Timing chain failure on the Dodge Challenger - Page 79 - Dodge Challenger Forum: Challenger & SRT8 Forums
 
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#781 (permalink) Old 08-04-2012, 12:16 AM
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I would be surprised if this alleged destructive resonance was at 2200-ish rpm. 1800 rpm + moderate engine load is where I would suspect a destructive resonance. Why are chains breaking at 70 mph in mds, then?...I suspect the damage/wear accumulates quickly during many incidents of the 1800 rpm scenario, and then long periods of 2200 rpm in mds afterwards is sufficient enough window for a catastrophic failure to finally unfold on a system that has been compromised by premature wear.

...just throwin' it out there, just from the standpoint of you can really feel the vibration going on there at 1800 rpm + moderate load. Just rolling along at a cruise (light load) at 2200 rpm seems pretty smooth, imo.

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Last edited by randycat99; 08-04-2012 at 11:26 AM.
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#782 (permalink) Old 08-04-2012, 06:59 AM
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Been reading this with interest and hope since my '10 (9/09 build date) is @42k miles.

With regards to the vibration issue, I found the following on Allpar discussing the reason for MDS on V8s and not V6s.

Quote:
Originally Posted by Allpar.com
Bob Sheaves discussed why the system is almost always used on V8s and not V6s:
"An Otto cycle engine requires two full revolutions of the crankshaft to fire all the cylinders. Two revolutions x 360 degrees equals 720 degrees of rotation. Dividing that total rotation by the number of cylinders to have an even firing engine (naturally balanced) will give you 120 degrees, which means that you have a cylinder firing every 120 degrees of rotation. When you take out 3 of the cylinders, you have increased the firing rotation to 240 degreees (720/3), still balanced between each firing of a cylinder. The catch is that you have increased the harmonic vibrations as the rpms increase. Deactivation of four cylinders in a V6 would mean losing the multiple of six cylinders, which intrinsically keeps the engine in primary balance. (The lack of natural balance is why balance shafts are often used in 90 degree V6s and larger inline 4 cylinder engines.)"
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#783 (permalink) Old 08-04-2012, 09:59 PM
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THe LS series timing chain is a standard single roller between a #30 and #40. The 09' + hemi chains are stronger in my opinion, they have twice as many links and are thicker than the LS units. I will run out to the shop tomorrow and post comparison pics.

Everyone keeps mentioning the Manley setup.............. it will not work.

THe VVT cam protrudes out the front of the block further, the guide plate will not work with the 09 and up oil pumps. I had a 2003 to 2008 setup and tried in on for size...... no sale.

That said, there is room for a thicker chain, the 2003/2008 chain is alittle thicker and would fit, however the tooth spacing on the gears is different.

There have been some pretty good theories put forth, the majority of which is a harmonic/vibration issue, which I fully support.

Last edited by Desert Bum; 08-04-2012 at 10:02 PM. Reason: added comment
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#784 (permalink) Old 08-04-2012, 10:16 PM
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Quote:
Originally Posted by dodge junkie View Post
I saw that picture, and to me it looked like a heavier chain. How much? Dunno!

Harmonics? Ya I believe it.
Tensioner or Guide? Probably a factor also.
MDS? Contributing also!
Chain? The one constant failure point.

Talked to my Service mgr. today via phone. Said the timing chain broke, and they are replacing the heads also! Asked a few questions, got really nowhere. Will be at their doorstep mon a.m. to take a look and maybe some photos if they've done squat. The service mgr. sounds like a real wizbang!!!!!!!!!

Asked him "why are you replacing the heads? Bent valves?" His answer "Thats what the factory is sending us!" I then asked "Did the valves make contact with the pistons?" Wizbang "We don't have the heads off yet but if there is further damage I will be talking to Chrysler" Me "Don't you f*****g think you should diagnose a little before you assume everything else is alright?" Wizbang "I'm sorry sir" I just told him I would see him first thing monday morning.
DJ,

THE MUST PULL THE AFFECTED PISTONS!!!!

The area where the valve smacks the piston is right behind the ring land. If the contact was severe, it will absolutely 100% with out a doubt compress the ring land and collapse the piston skirt as well. Hypereutectic pistons are extremely brittle and crack very easily......
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#785 (permalink) Old 08-04-2012, 10:22 PM
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LAST post by your favorite a$$hole, just to give the youngsters a quick, easy demo, that ANY of you that have an OHV, pullcord start lawnmower, of how MDS works, hokay?

