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Old 5th March 2008, 14:00   #1
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Default Understanding PUC (Pollution under control) certificate readings

Do the various numbers in the pollution control readings provide one with an understanding of the health/efficiency of the car?

I was comparing the readings for my car taken during summer 07 and winter 07, at Kolkata. On both occasions the car passed the check, but there seemed to be a lot of difference in the readings. Summer 07, Winter 07 readings for my car are given below.

Car: Baleno (Petrol)

CO - the regulation is 0.5% vol
0.004, 0.019 (% vol)

HC - the regulation is 750 ppm
1, 15 (ppm)

CO2 - no regulation specified
11.15, 4.93 (% vol)

O2 - no regulation specified
0.75, 11.63 (% vol)

Lambda - no regulation specified
1.047, 2.648

PEF - no regulation specified
0.542, 0.542

AFR - no regulation specified
15, 38

# Does this indicate that there is more carbon content/unburnt fuel in the exhaust, during the Winter 07 reading?

# Are the differences in figures acceptable?

# Why would these numbers change over a 6 month period?

Last edited by shuvc : 5th March 2008 at 14:03.
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Old 5th March 2008, 14:06   #2
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Winters always mean a heavier exhaust AFAIK. This is particularly true for the particulate matters. Its not only with your car but I guess with all others as well. I have seen this earlier even with a diesel car. So irrespective of the fuel type or the state of the car I am sure the exhaust discharges vary between season.

It has to do with the running temperature of the engine. That is why the pollution checking stations do not take reading if the engine is cold (at least they are not supposed to). Even in summers if you take the reading immediately after the car has been stationary overnight and just started you will find the discharge to be heavier.
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Old 5th March 2008, 15:23   #3
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Ok. But what about say AFR? Is that climate dependent? Is it ok if the figure goes from 15 to 38?
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Old 5th March 2008, 20:34   #4
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Default Afr

If AFR means air/fuel ratio then something is really wrong.. in petrol cars cant go so high as 38.. but not really sure what it means..
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Old 5th March 2008, 22:06   #5
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When I checked my Petrol Innova 6 months back I can see more value in reading compared to almost ZERO value when checked a week back. Guy asked me to raise the engine so he would get some reading instead of zero.

Regards,

Ravi.
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Old 6th March 2008, 00:14   #6
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First off, there are variables here which havent been (or cant be) controlled:

1) is this an average of multiple readings? If so, is the difference noted close to the std. deviation of the readings?

2) how closely was the engine temperature controlled? usually it is enough to warm up the car for a specific amount of time before the reading is taken.

3) was the idle at factory spec?

4) how well was the equipment calibrated?

For a friend's pre-final year project in engineering we did a comparative study of expansion chambers for two-stroke engines. A commercial 5-gas analyser was used to measure CO and HC values.

I dont remember the exact figures, but I do remember that the standard deviation of the values was larger than the change due to a different expansion chamber and jetting. So we concluded that using commercial emissions equipment to measure an engine's tune is rather, useless.


Quote:
Originally Posted by shuvc View Post
Lambda - no regulation specified
1.047, 2.648

AFR - no regulation specified
15, 38
something is definitely amiss here. A lambda of 2.6 is too lean. And nearly impossible specially at idle.
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Old 6th March 2008, 00:52   #7
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Quote:
Originally Posted by shuvc View Post
Do the various numbers in the pollution control readings provide one with an understanding of the health/efficiency of the car?

I was comparing the readings for my car taken during summer 07 and winter 07, at Kolkata. On both occasions the car passed the check, but there seemed to be a lot of difference in the readings. Summer 07, Winter 07 readings for my car are given below.

Car: Baleno (Petrol)

CO - the regulation is 0.5% vol
0.004, 0.019 (% vol)

HC - the regulation is 750 ppm
1, 15 (ppm)

CO2 - no regulation specified
11.15, 4.93 (% vol)

O2 - no regulation specified
0.75, 11.63 (% vol)

Lambda - no regulation specified
1.047, 2.648

PEF - no regulation specified
0.542, 0.542

AFR - no regulation specified
15, 38

# Does this indicate that there is more carbon content/unburnt fuel in the exhaust, during the Winter 07 reading?

# Are the differences in figures acceptable?

# Why would these numbers change over a 6 month period?
Yes, the pollution control reading tells u the health/efficiency of the car.
Its directly related but we should also consider the health of the cat also as the readings are taken downstream of the cat.
A decently tuned engine with a bad cat can give high readings also.
Need to consider your engine and your cat for this.
If engine gives mileage and power and emissions are crazy then u know its ur cat !!
An inefficient engine will not burn cleanly, u will notice loss in power and mileage.
Winter/summer will not make so much of a diff if the cooling "system" is working correctly...
I wouldn't go so far and say that summer/winter is causing this, I would consider the state of the engine at the time of taking the readings..
how well mantained/tuned was the engine at time of those readings.
I've never heard of AFR of 38
Your lambda readings say 1.047 and 2.648 , 2.648 sounds very lean.

