[Jaggu]

check timing and timing advance, (not sure wagon r has mech advance for the ecu) make sure the timing belt pully is aligned proper (1 tooth diff will advance the timings like hell) u can always retard 1 or 2 deg on timing (from manufacturer specs) make sure the engine is not over heating and engine smooth

valve clearance make sure the engine is cool before adjusting..

[speedsatya]

I too had the same @$%#%^ knocking problem in my Mpfi zen.
tried adding everything from Bahrdahl injector cleaner to system G,changed the petrol pump,using 93 petorl reduced it but not completely eliminated.
the knocking cud be heard even when u close the windows at 80kph in 5th gear.
then i got the tappet settings done ,and also the timing was adjusted.
but for the tappet setting ,allow the engine to cool down.
now its fine.

:otherwise go for a free flow so that u cannot hear the knocking.heheh, * * * * * *

satya

[SLK]

well... I have come to a conclusion that .. most of the supervisors and mechs at Maruti Service stations are..#*&*&#@... they don't know anything.
Every time I try to get something done.. my plan always blows-back into my face. They damage the car more than they repair.

Last time I only gave it for knocking.... and they.... short-circuited the main wiring... (main fuse blew up 5 times - I paid for those 5 fuses).... mis-adjusted the value clearances (I can hear tik-tik all the time).

I have tried all the big and supposed to be good workshops... and one also the biggest in India... all are shit.

Servicing is the most useless thing they do.... for all my 3 cars... I get a bill of 3k+ every service.. and all they do is... wash and return.

[Jaggu]

send an email to maruti udyog it works most of the time

[thoma]

Sorry for reviving this thread, but I am seriously confused over the real engine knocking from my engineering days. I vaguely remember that knocking is caused by abnormal / erratic combustion, might be multiple combustion from different heat zones within the combustion chamber.

But, many of us casually use the term 'knocking' when the engine is lugged in low RPM at high load. I really don't think that is the real engine knocking caused due to bad fuel or bad air-fuel ratio or anything. Please correct me if I am wrong.

But then what is the knocking like sound when we lug the engine? Or does actual engine knocking occur while lugging?

Please refer a similar thread - http://www.team-bhp.com/forum/techni...-knocking.html

[dhanushs]

Originally Posted by thoma

... that knocking is caused by abnormal / erratic combustion, might be multiple combustion from different heat zones within the combustion chamber..

.... But then what is the knocking like sound when we lug the engine? Or does actual engine knocking occur while lugging?

Yes, AFAIK, actual engine knocking does occur when lugging (not in all vehicles, I think). When lugging, the A/F ratio is rich in fuel (pedal to metal), and hence knocking occurs. ie.. abnormal / erratic combustion, might be multiple combustion from different heat zones within the combustion chamber.. like you mentioned.

[rajeev k]

Lugging is, in my opinion, more detrimental than real knocking. Lugging or flogging the engine at high gears in low speeds is to be avoided at all cost. There are some who believes that flogging in low speeds will save fuel. This does more harm than good.
Coming back to knocking, ignition happening in advance ie.,before the designated point can also cause knocking. This can occur in old engines due to hot spots developed after engine is hot. Hot spots could be some carbon deposits or a fouled spark plug which cause ignition in advance and the engine will knock.

[Aroy]

Actually knocking occurs when the fuel ignites prematurely. Some of the reasons are

- Lower Octane rating than recommended. To check put in some higher octane fuel. To get maximum effect put the fuel in a nearly empty tank. If knocking stops then the regular fuel is suspect.

- Spark timing advanced. Normally at low RPM the ignition is retarded and at higher RPM it is advanced. The job is done automatically by either vacuum advance in carburetor engines or by the ECU in fuel injected engines. As the retard mechanism has its limits, "lugging" or going at too low an RPM will result in knocking as the engine timing is advanced for that RPM. Get timing checked at a reputed workshop. Ask them to check timing at various RPM, from idling to the maximum.

- Another reason for knocking, is when a lot of carbon is deposited in the head. After some time the carbon glows and pre ignites the fuel. If knocking is absent when the engine is cold, but starts when the engine is hot, get the engine decarbonized.

- In rare cases, especially with CNG/LPG fitted, the engine knocks when the spark plug gaps are more than recommended (happens with age). Check the plugs and change them more frequently, say every 10k km instead of 15-20K km recommended.

[Sutripta]

Knocking, as used in the Indian context, is very different from what is internationally understood as knocking.
Here, more often than not, it refers to the uneven running, shaking and vibration as the engine is lugged. Abroad it means pinging or preignition.

Originally Posted by dhanushs

When lugging, the A/F ratio is rich in fuel (pedal to metal), and hence knocking occurs.

Floor the throttle => highest cylinder pressures => More chances of preignition.
Rich AF => Cooler charge => less chance of preignition.

Originally Posted by rajeev k

Lugging is, in my opinion, more detrimental than real knocking.

Preignition can hole a piston in a matter of seconds.

Regards
Sutripta

[thoma]

Is not fuel getting ignited before the spark actually termed as pre-ignition, a slightly different phenomenon from knocking/detonation? In knocking, mostly the residual fuel from the older cycle gets ignited from near the piston after the fresh fuel is ignited from the spark plug, and both heat waves are in somewhat opposite direction and hence a mild explosion.

