Rod bending observations
 

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.

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.:doh::banghead:

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

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.

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:veryhappy:, 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?

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.

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

you bought junk. . . :op:

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

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/

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.

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.

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

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.

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

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.

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

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

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 ;)

Thanks for taking away all my worries.

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...

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

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

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.

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

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!

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.

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!

What if you claim there is a manufacturing defect?

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

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

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

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

wont matter because if you were operating the engine out of stock spec their parts werent designed for that.

So were all fucked unless forged. Awesome

do compression check

What would it prove? Would an already bent/fatigued rod measure less compression?

It did on Cpolly's car

It's the steps where you add oil and watch the reactions during a compression check that show you the potential source of the problem

A bent rod will most likely affect your compression reading but that is not THE ONLY thing that will give you a poor compression reading.

Mine read down 5 psi on number 3 which is hardly conclusive of anything. The piston would have to be pretty cocked up for a long while to offset mill the rings enough to be an instant compression test giveaway. Best to run a leakdown and see where the leak is coming from. If it's done the rings, it'll blow through the oil fill cap hole. done the valves, out the exhaust or out the intake, depending on what's fucked. you can learn alot from this.

did you do the oil in there and see what happened?
another cylinder 3 down a little - man i really wish we could convince more folks to do compression tests and post the results - i'm done with this car and giving up, but for someone who really wanted to try to make a case to a dealer info like that would really help....

no valve issues, piston rings, head gasket, hell even imperfections in the cylinder wall are all potential causes of lower compression but doing this test with the oil at least points toward the source of the problem -
a total leak down test can pinpoint even further - but those are tougher to do

It was within spec for the cylinder so I didn't oil it. Oiling a cylinder will almost always raise compression values a little, even if there's no damage, especially if the test is done on a cold engine. I can't see how that would conclusively demonstrate anything beyond possibly isolating the ring seal being an issue. But, if it passes the objective #s test, what have you learned and what can you say to Mazda?

I now have a small compressor at home, maybe I'll buy a leakdown kit and run that test, if I can find one not too expensive.

oil follows the rules of everything else man - gravity - oil goes down into the piston ring making a temporary seal - if you get increased compression that's probably the source of the problem - i don't think it does the some thing to a valve stem - when you are turning the engine over it's not going to splash up past the base of a valve and make the same temporary seal on the stem before it enters the upper valvetrain area - so if it doesn't raise it's a valve leaking instead of a piston ring -
everything i'm saying is explained in the factory service manual page 01-10B-9
oil tests are not definite (they can point you in the right direction), but compression does not always raise every time you add oil - the other scenario is where you have one higher then the rest and if oil makes no difference here, you probably have head gasket leakage

So this is all pretty bad news

no easy fix here...Replace the bottom end or go home. I wouldn't take any chances. If you can pull the motor yourself, and tear off the head, you can probably replace the rods and pistons relatively inexpensively. It's a MUCH better option than needing a new block down the road.

Just when i was startin to have some small ounce of hope for this car. Another bomb gets dropped :( too bad i'm too deep into this thing to sell

i don't see any bombs. all i see is a great mazda. stay positive. How do u know that the internals he has aren't just a few coincidental bad ones. A lot of people beat the shit out of there cars and have no problems. Lenny is probably the worst. I take my own chances now. When i owned a SRT4 neon i wanted to go big turbo but i never did because i listened to the forums and they all said im gunna blow if i don't build. guess what. years later they find out how the motor is a solid mother fuker well capable of handling BT's on stock internals. FML for not staying SRT.... anyway i really feel that these motors get to this point because of knock and abuse. causing these clearances to increase. take good care of your car and change the oil and what not and hopefully ull be fine

It's just not worth the risk, monetarily. How much do rods/pistons cost? If you can do most of the work yourself, it's worth it.

Do it right the first time, or you'll end up knee deep in shit.

Also, lol @ all of those pistons being a 'coincidence'

H1N1 is bad...people actually die from it...and yeah, I hear and read a lot about it...it scares the shit outta me...but hey, I wake up in the morning, and put my pants on one leg at a time...

I'll get the vaccine once it comes out...but in the meantime, I bitchslap my car left right and centre and she loves it...

As others have stated.... The failure rate is FAR BELOW the recall threshold. Its possible that this defect is apparent in only a portion of the build. And it could be that this is a large contributor to those that blow.