#High CO is due to incomplete burning of air fuel mix , something which we see when engine is running rich.. e.g in the morning when the ECU is in open loop, it just adds more fuel , u end up with high CO readings.
the cat is not able to completely oxidise the gasses and u get higher readings
Now if an engine is having above average CO readings during normal operating temperture in closed loop u can guess there is something wrong with the tune/cat.
the readings for a 4 gas analyser such as the one used for your baleno takes readings while running at a high rpm ..so definately its at operating temp and not being affected by winter/summer..


High HC and CO are due to richer mixtures in engine and incomplete oxidation in the cat
O2 and CO2 increase with leaner mixtures .. because of more oxygen in the mix, this again causes more oxidation in the cat

# dont know what are the threshold values for these in India if they are good enough for clearing the pollution checks in India, is the Baleno EuroII or EuroIII compliant ?

#Within 6 months anything can happen, u may require valve clearance adjustment, o2 sensor replacement, may have damaged cat, spark plugs have become dirty, ignition timing may be out of spec,EGR valve and PCV valve maybe not working correctly etc etc its a huge list..
anything can make ur numbers fluctuate between ur 1st and 2nd set of readings
But atleast the summer/winter wont cause much deviation.
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Old 6th March 2008, 01:30   #8
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as far as i understand, the PUC equipment is meant to take readings at manufacturer-specified idle speed, no load.
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Old 6th March 2008, 01:59   #9
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There are a few things in this case worth mentioning.

The difference between the behaviour of this particular car, at the two instances of readings, has only been a considerable drop in FE.

The original thread is this

http://www.team-bhp.com/forum/techni...d-repairs.html (Baleno FE drop post flood repairs)

A first look at the Lambda readings suggested something wrong either to the Oxygen sensor/Lambda sensor, or there is an exhaust system leak (upstream). However how would the tailpipe emission probe catch that reading?

I guess it analyses the O2 content to be high and thus back calculates the Lambda (I dont think they connected a voltmeter to check it) and the AFR readings.

If the o2 content is high, could be because of incorrect signals from the lambda sensor itself, causing the car to run rich. He might not be noting the loss of power, as our roads and his driving style might hide that from him, but he definitely is seeing a drop in FE.

But something is definitely wrong. How does the mechs say that the Catcon is fine? Did they check the Lambda sensor?

Last edited by 1100D : 6th March 2008 at 02:13.
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Old 6th March 2008, 02:13   #10
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Quote:
Originally Posted by ananthkamath View Post
as far as i understand, the PUC equipment is meant to take readings at manufacturer-specified idle speed, no load.
Ok, PUC may have a diff procedure, maybe they do it at idle only.
Then my question is how do they check the EGR ? it doen't activate at idle so are they doing it incorrectly ?

Diff from what is done here for the smog checks.. low and hi speed run they run it idle + another rpm e.g 2500 rpm
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Old 6th March 2008, 02:34   #11
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Quote:
Originally Posted by chetanhanda View Post
Diff from what is done here for the smog checks.. low and hi speed run they run it idle + another rpm e.g 2500 rpm
In India, its at idle only. Morever no probe is connected to the car apart from the rpm sensor and the gas analyser stick.

Disregarding the Lambda and AFR readings (I think they are back calculated on these systems), the O2 is actually measured from the tail pipe emission.

Last edited by 1100D : 6th March 2008 at 02:36.
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Old 6th March 2008, 02:57   #12
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Quote:
Originally Posted by chetanhanda View Post
High HC and CO are due to richer mixtures in engine and incomplete oxidation in the cat
O2 and CO2 increase with leaner mixtures .. because of more oxygen in the mix, this again causes more oxidation in the cat

# dont know what are the threshold values for these in India if they are good enough for clearing the pollution checks in India, is the Baleno EuroII or EuroIII compliant ?

#Within 6 months anything can happen, u may require valve clearance adjustment, o2 sensor replacement, may have damaged cat, spark plugs have become dirty, ignition timing may be out of spec,EGR valve and PCV valve maybe not working correctly etc etc its a huge list..
anything can make ur numbers fluctuate between ur 1st and 2nd set of readings
The confusion is that, all this suggest a rich running car, reinforced by his car giving lower FE, EXCEPT the fact that, the O2 content is also high, which contradicts the Rich running theory.

