Rod bending observations

[Lex]

I have 4 bent/broken rods from 2 motors and I made an observation about these that threw me off. All the rods were bent towards the same side. They are bent towards cylinder #4. Thestaplegunkid's bearings showed one sided wear on all the rods - not just the broken ones. I started to think about the geometry of the situation and made some discoveries.

The pictures below tell an interesting story - sorry about the large size but it is needed. The small end bearing is lined up with the web of the rod that supports the loads that run along from the front to back axis of the motor. However, the flanges of the rod (that support side to side load) are NOT lined up with the web and the bearing itself.

Look through the pictures and you should see the imperfections. They are about 0.5mm off. This is what happens when you don't machine the entire surface of the rod. I can only imagine how many of these types of tolerances can stack up.

EDIT: This is something I saw in all the rods I have. It is likely a result of the forging process.

[glocK23]

I hope only a small percentage of MS3/MS6 motors have these forging imperfections.

[SpeedSixxx]

Originally Posted by glocK23 I hope only a small percentage of MS3/MS6 motors have these forging imperfections.

I would sure hope so as well.

If you think about it, most of the bent rod motors have gone at a pretty early age (low mileage) some of us are higher then others me being 50k in a week or so.

really I guess the only way to tell is to take our motors apart and take a look but hell, if you do that then I guess you should just replace everything with new parts.

Lex, can you fit one of those tiny micro scope cameras down in the crank case and check out the rods and bearings?.... is it even poss to tell from a scopes eye view if the imperfection is there? or you need a digital caliper?

again, hope it's only a small percent with these imperfections and I assume so cause it's not like you hear of everyone motors dropping like flies here on Msf.org...

One thing I think we should do is go back into the blown motor thread and ask all the members with blown motors to check their VIN and see what factory in Japan their car was built at. I know the speed 3 and 6 were built in two different cities factories in Japan.
Maybe it could be poss for the cars with the imperfections to have come from only one single factory.

or I could be all wrong---meaning

I would now assume that all the pistons and rods crank ect...are forged and manufatured in one plant and then sent to both factories. In that case I would assume that there are imperfected rods in cars from both factories.

maybe....the factories got their internals from different factories?....

there are so many variables but if we could pin point where the defective rods come from then we would have a better idea of who could potentially blow.

[superskaterxes]

lol can we get lex his own section? lol like NATOR LEX haha. atleast someway to get all his findings and threads together in one place

[BoostIsBetter]

lex, props to you for all your help to the community. maybe you should start your own company like RaceRoots and not charge up the ass for secrets but help the world instead, haha.

[darth vader]

Interesting so, if I understand you correctly, the top of the rod is bent towards 4, thus the bottom is pushed towards the pass side of the vehicle, engine in.

This may explain why we don't see rashes of blown CX-7 mills. Aside from the obvious fact that CX-7 owners aren't rev-happy punk-asses trying to squeeze 5000 hp out of the stock tune, there's a big mechanical difference: the auto trans. The auto has a big ass torque converter bolted to the flexplate and it doesn't impart hundreds of pounds of compressive side force to the crank, like happens when the clutch is used. The force is momentary but, large. I wonder what is an acceptable amount of crank float on these engines and whether the tolerance stack-up is leading some to be extreme in this regard? Are there indications of excessive movement at the other end of the crank like spalling on the inner side of the block or whatever kind of thrust plate limits this movement?

[Doc-1]

To me FORD has a hand in this. When I stopped buying US made cars in 83 this is exactly why. Had a 460 FORD motor go bad at 2,000 miles for just this reason. Will they ever learn. Quality Job 1.....right up your ass.

[cpolly69]

Did these still have the rings on them? How did they look?

