ptuomov wrote: ↑Mon Jan 22, 2018 7:51 am
The Japanese and German car manufacturers used to make the cranks very strong and stiff to start with and then induction harden the journals. I don’t know why they are so overbuilt, maybe the stiffness was needed to make the desired bearing clearances live and the strength was a by-product?
How much journal hardness does gas nitriding of the whole crankshaft add on top of the factory induction hardening of the journals?
It's to provide a hardened surface for greater durability that's all. You can tell an induction hardened by the heat marks because they only do the journals.
Nitriding treats the whole crank and makes it go grey, you wouldn't do both to one item. It can also bend a crank or cam if not done carefully enough and it also swells the journals so they have to be finished to size afterwards.
ptuomov wrote: ↑Mon Jan 22, 2018 7:51 am
The Japanese and German car manufacturers used to make the cranks very strong and stiff to start with and then induction harden the journals. I don’t know why they are so overbuilt, maybe the stiffness was needed to make the desired bearing clearances live and the strength was a by-product?
How much journal hardness does gas nitriding of the whole crankshaft add on top of the factory induction hardening of the journals?
It's to provide a hardened surface for greater durability that's all. You can tell an induction hardened by the heat marks because they only do the journals.
Nitriding treats the whole crank and makes it go grey, you wouldn't do both to one item. It can also bend a crank or cam if not done carefully enough and it also swells the journals so they have to be finished to size afterwards.
I also always thought that if it's induction hardened then gas nitriding doesn't really make much sense. Unless, that is, the crank has been offset ground thru the induction hardening. After that sort of surgery, our cranks have gone to gas nitriding heat treatment.
Fire suit on.
Every journal I have inspected and ground that had wear, the majority of the wear was always on the downstroke/tension/backside.
Always seemed logical to me. Once the compression force is pretty much depleted and it has to turn the corner to come back up again there is a "slop and slam" moment where it can rattle and slam the journal. More clearance likely aggravates it.
70 psi and 10K. Wear might be the price to be paid for success.
Why are most German and Japanese 4 cylinder cranks hardened? Most likely because they are a rattle monster.
Dave Koehler - Koehler Injection Enderle Fuel Injection - Nitrous Charger - Balancing - Nitrous Master software http://www.koehlerinjection.com
"Never let a race car know that you are in a hurry."
let me rephrase that. 4 cyls are rattle monsters, regardless of origin.
Dave Koehler - Koehler Injection Enderle Fuel Injection - Nitrous Charger - Balancing - Nitrous Master software http://www.koehlerinjection.com
"Never let a race car know that you are in a hurry."
You are concentrating on words. I know what the op meant and I think you do also.
If you read the second sentence you are saying essentially the same thing.
Dave Koehler - Koehler Injection Enderle Fuel Injection - Nitrous Charger - Balancing - Nitrous Master software http://www.koehlerinjection.com
"Never let a race car know that you are in a hurry."
exhaustgases wrote: ↑Mon Jan 22, 2018 2:38 pm.. There is no tension in the beam (rod) until it passes through TDC and gets the yank down.
From around 80° BTDC (max piston velocity) on up, the piston is being decelerated (negative upwards or positive downwards acceleration) by the rod and thus a tension load is on it and the journal. From TDC to the same angle after the rod is also applying a downward acceleration, still imposing a tension load. Of course gas loads are additional plus/minus factors.
exhaustgases wrote: ↑Mon Jan 22, 2018 2:38 pm.. There is no tension in the beam (rod) until it passes through TDC and gets the yank down.
From around 80° BTDC (max piston velocity) on up, the piston is being decelerated (negative upwards or positive downwards acceleration) by the rod and thus a tension load is on it and the journal. From TDC to the same angle after the rod is also applying a downward acceleration, still imposing a tension load. Of course gas loads are additional plus/minus factors.
If the rod big end has mass (and it does) I think that also needs to be taken into account in the force vector calculation on the rod journal and bearing.
The engine is wet sump, but sorted enough that it doesn’t see oil pressure dips during a pass. I run aluminum rods and about 0.003-0.0035 clearance on 50wt vr1. It is probably pretty foamy by the end of a pass and I’m changing to a dry sump system this year
I would be surprised if another .001-.0015 clearance didn't help a lot. Top Fuel can use up to .010 rod bearing clearance. The rod parting line pulls in toward the crankshaft pinching off some of the oil supplied through the crankpin oil holes literally wiping the oil off. Your motor, comparatively speaking, is like a Pro Mod and I know they use much more than you are.
Here is a bearing, one looks better and two look worse. The upper shell has around a dozen laps and I think the lower has more like 25-30.
Oh, side clearance is in the 0.016” range with extra reliefs to let the oil out. Been to the party with too little oil exit area on the sides, not a fun one there!
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The wear pattern look a little weird in the second pic, as if the journal was barrel-shaped, but the main issue I see is the contact right up to the parting line. Contact should be confined to about the center 2/3rds.
Either the rods bores have become distorted (pinched-in at the parting line) or are deflecting under load. In the latter case, the easy fix is a higher eccentricity bearing, such as a Clevite 'P' series, to prevent the oil film being 'squeegeed off'.
Some shops address this issue by truing the bore with the rod squeezed in a thous or more by a C clamp across the parting line, resulting in more eccentricity.
How does that Crank feed oil to the Rods?
Are you running half groove main bearings , or full , is the Crank crossdrilled, or does it have a special oiling layout?
You can cut a man's tongue from his mouth, but that does not mean he’s a liar, it just shows that you fear the truth he might speak about you!