But out of practical reasons, I get confused if it is the knocking/detonation that happens at low RPM (lugging the engine) in petrol engines. This is mainly because, in my Beat, the knocking (or whatever that sound is) keeps on going for a long time, as long as you either down the gear or the engine overcomes the load. Does not the knock sensors immediately correct the A/F ratio to avoid knocking if it was actually knocking?

Edit : Just saw Sutripta's post, and this adds to my confusion. Please, I am happy to know the exact difference.

Knocking, as used in the Indian context, is very different from what is internationally understood as knocking.

[rajeev k]

Originally Posted by Sutripta

Knocking, as used in the Indian context, is very different from what is internationally understood as knocking.
Here, more often than not, it refers to the uneven running, shaking and vibration as the engine is lugged. Abroad it means pinging or preignition.
Floor the throttle => highest cylinder pressures => More chances of preignition.
Rich AF => Cooler charge => less chance of preignition.
Preignition can hole a piston in a matter of seconds.

Originally Posted by thoma

Is not fuel getting ignited before the spark actually termed as pre-ignition, a slightly different phenomenon from knocking/detonation? In knocking, mostly the residual fuel from the older cycle gets ignited from near the piston after the fresh fuel is ignited from the spark plug, and both heat waves are in somewhat opposite direction and hence a mild explosion.

But out of practical reasons, I get confused if it is the knocking/detonation that happens at low RPM (lugging the engine) in petrol engines. This is mainly because, in my Beat, the knocking (or whatever that sound is) keeps on going for a long time, as long as you either down the gear or the engine overcomes the load. Does not the knock sensors immediately correct the A/F ratio to avoid knocking if it was actually knocking?

Edit : Just saw Sutripta's post, and this adds to my confusion. Please, I am happy to know the exact difference.

Knocking is detonation is pinging and can be controlled if operating conditions are altered like taking the paw off the accelerating, slowing down, downshifting etc to change engine speed..
Lugging results in stalling with a gearbox to engine speed mismatch and the resulting sound is not knocking. This knock may not be from engine but from the transmission components too as the engine may not be able to handle the load due to the lesser speed.
Pre ignition when it happens much degrees before the TDC can wreck havoc abruptly. Lugging will be a slow killer.

[Sutripta]

Originally Posted by thoma

Edit : Just saw Sutripta's post, and this adds to my confusion. Please, I am happy to know the exact difference.

Knocking or pinging are so called because that is exactly the sound you hear from the engine:- a knock or a ping. Like someone has taken a hammer to the insides of your engine.
Knocking/ pinging refers to the sound. Detonation/ preignition refers to the cause.
Uncontrolled combustion sets up vibrations in the combustion chamber. It is these vibrations which you hear, (and which are picked up by the knock sensor) and which, with heat, destroy engine internal parts, esp. pistons.

What is normally called 'knocking' in India is, as pointed out by Rajeev, a mix of lugging the engine and driveline backlash/ snatch resulting in an extremely unpleasant NVH experience.

Regards
Sutripta

[dhanushs]

Originally Posted by Sutripta

Knocking/ pinging refers to the sound. Detonation/ preignition refers to the cause...
... a mix of lugging the engine and driveline backlash/ snatch resulting in an extremely unpleasant NVH experience.

Hi Sutripta,

Does knocking happen in aged carburetor engines, while lugging (Pedal to metal, on an incline)? I was thinking more the fuel, chances of unburnt fuel/pre-igniton are more? Or, does the cooler temperature (due to more fuel) prevent it completley?

The reason I'm asking is, in our 14 year old Omni (LPG) there is a clear pinging sound while running in petrol and lugging the engine. As soon as the revvs build, the sound is gone. Or, is it only because of the below mentioned reason, and nothing to do with more fuel?

Originally Posted by Aroy

- In rare cases, especially with CNG/LPG fitted, the engine knocks when the spark plug gaps are more than recommended (happens with age).

[rajeev k]

Originally Posted by dhanushs

The reason I'm asking is, in our 14 year old Omni (LPG) there is a clear pinging sound while running in petrol and lugging the engine. As soon as the revvs build, the sound is gone. Or, is it only because of the below mentioned reason, and nothing to do with more fuel?

One more fact is that there has to be different advance of ignition timing for Petrol and LPG and that is the reason for this knock. Once tuned for LPG and if the ignition timing is more advanced it will knock on Petrol. 14 year old is an Omni with carburetor, I suppose.

[Sutripta]

Originally Posted by dhanushs

Hi Sutripta,

Does knocking happen in aged carburetor engines, while lugging (Pedal to metal, on an incline)? I was thinking more the fuel, chances of unburnt fuel/pre-igniton are more? Or, does the cooler temperature (due to more fuel) prevent it completley?

The reason I'm asking is, in our 14 year old Omni (LPG) there is a clear pinging sound while running in petrol and lugging the engine. As soon as the revvs build, the sound is gone. Or, is it only because of the below mentioned reason, and nothing to do with more fuel?

Hi,
I have no doubt that what you are hearing is actual knocking (detonation).
It can happen in any engine. And chances of it happening in older engines (which did not have very accurate control over ignition timing) are higher. But the predominant cause is that you are wanting maximum torque (maximum cylinder pressure) at that time.

Regards
Sutripta