Stock Rod Limit

[fusion13]

I don’t know if the rods would be weaker than its close cousin in the 2.0l ecoboost. I think that if the 2.3l is a stroked long rod 2.0l then the 2.3l would experience more lateral forces then the 2.0l predisposing the 2.3l to more rod related issues. Also a lot of it has to do with how the power comes on. With the small k03 in the 2.0l Eco boost torque hits hard however it does not reach the torque levels that you are seeing in the 2.3l on the stock turbo. Because the ones that are seeing more power have upgraded to a larger turbo their graphs are shifted more to the right with a gradual linear climb.

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[angermgmt14]

Newbie question. Does Foed engineering know thru testing where the stock limit is on all the parts, internals of the 2.3L? Although I suppose they wouldn't divulge that info to the public?

 

[Herr_Poopschitz]

If you don't have some kind of detailed metallurgical analysis, or inside information on the design limits of the stock pieces, you can't make a judgment just by looking at them. Lots of old engines may look like they have "beefy" components that doesn't mean they are stronger than brand new designs.

The limits can be established via testing...as was performed and is the subject of this thread. The limits can also be estimated, as various manufacturers/suppliers use the same methods of production, assuming similar materials, and using known dimensions. This isn't rocket science, not everything needs to be engineered to the nth degree when making simple comments.

Google "cracked rods" and this is the first image that comes up:

Cracked big ends are all good and fine, as they seem to work fine in the EB since there doesn't appear to be big end deformation...yet. The critical failure mode is due to insufficient beam moment of area in a crippling case at this point.

 

[Herr_Poopschitz]

Newbie question. Does Foed engineering know thru testing where the stock limit is on all the parts, internals of the 2.3L? Although I suppose they wouldn't divulge that info to the public?

I'm quite confident that these parts go through thorough FEM analysis, and more than likely physical testing....and no, engineering is proprietary.

 

[LeonBorden]

Believe it or not, in due time there will be "economy motors" breaking into the 800+hp range... Same goes for the truck motor in your GT. ;)

Like all platforms as well, there will be a few shops to pop motors, and a safe "torque limit" will be assumed throughout the community. Then there will be shops who make 500+ on stock bottom ends. It's up to the car owner to decide which is an anomaly.

 

[Tim Hilliard]

I was incorrect after spending some time looking at it tonight it was cylinder 2. I was in a rush today to get it off the dyno and trying to clean up the mess before my next tune showed up. Looks like the rod broke up high. Rod bolts are still in it and you can spin what is left around on the crank through the hole on either side of the block.

Lack of piston skirt support will cause excessive side load on the small end. That is usually a sign of pre-ignition. May have been caused by excessive leakdown in which you may want to lower the top ring a little if you are having custom pistons done.

 

[Tim Hilliard]

Public Service Announcement: The idea behind a cracked rod is the highly loaded big end, the part that takes the majority of the load maintains it's shape and bearing crush. The cracked end provides 1000's of times the location and surface tension to the cap. The result is massive strength, simplicity of manufacture on a massive scale, and reliable assembly (it fits together like 3D puzzle-it can not move or shift)

OEMS use this because it's extremely strong and cheap. It's also extremely light for it's designed loads. Every industrial OEM uses this design in Diesel and Natural Gas engines. They run at full rated load for 30-100K hours 24/7/365.

The OP found a limit, sometimes shit breaks, get over it. You have a long lever being pushed sideways. It could have been a bad part that under these conditions failed, it happens, move along.

 

[Herr_Poopschitz]

Public Service Announcement: The idea behind a cracked rod is the highly loaded big end, the part that takes the majority of the load maintains it's shape and bearing crush. The cracked end provides 1000's of times the location and surface tension to the cap. The result is massive strength, simplicity of manufacture on a massive scale, and reliable assembly (it fits together like 3D puzzle-it can not move or shift.

Agreed, but I'm not familiar w/ 'surface tension' being used like this. 'Surface energy', w/ solids, yes...but only in cases of say, pre-fracture. Can you explain what you mean a bit more?

 

[Trackaholic]

Agreed, but I'm not familiar w/ 'surface tension' being used like this. 'Surface energy', w/ solids, yes...but only in cases of say, pre-fracture. Can you explain what you mean a bit more?

