[chaudh2s]

Lucky for us here up north. PUC centers really never bother putting anything inside tail pipe, let alone open engine bay. Rs. 150 is all they need and it keeps everyone happy.
I recall once a test centre asked me to rev car at various rpms looking at tachometer while taking measurements but then it was a newly opened centre, the next time I went to him, he too was just interested in RS.150.

[viXit]

Originally Posted by dinu2506

It was on one of the alternator mounting bolts.

How the heck is he measuring RPM there??
like jeroen said , you shouldn't be getting any signal there

Originally Posted by condor

I face a similar issue on my 2013 Safari Storme. This has happened at the same testing centre at least twice in a row now, and I need to idle and run the engine at least 10 minutes before the test comes out successful. The issue wasnot there earlier, which was done at other testing centres. Hence plan to go to a different place next time.
.

Last time I did a PUC test for storme was in 2020 before I went for my license test. You need to have the PUC of the vehicle you're taking the test in.

He just stuck a probe into the tailpipe and I held the car at idle for a bit and then 2k .

What are they trying to measure by monitoring the rpm?

[dinu2506]

Originally Posted by viXit

How the heck is he measuring RPM there??
like jeroen said , you shouldn't be getting any signal there

Well, my guess is that its a vibration sensor using which the engine rpm is determined. It could be attached anywhere on the engine area where there is a vibration, alternator mounting bolt could well be a suitable point. I've seen it on injector tops as well.
There's lot of documentation on the net on vibration sensors for determining rpm for engines.

[jkrishnakj]

Didn’t even know such an issue can arise. I have never faced this with my A6. Had done it twice driving into Maharashtra. Both were at the same place, just after Belgaum and it was a very quick job.

[condor]

Originally Posted by viXit

He just stuck a probe into the tailpipe and I held the car at idle for a bit and then 2k .

What are they trying to measure by monitoring the rpm?

I think composition of exhaust gas at idling and at running RPM. Both need to be consistent (below limits)

[GeeTee TSI]

Originally Posted by kiran_cr

The RPM sensor lead was just placed on the engine casing just below the engine cover. Test was done only with RPM values and not tail pipe exhaust.

I feel the center is just taking a shortcut here as the primary attribute to be measured is the tailpipe emissions with the rpm merely the operating condition to be maintained

[Cresterk]

Originally Posted by superbad

I've only seen tail pipe emissions being checked. Have never seen any other test being conducted for PUC, nor done for any of my vehicles. Is the rpm test done only for high end diesel vehicles?

Yeah same experience here. They just stick a sensor in the exhaust pipe, tell me to turn the car on, generate a certificate and I leave all in like 5 mins. They have never asked me to rev the engine or anything and the first time I was rather confused whether the test had even started. I'm guessing we have been going to PUC centers that aren't actually conducting the tests

[Learner]

Originally Posted by dinu2506

...
There's lot of documentation on the net on vibration sensors for determining rpm for engines.

Since to get PUC certificate for diesel cars, engine is required to be revved that's why PUC centers have to determine the RPM. However I am not able to understand how RPM detection can lead to measurement of pollutants in the exhaust pipe.Maybe some knowledge person can explain the science behind this. I am guessing the PUC centre guy is generating fake reports so that he can earn the fee from every car that comes.

[anshumandun]

Originally Posted by superbad

An ultra noob question : if it's puc, why isn't it through the exhaust pipe?

Here's a noob answer: For petrol powered vehicles (Cars and motorcycles), emission testing is done by placing the sensor on the tail pipe end. For diesel powered vehicles, the sensor is placed in the engine bay.

I wish I knew WHY! Does anyone know?

[Jeroen]

There is absolutely No WAY to measure anything in the exhaust gasses in the engine bay. You need something in the exhaust pipe to measure the exhaust gasses. It is not just the engine but also the proper functioning of the catalytic converter that gets measured this way.

Whatever they attach inside the engine bay is just some pick up device for the RPM. But RPMs don’t and can’t tell you anything about what spews out of your exhaust pipe.

In some countries the MOT is done without the exhaust check on modern cars. As longs as your Check Engine Light doesn’t come on it is considered fine.

Jeroen

[RedOne]

My Montero too frequently have had this issue of no reading from engine bay points.

The way I have understood it, is that Pollution is measured as exhaust gas components at a certain RPM. When they have used an exhaust probe, they rev the engine to 2500 rpm and measure exhaust gases. About 50% of the time, the PUC check place does not do this and just connects two leads to the engine bay. When questioned, each guy gives a different answer as to why a exhaust probe is not used. Interestingly, my petrol car is always checked using an exhaust probe!

My guess is, the place which do not use an exhaust probe is not doing any pollution check and is simply printing a PUC certificate using the rpm readings, to get Rs 150.

[sgm]

For guys in Bangalore Indira Nagar or Old Airport road area, there is one in Jeevan Bhima Nagar IOC.
I faced the same issue with my C220d in Bangalore, near Old Airport area. I visited a couple of them and none was ready saying they won't get any reading. Finally I went to Jeevan Bhima Nagar area, IOC bunk where I had got it done last time. The guy was not interested but when I showed him last years’ PUC from him, he agreed and got it done. I was curious and quizzed he mentioned that it was a time waste for him as these cars take more time like 5-10min. There was none waiting and I was amused at his laziness

Now comes the real funny part. I took Corolla Altis petrol for PUC in Kormangala area and the guy really struggled get some reading and he did some jugaad to give me a PUC certificate with some reading, quite strange for a petrol car

[rakesh_r]

I am getting PUC for a period of 6 months only, reason, some genius at the RTO mapped my 2016 SCross 1.6 as BS3. This issue happened after i got the hypothecation removed with an update in my residential address which warranted a change in the RTO (MH12 to MH14).

[shankar.balan]

Originally Posted by rakesh_r

I am getting PUC for a period of 6 months only, reason, some genius at the RTO mapped my 2016 SCross 1.6 as BS3. This issue happened after i got the hypothecation removed with an update in my residential address which warranted a change in the RTO (MH12 to MH14).

I have 1 BS3 and 1 BS4 vehicle. They give only 6 months PUCC for these. It is only the BS6 vehicles whose PUCC’s are given for 1 year.

[rakesh_r]

Originally Posted by shankar.balan

I have 1 BS3 and 1 BS4 vehicle. They give only 6 months PUCC for these. It is only the BS6 vehicles whose PUCC’s are given for 1 year.

But the certificate clearly states "BS3" despite my car being BS4.