10/1972,

Les véhicules diesel mis en circulation à partir du 01/01/80.

cheers

Alan

Correct. My car being a 69 model year, it doesn't need the pollution test. I asked for the test on purpose, separately from MOT. It'seems on a voluntary base, I was curious.

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9 hours ago, c.hydes said:

I use standard supermarket petrol 95 RON, and have a fast road camshaft with a stage 2 conversion, as was a US 125 bhp but converted to 150 with higher compression . Tappets are 14 and 18 thou, vacuum at idle is 9/10" Hg, all BP6ES plugs are light brown, but still get pinking or what I believe is pinking.

Colin, definitely change to using super unleaded which will be at least 97-octane. Some super unleaded are even higher, such as Shell VPower (99) as DRD suggests. Personally I use Esso which doesn't have the dreaded ethanol in it round our way.

Cheers, Richard

 

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  • 2 weeks later...

Thanks everyone for your comments. Think I will try some of that "99 cocktail" petrol now, If it still pinks the your other suggestions will follow.

Regards Colin.

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On 7/12/2020 at 11:58 AM, c.hydes said:

Thanks for the input. To answer some of your questions:

The MOT printout  results do not give any other explanations other than what I highlighted in my first post.

I have retarded the timing from 11°BTDC to 8° and my advance is approx. 26 - 28 max at the crankshaft. I use standard supermarket petrol 95 RON, and have a fast road camshaft with a stage 2 conversion, as was a US 125 bhp but converted to 150 with higher compression . Tappets are 14 and 18 thou, vacuum at idle is 9/10" Hg, all BP6ES plugs are light brown, but still get pinking or what I believe is pinking.

My thoughts are:

  • Try 99 RON? 
  • Retard ignition further?
  • Tweek the MU to add a bit more richness?

Cheers, Colin.

Emission consists out of following measurements

CO

HC

CO2

O2

Lambda (calculated from above values)

1. CO and Lambda are NOT directly relatable. You can have a 3.30 CO with 1.077 Lamda. Do not go by any of the CO vs Lambda tables found on the internet. Lambda takes into consideration all values. Most "cheap" home testers only provide you with CO value.

2.Retarding ignition helps with HC and CO values (mostly high in combination with long duration cam). But only with electronic ignition since it pulls bad from low end. We did some tests playing with this. normally 9-10° advance, going to -2°. Modern cars go upto -10°.

3. Tweeking MU based only on CO value is not good. You need all values. Go to a garage, they have those nice Bosch Testers....pay them few € and get your results.

Jochem

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