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Gtir Motorsport club » General Discusion » Motorsport » Has anyone ever snapped their crankshaft?

Has anyone ever snapped their crankshaft?

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1Has anyone ever snapped their crankshaft? Empty Has anyone ever snapped their crankshaft? on 23rd November 2015, 8:45 pm

Cosmic73

Cosmic73
I've heard of cracked cranks being scrapped but has anyone ever actually snapped one? :anyone

2Has anyone ever snapped their crankshaft? Empty Re: Has anyone ever snapped their crankshaft? on 23rd November 2015, 8:48 pm

wrc

wrc
I have known of cranks snapping yes Smile

But in an sr20... never seen it. Although your cracking problem is very very common.

3Has anyone ever snapped their crankshaft? Empty Re: Has anyone ever snapped their crankshaft? on 23rd November 2015, 9:10 pm

Cosmic73

Cosmic73
@wrc wrote:I have known of cranks snapping yes Smile

But in an sr20... never seen it. Although your cracking problem is very very common.

Exactly! If most sr20det cranks have cracks but dont snap, Is scrapping them overkill? ball age

4Has anyone ever snapped their crankshaft? Empty Re: Has anyone ever snapped their crankshaft? on 23rd November 2015, 9:18 pm

Stu

Stu
Admin
Admin
I have never heard of a gtir crank snapping.
I think because of your line of work you are over analising things.
No doubt every gtir crank has cracks in it.
Have you spoke to Bob? He builds these engines all the time so should have a good idea of what to do..


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5Has anyone ever snapped their crankshaft? Empty Re: Has anyone ever snapped their crankshaft? on 23rd November 2015, 9:57 pm

gtir_woody

gtir_woody
moderator
moderator
I've never heard of a gtir one snapping either. However if it was going to happen there are 1000hp+ sr20dets out there so whether or not they have snapped one.

6Has anyone ever snapped their crankshaft? Empty Re: Has anyone ever snapped their crankshaft? on 23rd November 2015, 10:00 pm

shroom

shroom
moderator
moderator
Suppose its like the issue with the t28 turbo cracking. Guess its not until you strip the engine down and have the crank inspected who knows what state its in now lol think I will stick to my push bike haha


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7Has anyone ever snapped their crankshaft? Empty Re: Has anyone ever snapped their crankshaft? on 24th November 2015, 8:16 am

wrc

wrc
I would sat from a good guesstimate that between 80-90% of gtir cranks out there have some form of crack in for sure. Its very common.

Acceptable to a certain extent too if you are standard or just above standard power. Its when you up the power that you hit problems.

8Has anyone ever snapped their crankshaft? Empty Re: Has anyone ever snapped their crankshaft? on 24th November 2015, 12:03 pm

Mr B

Mr B
gtir technician
gtir technician
All down to where crack located & how bad it is, you do get a lot with cracks but from ones I handled over years I would say it 50/50 on ones with bad cracks. Talk to your engineers about it & perhaps get second opinion if not conclusive .

9Has anyone ever snapped their crankshaft? Empty Re: Has anyone ever snapped their crankshaft? on 24th November 2015, 4:56 pm

Cosmic73

Cosmic73
@Mr B wrote:All down to where crack located & how bad it is, you do get a lot with cracks but from ones I handled over years I would say it 50/50 on ones with bad cracks. Talk to your engineers about it & perhaps get second opinion if not conclusive .

I had a word with our metallurgy expert,
Nitrided case depth is a fraction of that for case carburised (typically <0.25mm v 1mm) but the surface is much harder and more brittle as a result.
He reckons it could be localised surface cracking which stops when it reaches the more ductile core, hence the reason why many cranks have cracks but none have failed.

Still, I'd rather have a pukka one. Smile

10Has anyone ever snapped their crankshaft? Empty Re: Has anyone ever snapped their crankshaft? on 24th November 2015, 7:39 pm

Mr B

Mr B
gtir technician
gtir technician
^ I would agree with that. with a cracked crank you ideally want xray to see full depth if intending using it .

11Has anyone ever snapped their crankshaft? Empty Re: Has anyone ever snapped their crankshaft? on 24th November 2015, 8:39 pm

Cosmic73

Cosmic73
@Mr B wrote:^ I would agree with that. with a cracked crank you ideally want xray to see full depth if intending using it .

Yeah, we talked about that and he reckons because the crack is square to the crank axis it might not be do-able to x-ray because you cant get close enough (side on) to the crack.

Bob might have a decent used crank to sell if not, i'll just buy new from Eric or that link you sent.
thinking

12Has anyone ever snapped their crankshaft? Empty Re: Has anyone ever snapped their crankshaft? on 24th November 2015, 9:19 pm

Cosmic73

Cosmic73
http://www.nismooc.com/index.php?threads/crankshaft-re-grinds.85263/

Shocked

13Has anyone ever snapped their crankshaft? Empty Re: Has anyone ever snapped their crankshaft? on 24th November 2015, 9:23 pm

GTI-R US

GTI-R US
Management
Management
Yes many of the cranks are cracked for example we have around 30 in stock, (threw a lot away when we moved int our big unit) and out of the 30 which remain I have around 4 which are crack free and do not need grinding, the rest all need to go to my engineer to be ground to see if cracks extend beyond nitride surface and if so then many of those are scrap too as I would not dream of using one in any of our engine builds.
And as you were correctly informed, the nitride surface goes down to around 0.25-0.30 on some and that's why its not a good idea to grind cranks any further than .25 as your getting close to the edge of that protective hardened surface which is very important on a turbo charged engine due to extreme loading the crank big end journals are under. if engine is na or fitted with a supercharger then the power delivery is much more linear throughout the rev range (no sudden force) so you have more leeway with regard to grinds.
Main journals are under just rotational force so you can get away with a lot more on those but generally if the shaft is cracked and it extends beyond a .25 grind (bigend journal) then its basically scrap

I will put up a photo etc tomorrow 'if I get time' of something you will find pretty astonishing and its a credit to just how strong these crankshafts and stock rods are Wink certainly surprised me.

And in answer to your question mr cosmic.........yes think I may have one in good order if needed, replied in your thread.


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14Has anyone ever snapped their crankshaft? Empty Re: Has anyone ever snapped their crankshaft? on 24th November 2015, 11:22 pm

Mr B

Mr B
gtir technician
gtir technician
on any engine crank pins/big ends are under tremendous shock load, the inertial load on crank pins caused from sudden change of direction of piston & it's related mass tends to exceed load from combustion process and is why you can so easily up power on stock motors without much concern on cranks & rods .
Mains & pins could take a .50 grind but it hassle sorting nitride treatment & bearings.
Don't chuck your crank until proper tests write it off as todays scrap maybe tomorrows reworked solution.

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