[mexicant]

Originally Posted by SpeedSixxx I would sure hope so as well. If you think about it, most of the bent rod motors have gone at a pretty early age (low mileage) some of us are higher then others me being 50k in a week or so. really I guess the only way to tell is to take our motors apart and take a look but hell, if you do that then I guess you should just replace everything with new parts. Lex, can you fit one of those tiny micro scope cameras down in the crank case and check out the rods and bearings?.... is it even poss to tell from a scopes eye view if the imperfection is there? or you need a digital caliper? again, hope it's only a small percent with these imperfections and I assume so cause it's not like you hear of everyone motors dropping like flies here on Msf.org... One thing I think we should do is go back into the blown motor thread and ask all the members with blown motors to check their VIN and see what factory in Japan their car was built at. I know the speed 3 and 6 were built in two different cities factories in Japan. Maybe it could be poss for the cars with the imperfections to have come from only one single factory. or I could be all wrong---meaning I would now assume that all the pistons and rods crank ect...are forged and manufatured in one plant and then sent to both factories. In that case I would assume that there are imperfected rods in cars from both factories. maybe....the factories got their internals from different factories?.... there are so many variables but if we could pin point where the defective rods come from then we would have a better idea of who could potentially blow.

you bought junk. . .

[Fagwagon]

You should break this down barney style for ppl that dont understand. Good work!

[NRSpeed]

I cant be bothered to search for the info, but wasnt TrickyTwelve inch going to blow the whole thing wide open and teach us all what was really the problem?

Lex, are these from the same year engine?

[8.5MS3]

Originally Posted by NRSpeed I cant be bothered to search for the info, but wasnt TrickyTwelve inch going to blow the whole thing wide open and teach us all what was really the problem? Lex, are these from the same year engine?

yes he was and check out how awesome his first draft was:

http://www.mazdaspeedforums.org/foru...engines-41236/

[Lex]

Originally Posted by darth vader Interesting so, if I understand you correctly, the top of the rod is bent towards 4, thus the bottom is pushed towards the pass side of the vehicle, engine in. This may explain why we don't see rashes of blown CX-7 mills. Aside from the obvious fact that CX-7 owners aren't rev-happy punk-asses trying to squeeze 5000 hp out of the stock tune, there's a big mechanical difference: the auto trans. The auto has a big ass torque converter bolted to the flexplate and it doesn't impart hundreds of pounds of compressive side force to the crank, like happens when the clutch is used. The force is momentary but, large. I wonder what is an acceptable amount of crank float on these engines and whether the tolerance stack-up is leading some to be extreme in this regard? Are there indications of excessive movement at the other end of the crank like spalling on the inner side of the block or whatever kind of thrust plate limits this movement?

There are crank counterweight marks on both sides of the big end of each rod I saw. If the rod is bend, the marks are deeper into the rod. If the rod is bent severely the counterweight hits the bottom of the pistons and material starts to come off.

Based on people's observations and my own, yes, the rod has some side to side movement and yes during a shift it would be offset towards the passenger side. This may be even more significant than the imperfect construction of the rod itself.

These rods seem to mainly bend along the left-right axis of the motor. This can very well be because the cylinder pressure is not centered on the load axis of the rod and the tolerances are not tight enough. This is part of the motor design - no motors are perfect - we are just seeing a combination of cylinder pressure (for various reasons) and enough tolerance deviation (it is mass produced after all) to overwhelm the ultimate tensile strength of the rod along that axis.

Also note that ALL the rods I have are constructed this way. They range from an MS6 to an 08.5 MS3. So there is no point in checking this inside your motor.

[Thestaplegunkid]

Lex, I just checked my 3 remaining Rods. They all show the exact thing you've measured. A 0.5mm difference in the small rod end centering. And they all correspond to the uneven bearing wear on the large rod end.

And #4's bend is also in the direction of the off center force caused by this.

Excellent find.

[RacingToaster]

Does that mean that the crank is shifting to one side causing this?

[Lex]

Originally Posted by Thestaplegunkid Lex, I just checked my 3 remaining Rods. They all show the exact thing you've measured. A 0.5mm difference in the small rod end centering. And they all correspond to the uneven bearing wear on the large rod end. And #4's bend is also in the direction of the off center force caused by this. Excellent find.

Thanks for looking into this. This is probably a large reason as to why we're bending rods all the time and say an Evo or SRT4 are not when the rod dimensions and forging are quite similar. The fact that we have a pretty long stroke really doesn't help as it amplifies the effects of the poor geometry.

More of a reason to limit torque, low RPM load, detonation, and flat foot shifting on the stock bottom end.

EDIT: Some cars will have poorer tolerance stack up (not just the rods, but all tolerances) than others and those are more susceptible to this problem.

[toprock]

Lex should have his own forum section for all his observations. My .02cents.

