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Old 29th November 2011, 18:39   #31
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Default Re: CNG'ed my 2002 ZEN MPFI : 1500 km's review

I am not able to see any link to PM you. Is it because I am a newbie ?
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Old 30th November 2011, 10:39   #32
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Default Re: CNG'ed my 2002 ZEN MPFI : 1500 km's review

Idea,

I tried to PM you. I got the following message on that page:

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You do not have permission to access this page. This could be due to the following reason:

Your user account may not have sufficient privileges to access this page.
Please refer to the Announcements section of this forum where different membership levels are explained in detail.
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So I dont think I will be able to PM you. Plz. PM your number/email id to me. I will call you.
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Old 16th December 2011, 12:17   #33
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Default Re: CNG'ed my 2002 ZEN MPFI : 1500 km's review

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Originally Posted by SAS View Post
2. The installation is an open loop system with advancer. I did not put a lamda sensor because i didn't want to complicate the installation. Besides I'm well versed on how to tune the AFR manually
You mentioned above that you are well versed with tuning a open loop cng system, so i got a few questions for you and other who know hw to tune a open loop cng system...

1. My car is original tuned and been running on the stock filter for 2500km. (open loop + advancer on a santro)
I tried fitting my old k&n conical filter back to the car. once the car was warmed, the car revved OK, but would not idle. it just died. refitted the stock filter and its idling fine.
I assume the extra air allowed by the k&n is messing up the AFR on idle.

How can i re-tune this myself to work with the K&n. I wish to see the effect of the k&n on power delivery and FE. And the installer is a bit too far away for this DIY.

Mine being a open loop system has a screw type nut instead of the stepper motor. Pic attached.

Any suggesting on the tuning process - increase gas flow by turning the flow screw nut, clockwise or anticlockwise, OR is there another method.
any other steps i need to follow to get the idling correct with the k&n.



My biggest concern is that this DIY should be completely revers-able, in case the effect of the k&n is not to my liking.

UM
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Last edited by UniqueMods : 16th December 2011 at 12:21.
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Old 16th December 2011, 21:13   #34
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Default Re: CNG'ed my 2002 ZEN MPFI : 1500 km's review

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You mentioned above that you are well versed with tuning a open loop cng system, so i got a few questions for you and other who know hw to tune a open loop cng system...

1. My car is original tuned and been running on the stock filter for 2500km. (open loop + advancer on a santro)
I tried fitting my old k&n conical filter back to the car. once the car was warmed, the car revved OK, but would not idle. it just died. refitted the stock filter and its idling fine.
I assume the extra air allowed by the k&n is messing up the AFR on idle.

How can i re-tune this myself to work with the K&n. I wish to see the effect of the k&n on power delivery and FE. And the installer is a bit too far away for this DIY.

Mine being a open loop system has a screw type nut instead of the stepper motor. Pic attached.

Any suggesting on the tuning process - increase gas flow by turning the flow screw nut, clockwise or anticlockwise, OR is there another method.
any other steps i need to follow to get the idling correct with the k&n.



My biggest concern is that this DIY should be completely revers-able, in case the effect of the k&n is not to my liking.

UM
Like you have correctly mentioned, the mixture has become lean with the K&N allowing more air and less CNG. Plus the fact that winter has set in also compounds the problem.

Don't worry about having to reverse or undo anything. There is absolutely no harm which can be done by tuning your car. If you are used to adjust older carburetor equipped vehicles, this process should be easier.

Here's how you tune the engine.

