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Old 18th December 2009, 14:26   #1
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Exclamation Both cams broken on brand new Swift DDiS!

The other I had gone with my father to get our swift VDi serviced. My father gets his car serviced from Dewar's and this time it was no different.

First thing that caught my sight was that there was some sort of strike going on with the staff being half its usual strength and the workshop being almost empty on a Saturday morning.

But coming to the point. While our car was going through regular maintainance, I saw a brand new white swift [I am presuming it had come from the dealership as the seats still had the plastics, and the car did not have a number plate.] had its engine completely taken out. I was eager to look as I had never seen the insides of internal combustion engine. On asking the mechanic who was working on it, he said that they suspected that one of the cams had broken. But when they opened the engine, I for one was taken aback. I saw both cams were broken. One was broken at two points and the other at one point. Even the mechanics were baffled at how such kind of damage could happen to a brand new car!

Unfortunately, I did not have a camera, and anyway they might not have let me take a picture.Even more, my father said that they were probably going to make repairs and sell this car to a customer.

What could be the reason for such damages? Has any DDiS owner suffered such problems?
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Old 18th December 2009, 17:32   #2
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Its not something new. MY Zen way back in 2000 broke its cam shaft only after about 15 days and about 300 kms. Ofcourse it was replaced FOC but then I think its known to happen to Maruti. I was also told that it had a defective cam shaft from the assembly line itself (unofficially though). But the car gave me no problems throughout the 7 years of ownership what so ever, after they had replaced the cam.
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Old 18th December 2009, 17:36   #3
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Default Poor Quality

Surely its a case of severe oil starvation or really bad quality of camshaft.
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Old 18th December 2009, 17:42   #4
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mostly seems the case of poor quality cam shaft in that vehicle, which is why it had came to replace.
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Old 18th December 2009, 17:55   #5
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Atrocious Casting and machining quality, I would guess.
Does anyone know who the vendor is?
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Old 18th December 2009, 17:57   #6
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Does this pose a question about the Maruti build quality, again? Hope this is not a common phenomenon and Maruti would take care about this, so that not many owners are affected, and they could still pull in more customers.
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Old 18th December 2009, 18:01   #7
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Broken cams! man thats pathetic QC, unless they did something stupid like filling the car with Petrol or it got hydrolocked??!
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Old 18th December 2009, 18:15   #8
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so i guess this (Swift Dzrie Vdi Rightful Insurance claim denied - Beware of Royal Sundaram CHEATERS !) was possible after all. So much for maruti's quality!
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Old 18th December 2009, 18:16   #9
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^

But in that case, won't the mechs be talking about the same issue?
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Old 18th December 2009, 18:48   #10
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Quote:
Originally Posted by nitrous View Post
Atrocious Casting and machining quality, I would guess.
Does anyone know who the vendor is?
CAMSHAFTS are FORGED and not cast.
camshafts are manufactured useing a high cromium - molybdenum steel heated to 1200 c and then forged. after that they are machined and HEAT TREATED . during this process of heat treatment (again heated to a temp 850 c and cooled in liquid media may be oil or polymer( called hardening) and then again heated up to 550-650 c which process is called as tempering.
after the process these parts are not in straight line but they are bend. not that much but within milimeter. so there is again a process called STRAIGHTENING OR COINING. after this they are perfectly alinged.
after that they are grinded and honned and made to exact size.
NOW failure of the said camshaft can be due to following reasons
1>a sub standard material used
2>forging cracks or laps which were not visible during inspection (QC)
3>non proper heat treatment.( temp . cycles are not maintained)
4>stresses induced during the straighting operations, which exeeds the permiseble limits as stress reliving cant reduce them. (QC )
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Old 18th December 2009, 18:55   #11
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Quote:
Originally Posted by nitrous View Post
Atrocious Casting and machining quality, I would guess.
Does anyone know who the vendor is?
Quite often these are done by the OEM in house.

Quote:
Originally Posted by quattroa4 View Post
CAMSHAFTS are FORGED and not cast.
camshafts are manufactured useing a high cromium - molybdenum steel heated to 1200 c and then forged. after that they are machined and HEAT TREATED
Cams are very much done by casting as well. The alloy used is chilled cast iron which is similar to gray iron.

Lately more cams are 'assembled' using steel shafts and PM lobes that are press fit.
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Old 18th December 2009, 20:33   #12
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Quote:
Originally Posted by Mpower View Post
Quite often these are done by the OEM in house.



Cams are very much done by casting as well. The alloy used is chilled cast iron which is similar to gray iron.

Lately more cams are 'assembled' using steel shafts and PM lobes that are press fit.
yes , Mr. Moderator , what you say is also true !
point noted and accepted !!!
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Old 19th December 2009, 11:30   #13
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This can happen because of Un-even load on the cam shaft. May be faulty assembly leading to uneven loads. Each cam shaft is designed to take a certain load + Factor of safety. The design is later proven by engine endurance and field tests. All the probable failures show up during tests and this allows the designer to take corrective actions. Along with the design, a assembly process is also drawn out indicating the best practice and poka-yoke to avoid failures. Inspite of all this, there can be failures and these are normally due to assembly or the base material itself.
Cam shafts are normally forged and later machined. this is the most optimum way considering the strength required over the life time + costs. As per analysis, forging process is much more robust and aslo gives the component more rigidity because of the grain flow of the material during forging. In a cam shaft, the load is normally radial. So the grain flow attained during forging is axial. The grain flow in forging can be achieved by intelligently placing the parting line. In casting, the major problem is porosity and blow holes. Any porosity / blow holes will lead to insufficient strength and premature failure. However there are various casting processes available which can avoid porosity / blowholes but they are damn expensive processes. The steel shaft with PM lobes is normally employed in higher end cars / sport cars.

Last edited by MCR : 19th December 2009 at 11:32.
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Old 19th December 2009, 13:43   #14
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what you are saying MCR is good , but in forging you can not place parting line on the camshaft in diametrical axis .
as it is a longitudanal part , the parting line will come along the length ( axially) only.
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Old 19th December 2009, 14:33   #15
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Quote:
Originally Posted by MCR View Post
This can happen because of Un-even load on the cam shaft. May be faulty assembly leading to uneven loads. Each cam shaft is designed to take a certain load + Factor of safety. The design is later proven by engine endurance and field tests. All the probable failures show up during tests and this allows the designer to take corrective actions. Along with the design, a assembly process is also drawn out indicating the best practice and poka-yoke to avoid failures. Inspite of all this, there can be failures and these are normally due to assembly or the base material itself.
Cam shafts are normally forged and later machined. this is the most optimum way considering the strength required over the life time + costs. As per analysis, forging process is much more robust and aslo gives the component more rigidity because of the grain flow of the material during forging. In a cam shaft, the load is normally radial. So the grain flow attained during forging is axial. The grain flow in forging can be achieved by intelligently placing the parting line. In casting, the major problem is porosity and blow holes. Any porosity / blow holes will lead to insufficient strength and premature failure. However there are various casting processes available which can avoid porosity / blowholes but they are damn expensive processes. The steel shaft with PM lobes is normally employed in higher end cars / sport cars.
@MCR
With all due respect, I doubt it was due to uneven stress on any one of the cams as in that case probably the other one would not have failed.

In the link provided by greenhorn, although I have not read the text, I have seen the pictures and the cams had broken in the very same manner as in the Dzire DDiS shown, only in this case both cams were broken.
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