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Old 16th January 2015, 11:10   #1
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Default DIY: Pictorial guide to tuning CNG & LPG systems

I was tired of going to numerous mechanics for CNG tuning, who will try to rip you off. Hence I did a course on LPG and CNG systems while I was in Europe.

Here is my guide to having a perfectly running and tuned CNG/LPG system. This guide applies only to Open loop/ Closed loop kits (venturi based systems).

Before we start, we are assuming that the following systems are fine:
  1. Engine is in good condition
  2. Ignition system is in good condition
  3. If your car has a distributor, then the vacuum advance mechanism works fine
  4. Your sparks plugs are in good condition and are gapped correctly to 0.5-0.7 mm
Once the above are done, you can continue.
  1. Switch off your car
  2. Remove the low pressure gas pipeline from the reducer to the mixer
  3. Tighten both the screws (Idle screw and sensitivity) on the mixer completely, be careful to write down the number of turns in-case you mess up
  4. My reducer has two electro-valves, but yours may have just one, this is not a matter of concern. Connect the POSITIVE contact of the valve to the battery directly, you will hear an audible click, signalling that the valve is open
  5. Form a soapy solution and apply it over the gas outlet tube on the reducer
  6. Then start to loosen the sensitivity screw 1/2 turn at a time till gas begins coming out of the tube and starts to inflate the bubble
  7. The moment gas begins to come out of the tube, re-tighten the sensitivity screw till gas stops coming out, giving it an extra half-turn for safety
  8. You have now successfully adjusted the sensitivity of the reduction unit
  9. Remove the wire you had attached to the battery -electro valve
  10. Connect the low pressure pipeline back to the reducer
  11. Now loosen the idle adjustment screw the same number of turns you had written down in step no. 3
  12. Start your car and unscrew the bolt holding down the screw on the peak adjustment flow valve
  13. Hold down the throttle to a steady RPM, then start tightening the flow valve till the engine starts to crumple, at this point loosen the valve till the engine revvs freely
  14. Then adjust RPM with the help of the idle adjustment screw, till the car runs smoothly
  15. Repeat steps 12-14, till no further improvements are gained
  16. Switch off the car and start it again. If it takes too long to start, adjust the idle screw by 1/4 of a turn
Remember, tightening the idle screw will make you run leaner, and loosening it will make it richer
The pictures I have taken are of the legendary Landi Renzo TN1 kit installed on the Padmini S1, but this guide applies to all Venturi-based kits.

If yours is a closed loop kit, please don't do step 13, as you will have a Lambda control module and stepper motor doing this for you.

This guide applies to both LPG and CNG systems.

Pictures follow:
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Last edited by GTO : 16th January 2015 at 12:10. Reason: Inserting attachments within the post :) Thanks for sharing!
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Old 16th January 2015, 21:36   #2
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Very nice information. Can we have something for sequential kit also. I know tuning it needs a laptop, but other aspects to get the service will be a nice help.

Last edited by GTO : 18th January 2015 at 14:28. Reason: Typos
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Old 17th January 2015, 10:49   #3
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Default Re: DIY: Pictorial guide to tuning CNG & LPG systems

Quote:
Originally Posted by saurabhkum View Post
Very nice information. Can we have something for sequential kit also. I know tuning it needs a laptop, but other aspects to get the service will be a nice help.
Thanks!
Well, technically, once the gas ECU has been calibrated it does not need to be done again, unless the calibration was incorrect.

I will post regarding sequential kits as well!

Last edited by GTO : 18th January 2015 at 14:29. Reason: Quoted post edited
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Old 17th January 2015, 14:50   #4
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Default Re: DIY: Pictorial guide to tuning CNG & LPG systems

I would recommend having a basic set of first aid necessities and also more importantly a fire extinguisher setup handy while dealing with compressed inflammable gases.
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Old 17th January 2015, 18:58   #5
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Default Re: DIY: Pictorial guide to tuning CNG & LPG systems

Quote:
Originally Posted by dileepcm View Post
I would recommend having a basic set of first aid necessities and also more importantly a fire extinguisher setup handy while dealing with compressed inflammable gases.

