[BikerKeeda]

Hi,

I recently installed a sequential CNG kit with a timing advancer in my 2013 Alto K10.

ODO: 80k ish when fitment was done. The engine is in top condition, as the car is single-hand used and maintained properly.

Issue after fitment:
At low rpms (800-1800) when I press the gas pedal ( literally a gas pedal), suddenly, the rpm goes down for a second and a half and then go up. It makes the car stall. This happens whenever I want more power and I want to drive with half clutch. If I press is hard, the rpm goes down and the engine stalls.

There is a clear lag between the accelerator being pressed and the response from the car.

I don't know how to put it in technical words. Apologies for that.

The mechanic reduced the Spark plug gap, but it worsened the problem. The car now shuts off at low speeds randomly. If anyone is well-versed with CNG components and their working, kindly help me find the fault. I don't want to keep revving my car hard.

Also, please suggest the spark plug gap for the Alto CNG. Will rectify it.

TIA! Cheers!

[svsantosh]

Find a better equipped CNG retrofitter in Pune. Your current mechanic knows very little about his job.

After a critical job like fuel system mod (LPG/CNG) you need to drive with the retro fitter along side with his laptop and he should tune the CNG system (2nd ECU) to suit your needs. It appears that he has set the tune to too lean to give you more than normal fuel efficiency.

You would need to drive the car and the tuner has to tune the system based on your driving style for over 30-50 kms, both in cold start and traffic conditions and mainly WOT.

Put back original and new MGE spark plugs and drive in petrol till you find a CNG shop who can read this post and say 'yes sir, I can help you out'.

[GTO]

Like a turbocharger, IMHO, a CNG fitment too is best done at the factory. 2nd choice, the authorised dealer with the manufacturer's support (as with some Hyundais). But I'm no fan of after-market CNG fitments. Whether in the short-term or long-term, have only heard of problems. Plus, the tuning is never as good.

To me, factory fit is factory fit. Just look at the new Tiago / Tigor CNG. What a perfectly-executed CNG installation. The quality is something aftermarket guys can only dream of.

[asit.kulkarni93]

Check the igniter and spark plugs. Preferably replace both of them. Clean the throttle body. Check the car on petrol after doing the above things. If it works well then take it to the CNG installer and get him to tune the kit.

[Shreyans_Jain]

Your installer screwed up. The tuning of the kit is not right. That’s kind of surprising, because it is very rare that someone messes up the tune of a sequential kit on a Maruti car. It’s their bread and butter! Clearly, that person didn’t know what he was doing. Take the car to another shop and let them have a go at it. I am assuming your air filter is new, throttle body is clean and the spark plugs and ignition coils are in good shape. A simple coding job with a laptop should set things right.

[Rshrey22]

Change spark plugs and ask the tuner to reflash the tune. Weak spark plug can cause plethora of problems in cng cars.

[deehunk]

Originally Posted by BikerKeeda

Hi,

I recently installed a sequential CNG kit with a timing advancer in my 2013 Alto K10.

I don't know how to put it in technical words. Apologies for that.

The mechanic reduced the Spark plug gap, but it worsened the problem. The car now shuts off at low speeds randomly. If anyone is well-versed with CNG components and their working, kindly help me find the fault. I don't want to keep revving my car hard.

TIA! Cheers!

The problem is at higher rpm, per my long experience and knowledge about LPG/CNG kits this can be an injector rail issue, there is not enough fuel at higher rpm, and the vehicle is getting stalled. It may have been that your installer has not tested the vehicle properly at higher RPMs while calibrating the CNG ECU. There is not much use in changing spark plugs. The vehicle needs proper tuning and no other issues.

[AutoNoob]

Originally Posted by BikerKeeda

Issue after fitment:
At low rpms (800-1800) when I press the gas pedal ( literally a gas pedal), suddenly, the rpm goes down for a second and a half and then go up. It makes the car stall. This happens whenever I want more power and I want to drive with half clutch. If I press is hard, the rpm goes down and the engine stalls.

There is a clear lag between the accelerator being pressed and the response from the car.

Originally Posted by svsantosh

you need to drive with the retro fitter along side with his laptop and he should tune the CNG system (2nd ECU) to suit your needs. It appears that he has set the tune to too lean to give you more than normal fuel efficiency.