1. Let the car warm up. The car should be nice and warm. At least a 15 minute run is recommended before trying to set this. Maybe you can do the tuning after you come back from an errand
2. Now mark the position where the screw is currently on the area where you have labelled as manual power valve. Use a marker, nail polish or any other thing with which you can get the position. This is important so that you can reverse the settings if you are not happy.
3. Rev the engine to around 2500 rpm or so by pulling on the throttle body and hold it in a constant position. Then begin to move the screw anticlockwise. This is just like opening or closing a tap. Mixture becomes richer when you open it and leaner when you close it.
4. The revs shall automatically rise further from where you are holding it. At the best mixture, it shall be the highest. If you make it more rich, it shall then drop. Do this till you arrive at the highest rpm. You can go by your ear if you don't have a tachometer.After you arrive at the best tuning, leave the throttle body and let the rpm drop to idling.
5. Once this is done, then the main adjustment has been set. Now you can proceed to adjust the idling.
6. The idling adjustment is on the reducer itself. It is another small screw. You should find it easily. Else post a pic and I'll help you.
7. Follow the same process. Open the screw (move it anticlockwise) to make it richer and the other way around to make it lean. If you have done it wrong, the car shall vibrate higher or switch off like in your case.
8. After both have been set, take your car for a test drive. If you find it getting choked (dying) when the rpm is low / moderate and you suddenly open the throttle, then the mixture is slightly rich. Minutely adjust the main valve by rotating it clockwise, but not more than 1/8th of a turn at a time. This road test type adjustment is necessary since when you adjust with step 4 above, there is very little load on the car. When you actually drive it, the car may perform marginally differently and you may get a slightly better tuning. At least this is my experience.
9. If you have to press the throttle hard to get power, then obviously the mixture is lean. Make it richer.
10. Once this is done, relax and take off on a nice drive with your spouse and be happy that you tuned your CNG car yourself

Don't worry about reversing anything. It can be easily done. There is no way you can harm your engine in any way. Take courage in the fact that if simple roadside mechanics who barely understand physics can tune your CNG car, you can do better with knowledge, love of your car and a more detailed understanding on how your car performs.
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Old 16th December 2011, 22:22   #35
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Default Re: CNG'ed my 2002 ZEN MPFI : 1500 km's review

HEY SAS,

Firstly thanks for the brilliant and very useful answer. I would also like to be benefitted from your knowledge. I too have a Santro fitted with CNG. During the CNG mode, the car runs like a dream, where as in petrol i could literally smell the unburnt fuel from the exhaust and the car runs with alot of jerks. the ride is not smooth at all.

Seems like, during petrol mode, O2 sensor is not working or being bypassed and the car is running is safe mode. I did try to solve it, but all the efforts has been in vain.

Thanks in advance.

Amit
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Old 17th December 2011, 11:31   #36
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Default Re: CNG'ed my 2002 ZEN MPFI : 1500 km's review

@amitpujbabi I'm not sure where the problem could lie. Is this a new problem occuring several months after CNG conversion or did it occur ever since you converted to CNG?

The best thing to do is take it to your auth service center which you normally give your car for servicing. Could be that the throttle body or the injectors are dirty. My wife's Santro too had a rough idle and it was diagnosed to the throttle body being dirty. The CNG installation IMHO should not affect your car's petrol performance, so I suggest you take it to the authorized service center.
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Old 17th December 2011, 13:53   #37
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Default Re: CNG'ed my 2002 ZEN MPFI : 1500 km's review

Hi SAS,

All being done, replacement of fuel filter, injector cleaning. throttle boddy cleaning what ever you can imagine i have done with the fuel system.But the problem still persists.

In the Petrol mode, the mileage is extremely low. In the exhaust pipe, i see the carbon of unburnt fuel.

Thanks

Amit
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Old 17th December 2011, 20:50   #38
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Default Re: CNG'ed my 2002 ZEN MPFI : 1500 km's review

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Hi SAS,

All being done, replacement of fuel filter, injector cleaning. throttle boddy cleaning what ever you can imagine i have done with the fuel system.But the problem still persists.

In the Petrol mode, the mileage is extremely low. In the exhaust pipe, i see the carbon of unburnt fuel.

Thanks

Amit
Is this a new problem occuring several months after CNG conversion or did it occur ever since you converted to CNG?
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Old 17th December 2011, 20:57   #39
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Default Re: CNG'ed my 2002 ZEN MPFI : 1500 km's review

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Originally Posted by amitpunjani View Post
Hi SAS,

All being done, replacement of fuel filter, injector cleaning. throttle boddy cleaning what ever you can imagine i have done with the fuel system.But the problem still persists.

In the Petrol mode, the mileage is extremely low. In the exhaust pipe, i see the carbon of unburnt fuel.

