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Thread: Vitz '02 - Acceleration and Top Speed

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    Red face Vitz '02 - Acceleration and Top Speed

    Hello Experts,

    I have Vitz 2002 Automatic installed with CNG and almost drive 90K kilometers.

    The car struggles to go beyond 90 KM/h and the pick drops right after any shift (it stays good if I accelerate it badly). Can someone please suggest me what should I be doing, changing plugs to 4 pins etc etc?

    I have already gone for a tunning but that didn't help at all. Also I have noticed the same behavior on Petrol but it is not as bad as it is on CNG.

    Please help!!!

    http://www.flickr.com/rkhurshid

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    does your car have the CAT installed? or did you get it removed?

    What is the condition of your spark plugs, when was the last time you changed the air filter?
    What do you mean by tuning?

    do you feel that your car is bogging down as soon as you press the throttle? both on CNG and petrol?

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    I don't know and why I should remove any factory fitted Sensor?
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    Quote Originally Posted by mrkhurshid View Post
    I don't know and why I should remove any factory fitted Sensor?
    not talking about any sensor, CAT = Catalytic converter.
    If you still have CAT installed in your car, it might be choked and is not letting the engine exhale properly.
    2 years ago, i removed it from my car.

    i have heard that some people got it cleaned, i wonder how. Wait for other people to comment on this.

    'do you feel that your car is bogging down as soon as you press the throttle? both on CNG and petrol?'

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    No there is no feel of bogging .... and if it ever tries to bog down car shifts automatically to the lower gear due A/T.

    Its more like... I need more power... might be my CNG setting or plug sucks.
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    you said the behavior is same on petrol in your first post? what is the condition of your spark plugs?

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    Spark plugs are not that bad but I think its the time to change them. But before doing that I need to sure that it will fix the problem.

    I am going for a road trip next week so don't have time for hit and try.
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    You're unable to accelerate in 4th gear right? Feels as if there's no power in 4th gear... it accelerates well in 3rd gear till wht ever speed and then when you stop accelerating, it shifts into 4th gear and then the comes down again to 90-100.

    If yes then its common in the vitz/platz on cng. I dont know the exact reason but mine used to stay around 90-95 in 4th gear with 5 people + cng but you can slightly improve it by doing the things below... Now my vitz in 4th gear accelerates perfectly between 90-115 max. (note that if you start running it on petrol and tune it properly then it won't have any issues like this)

    what you need to do is, make sue that

    -Your air filter is not choked.
    -your throttle body is serviced and CAT is removed and plugs are in good condition with proper gap.
    -All Tires properly inflated at 28 or 30psi
    And lastly but most important, your cng setting is tuned for performance and not economy. Make sure that your air intake is also blocked about 34-40%. Its not recommended by the experts but in this particular model of vitz, it helps in a way that the car changes gears at higher rpms and idling becomes much smoother. (If you have a proper venturi then its better not to do anything)

    For tuning, you can view this thread...
    https://www.pakwheels.com/forums/cng...king-issue-cng
    just make sure that you're not limited the car's ability to reach full rpm by limiting the in flow of cng. hope it helps..
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    Quote Originally Posted by mrkhurshid View Post
    Spark plugs are not that bad but I think its the time to change them. But before doing that I need to sure that it will fix the problem.

    I am going for a road trip next week so don't have time for hit and try.
    What are you doing here then? Goto your trusted mechanic.

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    Get the front CAT removed bro. the one near the engine n dont completely remove it...just get it broken in the centre portion NOT COMPLETELY.

    Only way i can understand of cleaning the cat is to clean it with acid (low intensity one like sweep) but i think a very slow pouring of acid frm top will be required n that too with CAT completely removed from the car plus u cant touch the sidewalls of the CAT aluminium body with acid from inside otherwise the cotton mesh in between the CAT and aluminium portion will get damaged.

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    have you checked the clutch plates by mechanic!
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    No I haven't got the clutch plates checked from mechanic, I don't think there is something wrong with the clutch plates.

    Between removing CAT will increase the engine noise, isn't it? There should be some other way.
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    Well vitz only have 1 O2 sensor.regarding poor resposne get the valve clearance checked aswell.Yet Cat can be culprit it gets choked due too much lead in our fuel so thts why we have to remove it.@ndly these engines are not at all designed for CNG so remove it if u want something out this engine or I would suggest u to buy Some mehran alto which can bear The CNG
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    well I didn't ask for the suggestion for replacing the car, i would appreciate if we stick to the topic.