Originally Posted by deehunk

The problem is at higher rpm, per my long experience and knowledge about LPG/CNG kits this can be an injector rail issue, there is not enough fuel at higher rpm, and the vehicle is getting stalled. It may have been that your installer has not tested the vehicle properly at higher RPMs while calibrating the CNG ECU.

True. Even I feel its tuning issue. If the CNG flow is too lean, it'll result in stalling. I have seen similar power-loss in initial batch of Hyundai CNG vehicles. CNG pressure drop in intake circuit due to calibration and delay between Engine ECU & CNG ECU were key root causes.

So, I agree with suggestions :

1. get your vehicle checked/ re-calibrated at another retro-fitter
2. revert to standard spark plugs as they may cause problems even in petrol mode

[X-Saint]

1. Which CNG Brand is fitted?
2. Is the Car Giving the same problem with Petrol or is it missing on Petrol?
3. The first step is to clean the throttle body.
4. If throttle body cleaning does not help, then scan it with an OBDII scanner, you can do it yourself by ordering the OBDII scanner from amazon (It costs around 350 INR).
5. If it shows Error Codes P300 to P304 with the error message Cylinder misfire detected, then the issue is mostly with Spark Plugs, Spark Plug Cables, or Spark Plug Coils. Do it step by step by first changing the plugs, then plug wires, then finally coils.

[Mechb63]

Faced a similar issue in my Grand i10 which also runs an aftermarket CNG kit.

As mentioned by other members, the first step I took was to change the spark plugs and have the throttle body cleaned.

Yet the problem persisted, only when running the car on CNG, everything was fine on petrol.

Then I took a trip to the place where the kit was fitted, had one of their guys join me for a drive and 30 minutes later, the car was tuned to my needs.

I was told that a bad spark plug on CNG cars can really mess with the CNG ECU and cause various problems like harsh vibrations, stalling at random rpm and loss of grunt to climb slopes. Gotta keep them in check from now.

Additionally, I've made it a standard practice to switch to CNG only when the car reaches its regular running temperature. The switch of fuels is instantaneous when the engine is hot enough.

[indianv2]

At 80K kms, your Alto is bordering on the life of the Ignition coils. With CNG, the toll on these is a bit higher. If you have never changed the spark plugs too, its the right time to change them - use NGK, they work well with CNG.

You might want to check the Air Filter hose as well - some installers reduce the diameter of the air filter hose by blocking some part of the pipe intake using duct/masking tape so that lesser air enters the air filter assembly.

As suggested by some members, the tuning for CNG is set to lean, typical of all installers as that's their first goal. Helps cabs though, we are better off setting it to a slightly higher tune.

Get the tuning done in a manner that the sequential gas injectors respond with additional gas when you step on the throttle.

If you have not installed a Timing Advance Processor (TAP), you might want to read/see a bit on the Internet/Youtube. It advances the engine timing by a bit when you run on CNG, helps negate the effect of the slow burning fuel i.e. CNG.

The Alto K10 is a pocket rocket on Petrol - this feel tapers off a bit once you start using CNG - a characteristic of the fuel since it burns a bit later and has a higher octane rating. You will get used to it once you start reaping the rewards of a higher mileage and lower cost on CNG.

[Herschey]

This looks like a typical case of poor tuning at the hands of the installer. Had it been weak spark-plugs or ignition coils, an expert installer would have pointed the same out right at the time of installation and tuning itself.

Since your engine has already done over 80k kms and seen quite a few years, the ignition coils might not be as strong and thus, a slightly lower gap of .65 - .75 mm can be maintained for the plugs. Check for the health of your ignition coils beforehand but don't extend the gap beyond .75 mm even if they look absolutely good to go.

The reason why a timing advancer is installed is because CNG is a dry fuel with a higher ignition temperature which can cause engine knocking under normal ignition cycle in vehicles using bi-fuel systems. A timing advancer basically advances the ignition timing by a few milliseconds to ignite CNG fuel a few milliseconds earlier than what the ECU typically would if the vehicle was running on petrol. A timing advancer thus helps in making the engine run smoother and perform better on the CNG system.