Thanks

Amit
I have no idea about the unburnt fuel thing, but my petrol mileage also decreased after CNG conversion. I think this is bound to happen. In a petrol only car, majority of your petrol consumption happens on the top gears. However, once you convert to CNG, the majority of your petrol driving happens in the lower gears - majority of the time, when you are in the higher gears, you are running on CNG. So obviously, your mileage on petrol is bound to decrease. This is also why I feel the reported CNG mileage (20-25 for a car which gave 13-14 on petrol) is inflated. The CNG mileage is inflated because your car starting (and other lower gear driving) doesn't happen on CNG.

To check the actual petrol mileage - do a full journey on petrol & check.

Last edited by carboy : 17th December 2011 at 20:59.
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Old 18th December 2011, 11:52   #40
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Default Re: CNG'ed my 2002 ZEN MPFI : 1500 km's review

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I have no idea about the unburnt fuel thing, but my petrol mileage also decreased after CNG conversion. I think this is bound to happen. In a petrol only car, majority of your petrol consumption happens on the top gears. However, once you convert to CNG, the majority of your petrol driving happens in the lower gears - majority of the time, when you are in the higher gears, you are running on CNG. So obviously, your mileage on petrol is bound to decrease. This is also why I feel the reported CNG mileage (20-25 for a car which gave 13-14 on petrol) is inflated. The CNG mileage is inflated because your car starting (and other lower gear driving) doesn't happen on CNG.

To check the actual petrol mileage - do a full journey on petrol & check.

What system are you talking about. Open, Closed or Sequential.

the switch has 3 options CNG, Duel and Petrol.

In open loop and closed loop system, once you put the switch to Duel (Pertol+cng), no petrol is used at all. Not in 1st 2nd or any gear. you drive from 1000rpm to 6000rpm in cng only. not petrol.

Only if the car cuts off, the duel setting will allow it to start in pertol again and drive only on cng. only starting the engine is on petrol. Moment you accelerate, it goes to cng and stays in cng all the time.

I drive in petrol mode, only when the car starting up, to heat up the engine. then switch to duel.

I don't know about sequential, your logic could be for that.

My Santro doesn't give 25 kmpl, but 22 kmpl in the city is achievable.
in petrol only, my last trip outside mumbai, on the highway it still gave 17kmpl.
Even in the city i dont see any drop in petrol avg from before cng and after.

the best way to calc FE is -
--------------------------
180 km in 8kg of cng = 22.5
heating up the car twice a day in petrol = 4km

if one cng tank last 5 days = 4x5 = 20km
minus 20 km from the 180km= 160 km only cng running
160/8 = 20km/kg of cng ... true cng FE

monthly 4 x 30 = 120km on petrol = 600 to 700 inr of petrol.




UM

Last edited by UniqueMods : 18th December 2011 at 12:17.
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Old 18th December 2011, 12:26   #41
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What system are you talking about. Open, Closed or Sequential.

the switch has 3 options CNG, Duel and Petrol.

In open loop and closed loop system, once you put the switch to Duel (Pertol+cng), no petrol is used at all. Not in 1st 2nd or any gear. you drive from 1000rpm to 6000rpm in cng only. not petrol.

Only if the car cuts off, the duel setting will allow it to start in pertol again and drive only on cng. only starting the engine is on petrol. Moment you accelerate, it goes to cng and stays in cng all the time.
You have misunderstood what I wrote. I fully agree with what you wrote above.

My point is that when you drive a CNG car, petrol is always used to start a car. Starting a car & driving it in the lower gears consumes more petrol(per distance covered) as compared to driving on top gear. CNG fitted cars are never in CNG mode for the starting for the car. Hence the CNG average of a CNG car is exaggerated. Likewise the petrol average of a CNG car comes down because the petrol driving in a CNG car is mostly for starting and the low gears, where mileage is low.
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Old 18th December 2011, 12:51   #42
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You have misunderstood what I wrote. I fully agree with what you wrote above.

My point is that when you drive a CNG car, petrol is always used to start a car. Starting a car & driving it in the lower gears consumes more petrol(per distance covered) as compared to driving on top gear. CNG fitted cars are never in CNG mode for the starting for the car. Hence the CNG average of a CNG car is exaggerated. Likewise the petrol average of a CNG car comes down because the petrol driving in a CNG car is mostly for starting and the low gears, where mileage is low.