I was wearing gloves and eye protection.
A fire extinguisher is always present in all my cars.
I was only dealing with the low pressure side of the gas, hence nothing to worry about!
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Old 17th January 2015, 19:57   #6
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Default Re: DIY: Pictorial guide to tuning CNG & LPG systems

IIRC, CNG is combustible at certain range of temperatures only and also escapes in to air very quickly. Compared to petrol, diesel or the worst of all - petrol fumes, it is many times less probable to catch fire or cause fire hazards. This is what I remember from reading on one of the many safety aspects of CNG. Someone could confirm this by posting appropriate links if available.

That being said, I am in desperate need of knowledge on sequential CNG kits. Especially, what maintenance is required and at what intervals. Any replacement parts et al.
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Old 17th January 2015, 20:05   #7
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Default Re: DIY: Pictorial guide to tuning CNG & LPG systems

Quote:
Originally Posted by jagzrk View Post
IIRC, CNG is combustible at certain range of temperatures only and also escapes in to air very quickly. Compared to petrol, diesel or the worst of all - petrol fumes, it is many times less probable to catch fire or cause fire hazards. This is what I remember from reading on one of the many safety aspects of CNG. Someone could confirm this by posting appropriate links if available.

That being said, I am in desperate need of knowledge on sequential CNG kits. Especially, what maintenance is required and at what intervals. Any replacement parts et al.
You are absolutely correct about it being safer than petrol.The density is much lower and hence it does not 'pool'

What exactly is the problem you are facing with yourCNG kit?

Maintainance in a sequential cng kit would be as follows:
  1. Replacing CNG filter, (this is look like a soda can, in between the reducer and the injector rail)
  2. Cleaning the MAP sensor
  3. Changing spark plugs and gapping themto about 0.5-0.7mm
  4. Draining the oil from the CNG reducer
  5. You may also need to clean the gas injectors,but this is very very rare
Do let me know what the symptoms you are facing
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Old 17th January 2015, 20:10   #8
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Default Re: DIY: Pictorial guide to tuning CNG & LPG systems

Quote:
Originally Posted by HimuraKenshin View Post
Do let me know what the symptoms you are facing
Thanks for listing out the check-list. Will definitely check with my installer as the CNG installation will be exactly one year old in Feb. I am facing no issues with the CNG kit as far as driving is considered and the drive is perfect. It is a minor niggling issue with the indicator as mentioned here (last post): http://www.team-bhp.com/forum/modifi...ersion-35.html (Advice on CNG Conversion)
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Old 17th January 2015, 21:40   #9
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Quote:
Originally Posted by HimuraKenshin View Post
Maintainance in a sequential cng kit would be as follows:
  1. Replacing CNG filter, (this is look like a soda can, in between the reducer and the injector rail)
  2. Cleaning the MAP sensor
  3. Changing spark plugs and gapping themto about 0.5-0.7mm
  4. Draining the oil from the CNG reducer
  5. You may also need to clean the gas injectors,but this is very very rare
Do let me know what the symptoms you are facing
Wow, this is amazing piece of information. Well as far as my fitment goes, it doesn't have cng filter installed. At least I couldn't find it anywhere in my installation. Coming to 2nd point of map sensor, how to get it cleaned ? Does the throttle body cleaning take care of map sensor also ? Spark plug gap in my car is at 0.9, the plugs used are ngk. The same plugs which are used in Stock santro, does it need to be corrected ? How to get the oil removed from reducer ? I don't know if it has been ever done in my car. I've a civic which has run 63k km out of which 34k km has been on cng. I'm very tempted to come to you and get these things done. Do let me know if you can help me on the same.

My issue faced is that sometimes on cng with ac on the car stalls. It happens only in traffic situations when the rpm and speed is very low. Can you help me in identifying the situation.

Last edited by GTO : 18th January 2015 at 14:31. Reason: Typos
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Old 17th January 2015, 21:42   #10
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Default Re: DIY: Pictorial guide to tuning CNG & LPG systems

Quote:
Originally Posted by jagzrk View Post
I am facing no issues with the CNG kit as far as driving is considered and the drive is perfect. It is a minor niggling issue with the indicator as mentioned here (last post): http://www.team-bhp.com/forum/modifi...ersion-35.html (Advice on CNG Conversion)
I read your problem. This most likely is caused because of a faulty CNG manometer (CNG pressure gauge)
These gauges have a variable resistor that increases and decreases resistance based on the pressure of gas available in the tank.
Ive noticed some CNG pressure gauges failing after a pressure wash/ contact with water.
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Old 18th January 2015, 00:44   #11
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Default Re: DIY: Pictorial guide to tuning CNG & LPG systems