There might be one more reason why your car is rapidly dropping revs under mild acceleration and it might be due to an excessively lean or rich CNG to Air mixture. Do know that if the CNG concentration in the mixture goes below 5%, it simply won't ignite and if the CNG concentration in the mixture goes above 15%, it simply won't ignite. It seems the most likely reason in your case is a leaner fuel mixture which can be easily corrected through tuning.

Do also check on your engine oil quality and levels and replace it if required. In case you're using synthetic engine oil, make sure to replace it every 9-9.5k kilometres or 11 months, whichever is earlier. Ensure that you run your car for about a kilometre or till it reaches ambient engine temperature when you start it in the morning and a km before you are about to park for the day. This would keep the engine valves in good health over time. Change the air filter every 4.5-5k kilometres or 6 months, whichever is earlier.

[yogeshnagpal]

Originally Posted by BikerKeeda

Hi,

I recently installed a sequential CNG kit with a timing advancer in my 2013 Alto K10.

ODO: 80k ish when fitment was done. The engine is in top condition, as the car is single-hand used and maintained properly.

Issue after fitment:
At low rpms (800-1800) when I press the gas pedal ( literally a gas pedal), suddenly, the rpm goes down for a second and a half and then go up. It makes the car stall. This happens whenever I want more power and I want to drive with half clutch. If I press is hard, the rpm goes down and the engine stalls.

There is a clear lag between the accelerator being pressed and the response from the car.

I don't know how to put it in technical words. Apologies for that.

The mechanic reduced the Spark plug gap, but it worsened the problem. The car now shuts off at low speeds randomly. If anyone is well-versed with CNG components and their working, kindly help me find the fault. I don't want to keep revving my car hard.

Also, please suggest the spark plug gap for the Alto CNG. Will rectify it.

TIA! Cheers!

Originally Posted by GTO

Like a turbocharger, IMHO, a CNG fitment too is best done at the factory. 2nd choice, the authorised dealer with the manufacturer's support (as with some Hyundais). But I'm no fan of after-market CNG fitments. Whether in the short-term or long-term, have only heard of problems. Plus, the tuning is never as good.

To me, factory fit is factory fit. Just look at the new Tiago / Tigor CNG. What a perfectly-executed CNG installation. The quality is something aftermarket guys can only dream of.

So, here's the thing - I've used CNG in over 5 cars since the year 2010.

Link to my earlier thread -

https://www.team-bhp.com/forum/long-...ms-review.html (CNG'ed my 2002 ZEN MPFI : 1500 km's review)

Here are the cars I used on CNG, and the type of kit-

1. 2002 Zen MPFI - Closed Loop - Done over 50k kms on CNG
2. 2004 Corolla H4 AT - Sequential CNG - Done 50-60k kms on CNG
3. 2009 Civic V AT - Sequential CNG
4. 2007 Corolla H4 AT - Sequential CNG - Done 40k kms on CNG
5. 2010 Altis VL AT - Sequential CNG - Done 20-30k kms on CNG


Each of the above cars were well over 1 lac kms when I sold them after using for a couple of years.


What matters the most in a CNG conversion is the component quality, followed by the way the kit is installed. Even if the kit is top notch, but installation isn't upto the mark, the performance will be poor.

There are hardware settings, and then there is a software map that decides the quantity of fuel that gets injected into the manifold, depending on various parameters. These parameters are detected basis hardware tuning. So it is of utmost importance that the hardware and the ECU map (CNG ECU
as well as your main ECU) are in sync.

In each of these cars, I NEVER faced any issues on CNG.

Everytime I got it done from the same workshop as indicated in my earlier thread.


They also have a branch at Pune - You may want to Google and connect with them. I'm sure they will be able to help you out.

Cheers,
Yogesh.

[BikerKeeda]

Originally Posted by svsantosh

Find a better equipped CNG retrofitter in Pune. Your current mechanic knows very little about his job.

You would need to drive the car and the tuner has to tune the system based on your driving style for over 30-50 kms, both in cold start and traffic conditions and mainly WOT.

He hardly accompanied for 5 kms for tuning and he as well as the owner refused to accept that the problem exists. Which frustrated me a lot and I decided to visit other centers for their diagnosis.