Thus, if you havent blown, then dont stress on it. Take care of your car and drive your car. Dont be a douche and do your regular car care and just pray to little baby GSR Jesus that your rods dont have the tolerance stackup issues.

Shit, your car could blow the fuck up because an injector dies... Does this mean you should stop driving? NO, get the fuck out there and have fun with life!


(FYI, Im going to knock on wood so I dont jinx myself KKTHX)

Lex,

I can send you my pistons/rings, rods/bearings, all four of them. My engine did not blow.

The guy at the Machine shop say they look perfectly fine, motor has 10k and I started pounding on it since it had 30 miles on it.

PM me where u want me to send them.

i love the car - i just got the shit end of the deal -
and as far a people running their cars and being fine - i gotta ask - are they just fine because they drive everyday and it still functions well enough to run - so they assume they don't have any issues or are they really doing scientific tests to know they are really "fine" the car will run on seriously decreased compression - i'm living proof of that - my things is - do some tests see where you really are - weigh your options and if you aren't where u are supposed to be - change the bottom end

I realize that all of this is alot of forum hype and crap but shit its hard to stay positive with all this negativity!!!! And cpolly69 as far as the comp check goes my cylinder 1 comp was so low it blew my pcv valve apart lol not a bent rod either i torched an intake valve shut and it woulda been runnin way lean but by the grace of God my injector was also leaking in the first cylinder so that extra fuel leakin in kept me safe i'm pretty sure. Dumb luck i suppose. Still not a cheap repair :(

my 07 ms3 blew up just over a year ago coming up an on ramp. i had only a tbe and cai, and they voided my warranty for mods. i solved this problem a few months ago by buying my brothers srt4. i can get everything i want out of it on stock bottom end. :)

sorry to hear about all the blown motors, and with this many, it is safe to say there is a problem with those cars from the factory.

heres a thread on my site with some pics, nothing technical, but if you want to see some pics theres are a few to browse.
BOOM! Now with pics! - Midnight-Racers


heres a pic of piston #3 after we pulled it

http://i24.photobucket.com/albums/c2...r/DSC00722.jpg

i think your the first picture i've seen of a piston breaking

part of the broken rod that was connected to that piston can be seen in the top right of that pic.

I built my motor and just got it back and am trying to put it in the egine bay. PITA anyway I looked at my stock rods and pistons and to the naked eye they look twisted and bent a little. I did take care of my car, always let off when I saw knock and regular oil changes. Lex if you want the rods and pistons I can send them to you. Just PM me and you can check if they really are bent and/or twisted.

Holy cracked piston batman! You musta really raped this car constantly!

Im getting mine back either Wednesday or Thursday!

Now just need a how to to pull engine and head. Wish some of these were doing oil analysis' to see metals spiking before they blew. Good info.

How to pull motor out of front of vehicle would be worth its weight in gold.

Pulling the motor out was hard. Putting it back in with the tranny still in the bay is a bitch. I got the tranny sitting on the ground with the driveshafts still in it, the block is up top with one motor mount and a jack under the oil pan. Doing this in my basement with no room. Hopefully I can
lift the tranny Ono place cuz dropping the motor then lifting the tranny up. Ugh so frustrated!!!!!!!

Fuck it i haven't had a motor in my car for 4 months now. I'm just gonna tear it down again and go forged. Shoulda done it right the first time

we have forged internal but obviously some have defect and boom...

but yes....aftermarket forged is better/:biggthumpup:

actually, it was rarely driven hard. most of the cars i hang out with would rape that pos anyways, so there was no point in racing it.

Thank you
 

I needed a good chuckle.:haha:

P.S. Mike.B,
I intend no offense nor do I question the sincerity of your post, but rather I find the message you relayed about the car amusing.

Since I have a broken down Speed3 in my driveway, I understand your frustration.

i love how everyone assumes a car was beaten on because it broke. there are stock speed vehicles blowing motors, thats shitty engineering. i didnt say i never raced it, of course i got on it sometimes, but all the time? definitely not. i'm not trying to prove anything, and if you dont believe me, i really dont fucking care. im just throwing this in the observation thread for reference purposes.

i used to read everyone's failures and say to myself "yeah they just treated it like shit" - i've never been to the drag strip - never been on a dyno - and never done a burnout - i had mild bolts ons and did a total of 2 drives at 18psi - i took my car's maintenance seriously changed oil on schedule (and proved that to a dealer w/ receipts) - i have low compression in one cylinder now - go figure

u didn't drive it hard enough thats why. Breaking that shit in WOT helps seal the rings better and u will get better compression.