Fire it up to be sure it runs. Now, remove the valve cover, if you dare, now, remove BOTH rocker arms, again, this is very advanced, YOU may never get it running again without calling a professional. Now pull the cord with no rocker arms...what IF the intake rocker arm was operational just long enough for the first gulp of 14-1 air fuel mixture, fired it as usual, THEN the rockers were off.....that air/fuel charge exploded one time, peak cylinder pressures rose ENORMOUSLY and then, they NEVER left the cylinder, which now has no rocker arms and YOU are TRYING to yank that cord to pull it through the next rotation with what started as maybe 175PSI & went maybe 10.5x that when the plug ignited it that one time before the rockers came off...think...no, go try the experiment, if you have a wrench or two & go ahead & show EVERYBODY what an idiot this guy is...but don't talk to me about it, I don't know sh!t....
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#786 (permalink) Old 08-04-2012, 10:32 PM
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Quote:
Originally Posted by Holeshot View Post
LAST post by your favorite a$$hole, just to give the youngsters a quick, easy demo, that ANY of you that have an OHV, pullcord start lawnmower, of how MDS works, hokay?

Fire it up to be sure it runs. Now, remove the valve cover, if you dare, now, remove BOTH rocker arms, again, this is very advanced, YOU may never get it running again without calling a professional. Now pull the cord with no rocker arms...what IF the intake rocker arm was operational just long enough for the first gulp of 14-1 air fuel mixture, fired it as usual, THEN the rockers were off.....that air/fuel charge exploded one time, peak cylinder pressures rose ENORMOUSLY and then, they NEVER left the cylinder, which now has no rocker arms and YOU are TRYING to yank that cord to pull it through the next rotation with what started as maybe 175PSI & went maybe 10.5x that when the plug ignited it that one time before the rockers came off...think...no, go try the experiment, if you have a wrench or two & go ahead & show EVERYBODY what an idiot this guy is...but don't talk to me about it, I don't know sh!t....
Holeshot you are correct, the cylinder will stay pressurized, that is until the cylinder pressure leaks through the ring end gaps. The crankshaft will bear all of the added stress of this condition.

However, you have taken the rocker arms out of the cycle, which would not place any additional pressure on the timing system, MDS "free floats" the lifters.
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#787 (permalink) Old 08-05-2012, 12:14 AM
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...and he forgets that mds is typically not operating at WOT engine loads, hence the gas charge, whether noted before or after combustion, can vary extremely with different scenarios. If it was just this "175 psi" figure regardless of throttle position, then throttles would be all well pointless as far as controlling engine output. Our Hemi would then only exist as either 0 torque (not running) or full torque @ rpm...no in between, at all.

I think this has been like his 3rd "last post", too.

Last edited by randycat99; 08-05-2012 at 12:19 AM.
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#788 (permalink) Old 08-05-2012, 07:46 AM
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This thread has become more about how MDS functions and why chains break then focusing on the fix to this problem, don't get me wrong, I think we have some great minds on this topic but it's time for theories on how to prevent this disaster from happening to these motors.Ive heard a few ideas, such as - 1) tuning out MDS with the predator- 2) changing the timing setup-3) using autostick. I don't believe dodge will address this mess, so I check in with this thread every day in search of a solution to this problem. So please keep the suggestions coming. Thank you all for your input so far. I do not want to get rid of this car, still hangin on.


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#789 (permalink) Old 08-05-2012, 07:51 AM
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Not a solution but first owners can purchase a lifetime powertrain warranty from chrysler. Its about $800.00.


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#790 (permalink) Old 08-05-2012, 08:33 AM
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Quote:
Originally Posted by Dodgeballz View Post
This thread has become more about how MDS functions and why chains break then focusing on the fix to this problem, don't get me wrong, I think we have some great minds on this topic but it's time for theories on how to prevent this disaster from happening to these motors.Ive heard a few ideas, such as - 1) tuning out MDS with the predator- 2) changing the timing setup-3) using autostick. I don't believe dodge will address this mess, so I check in with this thread every day in search of a solution to this problem. So please keep the suggestions coming. Thank you all for your input so far. I do not want to get rid of this car, still hangin on.


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I agree, the only fix will be from the aftermarket, if any. Allpar and several other sources tell the tale on how the MDS system was tested and only 5 percent of the buying public would exceed their benchmark. Are we witnessing this 5 percent? Every case thus far has cliaimed the failure happened while cruising at or around 70mph, most likely in MDS mode. A question that needs to be asked is how much of your daily commute is in MDS mode.....

I my case, I drive 122 miles round trip per day, on very flat terrain. I pop the cruise control on at 80mph and the car stays in MDS mode 99% of the time. Does that put me in the 5 percent club?? I can speak only on my challenger, but my MDS will engage at 90mph, as of where my wife's 2010 Ram won't engsge past 80mph..

And as far as Chrysler's testing goes, they claim testing cycles of over a million miles, etc...... The testing miles they speak of are based on calculations and projections of wear, not actual. The timing chain failure was never an issue while testing and analysis was evaluated, due to the fact it wasn't actual miles???? I'm guessing.......

And I'm with you, I have no intention of getting rid of the car, overall it is a fantastic automobile despite of a few flubs. The new Gen Hemi is a great engine, it could be a bulletproof package if A: the timing chain issue is corrected B: the SRT rods were used, C: forged crank and pistons with a sane ring width replaced the cast ones.
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  Dodge Challenger Forum: Challenger & SRT8 Forums > General, Performance, and Technical > General Challenger Discussion > Challenger Issues & Problems

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