Cranks

[Magnus]

Another thing I've noted lately is the 6.4 has the same firing. The few broken cranks I've seen and heard of over in their world are also at the first throw. Of course they're not quite as smart as this community because the dmax has been leading common rail progress for years so their fix as far as I've seen is to increase the rod ratio and reduce sidewall loading... Riiiiight

My buddy has one he's put a lot into and he'll listen to me when it comes to flow matching him some compounds, or designing a front parallel four link, but the second I suggest his 6.4 might have a bad firing order and is predestined to eat itself... Boy does he get upset and defensive! Yet he already KNOWS from his forums that if it fails it'll be the first throw.

 

[Fahlin Racing]

What about block flexing?

This is why I brought up misalignment. Especially when a block turns up with cracking main bore webs. In turn, whats block material and flaws within the casting design? Too thin? Stress risers? Only one more possibility to compound the problem.

 

[Magnus]

How many blocks turn up with cracking webs after running at stock power? The cranks have been proven to snap at any power level including stock, and just seeing the beef at the webbing I can't believe a properly cast block would lose main bearing alignment at stock power. Block strength is another area that's definitely improved over the years so it'd be interesting to see if any of those LBZ/LMM cranks that snapped at stock power had block issues, but I doubt it. Most things Isuzu has ever built are tough as nails. A stock 4BD1T even puts a 12valve to shame in some ways.

Again I'm no stranger to main webbing issues, as the 6.2 sucks there too. People went as far as filling outer stock main bolt holes and drilling and tapping new mains splayed out 30 degrees and deeper into the webbing, and fitting billet caps to those bolt layouts. But that was a few fanatics polishing a turd, and were talking about a MUCH BETTER design here. I can't believe the dmax mains deflect or fail at the webbing at STOCK POWER.

 

[Fingers]

I haven't read up on your cylinder pressure system yet, but I'll definitely look for it now. Is that why your dyno numbers look like some torque is tuned out? Optimized cylinder pressure through tuning? I'd imagine you've got it responding smoother than stock with doubled injector flow and 690 at the wheels. I always see everyone pushing 40% overs or whatever on crazy pulses and 700+hp and it never seems like a good idea to me.

Intercooler was leaking like crazy. Much better now with the replacement, but never got back on the rollers. Need to fix a cam timing issue before I spend the money on any more dyno.

The DAQ I've been using can sample 2 channels simultaneously at 100 S/sec. But only in bursts. So you end up with snap shot frames. It is more than adequate to log the twist in the crank through two revolutions.

 

[bigmackmiller]

sub'd

 

[Fingers]

I was going over the old software to adapt it to the twist thing and realized that I have a whole pile of crank pulse data. Most only in the 1/2° accuracy range, but still data.

My thoughts were if I could place a reference line where the pulses should be, any variation would stand out to the naked eye. So, I did that.

Nothing conclusive here since every engine I have data for still has a good crank in it. But even so, You can see about a one degree shift near 120° BTDC in several of the logs. And only in a given RPM range.

This is at least encouraging. Mainly because it means I should be able to pull some twist numbers strictly from the crank signal and also improve the granularity of the samples to within 1/8° or so.

 

[smarquis]

sweet. and thanks for the hard work Fingers!!

 

[LBZ]

I was going over the old software to adapt it to the twist thing and realized that I have a whole pile of crank pulse data. Most only in the 1/2° accuracy range, but still data.

My thoughts were if I could place a reference line where the pulses should be, any variation would stand out to the naked eye. So, I did that.

Nothing conclusive here since every engine I have data for still has a good crank in it. But even so, You can see about a one degree shift near 120° BTDC in several of the logs. And only in a given RPM range.

This is at least encouraging. Mainly because it means I should be able to pull some twist numbers strictly from the crank signal and also improve the granularity of the samples to within 1/8° or so.

What was the rpm range?
It would be interesting to see the same readings on an engine with an AF cam just to see what it looks like.

 

[Fahlin Racing]

How many blocks turn up with cracking webs after running at stock power? The cranks have been proven to snap at any power level including stock, and just seeing the beef at the webbing I can't believe a properly cast block would lose main bearing alignment at stock power. Block strength is another area that's definitely improved over the years so it'd be interesting to see if any of those LBZ/LMM cranks that snapped at stock power had block issues, but I doubt it. Most things Isuzu has ever built are tough as nails. A stock 4BD1T even puts a 12valve to shame in some ways.