[FearUndersteer]

I applaud your efforts!

So are quality aftermarket rods the answer, atleast to abate this issue?

[Lex]

Originally Posted by FearUndersteer I applaud your efforts! So are quality aftermarket rods the answer, atleast to abate this issue?

If pushing the motor and you don't want to take risks, it seems like a simplest solution.

[blackrs99]

So basically this is like a mini crankwalk? That's apparently a strain on already improperly manufactured rods? FML

i got the good set of 09 mazda rods as well as samsel450r

[wassup61]

I gawt me some pauterz??

Seriously though, the side loading of these rods is worrisome, but there was a correction in 08.5 with a diamond cut thrust washer (more precise tolerance) that was designed to prevent lateral deflection in the crankshaft.

[serium]

Originally Posted by wassup61 I gawt me some pauterz?? Seriously though, the side loading of these rods is worrisome, but there was a correction in 08.5 with a diamond cut thrust washer (more precise tolerance) that was designed to prevent lateral deflection in the crankshaft.

Makes me feel a little better with my 08.5 but i drive like an old lady now just because im soo no trying to pay for another engine :/

jeff are you serious???? i have an 09 woooo wooooooo

[JumpingJackson]

Originally Posted by wassup61 I gawt me some pauterz?? Seriously though, the side loading of these rods is worrisome, but there was a correction in 08.5 with a diamond cut thrust washer (more precise tolerance) that was designed to prevent lateral deflection in the crankshaft.

If i got a new thrust washer for my engine build, it would be the updated one right?

[Thestaplegunkid]

Originally Posted by JumpingJackson If i got a new thrust washer for my engine build, it would be the updated one right?

Don't worry about it... mine was an 08.5 and it blew up just as well as the earlier ones

[djuosnteisn]

Thanks for taking away all my worries.

[kgb]

So....Mazda designed our Mission Impossible ECU to target high loads, at low RPM on incorrectly sized rods with a long stroke? FOL (Fck Our Life)

Do you think they knew about the rod size problem....

I'm sure they will now...

[Lex]

Originally Posted by wassup61 I gawt me some pauterz?? Seriously though, the side loading of these rods is worrisome, but there was a correction in 08.5 with a diamond cut thrust washer (more precise tolerance) that was designed to prevent lateral deflection in the crankshaft.

Is there a way to check a part number for this? Thestaplegun's motor looked really bad in terms of side loading the rods and it was an 08.5

[SpeedSixxx]

Originally Posted by wassup61 I gawt me some pauterz?? Seriously though, the side loading of these rods is worrisome, but there was a correction in 08.5 with a diamond cut thrust washer (more precise tolerance) that was designed to prevent lateral deflection in the crankshaft.

just saying...lex did mention that his bent rods came from Ms6 to a 08.5 ms3....

[smakdown61]

I wonder if its possible to take it to a lawsuit if mazda denies your warranty claim due to mods. If you have a pre 08.5, this type of evidence plus the new diamond cut bearings they added in points to them trying to cover up a problem.

[superskaterxes]

they arent going to warranty shit if they claim you werent stock.

[NRSpeed]

So I googled up Crank walking and found this. Very good info. Also found another and they are all about DSMs.

So, it may be wearing on the thrust bearings in combination with possibly uneven rods? These two powers combined form Captain Capow!

[djuosnteisn]

It's funny, forzda on 6club was talking about the thrust bearing a long time ago. He even mentioned how to check for it with a 2x4, and what amount of movement was "ok".

HERE was forzda's thread.

[NRSpeed]

Yea, seems that Forda says the same thing in one of the links I posted about how important it is to jumper the clutch safety.

Ill be reading up on all this during lunch. Learnin is fun!

[smakdown61]

Originally Posted by superskaterxes they arent going to warranty shit if they claim you werent stock.

What if you claim there is a manufacturing defect?

[QuickSpool]

I forsee more intrest in PTP's crank straps and 06Speed6's possible billet main.

[DaleNixon]

So the diamond thrust washer in the 08.5+ should prevent this but plenty of 08.5's have blown?

[NRSpeed]

Still hear-say till we get a part number or someone finds the part breakdown.

[danesti]

this has something to do with some people reporting clutch vibrations leading to a rod exiting the block?