1uz, 2uz, 3uz rods any different...

[jibbby]

After some research - Also you may have seen this topic discussed and over looked in the blown motor thread in the General Discussion thread...

It's come to my attention that when the rods fail on Xuz-fe motors, the weakest portion of the rod is at the big base ring portion... When a rod is thrown it appears in more then one case it is the big ring portion that cracks and not the center portion of the rod...

Now with that being said the base ring portions of the all the Xuz-fe motor rods are identical in every way....This would make them all break at the exact same power output...Around 500whp...

Any thoughts on this new revelation of mine?... I honestly don't think any of the rods are stronger then the others as so many have suggested on all the forums for years now...

I am going to post pictures to show what I am talking about.. Look at the bottom portion of all the Xuz-fe rods including the forged ones and let me know if you think there is a difference... As illustrated in the destruction picture you can clearly see the rod failure ring portion, and that is common...I found to other rod failure threads on the forums where the ring portion fails and not the center rod portion... Go figure?

Bottom line is all the rods are equal in strength... Any thoughts on this fellas? Does somebody know something about this that I do not?... As commonly known the 1uz-fe rods are to be the strongest..I think after research that is an incorrect statement unfortunately...:shock:

Look for yourself.....

 

[jibbby]

Another pic of the 1uz-fe rod ring portion compared to the supposedly weaker 3uz-fe rod...

 

[rms]

jibbby,

That is the normal place that rods fail.
What we are dealing with in con rods is not really a strength issue, it is a fatigue strength/life problem.

The major load is not from the bhp increase. If you double bhp you double rod loads and the cyl pressure is not really that high. If you double rpm you increase rod load x 4 and the centrifugal load becomes huge. Coupled with that you increase the frequency of those loads, both cyl pressure and centrifugal.

So you have a condition where the rod shank has a slight flex every time it goes up/down. The 'big ring' is more rigid than the shank, so these loads are concentrated at the transition between the two.
It is like clamping a piece of sheet in a vice, bend it to and frow enough times, and it will crack and fail at the transition from rigid (clamped) to flexible.

The later xxUZ rods have a smaller shank so they flex more than early 1UZ rods and their fatigue life is lower. The early rod will break if you raise the rpm (flex it more often and more) or increase the bhp (flex it more).

After market rods have a stiffer shank (H beam stiffer still) and are made from higher grade material, but they also have a fatigue limit, it is just higher than most people require.

F1 engines used to do 1 meeting, everything apart from the block and head castings was trashed, 1 more meeting and the lot was trashed.
By the regs they now must use an engine (untouched) for 2 meetings, then the lot is trashed.

It is a fatigue problem.
It is why all aircraft components are 'lifed' and replaced after a certain time interval.
The real problem is not if it will break, but WHEN.

 

[V8Datto]

The rods broke a little away from the main bearing, here I'll draw a line on the top pic, and measure it.

I got the measurements by changing the image size to line up with one I have in front of me, (Argo rod). So they should be close to real size and then used a Digital vernier caliper to measure them

So it's not 100% but should give an idear to real thickness

In this case you can see why the early rods would be stronger.

My 2c, but ofcorse rms is right

 

[jibbby]

WOW, RMS that makes perfect sense to me....Thanks

V8Datto - I know and can see the rod thickness in the different rods as described with the line you presented in the pictures...It was the bottom big ring portion that I was comparing which looks all to be the same with all the rods....However, RMS has introduced the flex theory which has shed a new light on this thread....

 

[turboandrew]

Jibby, the picture you showed, look closely, they did not break on the very bottom of the big end. They broke between the rod portion and the big end (the top of the big end), exactly where V8Datto drew the line. That are is much stronger in the early 1UZ rods.

 

[JustenGT8]

LOL you should watch more Mr Squiggle Jibbby Upside down Miss Jane

 

[jibbby]

Jibby, the picture you showed, look closely, they did not break on the very bottom of the big end. They broke between the rod portion and the big end (the top of the big end), exactly where V8Datto drew the line. That are is much stronger in the early 1UZ rods.

I've seen two other destroyed 2uz and 3uz rods that actually broke at the bottom ring part..The picture I posted is not a common rod break and infact the break is not a complete break of the rod at all, it appears to be chipped... Let me try and find true failed rods and post a pic...

The rods don't typically fail at the fat middle part of the rod or at the red line that illustrated and drawn horizontally in the other above pic....

The above comparison picture that illustrates the arrows pointing at the weakest base bottom crank ring part of the 1uz and 3uz rods is where the failure usually occures in most every case...I researched rod failure on these stock Xuz.. rods and that is why I began to inquire about the differences and if there is actually one.....

I am not posting up hog wash...There is reason behind my insanity...:006:

 

[Lextreme II]

Dont forget when Wayne's engine blow up, those rods also broke the block too. The swinging of the rods impacting the block will break break the closest to the crank side. I do think the failure is at middle or the small end area. Due to the tendency of the post 95 rods failures with mild boost (12-15 psi) we set out to make some forged h beam rods especially for the UZFE engine.