I completely understand what your saying, and I am explaining where i believe your understanding is wrong.

1.
Quote:
Originally Posted by carboy View Post
CNG fitted cars are never in CNG mode for the starting for the car.
once the engine is heated up, it is in only cng mode all the time. when your idling at a signal in neutral , then 1st 2ng 3rd ... so on, all is on only CNG.
there is no petrol consumption on low end gears.

to include the engine heating up phase where only petrol is brunt, i follow the below method of calc FE
--------------------------
180 km in 8kg of cng = 22.5
heating up the car twice a day in petrol = 4km

if one cng tank last 5 days = 4x5 = 20km
minus 20 km from the 180km= 160 km only cng running
160/8 = 20km/kg of cng ... true cng FE

monthly 4 x 30 = 120km on petrol = 600 to 700 inr of petrol.

Hope you get what I am trying to say. Or else lets all mumbai CNG users meetup and have a good discussion over some tea / coffee or lunch.

UM
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Old 18th December 2011, 13:09   #43
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I completely understand what your saying, and I am explaining where i believe your understanding is wrong.
You explanation below shows you are still misunderstanding me.
1) A CNG car is never started on CNG - do you agree or not?
2) Starting a car consumes fuel & results in 0 distance travelled, thus lowering mileage calculations. Do you agree or not?
3) A CNG car very rarely is driven on petrol on anything but the lower gears. i.e. you don't drive a CNG car on petrol in the 4th & 5th gear usually. Do you agree or not?
4) Assume your petrol car gives an average of 15 km per litre. If you now travel 15 kms in your petrol car on 1st & 2nd gear only, will it still consume only 1 litre of petrol? No - it will consume far more than 1 litre - i.e. mileage will go down. Do you agree or not?

Points 1 & 2 cause exaggeration of the CNG average. Do you agree or not?

Points 3 & 4 cause an apparent lowering of the Petrol average. Do you agree or not?

Last edited by carboy : 18th December 2011 at 13:17.
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Old 18th December 2011, 13:26   #44
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You explanation below shows you are still misunderstanding me.
1) A CNG car is never started on CNG - do you agree or not?
2) Starting a car consumes fuel & results in 0 distance travelled, thus lowering mileage calculations. Do you agree or not?
3) A CNG car very rarely is driven on petrol on anything but the lower gears. i.e. you don't drive a CNG car on petrol in the 4th & 5th gear usually. Do you agree or not?
4) Assume your petrol car gives an average of 15 km per litre. If you now travel 15 kms in your petrol car on 1st & 2nd gear only, will it still consume only 1 litre of petrol? No - it will consume far more than 1 litre - i.e. mileage will go down. Do you agree or not?

Points 1 & 2 cause exaggeration of the CNG average. Do you agree or not?

Points 3 & 4 cause an apparent lowering of the Petrol average. Do you agree or not?




Yes. Why the emphasis? Did I say this isn't true?

point 1. agreed
point 2. agreed
point 3. disagree. first 2km in the morning is on petrol and does include 4th & 5th gear. same way you would drive any car in the morning.
point 4. "If you now travel 15 kms in your petrol car on 1st & 2nd gear only, will it still consume only 1 litre of petrol? No - it will consume far more than 1 litre" Agreed. But gearing depends on point 3.

But after the 2+2 km of petrol driving, you would drive only on CNG in all gears. so the substantial cost saving is say- daily 40km running - 4 km petrol = is still 36km of only cng running.

bottom line, one should account for the pertol being burnt in the driving process. Still in Mumbai traffic, getting a true cng avg of 20-22 is possible and there will be a additional cost of 600 to 700 Rs of petrol being consumed.

UM
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Old 18th December 2011, 13:38   #45
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point 1. agreed
point 2. agreed
point 3. disagree. first 2km in the morning is on petrol and does include 4th & 5th gear. same way you would drive any car in the morning.
'Rarely' doesn't mean 'never'. Your petrol driving in the lower gears as %age of your total petrol driving in a CNG car is lower than a similar percentage calculated in a purely petrol car.

I am out of this sub-discussion - it doesn't seem to be going anywhere
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