Maybe "surface area" for locating and interlocking the two pieces. The brittle fracture will have a nice, interlocking surface that will fit back together perfectly and which won't slip.

I've used rolling element bearings that use a similar technique to load the balls/rollers.

Seems like a great way of doing things.

-T

 

[Herr_Poopschitz]

Maybe "surface area"

Ah, ok, I'll go w/ that.

 

[Tim Hilliard]

Poor choice of words at 2:30am. Surface area is more correct but that is what I meant by 3D Puzzle pieces. Please ignore the crappy quality control from Europe.


This will not allow cap walk unlike the standard method of dowel locating pins which only locates the cap in one plane and do not control twisting forces. That's why aftermarket rods have very robust hardware.

 

[arghx7]

Correct me if I'm wrong, but torque output is a good indicator, no? You don't need physical pressure sensors for what's at best eyeball engineering in the aftermarket world.

Indicated torque is, but not so much brake torque, or wheel torque. I'll spare you a bunch of equations, but basically the combustion produces torque (called indicated torque) and then you keep subtracting all the losses - pumping losses, friction in the engine, friction in the drivetrain, and finally you get measured wheel torque, assuming you have a dyno that measures it directly.

Even then, the indicated torque could be high but if the combustion is retarded the peak pressure would then be lower. You could have high airflow and poor combustion.

Look at this graph of average peak cylinder pressure vs rpm for an Ecoboost 3.5. You can see peak pressure increases with speed. If you have a flat torque curve, your peak pressure still goes up with speed. 200 lb/ft at 2000rpm has lower peak pressure than 200 lb/ft at 4000rpm. The Ecoboost 3.5 stock tune already limits peak pressure to 80 bar, at least in a steady state engine dyno environment. Obviously you can exceed that in a quick chassis dyno pull. And we haven't talked about knock or preignition's effect on peak cylinder pressure

This thread explains it more http://forums.nasioc.com/forums/showthread.php?t=2687550 post #7

 

[Pumpkin419]

Isn't 400tq right about where the rods in the Mazdaspeed 3 engines tend to give out too?

 

[MAPerformance]

Indicated torque is, but not so much brake torque, or wheel torque. I'll spare you a bunch of equations, but basically the combustion produces torque (called indicated torque) and then you keep subtracting all the losses - pumping losses, friction in the engine, friction in the drivetrain, and finally you get measured wheel torque, assuming you have a dyno that measures it directly.

Even then, the indicated torque could be high but if the combustion is retarded the peak pressure would then be lower. You could have high airflow and poor combustion.

Look at this graph of average peak cylinder pressure vs rpm for an Ecoboost 3.5. You can see peak pressure increases with speed. If you have a flat torque curve, your peak pressure still goes up with speed. 200 lb/ft at 2000rpm has lower peak pressure than 200 lb/ft at 4000rpm. The Ecoboost 3.5 stock tune already limits peak pressure to 80 bar, at least in a steady state engine dyno environment. Obviously you can exceed that in a quick chassis dyno pull. And we haven't talked about knock or preignition's effect on peak cylinder pressure

This thread explains it more http://forums.nasioc.com/forums/showthread.php?t=2687550 post #7

Are you looking for work? :lol: Me and you would get along just fine.

 

[JJ@WMS]

Public Service Announcement: The idea behind a cracked rod is the highly loaded big end, the part that takes the majority of the load maintains it's shape and bearing crush. The cracked end provides 1000's of times the location and surface tension to the cap. The result is massive strength, simplicity of manufacture on a massive scale, and reliable assembly (it fits together like 3D puzzle-it can not move or shift)

OEMS use this because it's extremely strong and cheap. It's also extremely light for it's designed loads. Every industrial OEM uses this design in Diesel and Natural Gas engines. They run at full rated load for 30-100K hours 24/7/365.

The OP found a limit, sometimes shit breaks, get over it. You have a long lever being pushed sideways. It could have been a bad part that under these conditions failed, it happens, move along.

^^
Exactly.

However the middle to lower portion of that rod material is weak and brittle and will snap like a twig from detonation. You dont know how many times I have taken apart a modular Ford motor when the rod has broken and the big end is still intact and even spinning freely on the crank journal.

JJ

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