We are extremely to have these rods:




These rods are exact copy of the orginal and will directly replace all UZFE stock rods from 1989 to 2006 with proper offset too.

 

[V8Datto]

LOL you should watch more Mr Squiggle Jibbby Upside down Miss Jane

LMFAO..... I haven't laughed that hard in a while....

I would have thought the middle of the rod would be the weakest/ get the most flex

Jibbby show us some pictures,

 

[jibbby]

Ok, I am having trouble finding the original Xuz-fe busted rod pics, still searching on the CL forum... Still looking...

This is a pic of 1000hp + connecting rod... Look at the upper one as it is stout around the ring area as well as the long center portion...Now that is a stout rod...

 

[turboandrew]

That's because that "stout" is an aluminum rod! Seriously, the -only- reason a rod would fail on the very bottom of the big end is because the bolts failed. The only time there would be stress on the very bottom is when the rod is being slung upward. The most stress is where RMS stated, where the shank meets the big end.

 

[jibbby]

I gotta disagree with ya turboandrew, the ring portion does crack and seperate and the bolts stay intact in some cases... Or the bolts snap and the ring seperates that way like you say...

Either way if the flex action is the real cause of failure in the rods or rods ends then this thread is useless anyway... The meat portion of the rod is significant..

I am not a rod expert by any means and just go by what I see and makes sense..

 

[rms]

We really have to stop rateing rods by hp. It is meaningless and can lead us down the garden path.

The aluminium rod may cope with 1000hp in a nitro dragster but if you fitted them to a std 1uz with grandma driving, she won't get many trips to the shop before they fail.
They are meant to lessen the shock load on the piston and bearings, they do 1 or 2 passes and are then replaced. They don't have the fatique life.
Just the same as a 1uz rod may cope with 6-700hp but will not live at 9000rpm.

The rod breakages I have seen are just under the pin boss, just above the big end boss, or through the narrow sections at the bolt thread to bearing seat and the rod bolt head to bearing seat.

I am a little suspicious that the 2uz rod failures may be instigated by piston skirt failure. Just the fact it broke so many rods at the same time.

 

[jibbby]

That makes perfect sense..RMS.... I believe I am getting a better picture on what and how and why the rods fail...

That makes sense not to rate connecting rods by horsepower...However, with that being said isn't the pure force and flex of the downward action of the piston cause the most force on the rod?...As in directly after the combustion period in the chamber and the downward action?...Wouldn't that cause more stress then just higher rpm rotation?...

I am trying to work this out in my head... Why would higher rpms compromise the rods?

example -

1) One engine revs 7000 rpms and creates a peak HP rating of 500whp
2) Second engine revs 9000 rpms and creates a peak HP rating of 500whp

Would the same rods have more stress on the second motor just because they are rotating faster?... I guess they could when you consider gravity..

 

[mmmjesse]

I am trying to work this out in my head... Why would higher rpms compromise the rods?

example -

1) One engine revs 7000 rpms and creates a peak HP rating of 500whp
2) Second engine revs 9000 rpms and creates a peak HP rating of 500whp

Would the same rods have more stress on the second motor just because they are rotating faster?... I guess they could when you consider gravity..

I would stop rating by hp if i were you.

 

[rms]

jibbby,
It has been a long time since I calculated rod loadings. Give me a couple of days and I will post some figures. It is in tons though.

 

[jibbby]

RMS - I don't want to put you out on this...I am just always curious as to why things happen and work the way they do... If you have the time that's great if not it's ok...

mmmjessee - Gee you think so? In most threads on most forums rod strength is usually expressed and rated thru horse power holding capacity...Even though appears that should not be the case...

The connecting rods that are attached to the crank carry the pistons which carry increased weight load as the rotating action increases (rpms)... That's basic physic's (gravity, weight and speed) and that makes perfect sense.. I do agree that rods should be rated for strength thru rpm action and force...

Higher rpms create more load on the rods...

 

[JustenGT8]

Jibbby, very simply the forces involved in the rod/piston accelerating, stopping at the top (and bottom) of the stroke and accelerating again are far far more than the force the combustion process exerts of the top of the piston.

I think Corky Bell's Maximum boost has a good diagram that plots the forces thru a rpm cycle to illustrate.

That's why factory engines can take relatively huge boost increases no problem, but additional revs get you into trouble quick smart

 

[jibbby]

So what your saying Justin boost is more natural for the rods to handle stress rather then a high performance cam change that increases rpms?

I would have thought the power of the bang in the combustion chamber would have a instant jolting and thrusting motion on the rod itself...However, after looking at so many busted rods it uppers the breaks occure mostly on the upward motion where the pulling upward force would bust the nut or big ring bottom portion... If that's the case RPM's would be more probable for rod destruction rather then brute piston force..

Thanks guys I am getting a grip on this yet...