Originally Posted by asit.kulkarni93

Check the igniter and spark plugs. Preferably replace both of them. Clean the throttle body. Check the car on petrol after doing the above things. If it works well then take it to the CNG installer and get him to tune the kit.

Originally Posted by Rshrey22

Change spark plugs and ask the tuner to reflash the tune. Weak spark plug can cause plethora of problems in cng cars.

Plugs were installed 10K kms before the installation, sill thinking of changing them again, any recommendation on how can I check the coil's health?

Originally Posted by Shreyans_Jain

Your installer screwed up. The tuning of the kit is not right. That’s kind of surprising, because it is very rare that someone messes up the tune of a sequential kit on a Maruti car. It’s their bread and butter!

True that

Originally Posted by deehunk

The problem is at higher rpm, per my long experience and knowledge about LPG/CNG kits this can be an injector rail issue, there is not enough fuel at higher rpm, and the vehicle is getting stalled. It may have been that your installer has not tested the vehicle properly at higher RPMs while calibrating the CNG ECU. There is not much use in changing spark plugs. The vehicle needs proper tuning and no other issues.

Problem is at lower RPMs not higher, it stalls when vehicle needs power while running at 1000+- 100 rpm

Originally Posted by AutoNoob

So, I agree with suggestions :

1. get your vehicle checked/ re-calibrated at another retro-fitter
2. revert to standard spark plugs as they may cause problems even in petrol mode

Visiting other installers, will keep you posted

Originally Posted by X-Saint

1. Which CNG Brand is fitted?
2. Is the Car Giving the same problem with Petrol or is it missing on Petrol?

installed Tomasetto kit, and there is not problem in Petrol

Originally Posted by Mechb63

Faced a similar issue in my Grand i10 which also runs an aftermarket CNG kit.

Additionally, I've made it a standard practice to switch to CNG only when the car reaches its regular running temperature. The switch of fuels is instantaneous when the engine is hot enough.

I need to try this, seems like a good practice.

Originally Posted by indianv2

At 80K kms, your Alto is bordering on the life of the Ignition coils. With CNG, the toll on these is a bit higher. If you have never changed the spark plugs too, its the right time to change them - use NGK, they work well with CNG.

Get the tuning done in a manner that the sequential gas injectors respond with additional gas when you step on the throttle.

If you have not installed a Timing Advance Processor (TAP), you might want to read/see a bit on the Internet/Youtube. It advances the engine timing by a bit when you run on CNG, helps negate the effect of the slow burning fuel i.e. CNG.

Need to check coils, already using NGK plugs 12k kms old. Advancer is installed.

Originally Posted by Herschey

Since your engine has already done over 80k kms and seen quite a few years, the ignition coils might not be as strong and thus, a slightly lower gap of .65 - .75 mm can be maintained for the plugs. Check for the health of your ignition coils beforehand but don't extend the gap beyond .75 mm even if they look absolutely good to go.

Cheers,
Yogesh.

This is really informative. And thank you for the contact you provided, I visited the center this morning, the mechanic and owner checked the car and told me there is no problem with tuning or the kit and I need to replace the VALVE STRINGS from service center. It will cost me around 10k INR according to his estimate. He quoted VALVE STRINGS typically need a replacement @1Lac +-20k kms.

I will now visit 2-3 more installers for checking what they think about the problem before I go to service center for any head related work.

I've been searching about VALVE STRINGS and I couldn't find any information. Whenever I search valve strings I get results for Valve Springs (-_-)

If anyone has any idea about it, kindly share more details.

Thanks in advance!!

Cheers!!

[Rshrey22]

Originally Posted by BikerKeeda

Plugs were installed 10K kms before the installation, sill thinking of changing them again, any recommendation on how can check I coil health

Maruti coils don't fail so early, 80k kms are nothing. Just find some good spark plugs and ask the CNG guy to reflash the tune. Tomasetto kit is very good.

It does take one or two visits to the installer to fine tune the system. Be patient, drive the car a little bit so that the CNG ECU calibrates itself to maintain idling RPM. And visit the installer once to fine tune the sharp edges.