Would the possibility of an exhaust system leak, cause the higher O2 content, which is also being seen by the Oxygen sensor and thus causing the car to run rich? Or the Sensor itself has gone nuts. (Which is very much possible as the car was underwater for a few days). If the second one be the case, then we would not see higher O2 on the tailpipe probe.

The order of checking would be
exhaust system-> O2 sensor-> valve clearances -> Faulty injector solenoid.

What say?

Last edited by 1100D : 6th March 2008 at 03:01.
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Old 6th March 2008, 03:45   #13
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Quote:
Originally Posted by 1100D View Post
The confusion is that, all this suggest a rich running car, reinforced by his car giving lower FE, EXCEPT the fact that, the O2 content is also high, which contradicts the Rich running theory.

Lets only concentrate on low FE.
when was the car serviced last ?

Quote:
Originally Posted by 1100D View Post
Would the possibility of an exhaust system leak, cause the higher O2 content, which is also being seen by the Oxygen sensor and thus causing the car to run rich? Or the Sensor itself has gone nuts. (Which is very much possible as the car was underwater for a few days). If the second one be the case, then we would not see higher O2 on the tailpipe probe.
The ECU uses the primary o2 sensor located in in one of the header tubes in our case also if its a Baleno Im not sure if there is a second 02 sensor after the cat.

If there is a leak it would have to happen upstream of 1st o2 sensor in order to misguide the ECU, in this case it seems highly improbable that there could be a leak in that area.
So we can rule out the exhaust leakage affecting how the ECU controls the fuel trim

Quote:
Originally Posted by 1100D View Post
The order of checking would be
exhaust system-> O2 sensor-> valve clearances -> Faulty injector solenoid.
What say?
U said the car was underwater... , thats interesting.
Ok, there is a possibilty maybe ur o2 sensor got scewed up while it was underwater... but do u think the water can get into the header tube or even to the level of the o2 sensor to actually damage it somehow...
maye just swap the sensor with another Baleno and drive around to see if it makes a diff..
for now lets leave the valve clearance, injector etc
with valve clearance u would notice drop in power as the engine gets hotter as u drive around.

Last edited by chetanhanda : 6th March 2008 at 03:47.
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Old 6th March 2008, 10:04   #14
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Quote:
Originally Posted by chetanhanda View Post
Lets only concentrate on low FE.
when was the car serviced last ?



The ECU uses the primary o2 sensor located in in one of the header tubes in our case also if its a Baleno Im not sure if there is a second 02 sensor after the cat.

If there is a leak it would have to happen upstream of 1st o2/lambda sensor in order to misguide the ECU, in this case it seems highly improbable that there could be a leak in that area.
So we can rule out the exhaust leakage affecting how the ECU controls the fuel trim



U said the car was underwater... , thats interesting.
Ok, there is a possibilty maybe ur o2 sensor got scewed up while it was underwater... but do u think the water can get into the header tube or even to the level of the o2 sensor to actually damage it somehow...
maye just swap the sensor with another Baleno and drive around to see if it makes a diff..
for now lets leave the valve clearance, injector etc
with valve clearance u would notice drop in power as the engine gets hotter as u drive around.
Here's the actual scenario of the flooding, at the time it happened.
http://www.team-bhp.com/forum/574883-post25.html

As you see the headers are completely submerged, now if the O2 sensor on the Baleno is on a vertical section of the collector, it will be fine, as the trapped air will not let the water rise inside, but my guess is its just upstream of the cat and I dont see it having survived. If I am not mistaken, the Indian Baleno does not have the cat-con warning light necessitating the need for a downstream (to catcon) o2 sensor.

He got the car mobilised only after a complete checkup at Maruti. However, I doubt they would find any problem with the car. Most workshops dont relate to problems we face!

Now I have no doubts that the first check should be the O2 sensor, the question is what next?

Maybe why he does not face any drivability issues is because its always running open loop based on default lookup tables.

Last edited by 1100D : 6th March 2008 at 10:11.
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Old 6th March 2008, 11:21   #15
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And the open-loop lookup tables ALWAYS, ALWAYS, no matter what, cause the car to run pig-rich in the absence of any way for the ECU to know what's actually happening.

BTW, the Indian baleno has a cat integrated into the manifold (or atleast very close to it). The result being its also vertical so the O2 is right on top of the manifold.

Change the O2, and see if it improves. 1 km/l is too small of a change anyway to blame on anything else.
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