Again I'm no stranger to main webbing issues, as the 6.2 sucks there too. People went as far as filling outer stock main bolt holes and drilling and tapping new mains splayed out 30 degrees and deeper into the webbing, and fitting billet caps to those bolt layouts. But that was a few fanatics polishing a turd, and were talking about a MUCH BETTER design here. I can't believe the dmax mains deflect or fail at the webbing at STOCK POWER.

The amount of deflection within the block and your crankshaft, there is a video out there showing a cummins 5.9 being bored and the machinst give an example of block distortion BY HAND. he puts a gauge in the bore and twists the block by the deck and drops the gauge. Just imagine the load not just at stock power but at the point if breaks due to rpms between the rotating force and the 'give' the block allows to operate. Crack or no crack we don't know how much between the two as far as movement to compound and add into the eventual engine failure.

 

[Fingers]

I may have jumped the gun on the twist results from my archived data. Refining the software has made what I thought I saw inconclusive. I'll keep at it.

 

[Fingers]

ALL blocks flex, as do all cranks. It is the amount and the stress concentrations that matter.

By Fahlin's thinking we should never get on a plane. We have all seen those wings flex. Damn, they are going to break right off!!

:roflmao:

 

[coldLBZ]

ALL blocks flex, as do all cranks. It is the amount and the stress concentrations that matter.

By Fahlin's thinking we should never get on a plane. We have all seen those wings flex. Damn, they are going to break right off!!
:roflmao:

That suprised me my first time

 

[Stingpuller]

Flex

I wanted off the first time I flew! That just didn't look like something I wanted to ride in.

 

[minisub]

Ever been stuck in traffic on a long-span suspension bridge on a windy day? That's way worse than watching those pesky wings flex....

Sorry for the derail.

 

[Dirtymaxx03]

Ever been stuck in traffic on a long-span suspension bridge on a windy day? That's way worse than watching those pesky wings flex....

Sorry for the derail.

or a ski lift 50' off the ground when the winds decide to pick up. F that S

 

[JoshH]

Ever been stuck in traffic on a long-span suspension bridge on a windy day? That's way worse than watching those pesky wings flex....

Sorry for the derail.

I'll say!

[YOUTUBE]j-zczJXSxnw[/YOUTUBE]

 

[Magnus]

Theres an older model helicopter the army still flies with a 3 piece body and when you pick up enough forward airspeed the hull flexes tremendously and opens visible air gaps between the 3 sections and you can see the rivets holding it all together... They're actually airspeed limited by the hull strain, measured on a mechanical gauge back in the cargo area. Makes for a scary ride for anyone with a mechanical or materials background.

They actually had the craziest material failure I've ever seen recently too, but I'm not sure how public that is yet

 

[Fahlin Racing]

ALL blocks flex, as do all cranks. It is the amount and the stress concentrations that matter.

By Fahlin's thinking we should never get on a plane. We have all seen those wings flex. Damn, they are going to break right off!!

:roflmao:

Hahaha, thats funny.

I realize everything within flexibility. However when majority are reading but not posting and the ones posting as well as reading should also state how the nature of the operation occurrs to follow within the discussion, like I said its the amount of flex with all parts involved plus your stress concentrations. Perhaps bringing everything into open can bring another person with a reasoning for changing something.

Just another piece of the puzzle :thumb: Think about it, how much flex can happen before stress risers are amplified to increase failure rates?

 

[Jackblack99]

I will throw in my bit of info on the subject, my crank snapped in the same area as most. no spun bearing. My good friend works for cat took a look at it, he said that it looked to be a mfg flaw. the outer edge has smoothed fracture lines and got more rough toward the center meaning that it had been separated/separating for a long time.

Mine broke the same way. No spun bearing at the journal that broke. It did spun the bearing on the 2nd MAIN journal but broke at the 1st rod journal. It was running fine and started knocking so I shut it down. I brought both sections of the crank and the block with me to work (I work at Haisley Machine) and had Van look at them. He agree'd that it looked like the crank had some manufacturing defects that caused the failure which in turn caused the main bearing to spin which in turn junked my block.

 

[Mikey]

What about cap walk?
Is that a factor?
Will a girdle help?