Quote:
Originally Posted by saurabhkum View Post
My issue faced is that sometimes on cng with ac on the car stalls. It happens only in traffic situations when the rpm and speed is very low. Can you help me in identifying the situation.
Hi,
The plug gap needs to be reduced slightly for CNG as it requires a hotter spark to ignite, since you have a sequential kit, i would recommend .7mm
A CNG filter is extremely necessary in case of a sequential kit because of the following reasons:
  • because CNG is not a gas that is refined in a plant. Loosely speaking, CNG is a gas that has atleast 70%methane. The gas that you get is almost directly piped from a CNG well. Hence has some contaminents.
  • The CNG compressors in most of the pumps are worn out and spew compressor oil and other debris.
All these need to be filtered out before the gas reaches the injector rail as contaminants can block the injectors.


There is a small nut located below the reducer,(usually no 12) that needs to be opened to drain the oil out.


The CNG MAP sensor is different from the pre installed MAP sensor, and most retro-fitters tend to mount it externally. it just needs to be removed and cleaned.


About your car stalling isssue, it sounds like the gas supply being inadequate during slo acceleration. This is most likelycaused by the reducer sensitivity not being adjusted correctly.


Also, about coming to me for the work, im honoured, but i dont have a garage, and sadly i work in luxury brand marketing, rather than the automotive sector

But i'll be glad to help you out!

Last edited by GTO : 18th January 2015 at 14:32. Reason: Quoted post edited
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Old 21st January 2015, 17:43   #12
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Default Re: DIY: Pictorial guide to tuning CNG & LPG systems

Quote:
Originally Posted by HimuraKenshin View Post
Ive noticed some CNG pressure gauges failing after a pressure wash/ contact with water.
Spot-on! This problem appeared after an engine bay washing at Crystal Honda during the last service. This must be the reason. I really hope it isn't a pressing issue and can get it rectified when I hit the 20K (67K -> 87K) mark after installing CNG. That is when I plan to get the entire CNG kit checked and serviced. I am currently at 85K.

As far as I can understand, a sequential CNG kit can be serviced at a proper facility itself and may not be a DIY job. Also, its really hard to find good CNG servicing guys, though installers are in the many. Would be great to know someone in Pune / Mumbai who does a good job at maintaining / servicing CNG kits.
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Old 23rd January 2015, 18:47   #13
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Default Re: DIY: Pictorial guide to tuning CNG & LPG systems

Quote:
Originally Posted by jagzrk View Post
Spot-on! This problem appeared after an engine bay washing at Crystal Honda during the last service.
Do let me know what happens after you change the pressure gauge.

As i said before, if a sequential CNG system is tuned properly once, you neednt tune it again. but if it is not tuned well, you may need re-caliberation

The filters and other things can be done as a DIY. Since they are on the low pressure side of the system, they are only held in place by 2 pipe clamps..

Do post some pictures of the engine bay, ill try my best to help you
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Old 24th January 2017, 22:46   #14
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Default Re: DIY: Pictorial guide to tuning CNG & LPG systems

For the last one or two months particularly since the cold season started, I have been facing severe problems with the idling only while the vehicle is on CNG. It turns worse when the gas tank is filled. Each time I applied brakes or held the clutch, the engine would stall and during slow stalling, the vehicle vibrates with the RPM needle going up and down. I went through this thread and tried adjusting both the peak as well as what I assumed was the idle adjustment screw. However, the things have just gotten worse. My car used to work beautifully in terms of pickup. But I don't know what I did wrong but the pickup has turned worse. No alternations to the pickup adjustment screw is fixing it and instead only making it worse. The idle performance has become slightly better but I don't know what I should be doing to solve the acceleration issue. I can go up to 1500 RPM but not more. With the accelerator pressed to the fullest, it doesn't go beyond that. However, I should point out that when I accelerate very slowly and after the needle crosses 2500 RPM, it zooms ahead to as high as I want to raise it. When I have to increase the speed of the vehicle, I always have to bring it down to gear 3 and then accelerate because if lets say the car is moving at 40kmph on 4th gear at an RPM of 2000, I simply can't make it budge ahead unless I bring the gear down to 3rd.

Could you please guide me with what I should be meddling with to fix this problem?

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Last edited by aah78 : 25th January 2017 at 01:01. Reason: Text format tags removed.
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