    The point here is CAT is used for a good cause (converting CO to CO2) and that makes the car environment friendly. Isn't there any way using which I can clean it?

    Btw what is the price of new CAT? Also, do you all think that the problem I am facing is because of CAT?
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    Quote Originally Posted by Rawfay View Post
    You're unable to accelerate in 4th gear right? Feels as if there's no power in 4th gear... it accelerates well in 3rd gear till wht ever speed and then when you stop accelerating, it shifts into 4th gear and then the comes down again to 90-100.

    If yes then its common in the vitz/platz on cng. I dont know the exact reason but mine used to stay around 90-95 in 4th gear with 5 people + cng but you can slightly improve it by doing the things below... Now my vitz in 4th gear accelerates perfectly between 90-115 max. (note that if you start running it on petrol and tune it properly then it won't have any issues like this)

    what you need to do is, make sue that

    -Your air filter is not choked.
    -your throttle body is serviced and CAT is removed and plugs are in good condition with proper gap.
    -All Tires properly inflated at 28 or 30psi
    And lastly but most important, your cng setting is tuned for performance and not economy. Make sure that your air intake is also blocked about 34-40%. Its not recommended by the experts but in this particular model of vitz, it helps in a way that the car changes gears at higher rpms and idling becomes much smoother. (If you have a proper venturi then its better not to do anything)

    For tuning, you can view this thread...
    https://www.pakwheels.com/forums/cng...king-issue-cng
    just make sure that you're not limited the car's ability to reach full rpm by limiting the in flow of cng. hope it helps..
    Thanks for the info man, I am 101% facing the issue you described. I will do the things based on your recommendations. I hope it will be resolved.

    Did you also remove the CAT? is there any increase in engine noise?
    http://www.flickr.com/rkhurshid

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    It will be same either removing the CAT or cleaning as usualy people break comb inside it n ull have the same noise.
    Use NGK BKR CNG/LPG Plugs will improve ur car InshaAllah.
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    yes noise increases but because of pressure loss.....get a 95 civic japani dholki the one thats underneath the car in JDM models (cost is around 1500 to 2000) get it connected in between the first and 2nd cat at bottom of the car(same place where its located on JDM models) this will solve the noise as well as back pressure problem.

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    Yes the CAT was removed by breaking it inside then cleaned and welded the same dholki back. I cant really tell abt the difference in sound since i got it removed the day i got my car but there's clearly no unusual sound.
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    Quote Originally Posted by Rawfay View Post
    You're unable to accelerate in 4th gear right? Feels as if there's no power in 4th gear... it accelerates well in 3rd gear till wht ever speed and then when you stop accelerating, it shifts into 4th gear and then the comes down again to 90-100.

    If yes then its common in the vitz/platz on cng. I dont know the exact reason but mine used to stay around 90-95 in 4th gear with 5 people + cng but you can slightly improve it by doing the things below... Now my vitz in 4th gear accelerates perfectly between 90-115 max. (note that if you start running it on petrol and tune it properly then it won't have any issues like this)

    what you need to do is, make sue that

    -Your air filter is not choked.
    -your throttle body is serviced and CAT is removed and plugs are in good condition with proper gap.
    -All Tires properly inflated at 28 or 30psi
    And lastly but most important, your cng setting is tuned for performance and not economy. Make sure that your air intake is also blocked about 34-40%. Its not recommended by the experts but in this particular model of vitz, it helps in a way that the car changes gears at higher rpms and idling becomes much smoother. (If you have a proper venturi then its better not to do anything)

    For tuning, you can view this thread...
    https://www.pakwheels.com/forums/cng...king-issue-cng
    just make sure that you're not limited the car's ability to reach full rpm by limiting the in flow of cng. hope it helps..
    Assalam o Alaikum Rawfay, Quite beautifully and well explained, I feel the same problem with my 99Vitz, i can go upto 110 now, But i need to go a bit more high (like 120-130), do you feel I need to stick to this 110 or can this be improved?

    And Isb Freinds, Can somebody please tell me where shall i go to get the CAT Removed from my car (i don't know whether it is there or not, can some body tell how to check it's presence?)
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