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tri6kata

Why it is a conrod killer, can you help?

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Hi guys, I am new here and was provided with a task to deal with a problem in a map that has killed a few engines EJ20 and EJ25. Every time the problem was a broken connecting rod and barely achieved setup potential. Haven't worked with G4 till now, only stock ECU and its hard for me to compare the maps and make any conclusions. If anybody can check the values of advance, timing and fueling, is the ref limiter ok to be ign cut and etc. or just give me a tip to find the problem. Thank you in advance :)

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Are the failed conrods showing a tensile or compression type failure?  Are the big-end bearings and pistons from un-broken cylinders showing any signs of damage?

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The rods had sign of compression and the other bearings were in fine condition when dissasembled. My coleagues believe that the rod failures were related to rev limit/lunch control/flat shift.

 

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A rev limit is active there is no combustion so that removes all compressive load from the connecting rod so I dont think it could be related to that. 

When an engine is sitting on a limiter for an extended period of time, the irregular firing events does create more torsional vibration in the crankshaft and this is well known to shorten crankshaft life - but I cant see how this could place any more stress on the connecting rod.  The "adaptive" limiter mode is designed to minimise the extra crankshaft stress by randomizing the cut pattern to reduce harmonics.

I think if it were detonation related you would see effects on the piston, spark plugs and rod bearings first.

So, im my opinion if you are seeing compression related failures on the conrods and there are no signs of detonation then it would suggest you are exceeding the torque capability of the connecting rod.

 

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I am thinking that ignition cut could have something in common, if too much fuel was unburned and then combusted in the exhaust manifold, could that open the valves and colide the piston ?

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It is true that hydraulic lifters can "pump up" with lots of "pops" in the exhaust manifold and this can cause the exhaust valve to open more than expected, which would then may cause the valve to kiss the piston.  However the result is normally bent valve(s) or worst case a hole in the piston.  It is hard to imagine how a valve with only a 6mm diameter stem would be strong enough to bend or break the conrod.

Edited by Adamw
changed wording to make it clearer.

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I agree,  well then if that couldnt be the reason how about if the timing was too much and detonation occured and i can see that the knock control is off, what do you think?

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3 minutes ago, tri6kata said:

well then if that couldnt be the reason how about if the timing was too much and detonation occured and i can see that the knock control is off, what do you think?

 

See my earlier comment:

On 3/21/2019 at 5:10 PM, Adamw said:

I think if it were detonation related you would see effects on the piston, spark plugs and rod bearings first.

So, im my opinion if you are seeing compression related failures on the conrods and there are no signs of detonation then it would suggest you are exceeding the torque capability of the connecting rod.

 

 

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On 3/11/2019 at 5:01 PM, tri6kata said:

Hi guys, I am new here and was provided with a task to deal with a problem in a map that has killed a few engines EJ20 and EJ25. Every time the problem was a broken connecting rod and barely achieved setup potential. Haven't worked with G4 till now, only stock ECU and its hard for me to compare the maps and make any conclusions. If anybody can check the values of advance, timing and fueling, is the ref limiter ok to be ign cut and etc. or just give me a tip to find the problem. Thank you in advance :)

link.pcl 39.69 kB · 18 downloads

I believe you should reduce TQ, or install stronger rods. 

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