Don Terrill’s Speed-Talk

Ok guys a 12cyl. diesel engine with a 10.236in main journal turning 950rpm max 18-1 compression making 4500hp.
What would you run for clearance & what kind of oil pressure?
Thanks

https://www.nationalbronze.com/Tribolog ... ition).pdf

Section A9

Edit: ~260mm main

Best to consult the engine manufacturer for their recommendations on bearing clearance and oil pressure specs. I don't think any of us on a high performance site will have the background and experience to offer you any viable recommendations concerning this issue . . . . . . . . . .

Ship engine?
Maybe stationary powerplant?

Sorry, very little knowledge to share.

let us know what you come up with!

.010" oil clearance ?
100psi ?

Exactly which engine is it ? Make and model ?

Ok, I am not allowed to say what it is. They are running .003 clearance and 90psi. I really feel that is to little clearance and not enough pressure. Engineers say that is enough but we keep having failures.
Was just looking for other opinions.
Thanks

saleen385 wrote: ↑Sun Jan 12, 2020 8:42 pm Ok, I am not allowed to say what it is. They are running .003 clearance and 90psi. I really feel that is to little clearance and not enough pressure. Engineers say that is enough but we keep having failures.
Was just looking for other opinions.
Thanks

Check it against the Tribology handbook.

saleen385 wrote: ↑Sun Jan 12, 2020 8:42 pm Ok, I am not allowed to say what it is.

Why are you not allowed to share the make of engine with us? Secret Service project or FBI? Maybe powerplant for Bill & Hillary's yacht?? I smell BS.
Maybe a Cooper-Bessemer pump station type powerplant?? You are not going to get viable answers to your quiry on a high performance engine site, just too many variables. Contact the engine manufacturer or a factory authorized remanufacturer for accurate answers to your questions.

For instance, my recommendation for natural gas fueled pump station 12 cylinder engine with 38.25" bore, 44.50" stroke and 54.125" center to center connecting rods would be .0065" crankshaft oil clearance and 185# of oil pressure. Considering the use of 22.50 gallons of 70# oil in the crankcase.

No less than .0005 per 1 IMO
so, .0055" minimum

.003", no,
.03"mm maybe?! double check your units

So 0.05-0.1% of the journal diameter?

For the pressure, one would want to know what the rpm is and how the oil passages run.

guy, the oil pressure has been stated.

apologies....misread above post. rainy dreary monday.

GUY, the RPM has been stated!

I have studied this a little and will go out on a limb and say .008 .

bentvalves wrote: ↑Mon Jan 13, 2020 5:27 pm guy, the oil pressure has been stated.

apologies....misread above post. rainy dreary monday.

GUY, the RPM has been stated!

This to me? For oil pressure, very little should oil the mains. However the big question is how do the rod journals get oiled, given the large main journal diameter. At 950 rpm it shouldn’t require a lot of oil pressure even with that big main, compared to say (2.75”*7000rpm)^2.

If the engineers are saying the clearance and pressure are correct (presumably these are the OEM recommendations ) and engine failures are occurring regularly then it is logical to examine other possibilities.

If the engine uses a fluid damper then it could be the case that despite appearing okay visually it needs rebuilding or replacement. The article below points out that this is a common cause of heavy duty diesel engine failure.

Good luck.

http://www.engineprofessional.com/artic ... _64-72.pdf