I doubt that, highly.

Not to go too far off topic but i'm still fairly new to the whole heavily modifyin shit and i realize the longevity of any car eventually reaches zero but are these failing comp ratios gonna happen super quick with forged guts just like stock? If so whats the point? Thanks

Just to bring this back on topic. The reason for the rod imperfections is the manufacturing process. Without fully machining the entire rod surface to spec, you will see these imperfections. Fully machining the rod is left to aftermarket manufacturers where they can charge a premium for the parts.

NRSpeed know's all about Rod Bending....LOL...he has been practicing, it seems daily according to his avatar!!!
Sorry Lex,.could not help myself...
now PLEASE back on topic...

what is a early sign of knowing you have a rod going out or some kind of engine problem? I recently noticed my car is idling a bit rougher even after warmed up and driven for a little while. once i come to a complete stop and just sitting there the car feels more rough than i remembered. Car runs and drive fine other than the new found rough idling. I got an 09 with just about 12k miles and mods are just an intake and bov

it is called colder weather...

u had ur speed last winter of just got it?

change ur oil?

don't worry about it cuz ur gonna sell your car soon anyways:footinmouth:

I got my speed new about half a year ago. Oil changes every 3000 miles. But the idling started before the cold weather hit. And with this unpredictable Texas weather, it even idles rough at upper 70s now. Would going back to complete stock for winter help?

so this thread has gone from discussing the factory thrust bearing on the end of the crankshaft allowing the crankshaft to move ever so slightly and potentially lead to bent rods and failure of everything else - which could be diagnosed by funny feelings at the clutch pedal
to
swine flu, backwards walking betty, hell
just wanted to recap!

I have seen clutch pulsations, low compression, severe smoking/oil burning.

when you say clutch pulsation, does that mean it's loud clanking noise when at idle? my sister got a G35 and it makes that same clanking sound after a short drive

just about every manual transmission car out there makes a little different sound when the pressure plate is not depressed and the clutch plate is in contact with the transmission -
that's not what he's talking about

I am talking about vibrations or pulses that you feel in your foot that change frequency as you rev up/down with the clutch pushed in.

So, lex, are you saying stock rods are good if you pulled them and had them machined? Or the imperfections are just covered up or created by a machining post production?

Guess at that point you'd just replace em anyways.


Any one find any more info on that diamond cut washer that may be a savior to the later models?

While machining them might help, it might also bring about other failures at the wrist pin area. If you've got them out, replace them with aftermarket.

The small end imperfections would seem to place a lateral bending load on the rods on axis with the wrist pins. This would significantly stress both the rod and the wrist pin, as well as causing the wear patterns seen on one side of the rod bearings. I know we've seen broken wrist pins, so that supports this theory. I suspect most or all of the broken, and especially bent rods, would support the theory by having bent or broken in the same direction, specifically being bent toward cylinder 1.

As far as crankwalk, if it exists, it's not directly related to the rod issue, but it would exacerbate the problem, for sure.

well nrs my 2009 has serious power and is holding up just fine

How many miles do you have on your setup 18....? Like 100? hahaha. Wouldn't be a bad idea to start planning for a build sometime down the road. I think your motor will hold up fine for quite a while, but why not start saving and build when you get the chance. Then beat on it happily for years to come, haha.

i have been fully bolted for 10,000 miles and now this and is still running like the day i bought it

Good to hear, and Good luck on another 10,000.

If you pull the pan would there be any possible way to see the gap on the crankshaft/rod?

Using other failures as a guide, don't hold your breath for another 50k miles....

And brian, don't be scurred to launch your car, lol. Let's see a 1/4 mi time!

what's with all the sour grapes guys?

whether you drive the car hard or not, none of the findings suggest that the rod bending is the direct result of high-boost and high-power abuse. from the axial load findings, who says it can't be from ONE single drop clutch launch, but spends 90% of time cruising in the PT-knock range? [pure speculation]

there's a local 2007 MS3 on sale w/ close to 100K km or just over 60K miles on it...modded and tuned with SB @ 16psi for 310whp on a Dynapak dyno...that's more like 330whp on a Dynojet...car is completely beat on at the strip, road courses, highway and the streets...still runs like a champ...\

he did have a CP-e FP from very early on tho...

cp-e hpfp ftw! :p

drive it hard it likes it ;)

my cp-e pump should ship today, hopefully!